Sturgeon biodiversity and conservation

Sturgeonbiodiversity and conservation

Developments in environmental biology of fishes 17 

Series Editor 

EUGENE K. BALON

Sturgeon biodiversity and conservation 

Editors: 

VADIM J. BIRSTEIN, JOHN R. WALDMAN & WILLIAM E. BEMIS 

Reprinted from Environmental biology of fishes, Volume 48 (1–4), 1997 

with addition ofspecies and subject index 

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Contents 

Prelude to sturgeon biodiversity and conservation 

by E.K.Balon 9-11 

Sturgeon biodiversity and conservation: an introduction 

by W.E. Bemis, V.J. Birstein &J.R. Waldman 13-14 

Leo Semenovich Berg and the biology of Acipenseriformes: a dedication 

by V.J. Birstein & W.E. Bemis 15-22 

Part 1: Diversity and evolution of sturgeonsand paddlefishes 

An overview of Acipenseriformes 

by W.E. Bemis, E.K. Findeis & L. Grande 

25-71 

Osteology and phylogenetic interrelationships of sturgeons (Acipenseridae) 

by E.K. Findeis 73-126 

Phylogeny of the Acipenseriformes: cytogenetic and molecular approaches 

by V.J. Birstein, R. Hanner & R. DeSalle 127-155 

How many species are there within the genus Acipenser? 

by V.J. Birstein & W.E. Bemis 

157-163 

Part 2: Biology and status reports on sturgeonsand paddlefishes 

Sturgeon rivers: an introduction to acipenseriform biogeography and life history 

by W.E. Bemis &B. Kynard 

167-183 

Past and current status of sturgeons in the upper and middle Danube River 

by K. Hensel &J. Holcik 

185-200 

Endangered migratory sturgeons of the lower Danube River and its delta 

by N. Bacalbasa-Dobrovici 

201 -207 

Present status of commercial stocks of sturgeons in the Caspian Sea basin 

by R.P. Khodorevskaya, G.F. Dovgopol, O.L. Zhuravleva & A.D. Vlasenko 

209-219 

Species structure, contemporary distribution and status of the Siberian sturgeon, 

Acipenser baerii 

by G.I. Ruban 221-230 

Endemic sturgeons of the Amur River: kaluga, Huso dauricus, and Amur sturgeon, 

Acipenser schrenckii 

by M.L. Krykhtin & V.G. Svirskii 

231-239 

Biology, fisheries, and conservation of sturgeons and paddlefish in China 

by Q. Wei, F. Ke, J. Zhang, P. Zhuang, J. Luo, R. Zhou & W. Yang 

241-255 

Biology and life history of Dabry’s sturgeon, Acipenser dabryanus, in the Yangtze River 

by P. Zhuang, F. Ke, Q. Wei, X. He & Y. Cen 

257-264 

Observations on the reproductive cycle of cultured white sturgeon, Acipenser transmontanus 

by S.I. Doroshov, G.P. Moberg & J.P. Van Eenennaam 

265-278 

Contemporary status of the North American paddlefish, Polyodon spathula 

by K. Graham 279-289 

Life history and status of the shovelnose sturgeon, Scaphirhynchus platorynchus 

by K.D. Keenlyne 291-298 

The status and distribution of lake sturgeon, Acipenserfulvescens, in the Canadian provinces 

of Manitoba, Ontario and Quebec: a genetic perspective 

by M.M. Ferguson & G.A. Duckworth 299—309 

^

6 

Lake sturgeon management in the Menominee River, a Wisconsin-Michigan boundary water 

by T.F. Thuemler 311-317 

Life history, latitudinal patterns, and status of the shortnose sturgeon, Acipenser brevirostrum 

by B. Kynard 319-334 

Status and management of Atlantic sturgeon, Acipenser oxyrinchus, in North America 

by T.I.J. Smith & J.P. Clugston 

335-346 

Atlantic and shortnose sturgeons of the Hudson River: common and divergent life history 

attributes 

by M.B. Bain 347-358 

Biological characteristics of the European Atlantic sturgeon, Acipenser sturio, as the basis for 

a restoration program in France 

by P. Williot, E. Rochard, G. Castelnaud, T. Rouault, R. Brun, M. Lepage & P. Elie 359-370 

Part 3: Controversies, conservation and summary 

Sturgeons and the Aral Sea ecological catastrophe 

by I. Zholdasova 373-380 

Threatened fishes of the world Pseudoscaphirhynchus spp. (Acipenseridae) 

by V.J. Birstein 381-383 

Molecular analysis in the conservation of sturgeons and paddlefish 

by I.I. Wirgin, J.E. Stabile & J.R. Waldman 385-398 

Sensitivity of North American sturgeons and paddlefish to fishing mortality 

by J. Boreman 399-405 

Alternatives for the protection and restoration of sturgeons and their habitat 

byR.C.P.Beamesderfer & R.A.Farr 407-417 

Threatened fishesof theworld: Scaphirhynchus suttkusi Williams & Clemmer, 1991, 

(Acipenseridae) 

byR.L. Mayden & B.R. Kuhajda 418-419 

Threatened fishesof the world: Scaphirhynchus albus (Forbes & Richardson,1905) 

(Acipenseridae) 

byR.L. Mayden & B.R. Kuhajda 420-421 

Sturgeon poaching and black market caviar: a case study 

by A. Cohen 423-426 

The threatened status of acipenseriform fishes: a summary 

by V.J. Birstein, W.E. Bemis & J.R. Waldman 427-435 

Species and subject index, byAlice G. Klingener 

437-444 

This volume is dedicated to the memory of Leo Semenovich Berg 

Logo design by William E. Bemis inspired by the holarctic distribution of sturgeons and paddlefishes 

Numae is Anishnabe for sturgeon, a painting by the Chippewas of Nawash artist Adrian Nadjiwon of Cape Croker, 

Lake Huron: “In the painting I wanted to depict the balance that one existed between my ancestors and the sturgeon 

(the sturgeonbeing symbolic of all the fish species that the Old People subsistedon) with the fishing line symbolising 

a spiritual link and balancing point between the man and the sturgeon” (1992).

Portraits of three juvenile sturgeons which originated from the Black Sea stock bred at the Propa-Gen International Aquaculture Production 

R & D and Trading, Komadi, Hungary: the top photograph shows a 71 cm armored form of the Russian sturgeon, Acipenser gueldenstaedtii: 

the middle photograph shows a 77 cm naked form of A. gueldenstaedtii (note its smooth skin and absence of scutes): and the 

bottom photograph is of a 54 cm A. persicus Photographs by Paul Vecei. May 1996.

Environmental Biology of Fishes 48: 9-12, 1997. 

© 1997 Kluwer Academic Publishers. Printed in the Netherlands. 

Prelude to sturgeon biodiversity and conservation 

Soaring Eagle, you have angered Great Sturgeon, and he has taken your son because you 

took too many fish from the lake. 

Joe McLellan (1993) 

in‘Nanabosho, Soaring Eagle and the Great Sturgeon’, Pammican Publications, Winnipeg. 

It gave me great pleasure to help with the publication of this volume. The elusive beasts it deals with sustained my enthusiasm 

in the early days of work on the Danube River. Already then, 40 years ago. sturgeons were so rare 1 in the middle 

Danube (Figure 1), that I had to shift my attention to the wild carp 2.3 which have followed since many of the sturgeons into 

oblivion. 

Figure 1. Specimen of Acipenser gueldenstaedtii 35 cm long caught on 30.7.1967 in the Danube River near Radvan (river km 1749). 

Original drawing by Miriam Baradlai 1 . 

^ 

Often I was standing on the shore, where about 100 years ago,the Viennese court had their military fire cannon balls at 

giant beluga, Huso huso, and other sturgeon species ascending the river to spawn 4 . I was dreaming of arresting the present 

destruction 5.6 and of rebuilding the past (Figure 2). I envied Marsilius 7 who was able to witness here the processing of 

caviar (Figure 3) which I was privileged to spoon up in Russia only 30 years, no, 270 years later, and became addicted to. 

∨ 

1 Balon, E.K. 1968. Další nález mlade Acipenser güldenstaedti colchicus Marti, 1940 v ceskoslovenskom úseku Dunaja (A further discovery 

of a juvenile Russian sturgeon in the Czechoslovak part of the Danube). Ac. Rer. Natur. Mus. Nat. Slov. (Bratislava) 14: 95-100. 

2 Balon. E.K. 1974. Domestication of the carp Cyprinus carpio L. Royal Ontario Mus. Life Sci. Misc. Publ., Toronto. 37 pp. 

3 Balon. E.K. 1995. The common carp, Cyprinus carpio: its wild origin, domestication in aquaculture, and selection as colored nishikigoi. 

Guelph Ichthyology Reviews 3: 1-55. 

4 

∨ 

Hensel, K. & J. Holcik. 1997. Past and current status of sturgeons in the upper and middle Danube River. Env. Biol. Fish. 48 (this 

volume). 

5 

∨ 

Balon, E.K. 1967. Vývoj ichtyofauny Dunaja, jej súcasný stav a pokus o prognózuó d’alšich zmien po výstavbe vodných diel (Evolution of 

the Danube ichthyofauna. its recent state and an attempt to predict further changes after the construction of the planned hydro-electric 

power stations and diversion schemes). Biologické práce 13: 1-121 + 24 plates. 

6 Balon, E.K. 1968. Einfluß des Fischfangs auf die Fischgemeinschaften der Donau. Arch. Hydrobiol. (Suppl. Donauforschung 3) 34: 

228–249. 

7 Marsilius. A.F.C. 1726. Danubius Pannonico-Mysicus, observationibus geographicis, astronomicis, hydrographicis, historicis, physicis 

perlustratus et in sex Tomos digestus. Hagae Comitum, Amstelodami. 

^

10 

I like this volume for other reasons too. Sturgeons and paddlefishes seem to exist, like most modern fishes, in altricial 

and precocial forms. Becoming aware of this may ins 

pire future workers to pay closer attention to the 

evolutionary phenomena 8 . By doing so, the general usefulness of the theory of saltatory ontogeny 9 and of dichotomous 

processes in both development and evolution 10 may become more widely accepted. 

Figure 2. Reconstruction of amethod tocatch beluga on the Danubeaccording to description in Aelianus by Rohan-Csermak (1963) from 

Balon (1967) 5 . 

The Guest Editors of this volume agreed in advance on the order listed on the title page, although equal editorial effort 

should be recognized. Vadim Birstein, Robert Boyle and John Waldman convened the 1994 conference that was the source 

for the original drafts of most of the manuscripts included in this collection. William Bemis put the volume in final shape; 

he is also responsible for safeguarding the standards ofall contributions as the editorial representative of Environmental 

Biology of Fishes. Alice Klingener prepared the index with suggestions and help from William Bemis and Vadim Birstein. 

While this volume was being assembled a young scientific illustrator - Paul Vecsei of Montreal - became a sturgeon 

fanatic (Figure 4) and travelled to the Czech Republic, Hungary and Romania to obtain material for illustrations. Our 

second frontispiece and drawings reproduced on pp. 72,156,184, 208, 220, 230, 240, 290, 310, 384, 406 and 436 are only a few 

selected examples of his ambitious plan to illustrate the sturgeons of the world. His results on these pages may be compared 

to samples of earlier, historical illustrations of sturgeons on the leading pages of the three parts into which this 

volume is divided. 

I would like to thank Paul Vecsei for his timely completion of the illustrations, and René Mijs for his exceptional 

understanding and patience. David Noakes, beside other help, is to be thanked for drawing my attention to the native 

American source of the motto used in this Prelude, Steve Crawford for bringing to my attention and for arranging permission 

from Adrian Nadjiwon, the Native American artist to use his painting as the first frontispiece, Tony Lelek for information 

on the Hungarian-Russian enterprise at Komadi, and Christine Flegler-Balon for the many corrections and 

administrative assistance. 

Guelph,1 August 1996 

Eugene K. Balon 

− 

8 

Bemis, W.E. & B. Kynard. 1997. Sturgeon rivers: and introduction to acipenseriform biogeography and life history. Env. Biol. Fish. 48 

(this volume). 

9 Balon, E.K. 1986. Saltatory ontogeny and evolution. Rivista di Biologia/Biology Forum 79: 151-190 (in English and Italian). 

10 Balon, E.K. 1989. The epigenetic mechanisms of bifurcation and alternative life-history styles. pp. 467–501. In: M.N. Bruton (ed.) 

Alternative Life-History Styles of Animals, Perspectives in Vertebrate Science 6, Kluwer Academic Publishers, Dordrecht.

Figure 3. Sturgeon fishing, butchering and caviar processing on the Danube River at the time of Marsilius (1726) 7 , from Balon (1967) 5 . 

11

12 

Figure 4. Paul Vecsei on the Fraser River (Canada) holding a white sturgeon. Acipenser transmontanus. Photograph by Eugene Hoyano, 

August 1990 

The illustrator’s note 

Much time has passed since those rainy nights on the Fraser River. In the meantime my efforts to illustrate charrs of the 

world was initiated and delivered with pride to E.K. Balon. It caught him in the middle of a new project, the present 

volume on sturgeons. To join in, I took off to Europe, visiting the sturgeon farm in Hungary and ultimately the Grigore 

Antipa Natural History Museum in Bucharest... 

I consider dot stippling an unmatched medium in which important characters can be best emphasised. Most of my 

illustrations of sturgeons in this volume are images of live specimens, some originally from the wild now kept in ponds, 

others already hatchery offspring of wild caught parents. A few are from museum specimens preserved wet. The live 

specimens were anesthesized, laid out on a wet surface and then photographed. Care was taken to avoid parallax distortions 

by using long focal length lenses. 

The resulting slides were projected to facilitate enlarged drawings and detailed rendering of all structures. Often light 

glare on mucus or wet surfaces made some structures invisible on the photographs. Theses structures had to be drawn from 

other frames of the same specimen. Some heads were enlarged up to 15 times so that the finished drawings contain more 

information than can be seen by an unaided eye. For example, the two heads of Acipenser gueldenstaedtii on page 436 

represent over 100 hours of work. The complete views were done only about 45 cm long in order to present enough details 

when reproduced at 33% of their original size. My illustrations are exactly what you would see if you step far enough to 

avoid parallax distortions and block one eye in order to loose your stereoscopic vision. 

15 August 1996 Paul Vecsei

Environmental Biology of Fishes 48: 13 – 14, 1997. 

© 1997 KIuwer Academic Publishers. Printed in the Netherlands. 

Sturgeon biodiversity and conservation: an introduction 

William E. Bemis¹, Vadim J. Birstein 2 & John R. Waldman 3 

I 

Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of 

Massachusetts, Amherst, MA 01003, U.S.A. 

2 

The Sturgeon Society, 331 West 57th Street, Suite 159, New York, NY 10019, U.S.A. 

3 

Hudson River Foundation, 40 West 20th Street, Ninth Floor, New York, NY 10011, U.S.A. 

Key words: Acipenseriformes, Acipenseridae, Polyodontidae, status 

This volume includesmany of the papers presented 

at the International Conferenceon Sturgeon Biodiversity 

and Conservation which took place at The 

American Museum of Natural History (AMNH), 

New York, on 28-30 July 1994. The main goal of the 

Conference was to attract attention to sturgeons 

and paddlefishes, still the most speciose group of 

‘livingfossil’fishes, but now fast disappearing from 

our planet (Birstein 1993, Bemis & Findeis 1994, 

Waldman 1995). 

Some presentations at the conference described 

basic aspects of acipenseriform biology, including 

evolution, genetics, and life cycles. Others focused 

on the contemporary status of a particular species 

or a few species inhabitingthe samebasin or region: 

most of these contributions also addressed ongoing 

conservation efforts. Still other speakers examined 

current controversies at the interface between science 

and society, bringing information from a variety 

of sources to enrich our meeting. These three approaches 

are reflected by the three part organization 

of this volume: Part 1, Diversity and evolution: 

Part 2, Biology and status reports: and Part 3, Controversies, 

conservation and summary. We hope 

that the included papers offer a broad perspective 

about contemporarywork on the phylogeny of Acipenseriformes, 

as well as a review of the worldwide 

status of almost all of the species constituting this 

order. 

In preparingthe materials forpublication,we discovered 

several revisions in the scientific names of 

somespecies. Smith & Clugston (1997 this volume) 

follow Gilbert (1992),who showed that the name of 

the American Atlantic sturgeonhas been frequently 

misspelled in the literature and that the original 

correct spelling is Acipenser oxyrinchus (instead of 

the commonly used A. oxyrhynchus).Ruban (1997 

this volume) returns to the original spelling of the 

scientific name of the Siberian sturgeon, A. baerii 

(instead of A.baeri).We standardized the spelling 

of these species throughout the volume. Also, Birstein 

et al. (1997 this volume) presented genetic data 

showing that the Sakhalin sturgeon,usually considered 

as the same species as the American green 

sturgeon A. medirostris or as its Asian subspecies A. 

medirostris mikadoi, is in fact a distinct species, A. 

mikadoi, as it was described originally (Hilgendorf 

1892). Additional treatment of these and other 

questionsis takenup by Birstein & Bemis (1997 this 

volume). 

Because the materials presented in different papers 

cover a wide geographical range, literally the 

whole northern hemisphere, we tried to be consistent 

about geographic names and to follow (insofar 

as possible) one resource for names. We used the 

New York Times Atlas (1992) as our guide for unifying 

geographical names throughout the volume. 

The biogeography of sturgeons has intrigued zoologistsfor 

more than twohundred years, and to unify 

comments and analyses presentedby the authors of 

the status papers on separate species of Acipenseriformes, 

we wrote a new contribution overviewing 

the biogeography of the entire group (Bemis & Kynard 

1997).

14 

In addition to our primary affiliations, all three of 

us benefit from a network of institutions committed 

to the scientificstudy of fossil and recent fishes, and 

wish to thank our colleaguesat these institutions by 

formally noting our courtesy appointments with 

them. William E. Bemis is a Research Associate in 

the Department of Ichthyology at the American 

Museum of Natural History, New York and a Research 

Associate in the Department of Geology, 

Field Museum of Natural History, Chicago. Vadim 

J. Birstein is a senior scientist at the Koltsov Institute 

of Developmental Biology, Russian Academy 

of Sciences, Moscow, a visiting scientist at the 

American Museum of Natural History, New York 

and Adjunct Professor of Biology at the University 

of Massachusetts, Amherst. John R. Waldman is a 

Research Associate in the Department of Ichthyology 

at the American Museum of Natural History, 

New York. 

We are grateful to all persons and organizations 

who helped Vadim Birstein, John Waldman and 

Robert H. Boyle to organize the 1994 conference. 

Clay Hiles, Executive Director of the Hudson River 

Foundation for Science and Environmental Research 

(HRF, New York), and Robert Boyle, Co- 

Chairman of the Conference, Chairman of the 

Board of The Sturgeon Society (New York), and a 

member of the Board of Directors of the HRF, arranged 

funding for the conference through the 

HRF, the principal financial supporter of the conference. 

The President of the American Museum of 

Natural History (AMNH, New York). Ellen Futter, 

and Provost, Michael Novacek, encouraged us and 

provided the Kaufmann Theater of the Museum for 

the meetings. We also thank Thomas Lovejoy, Asssitant 

secretary for Enviroment and External Affairs 

of the Smithsonian Institution (Washington). 

and Joel Cracraft, Curator (Department of Ornithology, 

AMNH), for welcoming the participants at 

the opening ceremony.Also,we are thankful to Bill 

Murray, the actor, comedian, and supporter of 

aquatic environmental causes, for attending our 

opening ceremony and making a generous donation 

to the work of The Sturgeon Society.Stolt Sea 

Farms (California), provided aquacultured white 

sturgeon caviar (as an alternative to wild sturgeon 

caviar) for the conference. Pat Yazgi, President of 

Friends of Fishes (New York), organized two successful 

evening events. Finally, we thank Eugene 

Balon, the Editor-in-Chief of the journal Environmental 

Biology of Fishes,for his kind collaboration 

in publishing the materials of the conference as 

dedicated issues of the journal and a separate 

volume of Developments in EBF 17. 

References cited 

Bemis, W.E. & E.K. Findeis. 1994. The sturgeons’ plight. Nature 

370: 602. 

Bemis, W.E. & B. Kynard. 1997. Sturgeon rivers: an introduction 

to acipenseriform biogeography and life history. Env. Biol. 

Fish. (this volume). 

Birstein, V.J. 1993. Sturgeons and paddlefishes: threatenedfishes 

in need of conservation. Cons. Biol. 7: 773–787. 

Birstein, V.J. & W.E. Bemis. 1997. How many species are there in 

the genus Acipenser? Env. Biol. Fish. (this volume). 

Birstein, V.J.. R. Hanner & R. DeSalle. 1997. Phylogeny of the 

Acipenseriformes: cytogenetic and molecular approaches. 

Env. Biol. Fish. (this volume). 

Gilbert, C.R. 1992. Atlantic sturgeon. pp. 31-39. In: R.A. Ashton 

(ed.) Rare and Endangered Biota of Florida, Vol. 2, University 

of Florida, Gainesville. 

Hilgendorf, F, 1892, Über eine neue Stör-Art aus Nord-Japan 

(Acipenser mikadoi). Sitzungsber. Ges. naturf. Freunde, Berlin 

7: 98–100. 

Ruban, G.I 1997. Species structure, contemporary distribution 

and status of the Siberian sturgeon, Acipenser baerii. Env. 

Biol. Fish. (this volume). 

Smith, T.I.J. & J.P. Clugston. 1997. Status and management of 

Atlantic sturgeon, Acipenser oxyrinchus, in North America. 


Waldman, J. 1995. Sturgeons and paddlefishes: a convergence of 

biology, politics, and greed. Fisheries 20: 20–21, 49.

Enviromental Biology of fishes 48: 15-22, 1997. 


Leo Semenovich Berg and the biology of Acipenseriformes: a dedication 

Vadim J. Birstein¹ & William E. Bemis² 

¹ The Sturgeon Society, 331 West 57th Street, Suite159, New York. NY 10019, U.S.A. 

2 Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of 

Massachusetts, Amherst, MA 0I003, U.S.A. 

Received 5.3.1996 Accepted 23.5.1996 

Key words: T. Dobzhansky, A. Sewertzoff, T. Lysenko, Paleonisciformes, biogeography 

This volume is dedicated to the memory of Leo Semenovich Berg (1876-1950), a Russian ichthyologist and 

geographer. In the forewordto the English translation of Berg’s remarkabletreatise, ‘Nomogenesisor evolution 

according to law’, Theodosius Dobzhansky wrote: ‘Bergwas one of the outstanding intellects among 

Russian scientists. The breadth of his interests and the depth as well as the amplitude of his scholarship were 

remarkable. He had the reputation of being a ‘walking library’, because of the amount of information he could 

produce from his memory’ (Dobzhansky 1969, p. xi). Berg was prolific, publishing 217 papers and monographs 

on ichthyology, 30 papers on general zoology and biology, 20 papers on paleontology, 32 papers on zoogeography, 

320 papers and monographs on geography. geology, and ethnography, as well as 290 biographies, 

obituaries, and popular articles (Berg 1955, Sokolov 1955). 

Berg was born 120 years ago, on 14 March 1876, in 

the town of Bendery. According to laws of the Russian 

Empire, Berg could not enter the university as 

a Jew, so he was baptized and became a Lutheran, 

which allowed him to study and receive his diploma 

in zoology at the Moscow University in 1898. From 

1899 to 1904, he explored the fisheries and the general 

ecology of the Aral Sea and lakes in Turkestan 

and western Siberia. In 1904. Berg was appointed 

curator of the Ichthyology Department of the Zoological 

Museum (later Zoological Institute) at the 

Academy of Sciences in St. Petersburg. Later he 

held several positions in this and other institutions 

(Shapovalov 1951, Oliva 1951, 1952, Holcík 1976, 

Lindberg 1976. Oliva & Holcík 1977,1978). As one 

of the most talented biologists of his time, Berg was 

a target of Trofim Lysenko and his followers. In January 

1939, after discrediting Berg and an outstanding 

geneticist Nicolai Koltsov in the press, Lysenko 

and his accomplice, Nikolai Tsitsin, were elected in 

their stead as members of the Soviet Academy of 

^ 

^ 

Sciences. Berg was never formally recognized by 

the Soviet Academy for his accomplishments in 

biology, and only later (1946) was he elected a member 

of the Geography Branch of the Soviet Academy 

of Sciences (Figure 1). 

Sturgeons and the order Acipenseriformes were 

a central theme in Berg’s theoretical works and papers 

on systematics and zoogeography (Andriyashev 

1955, Lindberg 1976). In December 1936, he addressed 

a meeting of the Biology Branch of the Soviet 

Academy of Sciences on ‘Classification of fish 

es both living and fossil’. This fundamental work 

was published in Russian in 1940, although some 

general ideas in a short form appeared earlier in English 

and French (Berg 1935a, 1937). The entire 

book was translated into English in 1947 (Berg 

1947a. 1965). It was the most comprehensive study 

of its era on systematics and evolution of fossil and 

recent fishes, and it remains useful. An additional 

chapter,entitled ‘On the positionof Polypteridaein 

the system of fishes’ appeared as a separate paper

16 

Figure 1. Leo Semenovich Berg, ichthyologist and biogeographer 

the same year (Berg 1947b). In 1948, Berg published 

a second additional chapter. ‘On the position of 

Acipenseriformes in the system fishes’. These 

two chapters, as well as additional new material on 

fossil fishes, were included in the second Russian 

edition of the book which appeared only in 1955, 

after the author’s death. 

Unfortunately, the chapter on the Acipenseriformes 

was never translated into English. In 50 pages, 

Berg described the morphology, anatomy, and 

embryology of Acipenseriformes, comparing them 

to extinct Palenisciformes and modern Elasmo- 

branchii (Figure2). Berg’s conclusions contradicted 

the theory introduced by Aleksei Sewertzoff 

(1925, 1926, 1928), who considered acipenseriforms 

to be closely related to elasmobranchs. Berg wrote: 

‘Acipenseriformes belong to the same group of fishes 

as the Paleonisciformes, i.e., to the primitive Ac-

17 

b 

Figure 2. Berg’s original reconstructionsof a paleoniscid, Ganolepis gracilis (first publishedby Obruchev1955): a - Lateralview of the 

entire fish, b - reconstruction of skull (ang = angular, a op = anteoperculum, cl = cleithrum, clv = clavicle, d = dentary, d sph = dermosphenotic, 

fr = frontal, i.o.c. = infraorbital sensory canal, i orb = infraorbital, max = maxillary, m c = Meckel’s cartilage, na = nasal, op = 

operculum, pa = parietal, pcl - postcleithrum, p mx = premacilla, p o c = preopercular canal, p op =preoperculum, p r = postrostrale, pt = 

posttemporal, r br = branchiostegal rays, scl = supracleithrum, sklr = sclerotic ring, s o = suborbitalis, s o c = supraorbital canal, s op = 

suboperculum, st-it = supratemporal-intertemporal, tab = tabular). 

tinopterygii. There is no contemporary data supporting 

the hypothesis on the close relationship of 

acipenseriforms to selachians’ (Berg 1948a,p. 53). 

He identified three families within Acipenseriformes: 

‘Chondrosteidae (from the Lower Lias to 

the Lower Cretaceous), Acipenseridae (beginning 

from the Upper Cretaceous), and Polyodontidae 

(beginning from the Upper Cretaceous)’ (Berg 

1948a,p. 54). Berg’s understanding of Acipenseriformes 

as actinopterygians is fundamental to all 

contemporary views (Sokolov & Berdichevskii 

1989a, b, Grande & Bemis 1991, Bemis et al. 1997, 

this volume). 

Systematics of Acipenseridae was the topic of 

one of Berg’s early theoretical papers (Berg 1904). 

He included four genera in this family: Huso with 

two species, H. huso and H. dauricus; Acipenser 

with sixteen species; Scaphirhynchus with one species, 

S. platorhynchus; and Pseudoscaphirhynchus 

with three species, P. fedtschenkoi, P. hermanni, and 

P. kaufmanni. This division of Acipenseridae into 

fourgeneraisused by most contemporaryresearchers 

(but see Jollie 1980).In his first monograph on 

the fishes of Russia (Berg 1911), Berg divided Acipenser 

into three subgenera: (1) Lioniscus Bonaparte, 

1846, with one species,A. nudiventris; (2) Helops 

Bonaparte, 1846, also with one species, A. stellatus; 

and (3) Acipenser sensu stricto, which includes 

all other species ofAcipenser. Later, in 1948, 

in the last edition of his monograph on the Russian

18 

fish fauna, Berg changed the name Helops Bonapart 

1846, to Gladostomus Holly, 1936. Historical 

reviews of these divisions within Acipenser are given 

by Findeis (1997) and Birstein et al. (1997) in this 

volume, but it is clear that we are still far from an 

unambiguous, synapomorphy-based diagnosis of 

the genus Acipenser(also see Birstein & Bemis 1997 

this volume). 

In many monographs and papers, Berg gave classic 

descriptions of sturgeons inhabiting Russia, 

eastern Europe and Asia, including their zoogeography 

and biology (Berg 1905a, b, 1908a, b, 1909, 

1911–1913, 1916, 1923, 1932a, b, 1933, 1945, 1948b, c). 

His encyclopedic knowledge of the material allowed 

him to discuss hybrids as well as different 

forms within the same species. Extreme polymorphism 

is characteristic of many sturgeon species, 

which poses problems for morphological diagnoses. 

Berg’s approach was typical for his time: recognize 

and name distinctive subspecies from portions of 

the range. Many examples are known. For instance, 

in the Caspian Sea, besides the typical form of the 

Russian sturgeon, A. gueldenstaedtii, Berg recognized 

a subspecies A. gueldenstaedtii persicus Borodin, 

1897 or Persian sturgeon (Berg 1933, 1934a, 

1948). Later this form was elevated to the rank of 

species, A. persicus (Artyukhin 1979, 1984). This 

species also occurred in the Black Sea (Artyukhin 

& Zarkua 1986, Vlasenko et al. 1989). Berg (1948b) 

considered the Black Sea and Sea of Azov populations 

of A. gueldenstaedtii to be a distinct subspecies, 

A. gueldenstaedtii colchicus. Within the European 

sterlet, A. ruthenus, Berg (1911,1923,1948a) 

recognized two morphs. One, with a typical long 

and pointed rostrum he named ‘A. ruthenus morpha 

kamensis Lovetsky, 1834’, which was synonymous 

to A. gmelini Fitzinger & Heckel, 1834, and to 

A. ruthenus var. brevirostris Antipa, 1909. Berg described 

Siberian sterlet from the Ob River as A. 

ruthenus natio marsiglii (Berg 1949). 

Berg published several well-known articles on 

winter and vernal (or spring) races of anadromous 

fishes (Berg 1934b, 1934c, 1935b). The Englishspeaking 

audience learned about these definitions 

only 25 years later, when Berg’s article was translated 

into English (Berg 1959). He concluded that 

anadromous fishes, including sturgeons, typically 

consist of two main races, winter and vernal. Their 

characteristics are: (1) winter fish spend the coldest 

time of the year either in the river itself, or in the sea 

close to the river mouth, whereas vernal fish enter 

the river at higher temperatures in the spring. (2) 

During the coldest seasons, the winter fish are in a 

state of vegetative quiescence, eating little or nothing. 

Many ‘hibernate’ in holes. Vernal races have 

only a short period of vegetative quiescence and do 

not ‘hibernate’. (3) The vernal races spawn in the 

same season in which they enter the rivers. The winter 

races spawn the next year. (4) The winter races 

usually spawn earlier than the vernal races, i.e. in a 

given year they mature earlier. (6) The winter race 

is usually larger than the vernal race. (7) The winter 

race is usually more fertile than the vernal race. As 

typical examples of the two races, Berg analyzed 

the behavior of the four species of sturgeons in the 

northern part of the Caspian Sea: A. stellatus, A. 

gueldenstaedtii, H. huso, and A. nudiventris. Depending 

on the species, one of the two races usually 

predominates. One of the races can disappear completely. 

For example, there was only a winter race of 

the ship sturgeon, A. nudiventris, in the Aral Sea 

(now the Aral Sea population has disappeared 

completely, see Zholdasova 1997 this volume). Although 

the sterlet, A. ruthenus, is a freshwater resident 

species, there were two races (and two morphs, 

as mentioned above) in the Volga, Danube, and 

Dnieper rivers, which migrated along the rivers to 

the deltas and back. Differences in races of sturgeons 

remain even now, despite drastic changes in 

the Volga, Danube, and other rivers (see Bacalbasa- 

∨ 

Dobrovici 1997, Hensel & Holcík 1997, Khodorevskaya 

et al. 1997. Kynard 1997, all this volume). 

Long migrations of A. ruthenus in major European 

rivers are disrupted by dams (for the situation in the 

∨ 

Danube River see Hensel & Holcík 1996, Bacalbasa-Dobrovici 

1997, this volume). Migrating and riverine 

races (or populations) are discussed by: Ruban 

(1997 this volume) for Siberian sturgeon, A. 

baerii; Krykhtin & Svirskii (1997 this volume) for 

Amur River sturgeons; and Hensel& Holcík (1997 

∨ 

this volume) for sturgeons of the Danube River. 

Profound knowledge of the distribution of Acipenseriformes 

played a major role in Berg’s evolutionary 

(Berg 1922) and zoogeographic theories.

19 

Figure 3. At the Institute of Zoology in St. Petersburg, the presence of Lev Semenovich Berg is still strong 40 years after his death. 

Minutes after arrival on 18.6.1990 E.A. Dorofeeva seated Eugene Balon in the chair used by L.S. Berg. 

Amur River acipenserids (Berg 1909, 1911) were 

one of the elements of Berg’s hypothesis on the relic 

character of the fauna of the Amur River Basin 

(Berg 1912,1928). According to this hypothesis, the 

species constituting the Amur River fauna are remnants 

of the subtropical Upper Tertiary fauna that 

characterized the entire northern hemisphere, and 

which mostly disappeared as a result of cooling during 

the Quaternary. Berg also discussed problems of 

interrelationships of the Asian, European, and 

North American fish faunas (Berg 1950). Contemporary 

information about sturgeons of the Amur 

River is presented in two articles of this volume 

(Krykhtin & Svirskii 1997, Zhuang et al. 1997). 

Some of Berg’s other zoogeographic ideas are 

useful for understandingthe distribution and evolution 

of sturgeons in the northern hemisphere. For 

instance, in a hypothesis explaining the similarity of 

elements of the Pacific and Atlantic faunas, Berg 

suggested two periods of exchanges between elements 

of the faunas of the northern parts of the two 

oceans (Berg 1918, 1934d, e, 1947b). Also, Berg’s 

ideas on historic changes in the fauna of the Caspian 

Sea (Berg 1928c, d) are useful for understanding the 

Figure 4. A portrait of L.S. Berg in his office at the Zoological 

Institute, St. Petersburg. Lithograph by G. Vereisky, 1950.

20 

history and evolution of sturgeons in the Caspian 

and Black Sea basins. 

Berg gave his first short presentation on sturgeons 

in 1897, when he was a student (Berg 1898). It 

described experiments on artificial breeding of A. 

stellatus. Much later he returned to the problem of 

sturgeon development, describing juveniles of 

Pseudoscaphirhynchus kaufmanni caught in the 

Amu Darya River (Berg 1929). In this volume detailed 

information on the reproductive cycle ol the 

white sturgeon, A. transmontanus is given by Doroshov 

et al. (1997). 

Berg never stressed the ability of sturgeons to 

hybridize, but he described many sturgeon hybrids 

in detail (Berg 1911, 1932, 1948b). Some genetic 

aspects of acipenseriforms, including hybridixation, 

are discussed in this volume by Birstein et al. 

(1997). 

Berg lived and workedwhen the sturgeon crisis in 

Russia, Europe, and Asia had only started (Figure 

3, 4). The desperate need for conservation measures 

to save sturgeons was in the future. He published 

only a small article describing his concern 

about A. sturio in the Baltic Sea and especially in 

the Neva River (Berg 1935c). He suggested that a 

complete ban on the catch of this species should be 

established for at least the next 10-15 years. Unfortunately, 

since then most of the species of sturgeons 

and paddlefishes have become threatened or endangered, 

a theme of many papers of this volume, 

and one that surely would have saddened L.S. Berg. 

Acknowledgements 

We are very grateful to Raissa Lvovna Berg (L.S. 

Berg’s daughter) and Maria Berg (L.S. Berg’s 

granddaughter) for providing an unpublished photo 

of L.S. Berg. Eugene Balon gave his photo of L.S. 

Berg’s chair. 


Andriyashev, A.P. 1955. L.S. Berg as a zoogeographer. pp. 116- 

126. In: E.N. Pavlovskii (cd.) To the Memory of Academician 

L.S. Berg. Izdatelstvo Akademii Nauk USSR. Moscow (in 

Russian). 

Antipa, G. 1909. Fauna ichtiologica a României. Publicatiunile 

Fondul Vasilie Adamanchi, Academia Româna, Bucuresti 16: 

1-294. 

Artyukhin, E.N. 1979. Persian sturgeon in the rivers entering 

northern part of the Caspian Sea and perspecties of its harvest. 

pp. 105-115. In: Biological Fundamental of Sturgeon 

Management Development in the Water Bodies of the USSR, 

Nauka Press, Moscow (in Russian). 

Artyukhin, E.N. 1983. Differentiation of the Persian sturgeon 

populations and perspectives of its artificial breeding at the 

Volga River hatcheries. pp. 54-61,In: Biological Fundamentals 

of Sturgeon Managenent, Nauka Press, Moscow (in Russian). 

Artyukhin, E.N. & Z.G. Zarkua. 1986. On the problem of taxonomic 

rank of the sturgeon from the Rioni River (the Black 

Sea Basin). Voprosy Ikhtiologii 26: 61-67(in Russian). 

Bacalbasa-Dobrovici, N. 1997. Endangered migratory sturgeons 

of the lower Danube River and its delta. Env. Biol. Fish (this 

volume). 

Bemis, W.E., E.K. Findeis & L. Grande. 1997. An overview of 

Acipenseriformes. Env. Biol. Fish (this volume). 

Berg, L.S. 1898. Experiments on artificial breeding of sevruga 

sturgeon in the Ural River. Izvestiya Obshchestva Lyubitelei 

Estestvoznaniya, Antropologii i Etnografii, Vol. 86. Dnevnik 

Zoologischeskogo Otdeleniya Obshchestva i Zoologicheskogo 

Muzeya Moscovskogo Universiteta 2: 36 (in Russian). 

Berg, L.S. 1904. Zur Systematik der Acipenseriden. Zool. Anz. 

27: 665-667. 

Berg, L.S. l905a. Fishes of Turkestan. Scientific results of the 

Aral expedition. No. 6. St. Petersburg. 261 pp. (in Russian). 

Berg, L.S. 1905b. Verzeichnis derFische von Russisch Turkestan. 

Ezhegodnik Zoologischeskogo Muzeya Adademii Nauk 10: 

316-332(in Russian). 

Berg, L.S. 1908a List ot the Ob River basin fishes. Ezhegodnik 

Zoologischeskogo Muzeya Adademii Nauk 13: 69-107 (in 

Russian). 

Berg, L.S. 1908b. List of the Kolyma River fishes. Ezhegodnik 

Zoologischeskogo Muzeya Akademii Nauk 13: 221-228 (in 

Russian). 

Breg, L.S. 1909. Fishes of the Amur River basin. Zapiski Akademii 

Nauk 21: 1-270 (in Russian). 

Berg, L.S. 1911. Fishes (Marsipobranchii and Pisces). Fauna of 

Russian and adjacent countries, Vol. 3, Vypusk 1, Izdatelstvo 

Akademii Nauk, St. Petersburg. 337 pp. (in Russian). 

Berg, L.S. 1912. (Über die Zusammensetzung und Herkunft der 

Fischfauna des Amur-Flushes mit Bezug auf die Frage von den 

zoogeographischen Regionen für die Süsawasserfische. Zool. 

Jahrb. 32: 475-520. 

Berg, L.S. 1913. On the find of Acipenser medirostris (Ayres) in 

the lower reaches of the Amur River. Ezhegodnik Zoologischeskogo 

Muzeya Akademii Nauk 18: 16 (in Russian). 

Berg, L.S. 1916. Fishes of fresh waters of Russian Empire. Moscow. 

563 pp. (in Russian). 

Berg, L.S. 1918. On the causes of similarity in the faunas of the

21 

northern parts of the Atlantic and Pacific oceans. Izvestiya 

Rossiiskoi Akademii Nauk 16: 1835-1842(in Russian). 

Berg, L.S. 1922. Nomogenesis or evolution determined by law. 

Moscow. 200 pp. (in Russian, English translation published by 

The M.I.T. Press, Cambridge, 1926. 477 pp.) 

Berg, L.S. 1923. Fishes of fresh waters of Russia. 2nd ed. Gosudarstvennoe 

Izdatelstvo, Moscow. 365 pp. (in Russian). 

Berg, L.S. 1928a. Life style and geographic morphs in sevruga. 

Priroda 3: 294-296(in Russian). 

Berg, L.S. 1928b. Zoogeographical divisions for Far Eastern 

freshwater fishes. pp. 1041-1043. In: Proceedings of the Third 

Pan-Pacific Science Congress, Vol. 1, Tokyo. 

Berg, L.S. 1928c. On the origin of the northern elements in the 

fauna of the Caspian Sea. Doklady Akademii Nauk USSR, 

Seriya A 7: 107-112 (in Russian). 

Berg, L.S. 1928d. Mediterranean elements in the fauna of the 

Caspian Sea. Priroda 7/8: 753 (in Russian). 

Berg, L.S. 1929. Juvenile fishes from the lower Amu Darya River. 

Izvestiya Otdeleniya Prikladnoi Ikhtiologii 9: 225-230 (in 

Russian). 

Berg, L.S. 1932a. Übersicht der Verbreitung der Susswasserfische 

Europas. Zoogeographica 1: 107–208. 

Berg,L.S. 1932b. The freshwater fishes of the USSR and adjacent 

countries. 3rd ed. Part 1. Vsesoyuznyi Institute Ozernogo i 

Rechnogo Rybnogo Khozyaistva, Leningrad. 543 pp. (in Russian). 

Berg, L.S. 1933. The freshwater fishes of the USSR and adjacent 

countries. 3rd ed. Part 2. Vsesoyuznyi Institut Ozernogo i 

Rechnogo Rybnogo Khozyaistva, Leningrad. 545-903 pp. (in 

Russian). 

Berg, L.S. 1934a. Acipenser güldenstädti persicus, a sturgeon 

from the south Caspian Sea. Ann. Mag. Nat, Hist. Ser. 10, 13: 

317-318. 

Berg, L.S. 1934b. Summer and autumn races of anadromous fishes. 

Izvestiya Akademii Nauk USSR 5: 711-732 (in Russian). 

Berg, L.S. 1934c. Summer and autumn races of anadromous fishes. 

Priroda 4: 36-40 (in Russian). 

Berg, L.S. 1934d. On the amphiboreal (discontinuous) distribution 

of the marine fauna in the northern hemisphere. Izvestiya 

Gosudarstvennogo Geographicheskogo Obshchestva 66: 69- 

78 (in Russian). 

Berg. L.S. 1934e. Über die amphiboreale Verbreitung des Meeresfauna 

in der nördlichen Hemisphäre. Zoogeographica 2: 

393– 409 . 

Berg. L.S. 1935a. Sur les unités taxonomiques chez les poissons. 

Bull. Mus. Nat. Hist. Nat., 2-e sér. 7: 79-84. 

Berg, L.S. 1935b. Sommer- und Winterrassen bei den anadromen 

Fischen. Arch. Naturgesch. 4: 376–403. 

Berg, L.S. 1935c. On the necessity to save sturgeon in the Neva 

River basin. Za Rybnuyu Industriyu Severa 7: 30-31 (in Russian). 

Berg, L.S. 1937. A classification of fish-like vertebrates. Izvestiya 

Akademii Nauk USSR, Seriya Biologischeskaya 4: 1277–1280. 

Berg, L.S. 1940a. Classification of fishes both recent and fossil. 

Trudy Zoologischeskogo Instituta 5: 85–517 (in Russian). 

Berg, L.S. 1940b. On the position of Polypteridae in the system of 

fishes. Zoologischeskii Zhurnal 19: 727-740 (in Russian). 

Berg, L.S. 1945. On sterlet in the White Sea basin. Priroda 6: 66- 


Berg, L.S. 1947a. Classification of fishes both recent and fossil. 

I.W. Edwards, Ann Arbor. 437 pp. 

Berg, L.S. 1947b. Some thoughts on the origin of the terrestrial. 

fresh-water, and marine flora and fauna. Bulletin Moskovskogo 

Obshchestva Ispytatelei Prirody, Otdelenye Biologischeskoe 

52: 15-33 (in Russian). 

Berg, L.S. 1948a. On the position of Acipenseriformes in the system 

of fishes. Trudy Zoologischeskogo Instituta 7: 7-57 (in 

Russian). 

Berg, L.S. 1948b. The freshwater fishes of the USSR and adjacent 

countries. 4th ed., Part 1. Akademia Nauk USSR. Moscow & 

Leningrad. 466 pp. (in Russian, English translation published 

by Israel Program for Scientific Translations, Jerusalem, 1965. 

505 pp.). 

Berg, L.S. 1948c. Fishes of Gulf of Finland. Izvestiya VNIORKh 

23: 3-24(in Russian). 

Berg. L.S. 1949. The freshwater fishes of the USSR and adjacent 

countries, 4th ed., Part 3. Adademia Nauk USSR, Moscow & 

Leningrad. 927-1382pp. (in Russian). 

Berg, L.S. 1950. On the causes of the similarity of the fish faunas 

in the Volga, Don, and Dnepr rivers. Trudy Kaspiiskogo Basseinovogo 

Filiala VNIRO 11: 5-8 (in Russian). 

Berg. L.S. 1959. Vernal and hibernal races among anadromous 

fishes. J. Fish Res. Board Can. 16: 515–537. 

Berg, L.S. 1965. Classification of fishes both recent and fossil. 

Thai National Documentation Center, Bangkok. 304 pp. 

Berg, M.M. 1955. Systematic list of Academician L.S. Berg’s 

works. pp. 531–560. In: E.N. Pavlovskii (ed.) To the Memory of 

Academician L.S. Berg, Izdatelstvo Akademii Nauk USSR, 

Moscow (in Russian). 

Birstein, V.J. & W.E. Bemis. 1997. How many species are there 

within the genus Acipenser? Env. Biol. Fish (this volume). 

Birstein, V.J., R. Hanner & R. DeSalle. 1997. Phylogeny of the 


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Bonaparte, C. 1846. Catalogo metodico dei pesci europei. Atti. 

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Borodin, N.A. 1897. A report about a summer 1895 zoological 

expedition on board of the cruiser ‘Uralets’ in the northern 

part of the Caspian Sea. Vestnik Rybopromyshlennosti 1:1-3 

(in Russian). 

Dobzhansky, T. 1969. Foreword to paperback edition. pp. VII– 

XVI. In: L.S. Berg. Nomogenesis or Evolution Determined by 

Law, The M.I.T. Press, Cambridge. 476 pp. 

Doroshov, S.I., G.P. Moberg & J.P. Van Eenennaam. 1997. Observation 

on the reproductive cycle of cultured white sturgeon, 

Acipenser transmontanus. Env. Biol. Fish. (this volume). 

Findeis, E.K. 1997. Osteology and phylogenetic interrelationships 

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Fitzinger, L.J. & J. Heckel. 1836. Monographische Darstellung

22 

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of fossil and recent paddlefishes (Polyodontidae) 

with comments on the interrelationships of Acipenseriformes. 

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Part 1: Diversity and evolution of sturgeons and paddlefishes 

Acipenser, Aquipenser, Sturio -sturgeon woodcuts from Conrad Gesner (1558).

The three major commercial species of sturgeons from Caspian and Black seas: top - Huso huso, center -Acipenser stellatus, and bottom 

- Acipenser gueldenstaedtii (all modified from Fitzinger & Heckel 1 , plate 17, fig. 7, plate 16, fig. 6, plate 17, fig. 9, respectively). 

− 

1 Fitzinger, L.J. & J. Heckel. 1836. Monographische darstellung der Gattung Acipenser. Zool. Abh. Ann. Wiener Mus. Naturgesch. 1: 

262-326 (note: order of authorship is reversed in some bibliographic citations).



An overview of Acipenseriformes 

William E. Bemis 1 , Eric K. Findeis 1 & Lance Grande 2 

1 



2 

Department of Geology, Field Museum of Natural History, Chicago, IL 60605, U.S.A. 


Key words: Actinopterygii, Paleonisciformes, Acipenseridae, Polyodontidae. †Chondrosteidae, 

†Peipiaosteidae 

Synopsis 

Acipenseriformes occupy a special place in the history of ideas concerning fish evolution, but in many respects, 

phylogenetic studies of the group remain in their infancy. Even such basic questions as the monophyly 

of Acipenser (the largest genus) are unanswered. We define relationships based on comparative osteology, 

which allows us to incorporate well-preserved fossils into analyses. Acipenseriformes has existed at least since 

the Lower Jurassic (approximately 200 MYBP), and all fossil and recent taxa are from the Holarctic. Phylogenetic 

relationships among Paleozoic and Early Mesozoic actinopterygians are problematic, but most workers 

agree that Acipenseriformes is monophyletic and derived from some component of ‘paleonisciform’ fishes. 

(‘Paleonisciformes’ is a grade of primitive non-neopterygian actinopterygians, sensu Gardiner 1993.) Taxa 

discussed in comparison here are: †Cheirolepis, Polypterus, †Mimia. †Moythomasia, †Birgeria, †Saurichthys, 

Lepisosteus and Amia. We review generic diversity within the four nominal families of fossil and recent Acipenseriformes 

(†Chondrosteidae, †Peipiaosteidae, Polyodontidae, and Acipenseridae), and provide a cladogram 

summarizing osteological characters for those four groups. Monophyly of the two extant families is 

well-supported, but there are no comprehensive studies of all of the known species and specimens of †Chondrosteidae 

and †Peipiaosteidae. As a result, sister-group relationships among †Chondrosteidae, †Peipiaosteidae, 

and Acipenseroidei (= Polyodontidae + Acipenseridae) are unresolved. We discuss five features fundamental 

to the biology of acipenseriforms that benefit from the availability of our new phylogenetic hypothesis: 

(1) specializations of jaws and operculum relevant to jaw protrusion, feeding, and ram ventilation; (2) anadromy 

or potamodromy and demersal spawning; (3) paedomorphosis and evolution of the group; (4) the biogeography 

of Asian and North American polyodontids and scaphirhynchines; and (5) the great abundance of 

electroreceptive organs in the rostral and opercular regions. Finally, we summarize our nomenclatural recommendations. 

Introductionandhistorical overview 

This paper reviews the systematics of sturgeons and 

paddlefishes and their immediate fossil relatives in 

the order Acipenseriformes. We synthesize historic 

and current information in our effort to better understand 

the evolution, biogeography, and composition 

of the order. We emphasize generic and familial 

comparisons, and summarize information for 

all recent and well preserved fossil genera. In keeping 

with our objective of providing background, this 

paper includes several ‘evolutionary scenarios’ (in

26 

the sense of Gans 1986) which we hope will provoke (1833) and Fitzinger & Heckel (1836) to subdivide 

further basic work on the group. Additional recent the genus Acipenser into several subgenera, howtreatment 

of many of these taxa can be found in ever, were less successful. 

Grande & Bemis (1991, 1996a) and Findeis (1997 It was also in the middle of the 19th century that 

this volume). 

the first important fossil acipenseriform, †Chon- 

Acipenseriforms are central to historical ideas drosteus, was named by Agassiz (1844) and deabout 

the classification and evolution of fishes. scribed by Egerton (1858). Increasingly synthetic 

Sturgeons were often the largest freshwater ani- works on higher relationships of fishes also apmals 

in a fauna and quite naturally attracted atten- peared, exemplified by Müller (1846), who defined 

tion from early naturalists and systematists. Aci- three grades of bony fishes Chondrostei, Holostei 

penseriforms also are noteworthy because of their and Telcostei -- on the basis of increasing degrees of 

unusual mixture of characters, which caused early ossification. In doing this, Müller rejected the clasdebate 

about their classification. Two aspects of liv- sical idea that sturgeons are closely related to 

ing Acipenseriformes were especially problematic sharks and accepted them as osteichthyans. Sewertfor 

early ichthyologists: (1) reduced ossification of zoff (1925, 1926b, 1928) was the only 20th century 

the endoskeleton combined with presence of an ex- ichthyologist to seriously consider a closer link betensive 

dermal skeleton: and (2) the presence of a tween sturgeons and chondrichthyans. Sewertzoff 

hyostylic jaw suspension and protrusible palato- (1925) presented his conclusions as a phylogenetic 

quadrate recalling the jaws of sharks. The current tree, in which chondrosteans are shown as the sister 

conventional view (developed and refined by many group of all other bony fishes, and emphasized the 

authors, including Muller 1846, Traquair 1877, presence of a protrusible palatoquadrate in both 

Woodward I891, 1895 a,b, Regan 1904, Goodrich elasmobranchs and sturgeons. We now regard pala- 

1909,Watson 1925, 1928,Gregory 1933, Berg 1948b, toquadrate protrusion as derived independently 

Yakovlev 1977) holds that Acipenseriformes within chondrosteans (see additional discussion in 

evolved from a ‘paleonisciform’ ancestor via pae- the final section of this paper). Norris (1925) and 

domorphic reduction of the skeleton and special- others noted neuroanatomical similarities between 

ization of the feeding system. hut there is much sturgeons and sharks, but these are almost certainly 

more to the history of ideas about the systematics of plesiomorphic features (see Northcutt & Bemis 

this group. 

1993), and few workers ever accepted Sewertzoff’s 

Figure 1 highlights contributions to the system- view (see Berg 1948b and Yakovlev 1977 for addiatics 

of Acipenseriformes over the last 250 years. tional history and critique). 

From the time of Linnaeus through the early part of Representatives of two of the six extant genera of 

the 19th century, descriptions of most of the current- Acipenseriformes, Psephurus gladius (Martens 

ly recognized species and genera were made, in- 1862) and Pseudoscaphirhynchus fedtschenkoi 

cluding Acipenser Linneausaus 1758, PoIyodon Lacé- (Kessler 1872) were discovered in the latter part of 

pède 1797, and Scaphirhynchus Heckel 1836. the 19th century, but apart from early papers (e.g., 

Throughout this period most workers adhered to Handyside 1875a,b, Ivanzoff 1887), they remained 

the classical idea that sturgeons must be closely re- poorly studied for decades. Also in the latter part of 

lated to sharks because they appeared to share a the 19th century paleontologists described and inlargely 

cartilaginous endoskeleton and similar jaw terpreted fossil taxa relevant to Acipenseriforms. 

suspension. An obvious example of this was Wal- Traquair (1877,1887) considered that extant acipenbaum’s 

(1792) description of Polydon spathula as seriforms were derived from ‘paleoniseiforms’. Tra- 

‘Squalus spathula’. By the 1830s, the first serious at- quair’s (1887) ideas were the source for many subtempts 

to synthesize and revise the systematics of sequent interpretations of acipenseriform evolu- 

Acipenseriformes began, including Heckel’s (1836) tion, although we still do not sufficiently underdefinition 

of Scaphirhynchus as a genus distinct stand ‘paleoniseiforms‘ to allow us to make strong 

from Acipenser. Attempts by Brandt & Ratzeberg phylogenetic hypotheses about relationships within

27 

2000 Lu (1994) - description of †Protopsephurus 

Zhou (1992) - redescription of †Peipiaosteus 

Grande & Bemis (1991) - systematics of Polyodontidae 

Gardiner & Schaeffer (1989) - reviewed paleoniscoid taxa 

Gardiner (1984a,b) - fossil chondrosteans and interrelationships of Acipenseriformes 

1975 

1950 

1925 

Yakovlev (1977) - acipenseriform evolution 

Schaeffer (1973) - review of chondrostean systematics 

Gardiner (1967) - classification of fossil and Recent chondrosteans 

Liu & Zhou (I 965) - dcscribcd †Peipiaosteus 

Vladykov & Greeley (1963) - reviewed Atlantic species of Acipenser 

Wilimovsky (1956) - described †Protoscaphirhynchus 

Neilsen (1949) - †Birgeria and Polyodontidae 

Berg (1948a,b) - reviewed Russian acipenscrids and acipenseriform evolution 

MacAlpin (1941a) - described †Paleopsephurus 

Aldinger (1931, 1937) - diphyly of Polyodontidae and Acipenseridae 

Antoniu-Murgoci (1936a,b) - identified characters separating Huso and Acipenser 

Tatarko (1936) - anatomical studies of branchial arches of Acipenseridae 

Sewertzoff (1925) - acipenserids as sister group of Osteichthyes 

1900 Nikolskii (1900) - proposed genus Pseudoscaphirhynchus 

Woodward (1891, 1895a,b,c) - paleontology of †Chondrosteus, †Gyrosteus 

Traquair (1877, 1887) - Acipenseriformes derived from paleoniscoids 

1875 

1850 

Günther (1 873) - proposcd genus Psephurus 

Kessler (1872) - described Acipenser (=Pseudoscaphirhynchus) fedtschenkoi 

Duméril (1870) - extensive splitting of Acipenser, not accepted 

Brandt (1869) - elevation of subgenus Husones to genus Huso 

Egerton (1858) - anatomical description of †Chrondrosteus 

Müller (1846) - proposed Chondrostei, Holostei, Telcostei: sturgeons are Osteichthyes 

Bonaparte (1838) - proposed family name Polyodontidae 

Heckel (1836) - proposed genus Scaphiryhynchus 

Fitzinger & Heckel (1836) - proposed subdivision ofAcipenser 

Brandt & Ratzeberg (I 833) - proposcd subdivision of Acipenser 

1825 

Rafinesque (1820) - described Acipenser (=Scaphirhynchus) platorynchus 

1800 

Lacepède (1797) - proposed Polyodon 

Walbaum (1792) - described Squalus (= Polyodon) spatula: i.e., Polyodon originally 

considered to be a shark 

1775 Georgi (1775) - described Acipenser (=Huso) huso 

1750 Linnaeus (1758) - described Acipenser sturio: sturgeons regarded as related to sharks 

Figure 1. Selected events in the history of acipenseriform systematics since Linnaeus.

28 

Few workers ever accepted the Aldinger-Nielsen 

hypothesis (see Yakovlev 1977 for history and a detailed 

critique), and it was rendered even more unlikely 

by the cladistic definition of Acipenseroidei 

(Grande & Bemis 1991). 

Several additional extinct genera of Acipenseriformes 

based on relatively complete skeletons were 

described in the 20th century, and more are being 

found at the time of writing of this paper. New acipenseriforms 

include a Jurassic paddlefish, †Protopsephurus 

Lu 1994; a Cretaceous paddlefish, †Paleopsephurus 

MacAlpin 1941a (also see MacAlpin 

Figure 2. A partial growth series of Scaphirhynchus platorynchus 

larvae showing allometric lengthening of the rostrum. Like other 1941b, 1947); a Cretaceous sturgeon, †Protoscaphirliving 

acipenseriforms, growth of the rostral region is positively hynchus Willimovsky 1956; two Jurassic (or earliest 

allometric during early life. Scale marks are millimeters. 

Cretaceous) genera, †Stichopterus Reis 1910 (also 

see Yakovlev 1977,1986) and †Peipiaosteus Liu & 

the group, Cope (1883) described the first fossil pad- Zhou 1965 (also see Bai 1983, Zhou 1992, Grande & 

dlefish, †Crossopholis magnicaudatus, and Wood- Bemis 1996; see Jin 1995 and Jin et al. 1995 for more 

ward (1891,1895a,b,c, 1909) reviewed the fossil his- taxa described since this paper was accepted). Most 

tory of sturgeons in papers which remain useful to authors of the type descriptions of these fossil taxa 

this day. 

included comparisons with recent acipenseriforms, 

With the exception of Berg’s remarkable synthe- but the descriptions of all four genera pre-date the 

tic works (e.g., Berg 1940, also see Birstein & Bemis widespread application of cladistics to frame phylo- 

1997 this volume), 20th century ichthyologists rare- genetic questions and organize character informaly 

incorporated paleontological data into their tion. Another problem with some of these papers is 

ideas about acipenseriform systematics. Thus, the that reconstruction of the fossils was based on exichthyological 

tradition of this century emphasized tant sturgeons and paddlefishes, which makes it difregional 

faunas and keys for sturgeons and paddlef- ficult to separate observation from interpretation. 

ishes, such as for territories of the former Soviet Comments on relationships were provided by Liu 

Union (Berg 1911,1933,1948a), the western North & Zhou (1965), Nelson (1969) and Jollie (1980), but 

Atlantic (Bigelow & Schroeder 1953, Vladykov & none of these treatments explicitly traced relation- 

Greeley 1963), eastern Atlantic and Mediterranean ships of living and fossil forms, nor did they include 

(Svetovidov 1984), and European freshwaters synapomorphy schemes. It was not until later, when 

(Holcík 1989). Other collected works, such as Bin- Gardiner (1984b) published the first generic level 

kowski & Doroshov (1985), Williot (1991), and Ger- cladogram including fossil and recent Acipenserishanovich 

& Smith (1995) summarized much basic forms, that interest in their phylogenetic interrelabiological 

and distribution data, but did not attempt tionships began to grow. Gardiner’s (1984b) analyto 

examine acipenseriform interrelationships. sis was controversial because he suggested that pad- 

During the 1930s and 1940s, a period in which di- dlefishes were diphyletic, a conclusion rejected by 

phyletic origins were proposed for several groups Grande & Bemis (1991). More recently, Zhou 

(e.g., tetrapods; Holmgren 1933, Jarvik 1942), Ald- (1992) provided a different tree, which we criticize 

inger (1937) proposed that paddlefishes and stur- in our analysis below. 

geons were derived from separate early Mesozoic Molecular and karyological approaches to sysancestors. 

In a detailed study of a Triassic species of tematics of Acipenseriformes are still at the level of 

†Birgeria from east Greenland, Nielsen (1949) ex- initial surveys (e.g., Fontana & Colombo 1974, Dinamined 

and supported Aldinger’s hypothesis that gerkus & Howell 1976, Birstein & Vasiliev 1987), althis 

genus is closely related to living paddlefishes. though increasingly comprehensive (e.g., Birstein

et al. 1997 this volume). Published molecular phylo- netic allometry of paddle growth in Polyodon 

genetic research including Acipenseriformes is lim- spathula was concisely described by Thompson 

ited to questions concerning higher relationships (1934, also see Grande & Bemis 1991). At the start 

among Actinopterygii (e.g., Normark et al. 1991), of the feeding larva period, North American padand 

no study has yet included all living species of dlefishes have a barely detectable paddle. But soon 

sturgeons and paddlefishes. Nothing approaching afterwards, the paddle grows with positive allomthe 

comprehensive morphological-molecular-kary- etry to make up more than half of the total body 

ological-data sets now available for many groups of length. Later in life, paddle growth shows negative 

tetrapods (e.g., plethodontid salamanders, Wake & allometry with respect to total length. Even after 

Larson 1987) has been attempted for Acipenseri- Polyodon spathula achieves reproductive maturity. 

formes or indeed for actinopterygians generally. there can be significant qualitative morphological 

From this brief history, it is clear that phylogenet- changes, such as the appearance of new ossification 

ic studies of Acipenseriformes are still in their in- centers in the necurocranium (Grande & Bemis 

fancy. Some barriers to phylogenetic study seem ‘in- 1991). Many acipenseriforms achieve very large siztrinsic’ 

to these fishes. In particular, acipenseri- es at maturity, and may continue to grow for many 

forms often exhibit great individual and ontogenet- years thereafter, but most systematic studies and 

ic variation. It is critical to better understand and collections are disproportionately weighted todistinguish 

between these types of variation in any wards more easily studied (and stored) juvenile and 

comprehensive phylogenetic review, and this in it- ‘sub-adult’ specimens. We have already pointed out 

self is a daunting task. Extensive variation confused the necessity of collecting and including large adult 

systematists such as Duméril (1870), who proposed specimens in phylogenetic studies (Grande & Bemore 

than 40 new species of Acipenser that were mis 1991, 1997). In studying acipenseriforms, this 

rejected by later workers. Variation is frequently goal is often impractical, if not impossible, due to 

noted in other contexts. For example, in a large pop- depletion or extinction ofmany populations. In parulation 

study of shortnose sturgeon, Acipenser bre- ticular, members ofdepleted populations of acipcenvirostrum, 

Dadswell et al. ( 1 , p. 2) noted that speci- seriforms rarely achieve the historically reported 

mens ranged ‘. . . from sharp-plated, rough-skinned maximum sizes of individuals prior to exploitation 

individuals to flat-plated, smooth-skinned’ in the (e.g., Acipenser transmontanus, Galbreath 1985). 

St. John Estuary in New Brunswick. There is also Another example of an intrinsic barrier to phylogemuch 

individual variation in the pattern of skull netic study is the potentially large but unknown role 

roofing bones, as illustrated for A. fulvescens by Jol- of natural hybridization (see Birstein et al. 1997 for 

lie (1980, perhaps even more extreme than variation review), and varying anthropogenic impacts on hyin 

skull roofing bones reported for Amia by Jain bridization ranging from creation and release of 

1985 and Grande & Bemis 1997). Although it has new hybrids to selective overfishing of one species 

not been the subject of formal study, rostral shape in to large scale alterations in river systems. For exam- 

Scaphirhynchus is positively allometric during early ple, some workers suggest that the hybridization 

life, as shown by the photograph of a growth series frequency of shovelnose and pallid sturgeons (Scain 

Figure 2. The rostrum provides other well known phirhynchus platorynchus and S. albus) increased 

examples of variation. For example, rostral Iength as a result of dredging, damming, and channelizing 

and width of the North American species of Acipen- big-river habitats (Carlson et al. 1985, Phelps & Alser 

varies ontogenetically, geographically and inter- lendorf 1983). 

specifically (Vladykov & Greeley 1963). Ontoge- The main reason, however, why phylogenetic 

studies of Acipenseriformes are still in their infancy 

1 

is that few people have ever concentrated on the 

Dadswell, M.J., B.D. Taubert, T.S. Squires, D.Marchette & J. 

Buckleye.1984. Synopsis of biological data on shortnose stur- systematics of the group. This is unfortunate, because 

systematics offers the only mechanism for 

geon, Acipenser brevirostrum LeSueur 1818. NOAA Technical 

Report NMFS 14. 

comprehensive comparative studies, and such stud- 

29

30 

Figure3. Tree of ing craniates showing generally accepted interpretation of relationships for stem Actinopterygii. This tree is based on 

cladograms summarized by Patterson (1982), Lauder & Liem (1983), Maisey (1986), Schultze (1987), and Northcutt & Bemis (1993). Taxa 

enclosed in dotted outline arc those craniates possessing ampullary electroreception see Northcutt ( 1986) for discussion and analysis.

31 

Polypterus - Recent, Africa 

† Mimia Upper Devonian, Australia 

† Birgeria - Lower Triassic, Greenland 

Figure 4. Some living and fossil outgroups of Acipenseriformes: a – Polypterus represents a clade generally considered to be the living 

sister group of all other living Actinopterygii . The rhombic ganoid scales are omitted in this diagram (from Dean 1895). b -† Mimia is 

known from many beautifully preserved specimens (from Gardiner 1984a). c - †Birgeria from the Triassic of east Greenland (from 

Nielsen 1949). †Birgeria shares three synapomorphies with Acipenseriformes discussed in the text and tables. 

ies are critical to promoting awareness of a group. 

Acipenseriforms are increasingly threatened in 

their native ranges (e.g., Birstein 1993, Bemis & 

Findeis 1994), yet only recently has this translated 

into more rigorous systematic inquiry (Rochard et 

al. 1991). There are many outstanding systematic 

problems which could influence global conservation 

efforts for the group. For example, we cannot 

answer here such basic questions as: ‘is the genus 

Acipenser monophyletic?’ or ‘how many valid species 

of Acipenser should we recognize?’ These 

questions will necessarily absorb a great deal of future 

research because of the broad geographic 

range occupied by the species of Acipenser as well

32 

Family †Chondrosteidae 

†Chondrosteus - Jurassic, Europe 

Figure 5. Reconstruction of †Chondrosteus from Woodward (1895c). † Chondrosteus lacks body scales and has a projectile jaw system. 

as the several ‘intrinsic’barriers to study described 

in the preceding paragraph. 

Our research program on Acipenseriformes emphasizes 

generic level relationships using comparative 

osteology and developmental studies of the 

skeleton and other tissues. The skeleton provides 

an excellent source of phylogenetic data which can 

be reliably recovered from specimens prepared in 

many different ways. It also allows us to incorporate 

well-preserved fossils, which give other insights into 

the evolutionary history of actinopterygians. Acipenseriformes 

is an old group, known from as far 

back as the Lower Jurassic of Europe. Certain well- 

Table 1. Selected references for some outgroup taxa. 

known fossil taxa show that the basic body plans of 

living sturgeons and paddlefishes were well established 

by the end of the Cretaceous, and earlier fos- 

sils belonging to both of the extant families are be- 

ing found. For example, Lu (1994) recently de- 

scribed †Protopsephurus,an Upper Jurassic pad- 

dlefish from China, so that Polyodontidae is as old 

as the middle Mesozoic. All fossil Acipenseri- 

formes come from the northern hemisphere,which 

is consistent with the Holarctic range of living spe- 

cies. Finally, although sturgeons and paddlefishes 

are often loosely called ‘living fossils’, this does not 

mean that features present in living sturgeons and 

paddlefishes are necessarily primitive. Such hy- 

Sources of osteological data 

Table 2. Species and biogeographic ranges of †Chondrosteidae 

†Cheirolepis Pearson & Westoll 1979 Egerton 1858. 

Polypterus 

†Mimia 

Allis 1922 and pers. obs. 

Gardiner 1984a †Chondrosteus Agassiz 1844 

†Moythomasia Gardiner 1984a †C. acipenseroides Agassiz 1844 Lower Jurassic - England 

†Birgeria Nielsen 1949 †Strongylosteus Egerton 1858 

†Saurichthys Rieppel 1992. Stensiö 1925 †S. hindenburgi Pompeckj 1914 Lower Jurassic - Germany 

Lepisosteus Wiley 1976 and pers. obs. †Gyrosteus Agassiz 1844 

Amia Grande & Bemis 1997 †G. mirabilis Agassiz 1844 Jurassic - England

Family †Peipiaosteidae 

33 

†Peipiaosteus - Jurassic, China 

Figure 6. Reconstruction of †Peipiaosteus from Zhou (1992). See further comments and revised interpretations and drawings in Grande & 

Bemis (1996). 

potheses must be tested by outgroup comparisons 

to other actinopterygians. 

Selection of taxa for outgroup comparison 

Figure 3 shows the relationships of living Polypteridae, 

Acipenseriformes, Lepisosteidae, Amiidae, 

and Teleostei as currently understood (Lauder & 

Liem 1983). There is now widespread acceptance 

that, among living fishes, Polypteridae is the sister 

group of all other Actinopterygii (Goodrich 1928, 

Patterson 1982) and that sturgeons and paddlefishes 

together form the next extant group on the cladogram. 

Teleostei includes more than 20000 living 

species, whereas Polypteridae, Acipenseriformes, 

Lepisosteidae and Amiidae together only contain 

about 45 living species. Of these 45 living species, 27 

are Acipenseriformes, and this order also shows the 

largest total biogeographic range of any living clade 

Table 3. Species and biogeographic ranges of †Peipaiosteidae 

Liu & Zhou 1965 (also see Grande & Bemis 1996a). 

†Peipaiosteus Liu & Zhou 1965 

†P. pani Liu & Zhou 1965 Upper Jurassic/Lower Cretaceous 

- China 

†P. fengningensis Bai 1983 Upper Jurassic/Lower Cretaceous 

- China 

†Stichopterus Reis 1910 

†S. woodwardi Reis 1910 Lower Cretaceous - Trans-Baikal 

†S. popovi Yakovlev 1986 Lower Cretaceous - Mongolia 

of non-teleostean actinopterygians. Because of 

their diversity and phylogenetic position as a basal 

group within Actinopterygii, Acipenseriformes is 

essential for comparative studies within extant and 

fossil Actinopterygii. 

The earliest known complete skeletons of actinopterygians 

are from the Devonian (see Long 

1995), but isolated scales are reported from the Upper 

Silurian. By the Carboniferous their diversification 

had produced a great variety of fishes, commonly 

known as ‘paleonisciforms’ (a grade, see 

Gardiner 1993). ‘Typical’ Paleozoic and Mesozoic 

paleonisciforms have heavy, rhombic scales armoring 

the body, a heterocercal tail, a well ossified skull 

with solid bony cheeks, and large eyes. More than 

200 genera of paleonisciforms are known, but many 

are poorly preserved or inadequately studied. Increasing 

knowledge of the anatomy of certain Paleozoic 

genera such as †Cheirolepis (Pearson &Westoll 

1979, Pearson 1982), †Mimia and †Moythomasia 

(Gardiner 1984a) allows their placement with 

greater certainty within the phylogenetic scheme 

for recent actinopterygians, and we follow Gardiner 

& Schaeffer (1989) in placing these genera near 

the base of Actinopterygii and including them as 

outgroups in our analysis of Acipenseriformes. 

Several living and fossil genera are relevant outgroups 

for analyzing relationships among Acipenseriformes 

(Figure 4). Two Mesozoic genera often

34 

Figure 7. Aspects of the feeding system of the Chinese paddlefish, Psephurus gladius: a - A preserved specimen with its jaws in the 

projected position. This projection system is shared by all living and fossil Acipenseriformes except for North American paddlefish 

(Polyodon). b - View of the first typical gill arch to show gill rakers. The gill rakers of Psephurus are short, stubby and unsuited for filter 

feeding. This is the plesiomorphic condition for Polyodontidae (see Grande & Bemis 1991, fig. 26). 

linked with Acipenseriformes are †Saurichthys (a 

widespread and speciose genus from the Triassic 

and Early Jurassic, see Rieppel 1992 for review) and 

†Birgeria (particularly the species from the Triassic 

of east Greenland; see Nielsen 1949 and Yakovlev 

1977). In their summary phylogeny, Gardiner & 

Schaeffer (1989, their fig. 12; their ‘chondrostean 

group’ is equivalent to Acipenseriformes here) 

show a group containing †Saurichthys as the immediate 

sister group of Acipenseriformes. This position, 

however, is only one of several equally parsimonious 

possibilities from their cladistic analysis, 

and so must be regarded as uncertain. Rieppel 

(1992), in a review of the genus †Saurichthys, concluded 

that Acipenseriformes, †Saurichthys, and 

†Birgeria form an unresolved trichotomy. 

In selecting the outgroup taxa listed in Table 1, we 

were guided by their putative phylogenetic positions, 

the availability of detailed osteological descriptions, 

and the general desirability of including 

a spectrum of taxa. Better understanding of the relationships 

of Acipenseriformes to other groups of 

Actinopterygii can be achieved by a detailed specimen-based 

review of these and other taxa, including 

preparation of many of the known fossils (see 

Grande & Bemis 1996 for example of †Peipiaosteus), 

but this is far beyond our present purposes. 

Diversity of fossil and recent Acipenseriformes and 

specification of ingroup taxa 

In this section, we briefly review the known taxa 

and their geographic and geological ranges. We also 

identify which taxa were the sources of character 

information for our analysis. The text is supple- 

Table 4. Species and biogeographic ranges of fossil and extant Polyodontidae Bonaparte 1838. 

†Protopsephurus Lu 1994 - China 

†P. liui Lu 1994 

†Paleopsephurus MacAlpin 1941a - North America 

†P. wilsoni MacAlpin 1941a 

Psephurus Günther 1873 - China 

P. gladius (Martens 1862) 

†Crossopholis Cope 1883 - North America west of Rocky Mountains 

†C. magnicaudatus Cope 1883 

Polyodon Lacépède 1797 -North America east of Rocky Mountains 

P. spathula (Walbaum 1792) 

†P. tuberculata Grande & Bemis 1991 

Upper Jurassic - China 

Upper Cretaceaus - Montana 

Yangtze River drainage, China 

Lower Eocene - Wyoming 

Mississippi River drainage 

Lower Paleocene - Montana

35 

Figure 8. Green River paddlefish, † Crossopholis magnicaudatus. More than twelve complete specimens of this taxon are known, although 

it remains one of the rarest fishes in the Green River Formation (Grande & Bemis 1991). 

mented by tabular summaries (Tables 2-5) and illustrations 

(Figure 5-16). 

1. Family †Chondrosteidae Egerton 1858 

†Chondrosteus acipenseroides Agassiz 1844 from 

the Lower Jurassic of England is based on multiple, 

complete specimens. Some authors consider the genus 

†Srongylosteus (as represented by †S. hindenbergi 

Pompeckj 1914 from the Lower Jurassic of 

Germany) to be synonymous with †Chondrosteus; 

the few reported differences between these genera 

need new study. In the absence of modern studies, 

papers by Egerton (1858), Traquair (1887) and Hennig 

(1925) remain useful. Traquair (1887) emphasized 

morphological similarities between †Chondrosteus 

and acipenserids, including jaws free from 

the cheek, reduced scales, and reduced ossification, 

and his work provided the basis for the classic interpretation 

that † Chondrosteus and Acipenseridae 

are sister groups, an interpretation rejected by 

Grande & Bemis (1991, also see discussion of node 

Acipenseroidei below). 

†Gyrosteus mirabilis is known from several incomplete 

specimens from the Jurassic of England 

(summarized by Woodward 1891,1895a,b,c) which 

are not suited for detailed study. These were spectacularly 

large fish: the ossified portion of one hyomandibula 

exceeds 50 cm, compared to an entire 

hyomandibula only 12 cm long from a two meter 

Acipenser oxyrinchus. As far as we can tell, †Gyrosteus 

appears to be undiagnosable as a genus distinct 

from †Chondrosteus 

We used published data on †Chondrosteus 

acipenseroides and † Chondrosteus (= †Strongylosteus) 

hindenbergi from Egerton (1858), Traquair 

(1887) and Hennig (1925) in our phylogenetic analysis. 

2. Family †Peipiaosteidae Liu & Zhou 1965 

Yakovlev (1977,1986) does not consider that †Peipiaosteidae 

is distinct from †Chondrosteidae. We 

disagree, and find that the two families probably do 

not even form a monophyletic group. 

Two genera and four nominal species are recognized 

in †Peipiaosteidae (Table 3). †Peipiaosteus is 

known from two very similar species from the Upper 

Jurassic of Northern China. †Peipiaosteus pani 

was described from about 40 specimens (Liu & 

Zhou 1965). More recently, †P. fengningensis was 

described by Bai (1983). In a recent review, Zhou

36 

Figure 9. The living North American paddlefish, Polyodon 

spatthula: a – A pond-reared specimen from a commercial fish 

farm in Missouri. b – Gill rakers and entrapped plankton in an 

adult Polyodon. 

(1992) provided a new reconstruction (Figure 6). 

†Stichopterus woodwardi Reis 1910 occurs in the 

Lower Cretaceous of Trans Baikal; this species was 

treated in more detail by Yakovlev (1977). A second 

species, †Stichopterus popovi Yakovlev 1986 comes 

from the Lower Cretaceous of Mongolia. Yakovlev 

(1977) questioned whether †Stichopterus and †Peipiaosteus 

warrant separate generic status. In answering 

this question, Zhou (1992) summarized 

some striking differences between the two genera, 

such as the presence of an endopterygoid and palate 

in †Stichopterus (not found in †Peipiaosteus) and 

the presence of rhombic scales in the upper lobe of 

the caudal fin in †Stichopterus (not found in †Peipiaosteus). 

All of this material warrants new additional 

specimen-based study. 

We used published data on †Peipiaosteus pani 

from Liu & Zhou (1965) and Zhou (1992) for our 

analysis (see Grande & Bemis 1996 for data on †Peipiaosteus 

collected after this paper was prepared; 

two additional genera, †Yanosteus and †Spherosteus 

are treated there). 

Unlike sturgeons, paddlefishes are usually regarded 

as primary freshwater fishes (e.g., Swift et al. 

1986), and although individuals may occasionally 

stray into coastal marine environments (Vladykov 

& Greeley 1963) all fossil paddlefishes are from 

freshwater deposits. This makes the family particularly 

useful for biogeographic interpretation. 

Grande & Bemis (1991) studied osteology and relationships 

among four genera of paddlefishes (†Paleopsephurus, 

Psephurus, †Crossopholis and Polyodon; 

Table 4). Recently, a new Mesozoic genus 

†Protopsephurus was described (Lu 1994) and putatively 

assigned to Polyodontidae. †Protopsephurus 

3. Family Polyodontidae Bonaparte 1838 

Figure 10. A cleared and double stained juvenile specimen of beluga, 

Huso huso. Bone is stained red, cartilage stained blue. Note 

the endochondral rostrum sheathed by dorsal and ventral rostral 

bones, the projectile jaws, reduction of the lateral line canals to 

simple tubular bones, and the series of scutes on the trunk.

37 

does have a paddle-shaped rostrum and the large 

jaws characteristic of other paddlefishes and Lu 

(1994) reports (but does not illustrate) the presence 

of stellate bones in this material. This placement 

seems reasonable, but more study of this material is 

needed. 

†Paleopsephurus wilsoni MacAlpin 1941a from 

the late Cretaceous Hell Creek formation of Montana 

is the only species of the genus. It is known 

from a single partial skull and caudal fin (MacAlpin 

1941b, 1947). Further preparation of the remaining 

material revealed important new details, such as the 

presence of stellate bones in the paddle, which had 

been overlooked or misinterpreted by MacAlpin 

(see Grande & Bemis 1991). This species has short, 

triangular-shaped gill rakers, so it clearly was not 

specialized for filter feeding. 

The large, piscivorous Chinese paddlefish, Psephurus 

gladius, is restricted to the Yangtze River 

(Figure 7). Described as Polyodon gladius by Martens 

(1862), it was transferred to the new genus Psephurus 

by Günther (1873) because of its moderate 

number of comparatively shorter gill rakers and its 

smaller number of large caudal fulcra. Relatively 

few papers focus on Psephurus (Handyside 1875a,b, 

Nichols 1928, 1943, Tatarko 1936, 1939, MacAlpin 

1947, Vasetskiy 1971, Liu & Zeng 1988, Yu et al. 

1986, Grande & Bemis 1991, Liu et al. 1995). Although 

it probably never reached the 7 meters total 

length commonly cited for this species, Psephurus 

reached at least 4 meters (Grande & Bemis 1991). 

Table 5. Species and geographic ranges of some fossil and all recent Acipenseridae, Bonaparte 1831. Additional fossil species are listed in 

Wilimovsky(1956). 

Huso Brandt 1869 - Eurasia 

H. huso (Linnaeus 1758) 

H. dauricus (Georgi 1775) 

Acipenser Linnaeus 1758 - Holarctic 

A. oxyrinchus Mitchill 1815 

A. brevirostrum Le Sueur 1818 

A. fulvescens Rafinesque 1817 

A. sturio Linnaeus 1758 

A. naccarii Bonaparte 1836 

A. stellatus Pallas 1771 

A. gueldenstaedtii Brandt & Ratzeberg 1833 

A. persicus Borodin 1897 

A. nudiventris Lovetzky 1828 

A. ruthenus Linnaeus 1758 

A. baerii Brandt 1869 

A. schrenckii Brandt 1869 

A. dabryanus Duméril 1868 China 

A. sinensis Gray 1834 

A. medirostris Ayres 1854 

A. transmontanus Richardson 1836 

†A. albertensis Lambe 1902 

†A. toliapicus Agassiz 1844 

†A. ornatus Leidy 1873 

Scaphirhynchus Heckel 1836 - North America 

S. platorynchus (Rafinesque 1820) 

S. suttkusi Williams & Clemmer 1991 

S. albus (Forbes & Richardson 1905) 

†Protoscaphirhynchus Wilimovsky 1956 - Montana 

†P. squamosus Wilimovsky 1956 

Pseudoscaphirhynchus Nikolskii 1900 - Aral Sea drainages 

P. kaufmanni (Bogdanow 1874) 

P. hermanni (Severtzoff in Kessler 1877) 

P. fedtshenkoi (Kessler 1872) 

Black, Caspian, Mediterranean seas 

Amur River drainage 

North America - Atlantic coast 

North America – Atlantic coast 

North America – central United States 

Europe - Atlantic coast, Mediterranean Sea 

Adriatic Sea 

Black, Caspian, Mediterranean seas 

Black, Caspian seas 

Black, Caspian seas 

Black, Caspian, Aral seas 

Rivers of east-central Europe 

Rivers of north coast of Russia 

Amur River drainage, Sea of Okhotsk 

China, south Japan 

North America, Asia - Pacific coast 

North America - Pacific coast 

Upper Cretaceous -Alberta 

Lower Eocene - England 

Miocene - Virginia 


Mobile Bay drainage 


Upper Cretaceous - Montana 

Syr-Darya River 

Syr-Darya River 

Amu-Darya River

38 

Figure 11. A large specimen of kaluga. Huso dauricus. from the Amur River near Khabarovsk. Siberia. Photograph courtesy of Viktor 

Svirskii, TINRO, Vladivostok. 

Large specimens are especially poorly represented 

in systematic collections,and this species is now severely 

threatened owing to construction of dams 

and overfishing (Wei et al. 1997this volume). 

Although †Crossopholis magnicaudatus (Figure 

8) is comparatively rare in the extensively collected 

fauna of Fossil Lake (Lower Eocene of Wyoming) it 

is known from an excellent series of complete specimens 

(Grande & Bemis 1991). Originally described 

by Cope (1883) and later redescribed in detail by

39 

Figure 12. Two North American species of Acipenser: a - A 

shortnose sturgeon, Acipenser brevirostrum, being stripped by 

B. Kynard and a student for captive production of eggs; b - lake 

sturgeon, Acipenser fulvescens juvenile. 

Grande & Bemis (1991), †Crossopholis is a modestly 

sized polyodontid that was clearly piscivorous as 

evidenced by the presence of fish in the body cavity 

of several specimens. Interestingly, traces of ampullary 

organs can be seen between stellate bones in 

the paddle of some specimens. 

The extant North American paddlefish, Polyodon 

spathula (Figure 9) is an intensively studied 

species (see bibliographies in Grande & Bemis 1991, 

Dillard et al. 1986 and Graham 1997 this volume). 

Polyodon is perhaps best known for its filter-feeding 

habit based on numerous thin, elongate gill rakers 

unique to this genus among Acipenseriformes. 

Polyodon spathula occurred as far north as Lake 

Erie (Trautman 1981), but the species typically inhabits 

large river systems, and, prior to commercial 

exploitation, was common in the Mississippi River 

and its tributaries (Gengerke 1986, Russell 1986, 

Graham 1997). A Lower Paleocene species from 

Montana, †Polyodon tuberculata Grande & Bemis 

1991, shares the elongate gill rakers. 

†Pholidurus disjectus, from the Jurassic of England, 

historically regarded as a polyodontid 

(Woodward 1895) was removed from Polyodontidae 

by Grande & Bemis (1991). Thus, the family Polyodontidae 

as presently known is restricted to 

North America and Asia. 

We used representatives of the four better known 

genera of paddlefishes (†Paleopsephurus wilsoni, 

Psephurus gladius, † Crossopholis magnicaudatus 

and Polyodon spathula) in our phylogenetic analysis. 

Because only a few details are available concerning 

†Protopsephurus Lu 1994, we leave it as an 

unresolved multichotomy with other paddlefishes. 

4. Family Acipenseridae Bonaparte 1831 

As summarized in Table 5, the family Acipenseridae 

includes four extant genera (Huso, Acipenser, 

Scaphirhynchus and Pseudoscaphirhychus) and 

one putative fossil genus (†Protoscaphirhynchus). 

Other fossil and subfossil material has been described, 

but most of it is fragmentary. Many populations 

of sturgeons are severely depleted (e.g., 

∨ 

Holcík et al. 1989, Birstein 1993 and many papers in 

thisvolume) or extinct (e.g., Aral Sea ship sturgeon, 

A. nudiventris, see Zholdasova1997 this volume). A 

thorough anatomical description of one species, the 

sterlet, A. ruthenus, is available (Marinelli & Stren-

40 

Figure 13. Map of eastern Europe and Asia showing a region of high diversity for Acipenseridae. Three of the four extant genera of sturgeons occur in the area of eastern Europe 

and central Asia shown in the enlargement at the bottom of the page.

41 

Figure 14. An interpretation of phylogenetic relationships within 

Acipenser based on Artyukhin (1995a and pers. comm.). This 

tree is based on karyological data and biogeographic interpretation; 

this genus is in need of much additional study. 

ger 1973). Sturgeons are also the subject of many 

comparative anatomical treatments (e.g., Jessen 

1972,1973) and much developmental research (e.g., 

Ginsburg & Dettlaff 1991, Dettlaff et al. 1993). Findeis 

(1997) described and reviewed skeletal anatomy 

of extant sturgeons to make a cladistic analysis of 

their interrelationships. 

The genus Huso Brandt 1869 is known from two 

extant species from Eurasia (Figure 10,11). Commonly 

known as beluga, H. huso is the largest fish to 

enter freshwater, historically reaching lengths of 6 

to 10 meters (Balon 1967, 1968, Pirogovskii et al. 

∨ 

1989, Barus & Oliva 1995). The kaluga, H. dauricus 

inhabits the Amur River system, where it is a target 

of an aggressive fishery (Krykhtin & Svirskii 1997 

this volume). Even as juveniles, these preferentially 

piscivorous sturgeons target fish as prey. The status 

of Huso as a genus separate from Acipenser was unclear 

to many 19th century workers, who considered 

it a subgenus of Acipenser (e.g., Fitzinger & Heckel 

1836). Recently, Jollie (1980) perpetuated this interpretation, 

although since Brandt (1869), Berg 

(1904), and Antoniu-Murgoci (1936a,b), it has been 

easy to distinguish this genus. Findeis (1997) provided 

additional new characters separating Huso from 

all other extant acipenserids. Unexpectedly, molecular 

data given by Birstein et al. (1997) consistently 

nest Huso within Acipenser. 

With 17 extant species, Acipenser is the most spe- 

Figure 15. Color photograph of an aquarium specimen of the 

large Amu-Darya shovelnose sturgeon, Pseudoscaphirhynchus 

kaufmanni. These sturgeons are threatened due to environmental 

degradation in the region of the Aral Sea. Photograph courtesy 

of Boris Goncharov, Koltsov Institute of Developmental Biology, 

Moscow. 

ciose and problematic taxon within Acipenseriformes 

(Figure 12). The fossil record of Acipenser 

has not helped phylogeneticists. Most described 

fossil species are known only by fragmentary material 

insufficient for differential diagnosis. There has 

never been a comprehensive phylogenetic study of 

the genus, no doubt due to its vast geographic range 

and difficulties obtaining certain species for study. 

The validity of several recent species, such as Aci - 

penser mikadoi is generally questioned, although 

other evidence suggests that this species is distinct 

from A. medirostris (see Birstein et al. 1993,1997). 

Many species of Acipenser are endemic to eastern 

Europe and Asia (Figure 13) and are poorly known 

outside of this region. Traditional ideas about relationships 

within Acipenser relied on biogeography 

Figure 16. Color photograph of a captive reared specimen of the 

common shovelnose sturgeon. Scaphirhynchus platorynchus 

from the central United States.

42 

Figure17. Preliminary cladogram of acipenseriform interrelationships. Character numbers correspond to Tables 6 and 7. Arrangement of 

Cheirolepis, Polypterus and I Mimia follows Gardiner & Schaeffer (1989), and placement of I Saurichthys follows Rieppel (1992). For 

characters used in interpreting relationships of outgroups, see Rieppel (1992). For characters used in interpreting intrafamilial relationships 

of Polyodontidae, see Grande & Bemis (1991). For characters used in interpreting intrafamilial relationships of Acipenseridae, see 

Findeis (1997). Acipenseriform interrelationships are further resolved in Grand & Bemis (1996, see note added in proofs on page 71). We 

follow current convention for arrangement of neopterygians (see Grande & Bemis 1997).

43 

as a first approximation (Figure 14, courtesy of E. 

Artyukhin, see Artyukhin 1994, 1995a,b; also see 

Birstein et al. 1997). Meaningful biological generalizations 

are difficult. for species of Acipenser range 

in size from the tiny sterlet (A. ruthenus) and shortnose 

sturgeon (A. brevirostrum) to the immense 

white sturgeon (A. transmontanus), Atlantic sturgeon 

(A. oxyrinchus) and common sturgeon (A.sturio). 

Several species have some cxclusivcly freshwa- 

ter populations (e.g., A. fulvescens Vladykov & 

Greeley 1963, A. baerii in Lake Baikal, Ruban 1997 

this volume). while stocks of other species spend a 

great percentage of time at sea (e.g., A. medirostris). 

Findeis (1997) studied seven species of Acipenser 

(A. brevirostrum, A. oxyrinchus. A. transmontanus 

A. fulvescens. A. medirostris and A. ruthenus), but 

failed to find any osteological synapomorphies of 

the genus. Acipenser may be paraphyletic, and it 

Table 6. Character key. Characters for acipenseriform outgroups taken from sources listed in Table 1. 

Synapomorphies of †Birgeria + Acipenseriformes 

1. Reduction of the opercle 

2. Elongate posterior extension of parasphenoid 

3. Body scaling reduced to tiny isolated elements or absent 

Synapomorphies ofAcipenseriformes 

4. Palatoquadrates with an anterior symphysis 

5. Palatoquadrate with broad autopalatine portion, palatoquadrate bridge, and quadrate flange 

6. Presence of a triradiate quadratojugal bone 

7. Gill-arch dentition confined to first two hypobranchials and upper part of first arch 

8. Subopercle possesses an anterior process 

9. Preopercular canal in a series of ossicles. mandibular canal short or absent 

10. Infraorbital sensory canal in a series of ossicles 

11. Loss of premaxillary and maxillary bones 

Synapomorphies of†Peipiaosteidae 

None here; see Grande & Bemis (1996, written after this paper was accepted 

Synapomorphies of Chondrosteidae 

12. Anterior part of palatopterygoid club-shaped 

13. Complete loss of trunk scalation 

Synapomorphies ofAcipenseroidei 

14. Loss of opercle 

15. Reduction in number of branchiostegals supporting gill cover 

16. Endocranium with extensive rostrum 

17. Dorsal and ventral rostral bones 

18. Ventral process of posttemporal bone 

Synapomorphies of Polyodontidae 

19. Many small stellate bones make up lateral supports for the paddle 

20. Series of very elongate dorsal and ventral medial rostral bones, with cylindrical cross-sections 

21. Unique shape of subopercle 

22. Elongate anterior and posterior divisions of the fenestra longitudinalis in the skull roof 

23. Posttemporal with elongate anterior arm suturing into the dermosphenotic 

24. Single branchiostegal with branched posterior edge 

Synapomorphies of Acipenseridae 

25. Five scute rows along trunk 

26. Pectoral fin spine 

27. Antorbital bone 

28. 

29. 

30. 

31. 

32. 

33. 

Commissure of occipital canals in median extrascapular bone (see Grande & Bemis 1996 for correction 

Rostral canals curve lateral to barbels 

Supracleithrum tightly joined to dermal skull roof 

Opercular wall formed by cleithrum and clavicle 

Cardiac shield formed by clavicle 

Cleithral process limits mobility of pectoral fin spine

44 

certainly warrants much additional systematic re- come extinct in the recent decades, and the third 

search. One important point, however, is that all species (P. kaufmanni) is threatened (see Birstein 

seven of the species surveyed here share twelve os- 1993 and Zholdasova 1997 for review). They were 

teological synapomorphies with the tribe Scaphir- endemic to the Amu-Darya and Syr-Darya rivers, 

hynchini (Findeis 1997). This conclusion is reflected tributaries of the Aral Sea in Central Asia (Kazakhin 

our classification below. 

stan, Uzbekistan and Turkmenistan; see Berg 

The systematic and conservation status of the 1948a, Tleuov & Sagitov 1973). This region has been 

three nominal species of central Asian Pseudosca- subjected to extreme environmental degradation, 

phirhynchus is unclear. These are the smallest ex- including pesticide pollution and water diversion 

tant sturgeons (Figure 15). and can be readily distin- projects (Ellis 1990). Sonic classical anatomical deguished 

from Scaphirhynchus by differences in gill scriptions of Pseudoscaphirhynchus were made 

raker anatomy and the scalation of the caudal pe- (e.g., Ivanzoff 1887, Sewertzoff 1925), as well as reduncle 

(Findeis 1997). Two of the three species (P. cent embryological studies (Goncharov et al. 1991, 

fedtschenkoi and P. hermanni) appear to have be- Schmalhausen 1991), but very few specimens of 

Table 7. Preliminary survey of characters for Figure 17, mostly based on literature (Table 1) (? =unknown, N = inapplicable, P = polymorphic). 

See Grande & Bemis (1966) for analysis made after this paper was written ( * this character should he scored as a ‘1’). 

Char Pol Bir Cho Pei Pal Psep Cro Pol Hus Aci Psu Sea Lep Ami 

I. 0 1 1 1 1 1 1 1 1 1 1 1 0 0 

2. 0 1 1 1 1 1 1 1 1 1 1 1 U 0 

3. 0 1 1 1 1 1 1 1 1 1 1 1 0 0 

4. N 0 1 1 ? 1 1 1 1 1 1 1 N N 

5. N 0 1 1 ? 1 1 1 1 1 1 1 N N 

6. 0 ? 1 1 1 1 1 1 1 1 1 1 0 0 

7. 0 ? ? 1 ? 1 1 1 1 1 1 1 0 0 

8. 0 0 1 1 1 1 1 1 1 1 1 1 0 0 

9. 0 0 1 1 1 1 1 1 1 1 1 1 0 0 

10. 0 0 1 1 1 1 1 1 1 1 1 1 U U 

11. 0 0 1 1 1 1 1 1 1 1 1 1 1 0 

12. N 0 1 0 0 0 0 0 0 0 0 0 N N 

13. 0 0 1 0 ? 0 0 0 0 0 0 U 0 0 

14. 0 0 0 0 1 1 1 1 1 1 1 1 0 0 

15. 1 0 0 0 1 1 1 1 1 1 1 1 0 0 

16. 0 0 0 0 1 1 1 1 1 1 1 1 0 0 

17. 0 0 0 0 1 1 1 1 1 1 1 1 0 0 

18. 0 ? 0 0 1 1 1 1 1 1 1 1 0 0 

19. 0 0 0 0 1 1 1 1 0 0 0 0 0 0 

20. 0 0 0 0 1 1 1 1 0 0 0 0 0 0 

21. 0 0 0 0 1 1 1 1 0 0 0 0 0 0 

22. 0 0 0 0 1 1 1 1 0 0 0 0 0 0 

23. 0 0 0 0 1 1 1 1 0 0 0 0 0 0 

24. 0 0 0 0 1 1 1 1 0 0 0 0 0 0 

25. 0 0 0 0 0 0 0 0 1 1 1 1 0 0 

26. 0 0 0 0 0 0 0 0 1 1 1 1 0 0 

27. 0 0 0 0 ? 0 0 0 1 1 1 1 0 0 

2s. P 0 ? 0 0* 0 0 0 1 1 1 1 P 0 

20. N 0 0 0 ? 0 0 0 1 1 1 1 N N 

30. 0 0 0 0 0 U 0 0 1 1 1 1 0 0 

31. 0 0 0 0 0 0 0 0 1 1 1 1 0 0 

32. 0 0 0 0 0 0 0 0 1 1 1 1 0 0 

33. 0 0 0 0 0 0 U 0 1 1 1 1 0 0

45 

Pseudoscaphirhynchus are available in systematic 

collections outside Russia and Uzbekistan, and 

there has never been a modern specimen based systematic 

review of all three species. For example, P. 

kaufmanni has been described as having two 

‘morphs’ in the Amu-Darya river. with only the diminutive 

morph persisting as of the last available 

information, but whether these were two separate 

species is unclear (see Berg 1948a). 

The genus Scaphirhynchus (American shove1- 

nose sturgeons) is represented by three nominal 

species from North America (Figure 16). They are 

restricted to freshwater rivers and prefer open, 

free-flowing reaches with soft, silty bottoms. Scaphirhynchus 

distinctively possesses an elongate, armored 

caudal peduncle and several osteological 

characters defined by Findeis (1997). Common 

shovelnose sturgeon (Scaphirhynchus platorynchus) 

rarely exceed one meter total length, but pallid 

sturgeon (S. albus) can be much larger (Bailey & 

Cross 1954). Pallid sturgeons are endangered, and 

apparently readily hybridize with common shovelnose 

sturgeons. The rare Alabama sturgeon (S. sutkussi) 

closely resembles common shovelnose sturgeon; 

its status as a distinct species is debated. 

A partially intact fossil from the Upper Cretaceous 

of Montana was described as †Protoscaphirhynchus 

squamosus Wilimovsky 1956. Although 

Gardiner (1984b) questioned its placement within 

Acipenseridae, the specimen does possess an clongate 

caudal peduncle with armoring scales extremely 

similar to those of Scaphirhynchus. No features 

clearly distinguish it from Scaphirhynchus, so † Protoscaphirhynchus 

may not warrant separate generic 

status. It appears to belong in Scaphirhynchini (as 

used here) indicating that the tribe was definitely 

present in North America at least 65 million years 

before present. 

Material described as an acipenserid from the 

Selma Formation of Alabama († Propenser Applegate 

1970) is now interpreted as portions of a coelacanth 

and a pycnodont. 

We used Huso huso, Acipenser brevirostrum 

Scaphirhynchus platorynchus, and Pseudoscaphirhychus 

kaufmanni for our phylogenetic analysis 

(Table 7, Figure 17). 

Figure 18. Palate of Acipenser brevirostrum in anterior (aboral) 

view. In the top figure, the palatoquadrate cartilage is shown 

without its dermal investing bones. The only center of ossification 

within the cartilage that has developed in this specimen is 

the autopalatine (a) bone, a thin perichondral sheet near the 

symphysis. In a few individuals, another center of ossification 

develops in the region of the quadrate flange. In the lowerfigure, 

the palatoquadrate cartilage is indicated with heavy stipple. It 

has four investing dermal bones: dp, dermopalatine; ecpt, ectopterygoid, 

qj, quadratojugal, and enpt, entopterygoid. The entopterygoid 

bone extends on both the oral and aboral surfaces of the 

palate; very light stippling demarcates the oral portion of the entopterygoid 

as seen through the palatoqudrate cartilage. Total 

length of specimen: 870 mm. UMA 24-116-2-47. 

Phylogenetic interpretation 

This section surveys characters and interpretations 

for the generic-level phylogenetic analysis summarized 

in Figure 17. The characters are listed or described 

in the test and Table 6 and 7. All characters

46 

could be reliably scored in at least 16 of the 18 taxa 

listed in Table 7, but most soft-tissue and cartilaginous 

characters cannot be scored in the fossil taxa 

(see Grande & Bemis 1997 for additional explanations 

of this approach). Incorporated into this diagram 

are published interpretations of relationships 

for the genera of Polyodontidae (from Grande & 

Bemis 1991) and Acipenseridae (from Findeis 1993. 

1997). Consult those references for characters within 

the two families. 

The starting points for our analysis are Patterson 

(1982), Gardiner & Schaeffer (1989), Grande & Bemis 

(1991), Rieppel (1992) and Findeis (1997). For 

those characters that are well-known, and explained 

in detail elsewhere, we provide abbreviated 

descriptions. For other characters, new information 

warrants presentation, and in a few cases, new illustrations 

to clarify definitions. Each subsection 

concludes with notations on other potential characters, 

comments on alternative interpretations, and a 

statement concerning the robustness of the clade. 

Characters of †Birgeria + Acipenseriformes 

We specify three characters as synapomorphic for 

this group. 

Figure 19. Lateral views of the opercular series of four taxa of 

Acipenseriformes to show loss of the opercle in Acipenseroidei 

(Polyodontidae + Acipenseridae), hypertrophy of the subopercle. 

and reduction in the number of branchiostegal bones: 

† Chondrosteus acipenseroides (from Traquair 1887), †Peipiaosteus 

pani (from Zhou 1992), Psephurus gladius (from Grande & 

Bemis 1991), and Huso huso (original, CAS 37541). 

Character 1. Reduction in size of the opercle 

This character was noted by Gardiner & Schaeffer 

(1989). The largest element of the opercular series 

of Acipenseriformes is the subopercle bone (Figure 

19). It is the most dorsal element of the opercular 

series in acipenserids and polyodontids, but a 

smaller, more dorsal opercle bone is present in 

†Chondrosteus and †Peipiaosteus. The opercle of 

†Birgeria is also small (Nielsen 1949, Gardiner & 

Schaeffer 1989). In Polypterus, †Mimia, †Moythomasia, 

Lepisosteus, Amia and most other actinopterygians 

(McCallister 1968), the opercle is the largest 

element of the opercular series, and we interpret its 

reduction to a small bone (as in †Chondrosteus and 

†Peipiaosteus) as synapomorphic for Acipenseriformes. 

The opercle is eventually lost in Acipenseroidei 

(character 14, below). 

Character 2. Elongate posterior extension of parasphenoid 

The parasphenoid of all Acipenseriformes has an 

elongate posterior extension. The extension underlies 

a series of vertebral segments partially or completely 

fused into the occipital region of the neurocranium. 

The parasphenoid bones of † Chondrosteus 

and †Peipiaosteus are shorter than those of living 

Acipenseriformes, but still much longer than in 

any of the outgroups, including †Birgeria, which is 

noted for having a more elongate parasphenoid 

than other paleonisciforms (Nielsen 1949). In the 

outgroup taxa, a vertebral joint close to the neurocranium 

is probably necessary if head-lift is to play 

any role in raising the upper jaw (discussed in final 

section of this paper). Because acipenseriforms 

project their jaws and do not utilize head-lift when 

feeding, the elongate parasphenoid and extension 

of the neurocranium present no interference.

47 

Character 3. Body scaling reduced to tiny isolated 

elements or absent 

This character was defined by Patterson (1982), 

noted by Gardiner & Schaeffer (1989) and accepted 

by Grande & Bemis (1991, character 5). The scales 

of †Cheirolepis are not typical for stem actinopterygians 

in that they are small tubercles, but they are 

not isolated from each other as in our ingroup taxa. 

Acipenseriformes differ from all of the outgroups 

we considered except †Birgeria, which has reduced 

scalation that Nielsen (1949) regarded as very similar 

to that of Polyodon. 

Discussion of clade †Birgeria + Acipenseriformes 

Like Berg (1948b) and Yakovlev (1977) and in contrast 

to Aldinger (1937) and Nielsen (1949), our 

analysis does not support a sister group relationship 

between †Birgeria and paddlefishes. However, 

†Birgeria shares at least three features with Acipenseriformes. 

These three characters warrant additional 

specimen based study in †Birgeria and other 

outgroups not considered here. 

Characters of Acipenseriformes 

We report eight osteological synapomorphies of 

Acipenseriformes keyed to the cladogram in Figure 

17. 

Character 4. Palatoquadrates with an anterior symphysis 

Woodward (1891) and many others have noted this 

feature, but it was more explicitly defined by Patterson 

(1982). Gardiner & Schaeffer (1989) and 

Grande & Bemis (1991, character 1) regarded this 

feature as an acipenseriform synapomorphy. The 

symphysis is a flexible cartilaginous connection in 

all recent Acipenseriformes, and even though the 

cartilage is not preserved, the configuration of the 

upper jaw suggests its presence in † Chondrosteus 

and †Peipiaosteus. (More study of this character in 

†Peipiaosteus is needed, however.) The palatoquadrate 

symphysis appears to be absent in †Cheirolepis, 

Polypterus, †Mimia, †Birgeria, Amia, and other 

actinopterygians. Gardiner & Schaeffer (1989) in- 

cluded as part of their character definition that the 

palatoquadrates of Acipenseriformes ‘do not articulate 

with the neurocranium’, but we note that the 

palatoquadrate is guided by the cartilaginous basitrabecular 

processes during projection, so their additional 

qualification is unclear (see discussion under 

‘Putative and problematic characters of Acipenseriformes’, 

below). 

Character 5. Palatoquadrate with broad autopalatine 

portion, palatoquadrate bridge, and quadrate 

flange 

Schaeffer (1973) and Patterson (1982 ) considered 

palatoquadrate shape to be an acipenseriform character, 

but did not specify which aspects are synapomorphic. 

An illustration of the palatoquadrate of a 

large adult Acipenser brevirostrum is shown in Figure 

18. All acipenseriform palatoquadrates have a 

broad autopalatine plate (Figure 18a), a narrow palatoquadrate 

bridge (pqb), and a quadrate flange 

(qf). In comparison, †Cheirolepis, Polypterus, †Mimia, 

and Amia possess roughly triangular palatoquadrates 

with thin anterior tips that extend to contact 

the ethmoid region of the neurocranium. 

Character 6. Presence of a triradiate quadratojugal 

bone 

This character was defined by Patterson (1982) and 

accepted by Grande & Bemis (1991, character 6). 

The condition of the quadratojugal is unknown in 

†Birgeria (Nielsen 1949). Figure 18 shows the quadratojugal 

of Acipenser brevirostrum. An example of 

the triradiate quadratojugal in a polyodontid is illustrated 

in Grande & Bemis (1991, fig. 35A,C). 

Character 7. Gill-arch dentition confined to first two 

hypobranchials and upperpart of first arch 

This character was discussed by Nelson (1969, p. 

257) defined by Patterson (1982), noted by Gardiner 

& Schaeffer (1989) and accepted by Grande & 

Bernis (1991, character 2). It is illustrated in Grande 

& Bemis (1991, fig. 17D). More information on this 

character in †Birgeria is needed. 

Character 8. Subopercle possesses an anterior process 

The subopercle possesses an anterior process that

48 

Figure 20. Scanning electron micrographs of Polyodon spathula larva: a - Lateral view of the head. The infraorbital lateral line canal is still 

a groove at this point in development and can be seen continuing onto the rostral region. The olfactory pit has not yet completely 

subdivided into anterior and posterior nares. Many clusters of ampullary electroreceptors are visible on the cheek region dorsal to the 

upperjaw (see Bemis & Grande 1992). b-Oral view of the upper jaw of a similar specimen. The teeth of the upperjaw are eruptingin two 

series. Additional erupting teeth can be seen at the leading edge of infrapharyngobranchial 2 (see Grande & Bemis 1991 fig. 17B). 

overlaps the hyomandibula and attaches the subopercle 

to the hyoid arch (Figure 19). The process is 

present, but smaller in †Chondrosteus and †Peipiaosteus 

than in acipenserids and polyodontids. It 

was included as part of a polyodontid character by 

Grande & Bemis (1991, character 17) but redefined 

by Findeis (1993) as an acipenseriform character. 

Nielsen (1949, p. 302, #13) considered the unusual 

subopercle of †Birgeria ‘lobate’ and similar to that 

of Polyodon. This appears to be a superficial similarity, 

and in any event †Birgeria lacks the anterior 

process of the subopercle. † Cheirolepis, Polypterus, 

†Mimia, Lepisosteus, and Amia possess oblong or 

circular subopercles lacking the anterior processes. 

Character 9. Preopercular canal in a series of ossicles, 

mandibular canal short or absent 

This character was discussed by Jollie (1980), defined 

by Patterson (1982) and redefined in modified 

form by Gardiner & Schaeffer (1989) and Grande & 

Bemis (1991, character 4). It may be linked to the 

next character. 

Character 10. Infraorbital sensory canal in a series of 

ossicles 

In recent acipenseriforms, †Chondrosteus and †Peipiaosteus, 

the infraorbital sensory canal is carried 

by a series of small canal bones. This contrasts with 

the condition in † Cheirolepis, Polypterus, †Mimia, 

†Birgeria, Amia and other outgroups in which large 

circumorbital bones carry the infraorbital sensory 

canal. 

Character 11. Loss of premaxillary and maxillary 

bones 

This interpretation derives from observations of a 

developmental series of Scaphirhynchus made by 

Findeis (1991). In contrast to the solid bony cheek 

found in outgroups such as †Cheirolepis, Polypterus, 

†Mimia, †Birgeria and Amia, the cheek of recent 

sturgeons and paddlefishes is composed largely 

of skin, and none of the tooth bearing bones of 

the upper jaw are exposed on the surface of the 

cheek. There is no bone in the upper jaw of acipenseriforms 

homologous to the premaxilla of the outgroup 

osteichthyans surveyed. Most historic and 

contemporary authors (e.g., Traquair 1887, Parker 

1882, Woodward 1891, Sewertzoff 1928, Jollie 1980,

49 

Grande & Bemis 1991) have regarded the bone on 

the leading edge of the upper jaw of Acipenseriformes 

as homologous to the maxilla of other osteichthyans. 

Instead, Findeis (1991) interpreted this 

bone as a dermopalatine, one of a series of investing 

bones of the palatoquadrate present in many osteicthyans 

(e.g., dipnoans, Rosen et al. 1981). A new 

illustration labeled with this interpretation is shown 

in Figure 18. If the upper jaw of Acipenserifornies is 

a composite of only the palatoquadrate and its investing 

bones, then both the maxilla and premaxilla 

must have been lost. 

Putative and problematic characters of Acipenserformes 

This section describes some additional features 

which either cannot be surveyed in all acipenseriform 

taxa or which we cannot easily define. For example, 

sensory barbels were probably present at 

this node, but we cannot evaluate their condition in 

fossils nor are they present in living outgroups, so 

we do not know whether 2 barbels (as in living Polyodontidae) 

or 4 barbels (as in living Acipenseridae) 

is the plesiomorphic condition. Similarly, 

alone among living actinopterygians, embryonic 

paddlefishes and sturgeons share a hairpin-loop 

shaped pronephros (Ballard & Needham 1964, Bemis 

& Grande 1992). 

Three cranial character complexes provide most 

of the characters of Acipenserifornies: the cheek region, 

the jaws and the opercular series. It is possible 

that some of the characters within these complexes 

are linked. For example, paedomorphosis is 

thought to cause ‘global’ changes in morphology 

(Bemis 1984). so that several seemingly distinct 

skeletal characters actually change as a unit. In Acipenseriformes, 

the apparent loss of cheek bones 

and presence instead of small ossicles to carry the 

sensory canals might be linked to such a common 

underlying process. Evaluation of this putative 

character complex, however, requires far more information 

about the development of the skeleton 

than is currently available. 

The cartilaginous basitrabecular processes on the 

midventral surface of the neurocranium of recent 

Acipenseriformes serve as ‘pivot points’ guiding 

projection of the palatoquadrates. These processes 

are present in all Acipenseridae and Psephurus 

The loss of these processes in Polyodon is a secondary 

condition associated with immobility of the upper 

jaw. Sewertzoff (1928) described ligaments connecting 

the basitrabccular processes and the palatoquadrate, 

but Findeis (1993) found no discrete ligaments 

in this position in any of the nine species of 

acipenserids he surveyed for this character. Because 

they also possess hyostylic jaw suspensions, 

we infer (but did not feel certain about scoring) that 

basitrabecular processes were present in †Chondrosteus 

and †Peipiaosteus. †Cheirolepis, Polypterus, 

†Mimia, Lepisosteus, and Amia lack basitrabecular 

processes. 

Gardiner & Schaeffer (1989) regarded a large, 

blade shaped hyomandibula as a synapomorphy of 

Acipenserifornies. This may be true, but is difficult 

to define in an unambiguous way. It is difficult to 

decide, Tor example, whether the hyomandibula of 

†Mimia (which is integrated into a more typical actinopterygian 

suspensorium) is ‘blade shaped’. Also, 

in all recent Acipenseriformes, the interhyal is 

hypertrophied. Interhyal hypertrophy was regarded 

by Gardiner & Schaeffer (1 989) and Grande & 

Bemis (1991, character 3) as a synapomorphy of 

Acipenseriformes. Although this is probably correct, 

it is impossible to evaluate this character based 

only on published descriptions of the fossil taxa surveyed 

here because the interhyal is cartilaginous. 

Gardiner & Schaeffer (1989) noted that the basisphenoid 

of Acipenseriformes lacks a parabasal 

canal; as we understand their description, this appears 

to be plesiomorphic for the group. Similarly, 

the polarity of change in myodome characters 

noted at this level by Gardiner & Schaeffer (1989) is 

not obvious to us. The myodomes present in Acipenseridae 

are small and separated, but similar to 

those of †Mimia. 

We do not understand a putative acipenseriform 

character noted by Gardiner & Schaeffer (1989, p. 

176): ‘rostral bones reduced, numerous’, for rostral 

bones are not particularly large or stable features in 

any of the stem actinopterygians known to us. 

Many workers assert that absence of jaw teeth 

characterizes Acipenseriformes or some clade 

within the order (e.g., Gardiner 1984b, character 

12). However, as stated, this character is problem-

50 

atic because acipenseriform larvae and juveniles 

possess jaw teeth. Figure 20 shows the oral region of 

a Polyodon larva, with two rows of conical teeth 

erupting in the upper jaw and a single row in the 

lower jaw (see also Bemis & Grande 1992). In large 

adult Polyodon, however, (>25 kg) teeth are not visible 

from the surface of the bone, and sections show 

that they are completely embedded in the jaw. The 

pattern of ontogenetic tooth loss is different in sturgeons: 

larvae have teeth, but the teeth and their attachment 

bones are absent in adults, and are generally 

considered to be shed during growth. (The biting 

surfaces of adult sturgeons are composed of 

thick collagenous pads, Nelson 1969.) Thus, this 

character is more complicated than usually stated, 

and available data for †Peipiaosteus and †Chondrosteus 

are inconclusive concerning the mode of 

ontogenetic tooth loss. 

Gardiner & Schaeffer (1989) also noted that acipenseriform 

scales are devoid of normal peg and 

socket articulations, except on the caudal lobe of 

†Chondrosteus. By analogy with phylogenetic 

changes in scales of dipnoans (Bemis 1984), we suspect 

that the loss of peg and socket articulations is 

related to the general phenomenon of loss of scalation 

in acipenseriforms (character 3 above), and 

that both might be interpreted as paedomorphic. 

Similarly, Gardiner & Schaeffer (1989) regarded 

the absence of ganoin from fin rays as an acipenseriform 

character: this also could result from paedomorphosis 

(see Bemis 1984 for discussion of phylogenetic 

loss of ornament in dipnoans). There are 

typically a few ganoid tubercles along the leading 

edge of the pectoral fin in, for example, Acipenser 

oxyrhynchus, but these do not extend into the area 

of the fin membrane proper. Both of these putative 

characters deserve study. 

Discussion of clade Acipenseriformes 

Based on the taxa and characters surveyed, there is 

little doubt concerning monophyly of Acipenseriformes. 

Questions concerning sister-group relationships 

of the two Mesozoic families †Chondrosteidae 

and †Peipiaosteidae arc discussed below, but 

on the basis of available evidence we cannot reach 

any conclusion and thus Figure 17 shows †Peipiaosteidae, 

†Chondrosteidae and Acipenseroidei as an 

unresolved trichotomy (see Crande & Bcniis 1996 

for new information on this trichotomy). 

Characters of †Peipiaosteidae 

Characters of this group are the subject of another 

study (Crande & Bemis 1996). and at present, we do 

not accept any of the characters proposed by earlier 

workers. 

Putative and problematic characters of † Peipiaosteidae 

A character often cited as evidence of monophyly 

of †Peipiaosteus is paired lateral line scales (Liu & 

Zhou 1965, Zhou 1992). We think this is probably a 

misinterpretation, for in several of the figured specimens, 

the right and left trunk canals are preserved 

as small tubular ossicles in close proximity to each 

other as we have round for taxa such as †Crossopholis 

(Grande & Bemis 1991). 

Zhou (1992) noted several characters may be synapomorphies 

of †Peipiaosteus and †Stichopterus. 

For example, the parasphenoid of† Peipiaosteus has 

a broad anterior process, but this character has not 

been fully assessed in †Stichopterus. In view of the 

reported differences between these two genera 

(Zhou 1992), it is important to make additional 

specimen based study and comparison before accepting 

them. 

†Peipiaosteus shares with Polyodontidae and 

Acipenseridae the presence of small, tripartite denticles 

on the shoulder girdle (Liu & Zhou 1965). Although 

this character is presently unknown in †Stichopterus 

and †Chondrosteus, it may be a synapomorphy 

of Polyodontidae, Acipenseridae and †Peipiaosteidae. 

Liu & Zhou (1965) also noted that in †Peipiaosteidae, 

Acipenseridae and Polyodontidae, the pelvic 

fins originate anterior to the position of origin of 

the dorsal fin, whereas in † Chondrosteus, the pelvic 

fins originate opposite the dorsal fin. Again, this 

may be a synapomorphy of Polyodontidae, Acipenseridae 

and †Peipiaosteidae. 

Finally, †Peipiaosteus shares with Polyodontids 

the presence of branchiostegals (there is only a single 

branchiostegal in paddlefishes) with branched

51 

posterior tips. This condition also occurs in †Stichopterus. 

Specimen based study is needed before 

proposing it as a synapomorphy of †Peipiaosteidae 

and Polyodontidae. 

Discussion of †Peipiaosteidae 

Too little information is currently available to demonstrate 

the monophyly of this group. Indeed, only 

with additional specimen study will we be able to 

determine whether †Stichopterus and †Peipiaosteus 

are congeneric, as proposed by Yakovlev (1977) and 

rebutted by Zhou (1992). Also, Zhou (1992) considered 

†Peipiaosteidae as the sister group of Acipenseridae. 

As discussed under clade Acipenseroidei 

(below), we disagree with Zhou’s (1992) analysis 

(see Grande & Bemis 1996 for new information on 

†Peipiaosteidae). 

Characters of † Chondrosteidae 

Osteological apomorphies of †Chondrosteidae are 

listed in Table 6, coded in Table 7, and keyed to the 

cladogram in Figure 17. 

Character 12. Anterior part of palatoptevygoid clubshaped 

In contrast to all other Acipenseriformes, the palate 

of †Chondrosteus has a complete sheathing of bone 

on its oral surface. This is because the anterior end 

of the palatopterygoid is club-shaped, rather than 

deeply notched and having a distinct ectopterygoid 

process (see Figure 18 for palatoquadrate of Acipenser; 

additional illustration in Grande & Bemis 

1991 fig. 79 ). We do not interpret this condition as a 

fusion of an autopalatine ossification with the palatopterygoid, 

although the effect on the shape of the 

bone would be similar. 

Character 13. Complete loss of trunk scalation 

Liu & Zhou (1965) noted this as a feature distinguishing 

†Chondrosteus from all other Acipenseriformes. 

This character warrants additional specimen 

based study of well preserved †Chondrosteus, 

especially because the scales present in †Peipiaosteus, 

Polyodontidae and Acipenseridae are very 

Phylogeny of Acipenseriforrnes from Zhou (1992) 

with our interpretation of Zhou's characters Z1-Z9 

Z1. Quadratojugal sickle shaped 

Z2. Infraorbital canal "L" shaped 

Z3. Mandibular canal lost 

Z4 Palatoplerygoid short and broad 

Z5.Suprangular absent 

Z6.

52 

defining Acipenseroidei, which we modify and supplement 

here. 

Character 14. Loss of opercle 

This character was defined by Grande & Bemis 

(1991, character 7) as a synapomorphy of Acipenseroidei. 

As defined in character 1 above, the subopercle 

replaces the opercle as the largest bone of 

the opercular series in Acipenseriformes. However, 

†Chondrosteus and †Peipiaosteus retain small opercles, 

which are entirely missing in Polyodontidae 

and Acipenseridae. 

Character 15. Reduction in number of branchiostegals 

supporting gill cover 

This character was defined as an acipenseroid synapomorphy 

by Grande & Bemis (1991, character 8). 

†Chondrosteus possesses at least eight branchiostegals 

in a continuous series along the lateral and ventral 

faces of the operculum. †Peipiaosteus possesses 

at least seven branchiostegals. Acipenserids typically 

possess two (occasionally three branchiostegals 

are present; see Findeis 1997 this volume). The 

branchiostegals are elongate in Huso and some species 

of Acipenser (e.g., A. oxyrinchus ), shorter in 

other species of Acipenser (e.g., A. brevirostrum), 

and much shorter in scaphirhynchines. With the 

possible exception of †Protopsephurus, polyodontids 

possess only a single branchiostegal separate 

from the subopercle (character 24, below). 

Character 16. Endocranium with extensive rostrum 

Grande & Bemis (1991, character 9) defined this 

character. This extension of the ethmoid region of 

the endocranium ranges from an elongate, thin 

sword or paddle shaped structure in polyodontids 

to a broad, flattened shovel shape in scaphirhynchines. 

It is absent in †Peipiaosteus, †Chondrosteus, 

†Birgeria, †Cheirolepis, †Mimia, Polypterus and 

Amia. †Saurichthys is sometimes regarded as a potential 

sister group of Acipenseriformes (e.g., Gardiner 

& Schaeffer 1989, Rieppel 1992), partly because 

of its rostral shape. However, the rostrum of 

†Saurichthys is based upon extended jaws, superficially 

similar to those of Lepisosteus, so its rostrum 

is not homologous with that of acipenseroids. 

Character 17. Dorsal and ventral rostral bones 

Grande & Bemis (1991, character 10) defined this 

character. In our initial formulation, only the ventral 

keel of rostral bones was emphasized, but the 

presence of dorsal rostral bones should be included 

as well. Dorsal and ventral rostral series are always 

present in Polyodontidae and Acipenseridae. Rostral 

bones of polyodontids are so constant that homologues 

are readily recognizable throughout the 

family, but acipenserids lack this constancy. Some 

variation in the rostral bones of sturgeons correlates 

with the underlying shape of the rostrum, but 

the number and arrangement also vary between individuals 

with comparably shaped rostra (e.g., Jollie 

1980). Neither † Chondrosteus nor †Peipiaosteus 

possesses extensive series of bones anterior to the 

frontals and parasphenoid, much less entire series 

of bones, and, based on outgroup comparison with 

†Cheirolepis, Polypterus, and other basal actinopterygians, 

the absence of rostral bones is plesiomorphic. 

Character 18. Ventral process ofposttemporal bone 

The posttemporal bones bear prominent ventral 

processes that closely articulate with the neurocranium. 

Among sturgeons and paddlefishes, these 

ventral processes of the posttemporal bone are always 

present, although most strikingly developed in 

Polyodon (e.g., Grande & Bemis 1991, fig. 10B). The 

extreme condition in Polyodon was noted as a putative 

synapomorphy of this genus (Grande & Bemis 

1991, character 39). The posttemporal bones of 

†Chondrosteus lack a ventral process and are separated 

from the dermal skull roof by the lateral extrascapular 

bones. Similarly, the posttemporal bone 

of †Peipiaosteus is not integrated into the skull roof, 

so that there was not a close association between its 

dermal skull roof and neurocranium in this region. 

No similar feature of the posttemporal bone occurs 

in Polypterus, †Mimia, or other actinopterygians. 

Putative and problematic characters of Acipenseroidei 

Some skeletal features at the level of Acipenseroidei 

are parts of character complexes. For example, 

the endochondral rostrum and rostral bones (characters 

16 and 17) are presumably coordinated neo-

53 

morphic features because the bones more or less 

closely ensheath the underlying endochondral rostrum. 

For now we accept these as separate characters. 

Discussion of clade Acipenseroidi 

The monophyly of Acipenseroidi sensu Grande & 

Bemis (1991) was questioned by Zhou (1992). 

Zliou’s tree is shown in Figure 21, as well as a table 

summarizing the nine characters he identified to 

challenge the monophyly of Acipenseroidei. 

Zhou’s (1992) analysis is problematic for three 

basic reasons. First, the polarity of change in the 

proposed characters was not explained and cannot 

be assessed without explicit outgroup comparisons 

to non-acipenseriforin taxa not included in Zhou’s 

paper. This problem applies in particular to characters 

Z1 (quadratojugal sickle shaped) and 22 (infraorbital 

canal ‘L’ shaped). Second, apparently 

only some of the taxa included in Zhou’s phylogeny 

were examined for all characters. For example, 

Zhou interpreted characters Z6 (the presence of 

fewer than 7 opercular boncs) and Z7 (branched 

opercular bones) as synapomorphies of a clade including 

†Peipiaosteidae + Acipenser. But both of 

these characters are also present in PoIyodon and 

† Paleopsephurus, so Zhou’s tree requires these two 

characters to be derived at least twice. Third, 

Zhou’s scoring or definitions for at least three characters 

are problematic. Character 23 (loss of mandibular 

canal) applies to PoIyodon and †Paleopsephurus 

as well as to all of the other taxa in Zhou’s 

analysis (see our character 9 above). The definition 

of character Z8 (broad opercular-pectoral gap) is 

vague, and in any event problematic to score in fossils. 

Finally, character Z9 (hook-like rostral bones 

in juveniles) is an ontogenetic feature with unknown 

development in extant taxa. Zhou’s rostral 

bones seem to be canal boncs bearing rostral portions 

of the infraorbital canal, and we doubt that 

this shape character is actually sufficiently similar in 

Acipenser and †Peipiaosteus to warrant recognition 

as a synapomorphy. 

We scored characters Z1-Z9 as well as we could 

determine (Figure 21), and found that Zhou’s proposed 

tree is two steps longer than the tree we 

would propose for these taxa (CI: 1.00 versus CI: 

0.78). In view of this and our five well investigated 

synapomorphies (characters 14-18 above), we retain 

Acipenseroidei sensu Grande & Bemis (1991). 

Characters of PoIyodontidae 

In this section, we simply list the characters described 

by Grande & Bemis (1991) with minor modifications. 

Figure 17 shows the same branching pattern 

within Polyodontidae as reported by Crande & 

Bemis (1991). The recent description of a new fossil 

polyodontid, † ProtopsephurusLu 1994, raises some 

questions that can only be answered by a side-byside 

analysis of specimens. This discovery pushes 

back to the Mesozoic the presence of polyodontids 

in Asia. Based on current information, however, we 

cannot specify the phylogenetic placement of †Protopsephurus 

relative to the other members of the 

family, and so indicate it as a basal multichotomy 

within Polyodontidae. 

Character19. Many small stellate bones make up lateral 

supports for the paddle 

This character was delined by Grande & Bemis 

(1991, character 15) as a synapomorphy of Polyodontidae. 

These bones may be present in †Protopsephurus 

(Lu 1994), but additional clarification and 

illustration is needed. 

Character 20. Series ofvery elongate dorsal and ventral 

medial rostral bones, with cylindrical cross-sections 

This character was defined by Grande & Beinis 


Findeis (1993) proposed that the cylindrical 

cross sectional shape should also be noted to 

help differentiate these bones from the elongate 

rostral bones present in some sturgeons. Elongate 

rostral bones are present in †Protopsephurus (Lu 

1994). 

Character 21. Unique shape of subopercle 



The anterior arm of the subopercle, although 

more elongate in Polyodontidae than in any

54 

other Acipenseriformes, is present in all Acipenseriformes 

(character 8, above), but the fan of rodlike 

ossifications in combination with it are unique 

to Polyodontidae. This feature is not well understood 

in †Protopsephurus (Lu 1994). 

Character 22. Elongate anterior and posterior divisions 

of the fenestra longitudinalis in the skull roof 



This feature is not well understood in 

†Protopsephurus (Lu 1994). 

Character 23. Posttemporal with elongate anterio r 

arm suturing into the dermosphenotic 



It appears to be present in †Protopsephurus 

(Lu 1994). 

Character 24. Single branchiostegal with branched 

posterior edge 


(1991, character 20) as a synapomorphy of Polyodontidae 

(also see Nielsen 1949, p. 302). Lu (1994) 

noted that several branchiostegals occur in † Protopsephurus. 

It is important to confirm this in additional 

specimens, because if true, then it would help 

to place †Protopsephurus within Polyodontidae. 

Putative and problematic characters of Polyodontidae 

Findeis (1993) noted that in Psephurus and Polyodon, 

the incurrent arid excurrent nares, as well as 

the bulk of the olfractory capsule, lie dorsal to a line 

drawn through the longitudinal axis of the eye. In 

sturgeons, the nares and olfactory capsule lie ventral 

to a line drawn through the eye. It is difficult to 

polarize this character, because of variation within 

outgroup genera such as Polypterus, and impossible 

to score it reliably in fossils. Nevertheless, the dorsal 

location of the olfactory system in paddlefishes 

may be synapomorphic for Polyodontidae. 

In living and fossil paddlefishes, the supracleithrum 

attaches by ligaments to the cleithrum, unlike 

the condition in living sturgeons and †Chondrosteus, 

which have an immobile sutural connection 

between these two bones. Based on our outgroup 

comparisons, the ligamentous attachment is probably 

a synapomorphy of Polyodontidae, although 

we do not yet know the condition in †Peipiaosteus. 

In the pectoral fin skeleton of living polyodontids, 

a single radial caudal to the propterygium articulates 

with the scapulocoracoid (Grande & Bemis 

1991). This differs from the condition in sturgeons, 

and most of our outgroup taxa, which have 

three independent radials articulating with the scapulocoracoid 

(Findeis 1993). This cartilaginous 

character cannot he scored in fossil acipenseriforms 

because it is not preserved. 

Discussion of clade Polyodontidae 

There is little doubt of the monophyly of Polyodontidae. 

With the exception of the new genus †Protopsephurus, 

intergeneric relationships within the 

family are well understood (Grande & Bemis 1991). 

I t seems probable that † Protopsephurus will 

emerge as the sister group of all other Polyodontidae, 

for it appears to share most of the polyodontid 

characters except for the single branchiostegal 

(character 24, above). 

Characters of Acipenseridae 

Characters of Acipenseridae listed here derive 

from Grande & Bemis (1991) and Findeis (1997 this 

volume). Osteological synapomorphies of Acipenseridae 

are listed in Table 6, coded in Table 7, and 

keyed to the cladogram in Figure 17. Figure 17 reports 

the same branching arrangement within Acipenseridae 

proposed by Findeis (1997). 

Character 25. Five scute rows along trunk 

This character of sturgeons was originally mentioned 

Bemis Linnaeus (1758) and has been noted by 

many workers since. Grandc & Bemis (1991, character 

11) and Findeis (1997) regard this as a synapomorphy 

of Acipenseridae. Gardiner & Schaeffer 

(1989), however, suggested that up to six rows of 

scutes may be present in acipenserids, but we are 

unaware of any examples of six scute rows in fossil 

or extant sturgeons.

55 

Character 26. Pectoral fin spine 

The presence of a pectoral fin spine was accepted by 

Grandc & Bemis (1991, character 13) as a synapomorphy 

of Acipenseridae. A redefinition of this 

character was made by Findeis (1997), who found 

that independent fin rays do not actually fuse to 

form the spine (see Jollie 1980) but are instead encased 

in a sheath of dermal bone. 

Character 27. Antorbital bone 

One of the last bones to form in the dermal skull 

roof of all acipeiiserids surveyed is the discrete antorbital 

bone lying on tlie postnasal wall between 

the orbit and olfactory bulb (Findeis 1997). It is absent 

in polyodontids, †Chondrosteus and †Peipiaosteus. 

This bone does not carry any portion of the 

supraorbital lateral line canal, and so is not homologous 

to the nasal bone in our actinopterygian outgroups. 

Character 28. Commissure of occipital canals in 

median extrascupular bone 

In all acipenserids, the median extrascapular bone 

is present and prominent in the posterior part of the 

skull roof because it bears the commissure of the 

occipital canals. The bone develops late in ontogeny, 

but unlike the surrounding anamestic bones, has 

an unusually constant shape (triangular) throughout 

Acipenseridae (Findeis 1997). No other acipenseriforms 

possess a median triangular bone in this 

region of the skull (see Grande & Bemis 1991 on the 

nuchal bone of †Paleopsephurus, which does not 

carry lateral line canals). This character is defined 

by Findeis (1997 this volume). 

Character 29. Rostral canals curve lateral to barbels 

The sensory canals extending into the rostrum of 

paddlefishes and sturgeons are continuous with the 

infraorbital canal. In sturgeons, the canals curve laterally 

around the outer pair of barbels, and then 

converge toward the ventral midline of the rostrum. 

In paddlefishes, the canal leading into the rostrum 

is straight. No other acipenseriforms or outgroup 

taxa surveyed exhibit the laterally curved condition. 

This character is defined by Findeis (1997). 

Character 30. Supracleithrum tightly joined to dermal 

skull roof 

An elongate dorsal process of the supracleithrum is 

tightly bound by connective tissue to the inner surlace 

of the posttemporal bone. This strong connection 

of the pectoral girdle to the skull roof is unique 

to acipenserids among acipenseriforms and basal 

actinopterygians generally. This character is defined 

by Findeis (1997 this volume). 

Character 31. Opercular wall formed by cleithrum 

and clavicle 

In all sturgeons, a vertical wall of bone defines the 

posterior wall of the opercular chamber. The opercular 

wall is composed of thin medial laminae of the 

cleithrum and clavicle. It is unique to acipenserids 

among all taxa surveyed. Also see Findeis (1997). 

Charcter 32. Cardiac shield formed by clavicle 

The cardiac shield is formed by laminar extensions 

of the clavicle, which cxtcnd toward the ventral 

midline to form a dermal ‘shield’ overlying the pericardial 

cavity. No other actinopterygians surveyed 

possess this feature. It is illustrated by Findeis 

(1997). 

Character 33. Cleithral process limits mobility of 

pectoral fin spine 

A process of the cleithrum extciids laterally to 

brace the fin spine. It is present in all acipenserids, 

but absent in all other taxa surveyed. It is probably 

part of a character complex including the presence 

of the fin spine (character 26, above). See Findeis 

(1997) for illustration and further discussion. 

Putative and problematic characters of Acipenseridae 

Synapomorphies of Acipenseridae derive principally 

from the skull roof, the pectoral girdle, and 

dermal ossifications such as scutes. Many other 

characters which could be included at this level of 

analysis are cartilaginous. and thus difficult or impossible 

to score in fossils. They are, however, helpful 

in studying relationships among recent Acipenseridae 

(Findeis 1997). 

We noted the reduction in the number of branchiostegals 

as a character of Acipenseroidei (char-

56 

Figure 22. Functional morphology of jaw projection in a juvenile white sturgeon, Acipenser transmontanus. In the photograph, an individual 

is shown with the jaws near maximum projection and gape. The bottom four line drawings traced from high speed film, show 

kinematics of jaw projection and the skeletal elements involved in jaw projection (based on ‘dimpling’ of the overlying skin and manipulated 

incleared and double stained specimens). Jaw projection can be very rapid, and it involves at least three discrete stages: projection 

itself (40msecs); adduction of the jaws (60msecs); and recovery of the jaws to the resting position (140 msecs and beyond). Also note that 

opercular abduction occurs during the jaw recovery phase (arrows). h = hyomandibula; ih=interhyal; Ij = lower jaw; s = subopercle; uj = upper 

jaw.

Figure 23. Functional morphology of feeding in North American paddlefish, Polyodon spathula. The top photograph shows a juvenile too 

small to filter feed; at this size, the gill rakers are not yet developed and reeding is raptorial. Such individuals can eat surprisingly large food 

items relative to their size including other juvenile paddlefishes (Yeager & Wallus 1982). The bottom figures show a filter feeding juvenile 

with the jaws closed (left column) and open (right column). The bright white objects in the photographs are individual Daphnia; one can 

be seen directly in front of the open mouth in the upper right photograph. The tracings of the photographs show in dotted outlines the 

positions of the major visible bony elements. Note that unlike the Chinese paddlefish Psephurus (shown in Fig. 7), the upper jaw of 

Polyodon is fixed at its anterior contact with the neurocranium. This fixed condition is clearly derived within Polyodontidae (see Grande 

& Bemis 1991) (bb = basibranchial series, cb = ceratobranchial; see Figure 7 for other abbreviations). 

57

58 

acter 15). One to three branchiostegals are present 

in Acipenseridae. whereas there is consistently a 

single branchiostegal in Polyodontidae (with the 

possible exception of † Protopsephurus; see Lu 

1994). 

Findeis (1993) noted that the jugal bone has a 

prominent anterior process that extends beneath 

the orbit to contact the rostrum. uniting the dermal 

sk ull with the rostrum . Alt hough li ving paddlefish - 

es and outgroup actinopterygians lack this anterior 

process of the jugal, it is impossible to score it in 

†Chondrosteus and † Peipiaosteus based on currently 

available descriptions. 

In all living sturgeons. the postero-dorsal margin 

of the operculum is emarginate. This allows a respiratory 

current of water to flow into the dorsal portion 

of the opercular chamber. over the gills. and 

then exit the opercular chamber ventrally (Burggren 

1978). This character complex includes specializations 

in the shapes of the gill arches and filaments 

(Findeis 1989). Living paddlefishes lack the 

special respiratory water-flow and the associated 

branchial specializations. but. depending on how it 

is defined, paddlefishes can be considered to have a 

dorsally emarginate operculum. Moreover, few of 

the features comprising this system can be scored 

reliably in fossils because they arc soft tissues. Thus 

we consider that the opercular water flow system is 

probably synapomorphic for sturgeons. but cannot 

assess this with certainty. 

Supraneurals are absent in the caudal peduncle 

of sturgeons (Findeis 1993). In contrast. polyodontids 

and † Chondrosteus have a complete row of supraneurals 

in this region of the axial skeleton 

(Grande & Bemis 1991). The condition in † Peipiaosteus 

is unclear, and in outgroup taxa such as 

Polypterus and † Mimia, it is variable. so we defer 

analysis of this character until it is better understood. 

Cartilaginous components of the pectoral girdle 

may provide characters useful for understanding 

relationships within Acipenseridae. but these features 

cannot be scored in † Peipiaosteus and † Chondrosteus 

based on available descriptions. For example, 

a coracoid shelf. formed by the flattening of the 

coracoid wall of the scapulocoracoid along the cardiac 

shield. is probably synapomorphic for Acipenscridae 

because its presence is correlated with that 

of the cardiac shield (character 32; Findeis 1997 uses 

aspects of this character in intrafamilial phylogenetic 

analysis of Acipenseridae). Similarly. the supracleithral 

cartilage on the ventral surface of the 

supracleithrum appears to be unique to acipenserids. 

A feature unique to Acipenseridae among living 

basal actinopterygians is a basipterygial process extending 

ventrally from the antero-ventral edge of 

the basipterygium. Unfortunately. because the process 

is cartilaginous. the condition is unknown in 

†Chondrosieus and † Peipiaosteus. 

Among living actinoplerygians, sturgeons 

uniquely possess a palatal complex composed of 

several plates of cartilage (Findeis 1997). This probably 

plays an important role in feeding because it 

forms one of the two opposing surfaces used in 

crushing food (Findeis 1993). Unfortunately, this 

cartilaginous feature cannot be studied in † Peipiaosteus 

and † Chondrosieus. 

For the present analysis, we also disregard several 

interesting cartilaginous features of the hyoid 

arch and branchial skeleton described by Findeis 

(1997). 

Discussion of clade Acipenseridae 

Many characters confirm that this clade is monophyletic. 

Additional characters relevant to recovering 

a generic-level phylogeny of living Acipenseridae 

are given by Findeis (1997). 

Evolutionary questions and scenarios 

Sonic interesting aspects of acipenseriform evolution 

concern the distribution of functional characters 

such as feeding systems or reproductive features. 

These features cannot be confirmed in fossils 

and have incongruent distributions among living 

Osteichthyes. We also are intrigued by the current 

biogeographic distribution of paddlefishes and 

shovelnosed sturgeons. as well as such issues as the 

origin of the rostrum and its extreme hypertrophy 

in Polyodontidae. In each of the five cases we discuss, 

the cladogram presented in Figure 17 serves to 

organize our discussion.

59 

Feeding systems, jaw protrusion and ram ventilation 

The feeding system derived for all Acipenseriformes 

is based on a jaw projection system very different 

from that of late Paleozoic and early Mesozoic 

paleonisciforms. As exemplified by outgroup 

taxa such as †Cheirolepis, †Mimia, Polypterus and 

Lepisosteus, the premaxilla and maxilla were primitively 

sutured into the bones of the cheek, so that 

forward projection of the jaws was impossible 

(Schaeffer & Roscn 1961). Although the maxilla is 

not sutured to the cheek in bowfins, jaw protrusion 

in Amia calva is still very limited (Lauder 1980). 

Head lift is also an essential aspect of jaw opening 

and feeding in outgroup actinopterygians (Lauder 

1980) and sarcopterygians (Bemis & Lauder 1986, 

Bemis 1987a). The importance of head lift and limitations 

to jaw protrusion are most parsimoniously 

interpreted as plesiomorphic conditions in Actinopterygii. 

Living sturgeons and primitive paddlefishes (i.e., 

polyodontids other than Polyodon) stand in sharp 

contrast to all of these outgroup taxa. Their jaws are 

highly mobile, so that the upper jaw can be ‘projected’ 

far out to capture prey, and head lift plays no 

role in feeding at all. This is illustrated in the case of 

a white sturgeon, Acipenser transmontanus, in Figure 

22. Within acipenserids, progressive modifications 

of the jaw projection system allow even 

greater specialization on benthic prey (Findeis 

1997). Psephurus gladius can also project its jaws, as 

shown in Figure 7 (also see Grande & Bemis 1991, 

figures 28C and 33B). This ability allows sturgeons 

and Psephurus dietary variety, including both fast 

moving (fish) and benthic (mollusk and other invertebrate) 

prey. Interestingly, within Polyodontidae, 

Polyodon exhibits secondary reduction in mobility 

of its uppcr jaw, a specialization associated with filter 

feeding in this genus. In the top of Figure 23, a 

young juvenile Polyodon is shown; at this size, it is 

incapable of filter feeding both because of hydrodynamic 

considerations and becausc its gill rakers are 

not yet long enough to function as a filtering mechanism 

(Rosen & Hales 1981). Note that the upperjaw 

is firmly attached to the head. In the bottom four 

photographs of Figure 23, the maximum extent of 

mouth opening during filter feeding is shown. 

Again, the upper jaw remains firmly attached to the 

neurocranium. A photograph of filled gill rakers is 

shown in Figure 9b. Thus, sturgeons and Polyodon 

specialize the feeding apparatus in different directions, 

one primarily towards benthic prey and the 

other toward pelagic prey (see Yakovlev 1977, for 

much the same idea). 

Another functional anatomical aspect is the protractor 

hyomandibularis muscle, which is not preserved 

in fossils, but which is probably a synapomorphy 

of all Acipenseriformes. In Acipenser, this 

muscle develops as a slip of mandibular arch musculature 

which migrates to its new attachment sites on 

the neurocranium and hyomandibula (Sewertzoff 

1928). The protractor hyomandibularis muscle is 

large in all acipenseriforms (e.g., Danforth 1913, 

Luther 1913). It plays an important role in protruding 

the jaw, and, via a simple mechanical linkage, 

also facilitates the opening of the jaws. Amongst all 

vertebrates, it is very unusual for a mandibular arch 

muscle to function in jaw opening (Bemis 1987b). 

Many unresolved issues concern the morphological 

transformation from a typical paleonisciform 

feeding system to the acipenseriform system. The 

seeming absence of clearly intermediate morphotypes 

and questions about the functional adequacy 

of such an intermediate form has provoked several 

speculations, perhaps most comprehensively by Yakovlev 

(1977), Yakovlev (1977) interpreted that the 

transformation in jaw morphology and function 

must have occurred very rapidly, and that it probably 

took place in the Triassic in northern Asia. Yakovlev 

(1977) further suggested that transformation 

of the feeding system was initially driven by paedomorphosis, 

and that subsequent stabilization of the 

new morphology occurred because it offered a 

feeding specialization unique among early Mesozoic 

fishes -- benthophagy. 

Our approach to studying such transformations is 

different: instead of focusing on the absence of morphotypes, 

or any other type of negative data, we 

stress the importance of producing a phylogenetic 

hypothesis or cladogram on which to map and construct 

putative functional systems. By turning our 

focus away from ancestor speculation to the comparative 

analysis of outgroups, we think headway 

will be made in understanding many aspects of cra-

60 

Figure 24. Direct evidence for paedomorphosis in the neurocranium of Acipenser brevirostrum. In a few cases we can directly observe 

post-reproductive changes in morphology. such as the neurocranium of this large shortnose sturgeon, which exhibits four ossification 

centers within the neurocranium. Only the very largest (=oldest) individuals exhibit these bones. These neurocranial ossifications serve 

no obvious function, and they are highly variable from one individual to the nest These four neurocranial bones are readily homologized 

to those of other basal osteichthyans. and we regard their variable presence as direct evidence of paedomorphosis. fII =foramen for optic 

nerve; fIII=foramen for oculomotor nerve; fIV=foramen for trochlear nerve; fX = foramen for vagal nerve; fsp = foramen for spinal 

nerve; tfc=trigeminofacialis chamber. Total length of specimen: 870 mm. UMA 24-116-2-47. 

nial specialization in acipenseriforms. Related issues 

we consider essential are fresh re-examinations 

of traditional homologies using extensive developmental 

material. This may provide alternative 

interpretation for certain structures, such as Findeis’ 

(1991) conclusion that the so-called maxilla of 

Acipenseriformes is actually a dermopalatine (see 

discussion of character 11 above). This reinterpretation 

is pivotal to understanding the loss of many 

bones from the cheek region of Acipenseriformes. 

Ram ventilation and the origin of filter feeding 

A characteristic observation about Polyodon spathula 

in aquaria or rearing ponds is that they never stop 

swimming, and if confined in a container too small to 

allow swimming, then they sink to the bottom. Sinking 

occurs because the volume of air in the swim 

bladder is not sufficient to achieve neutral buoyancy. 

Constant swimming by paddlefishes also generates a 

constant flow of water over the gills which allows for 

ram ventilation. Polyodon depends on ram ventilation, 

as evidenced by the absence of a buccal valve 

and the inability to completely close either the opercular 

chamber or the mouth. As further evidence of 

the critical role of ram ventilation, Burggren & Bemis 

(1992) found that juvenile paddlefishes are nearly 

as aerobic as cruising bluefin tuna, Thunnus thunnus. 

Speculating on the connection between ram 

ventilation and the evolution of filter feeding within 

Polyodontidae, they linked the potential to evolve 

filter feeding to the prior evolution of ram ventilation. 

According to this reasoning, many of the specializations 

associated with filter feeding in Polyodon 

(flattened gill arches, elongate gill rakers, and 

secondary fixation of the upper jaw to the neurocranium) 

were possible only because buccal-opercular 

pumping and branchial arch mediated respiratory 

movements were unnecessary. 

Unlike Polyodon, sturgeons such as Acipenser 

and Scaphirhynchus can buccal pump to generate 

respiratory flow (e.g., Burggren 1978), which allows 

them to be more sedentary than paddlefishes. What 

is missing, however, are basic data on the possible 

coupling of respiration with locomotion in Huso 

and Psephurus, which our current phylogenetic 

analysis indicates as critical for understanding the

61 

evolution of respiration in Acipenseroidei. Living 

stem actinopterygians and sarcopterygians are not 

likely to help in a broader analysis of the evolution 

of ram ventilation because none of them exhibits 

constant, sustained swimming. 

Potamodromy, anadromy and demersal spawning 

All living species of sturgeons and paddlefishes migrate 

upstream to spawning sites, and many species 

of Acipenseridae are anadromous. Spawning runs of 

some species of sturgeons are legendary, exceeding 

2500 km for Huso huso in the Danube and Volga basins 

(Balon 1967, &Hensel Holcík 1997 this volume, 

∨ 

Khodorevskaya et al. 1997 this volume). Typically. 

living acipenseriforms spawn very large numbers of 

eggs onto shallow, gravely sites (e.g., Ryder 1888, 

Disler1949,Soin1951,Dragomirov1953,1957,Buckley 

& Kynard 1985). Adults depart the site soon after 

egg deposition, and do not provide any parental care. 

The phylogenetic distribution of spawning modes 

in the other living lion-teleostean actinopteryg ians 

offers little information about the evolution of these 

reproductive features (see Balon 1975, 1985). None 

Of the other living species of non-teleostean actinopterygians 

typically inhabits salt water, and none exhibits 

such extensive upstream spawning migrations 

(for general review, see Breder & Rosen 1966). 

Spawning Polypterus deposit small numbers of individual 

eggs on leaves, rocks or other substrates. At 

least some species of Lepisosteus migrate upstream 

to spawn, but spawn far fewer eggs than do sturgeons 

and paddlefishes and typically deposit them on 

structures in the water, such as Ieaves. Amia spawn 

in nests defended by the male (Ballard 1986). 

Extant stem sarcopterygians are similarly uninformative 

on the question: coelacanths are combined 

livebearers (Wourms et al. 1991, Balon 1985, 

1990, 1991), and lungfishes either spawn individual 

eggs onto aquatic vcgctation (as in Neoceratodus, 

Kemp 1987) or the males guard the eggs in a nest (as 

in Protopterus and Lepidosiren, Greenwood 1987, 

Kerr 1919). 

Evidence for anadromy or spawning migrations 

in fossil Acipenseriformes or outgroups is obviously 

uncertain, but this has not prevented speculation. 

Figure 25, Method for analyzing ‘less direct’ evidence of paedomorphosis. 

The cladogram for taxa U through Z is based on character 

information other than the development characters 

shown. Development is studied in taxa U through Z. It is found 

that state’a’ always gives rise to state ’b’ during ontogeny and that 

in most clades, state ’b’ goes on to form state ‘c’. This information 

is then ‘laid out’ on the cladogram; in taxa X and Z, devevplment 

has been truncated at state ‘b’, providing indirect evidence that 

paedomorphosis has occurred. Modified from Bemis (1984). 

Zhou (1992) suggested that †Peipiaosteus may have 

been anadromous based on the geographic distribution 

of fossils. Nielsen (1949) noted that specimens 

of †Birgeria greonlandica occurred in small 

and large sizes only, and regarded the absence of 

intermediate sizes as evidence of migration. Yakovlev 

(1977) also speculated on the evolution of reproductive 

mode in acipenseriforms. At present, however, 

we cannot provide a compelling explanation 

for the evolution of characteristic spawning patterns 

of Acipenseriformes. 

Paedomorphosis 

Paedomorphosis has long been invoked in explaining 

many anatomical features of living Acipenseriformes, 

chiefly the largely cartilaginous endoskele-

62 

ton (Traquair 1887, Woodward 1891, I895a,b,c). 

Many workers equated these changes with ‘degeneracy’ 

of the skeleton (Goodrich 1909), which is 

merely another way of emphasizing that this is a 

secondary condition. Some workers speculate that 

paedomorphosis was the driving force behind many 

changes in acipenseriform anatomy. Paraphrasing 

Yakovlev (1977, p. 141), paedomorphosis (‘fetalization’) 

played a decisive role in destroying the archaic 

structure of the paleonisciform type of jaw, a 

critical step leading to formation of the acipenseriform 

jaw (see also Tsessarsky 1992). 

is because without a cladogram to specify the arrangement 

of taxa, it is not possible to organize the 

developmental data within a phylogenetic context. 

Moreover, the analysis shown in Figure 17 confirms 

that many of the most relevant outgroups are fossil 

taxa, which are unlikely to provide the necessary 

developmental information for a formal analysis. 

Finally, we note that only recently have ontogenetic 

data become available for the skeleton in taxa such 

as Polypterus (e.g., Bartsch & Gemballa 1992) 

which are necessary for any study of paedomorphosis 

in Acipenseriformes. 

Paedomorphosis is of both theoretical and practical 

interest in systematics (Nelson & Platnick 1981, 

Fink 1982), and many groups of fishes. such as lung- Pacific biogeography of Polyodontidae and Scafishes 

(Dipnoi), provide clear examples of paedo- phirhynchinae 

morphic loss of skeletal elements and degree of ossification 

(Bemis 1984). There are only two types of An interesting aspect of acipenseriform biology 

evidence available to support hypotheses of paedo- concerns links between Asian and North American 

morphic change. The first is ‘relatively direct evi- freshwater taxa (Grande & Bemis 1991). Yakovlev 

dence’, such as that provided by Grande & Bemis (1977) asserted that Acipenseriformes originated in 

(1991) for paddlefishes. Large adult paddlefishes freshwaters of northeastern Asia in the Triassic and 

continue to ossify new endochondral bones after subsequently dispersed throughout the Holarctic. 

onset of reproductive maturity. We note here that His interpretation is based on the occurrence of taxa 

this phenomenon also occurs in sturgeons, such as a such as †Stichopterus in the Jurassic of Northeastern 

series of adult Acipenser brevirostrum that demon- Asia. A problem with his interpretation is that the 

strates progressive ossification of at least four neu- location of the earliest fossils is not a reliable clue to 

rocranial bones (Figure 24). Additional observa- identifying a place of origin for a group (Grande 

tions of large A. breviostrum confirm delayed ossi- 1985). Also, Yakovlev (1977) did not consider sister 

fication of several hyobranchial elements. ‘Less di- group relationships of Acipenseriformes (see Bemis 

rect evidence’, such as that provided for dipnoans & Kynard 1997 lor such analysis, which suggests Euby 

Bemis (1984) derives from a combination of phy- rope as the place of origin for the group). 

logenetic analysis and developmental data from A basic question about the biogeography of Aciother 

taxa. For example, if the ontogeny of a struc- penseriformes is to explain the presence in North 

ture is studied in an outgroup and found to proceed America of †Crossopholis, Polyodon, †Protoscafrom 

state A to state B to state C during develop- phirhynchus, and Scaphirhynchus, which have 

ment, whereas the ontogeny of the same structure Asian sister taxa, † Protosephurus, Psephurus and 

in the ingroup always stops at state B, then pacdo- Pseudoscaphirhynchus. Patterson (1981) clearly 

morphosis can be hypothesized to have occurred outlined the criteria for analyzing the biogeography 

(Figure 25). Thus, recognition of paedomorphosis of primary freshwater fishes. His central point is the 

by less direct means relies solely on the relative con- need to resolve three taxon statements for endemic 

gruence (or lack thereof) of developmental pat- taxa to identify vicariant distributions. Our phyloterns 

within a phylogenetic framework. 

genetic analyses allow some progress on this both 

Apart from the direct evidence of paedomorpho- for Polyodontidae and Scaphirhynchini, although 

sis presented by Grande & Bemis (1991), no study to the placement of the two taxa of greatest interest 

date has provided adequate analysis of the role of (†Protopsephurus and †Protopsephurus) 

paedomorphosis in acipenseriform evolution. This needs additional study.

As noted above, recent and fossil paddlefishes 

are restricted to freshwater. Although we cannot 

conclude this with certainty, †Protopsephurus appears 

to be the sister taxon of all other paddlefishes 

(see discussion of clade Polyodontidae above). If 

we add †Protopsephurus to our earlier analysis 

(Grande & Bemis 1991), and still assume strict vicariance, 

then we conclude that North America and 

China shared a link at least as early as the Upper 

Jurassic. This trans-Pacific affinity is intriguing because 

many taxa of fishes from the western United 

States share trans-Pacific ties (Grande 1985,1994). 

Similar conclusions were reached by Jin (1995) in an 

article received after this manuscript was accepted; 

see Grande & Bemis (1996) for discussion of Jin 

(1995). 

We regard †Protoscaphirhynchus as a member of 

tribe Scaphirhynchini, and note that no characters 

clearly distinguish it from Scaphirhynchus. All recent 

members of the tribe Scaphirhynchini are confined 

to large rivers, and generally prefer a strong 

current and soft, silty bottoms. Thus their known 

distribution is more likely to have resulted from vicariance 

rather than trans-oceanic dispersal. In this 

case, the trans-Pacific link between central Asia and 

North America east of the Rocky Mountains must 

be at least as early as the late Cretaceous because of 

the presence of †Protoscaphirhynchus in eastern 

Montana. We predict that scaphirhynchine fossils 

will eventually be recovered from late Mesozoic deposits 

of eastern Asia. 

gans than any other groups, with estimates of 70000 

organs in an adult Polyodon (Nachtrieb 1912). The 

chief location of these organs is the rostrum, where 

the organs are surrounded by stellate bones in the 

case of paddlefishes or contained in pockets between 

the rostral bones of sturgeons. Although different 

workers use different terminologies (e.g., 

Norris 1925, Nikolskaya 1983), the ampullary organs 

of Polyodon are distributed on the paddle, 

cheek, and opercular flap in a characteristic way 

that is constant from individual to individual (Bemis 

& Northcutt personal observation). Ampullary 

organs of Polyodon increase in number throughout 

life by subdivision of existing organs. There is one 

important unanswered question concerning Polyodon: 

does it use electroreception to detect swarms 

of zooplankton, and if so, how? This will be a challenging 

behavior to study, for it is difficult to measure 

or to mimic the electrical field of a plankton 

swarm, and it is probably impossible to completely 

denervate electroreceptive input (see Kalmijn 1974 

for discussion of plankton and electroreception). 

Interesting differences in two other sensory systems 

of sturgeons and paddlefishes say much about 

their different sensory worlds. First, polyodontids 

have two small barbels on the ventral surface of the 

rostrum in contrast to the four, large, often fimbriated 

barbels on the rostrum of acipenserids. In both 

families, the surfaces of the barbels are covered 

with chemoreceptive organs (taste buds), although 

sturgeons have many more chemoreceptive organs 

on their barbels than do paddlefishes. This may be 

linked to the evolution of benthic habits in Acipen- 

Electroreception as the dominant sensory system of seridae in contrast to the mid-water habits of padpaddlefishes 

dlefish. The second basic difference in the sensory 

systems of paddlefishes and sturgeons concerns the 

Chondrichthyans, sarcopterygians, amphibians, relative sizes of their eyes. Paddlefishes have absoand 

non-neopterygian actinopterygians share a lutely smaller eyes than do comparably sized sturcommon 

organ system for electroreception (groups geons. The behavioral meaning of this has never 

enclosed by dotted outline in Figure 3). The sense been rigorously evaluated, but it suggests that viorgans 

of this system are known variously as ampul- sual information may be less important for adult 

lae of Lorenzini (chondrichthyans), rostral organ paddlefishes than for sturgeons. The relative de- 

(coelacanths), or ampullary organs (aquatic am- emphasis on chemosensory and visual systems in 

phibians, lungfishes, polypterids, sturgeons and paddlefishes is possibly countered by their extraorpaddlefishes; 

see Jorgenson et al. 1972 and North- dinarily high number of ampullary organs. These 

cutt 1986 for review). Among all of these taxa, pad- ideas might be tested by comparing the size of tardlefishes 

have many more individual ampullary or- get areas in the brain for each sensory system (e.g., 

63

64 

Northcutt 1978, New &Bodznick 1985) or by a combination 

of physiological and behavioral approach- 

Genus †Chondrosreus Agassiz 1844 

Family †Chondrosteidae Egerton 1858 

Genus †Gyrosteus Agassiz 1844 

es. 

Suborder Acipenseroidei sensu Grande & Bemis 1991 

As in all of the groups enclosed by dotted outline 

Family Polyodontidae Bonaparte 1838 

in Figure 3, the ampullary organs of Acipenseriformes 

are restricted to the head. There are two 

Genus †Protopsephurus Lu 1994 

incertae sedis 

types of exceptions which prove this rule. First, in 

Subfamily †Paleopsephurinae Grande & Bemis 1991 

Tribe †Paleopsephurini Grande & Bemis 1991 

some taxa, such as skates of the genus Raja, very 

Genus †Paleopsephurus MacAlpin 1941a 

long ampullary organs radiate onto the broad pectoral 

fins from sensory capsules located on the head 

Tribe Psephurini Grande & Bemis 1991 

Subfamily Polyodontinae sensu Grande & Bemis 1991 

(Raschi 1986). In this case, the ampullary organ 

Genus Psephurus Günther 1873 

tube has been lengthened so that the organ may be 

Tribe Polyodontini sensu Grande & Bemis 1991 

Genus †Crossopholis Cope 1883 

sampling a different environment, but the sensory 

Genus Polyodon Cope 1883 

epithelium is still based in the head region. Second, 

Family Acipenseridae Linnaeus 1758 

in taxa such as the Australian lungfish, Neoceratodus 

forsteri, the presence of ampullary organs on 

Genus Huso Brandt 1869 

Subfamily Husinae sensu Findeis 1993 

the trunk is linked to a recurrent branch of the anterior 

lateral line nerve (Northcutt 1986). The func- 

Subfamily Acipenserinae sensu Findeis 1993 

Tribe Acipenserini sensu Findeis 1993 

Genus Acipenser Linnaeus 1758 

tional significance of locating the sampling portion 

Tribe Scaphirhychini Bonaparte 1846 

of an electroreceptor caudal to head in each of the 

Genus Scaphirhynchus Heckel 1836 

two cases (taxa) is untested, but perhaps it allows 

Genus Pseudoscaphirhynchus Nikolskii 1900 

better localization of point electrical fields by triangulation 

(Kalmijn 1974). If this idea is correct, then 

Genus †Protoscaphirhynchus Wilimovsky 1956 

it may help explain the unusual body shape of 

paddlefishes. We propose that the long rostrum and Conclusions 

trailing opercular tip of paddlefishes reflect extreme 

specialization for electroreception. In a We have four basic conclusions: 

juvenile paddlefish, the rostrum and operculum together 

extend for more than one half the body need of additional testing. A more detailed analysis 

(1) The phylogeny for Acipenseridae is still in 

length, so that the long trailing tip of the operculum of acipenserid phylogeny is needed for planning for 

functionally places electroreceptors far more taudal 

than might otherwise be possible given that ing their evolutionary history and biogeography. 

the conservation of sturgeons and for understand- 

electroreceptors are plesiomorphically restricted to Therefore, it is very important to conduct broad, 

the head. We think too little attention has been paid comparative morphological developmental and 

to the dominance of this sensory system in Polyo- molecular studies of the species of Acipenseridae. 

dontidae. 

Ideally, a future comparative morphological investigation 

should emphasize completeness by including 

all well-preserved fossil and extant species of 

Nomenclatural recommendations 

Acipenseridae. Fossil taxa are, in most cases, known 

only from the type descriptions and a number of 

Our current classification of the genera of Acipenseriformes follows: 

Order AcipenseriformesBerg 1940 

incertae sedis 

Family †PeipiaosteidaeLiu & Zhou 1965 

Genus †Stichopterus Reis 1910 

Genus †Peipiaosteus Liu & Zhou 1965 

Suborder †chondrosteoidei sensu Grande & Bemis 1991 

newly discovered nearly complete skeletons remain 

undescribed. In addition to reexamining the patterns 

of generic interrelationships proposed by 

Findeis (1997 this volume) and reviewed here, future 

work should specifically target the question: Is 

Acipenser monophyletic? There should be a serious 

effort to examine all existing specimens, particular-

ly type series, held in systematic collections in easternEurope 

and Asia. It will be vital to undertake at 

least some new field work to collect the specimens 

needed for comprehensive study, but because of 

current threats to many species of Acipenseriformes, 

any sampling must be done in such a way 

that it does not furtherthreaten already diminished 

populations. The effort to better understand acipenserid 

biodiversity should not be postponed for 

even a short period, or we may not know in time 

which taxa are in most need of conservation. 

(2) Our information about living and fossil Polyodontidae 

is more completethan for any other clade 

within Acipenseriformes. Still, there is much to do, 

including incorporation of the newly described 

†Protopsephurus into a phylogenetic framework, 

and attention to the functionalmorphology of feeding 

and, in particular, electroreception. Especially 

needed are new anatomical studies of Psephurus, 

including its development. 

(3) Future paleontological work On fossil Acipenseriformes 

should focus on redescription and 

analysis of †Chondrosteidae and †Peipiaosteidae. 

In particular, it is important to resolve whether 

†Peipiaosteus and †Stichopterus are congeneric as 

suggested by Yakovlev (1977). Our currently available 

osteological characters for paddlefish and sturgeons 

will also need to be reassessed as more com- 

plete and detailed descriptions of †Chondrosteidae 381–433. 

and †Peipiaosteidae become available. Finally, it 

will also be important to restudy Mesozoic and Paleozoic 

actinopterygians, particularly †Birgeria, 

†Saurichthys, and †Phanerorhynchus, to better assess 

the sister group of Acipenseriformes. 

(4) In any future studies of acipenseriform sys- 

tematics it is vital to include a control for Ontogenetic 

and individual variation. As noted above, the 

documented variations in morphology, including 

post-reproductive changes in ossification patterns, 

mean that growth series of individuals need to be 

studied. 


We thank Vadim Birstein, John Waldman, Robert 

Boyle, and the Hudson River Foundation for orga- 

65 

nizing the International Conference on Sturgeon 

Biodiversity and Conservation. Penny Jaques, Nancy 

Ruddock and Judy Shardo helped in manuscript 

and figure preparation. Vadim Birstein provided 

advice and translation help for Russian papers. 

Wen Jun Li and Dan Hui assisted with Chinese papers. 

John Waldman, Vadim Birstein and two anonymous 

reviewers improved our manuscript. Our 

work has been supported by grants from NSF (BSR 

8806539 and BSR 9220938), the Whitehall Foundation, 

and the Tontogany Creek Fund. 


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(1996). Thus, Grande & Bemis (1996) provide some additional 

information on phylogenetic interrelationships of acipenseriforms 

(particularly †Chondrosteidae and †Peipiaosteidae) that

a 

b 

Sturgeons of the Danube River and one of their hybrids: a - Acipenser ruthenus 43 cm TL from the Fish Culture Research Institute, 

Szarvas, Hungary; b - a large A. ruthenus 76 cm TL from an old collection at the Grigore Antipa Natural History Museum, Bucharest, 

Romania; c - dorsal view of an early juvenile Huso huso 23 cm TL from Royal Ontario Museum collection; d - aF 2 bester (= beluga × 

sterlet) 69 cm TL, a cross of F 1 A. ruthenus × H. huso from the captive breeding at Propa-Gen International (Aquaculture Production 

R & D and Trading)’, Komadi, Hungary. Originals by Paul Vecsei, 1996.

Environmental Biology of Fishes 48: 73-126,1997. 


Osteology and phylogenetic interrelationships of sturgeons (Acipenseridae) 

Eric K. Findeis 

Department of Biology, University of Massachusetts, Amherst, MA 01003-0027, U.S.A. 

Current address: Department of Biology, Wake Forest University, Winston-Salem, NC 27109, U.S.A. 


Key words: Actinopterygii, cladistics, evolutionary morphology, benthic fishes, peramorphosis, Huso, Acipenser, 

Pseudoscaphirhynchus, Scaphirhynchus 

Synopsis 

Sturgeons (Acipenseridae) are an ancient and unique assemblage of fishes historically important to discussions 

of actinopterygian evolution. Despite their basal position within Actinopterygii, rigorous comparative 

morphological studies of acipenserids have never been made, and most ideas about acipenserid evolution 

hinge on an untested impression that shovelnose sturgeons (Scaphirhynchini) are phylogenetically primitive. 

This impression promoted ideas that: (1) the earliest acipenserids were highly benthic and evolved secondarily 

into pelagic predators, and (2) paedomorphosis has dominated mechanisms affecting their morphological 

change. Using cladistic methods, this study examines generic level interrelationships within Acipenseridae. 

Representatives of the four acipenserid genera Huso, Acipenser, Pseudoscaphirhynchus, and Scaphirhynchus, 

as well as their acipenseriform outgroups Polyodontidae, †Peipiaosteidae, and †Chondrosteidae, were 

surveyed for skeletal characters. Sixty-nine characters are identified and described to support the first generic 

level cladogram of Acipenseridae. Huso is phylogenetically primitive within Acipenseridae and the sister 

group to a redefined subfamily Acipenserinae. Acipenser is not supported by any characters identified in this 

study, but the tribe Scaphirhynchini comprising Scaphirhynchus and Pseudoscaphirhynchus is found to be 

monophyletic. The cladogram contradicts historical ideas about acipenserid evolution because Huso defines 

an outgroup morphology and life history founded on pelagic habitats and piscivory. In contrast, acipenserines, 

and more markedly scaphirhynchines, are benthic predators possessing character complexes for benthic feeding, 

respiration, locomotion, and protection. Also, the pattern of character acquisition within Acipenseridae 

suggests that peramorphosis played a central role in acipenserid evolution. Peramorphic addition and enlargement 

of the skeleton and scalation defines most characters at all nodes within Acipenseridae, and repudiates 

paedomorphosis as a major trend in evolution within the family Acipenseridae. 

Introduction 

(†Chondrosteus Egerton, 1858). Acipenserids are 

distinctive in morphology and behavior, with nu- 

The family Acipenseridae includes 25 species in merous features such as armoring trunk scutes, a 

four currently recognized genera in a Holarctic dis- ventral mouth, rostral chemosensory barbels, and a 

tribution. This is an ancient assemblage with recog- flattened body contributing to their benthic habnizable 

acipenserid fossils known from the Upper itats and behaviors. Their commercial importance, 

Cretaceous and fossil relatives extending the origin uniqueness, and almost universal endangered staof 

Acipenseriformes into the Lower Jurassic tus (see Birstein 1993) has promoted a modern

74 

ground swell of interest in sturgeon biology (e.g., 

Binkowski & Doroshov 1985, Williot 1991, Gershanovich 

& Smith 1995), including their systematics 

and evolution (Bemis et al. 1997 this volume). 

A better understanding of acipenserid interrelationships 

is central not only to organizing modern 

studies in sturgeon biology, but to examining evolutionary 

and functional attributes of the lineage. Out 

of only four extant clades of non-teleostean actinopterygians 

(Lauder & Liem 1983), acipenserids 

are the most speciose and have the largest biogeographic 

range. As such, they are pivotal to evolutionary 

studies of Actinopterygii and more precise 

understanding of their morphology and phylogenetic 

position is crucial for cladistic comparison to 

other taxa. Further, given their age and unique adaptations, 

extant acipenseriforms differ markedly 

from other actinopterygians, with distinct, parallel 

evolutionary solutions to the challenges of aquatic 

life faced by all fishes. 

The history of acipenserid systematics is long, 

with major studies from the 19th century addressing 

species and generic recognition (Rafinesque 1820, 

Brandt & Ratzeberg 1833, Fitzinger & Heckel 1836, 

Brandt 1869, Dúmeril 1867, 3870). Unfortunately, 

there has never been a consensus about recognition 

of genera or subgenera with current usage accepting 

the genera Huso, Acipenser, Scaphirhynchus, 

and Pseudoscaphirhynchus. As many as six subgenera 

(or genera) have been proposed to subdivide 

Acipenser, and most attempts subsumed Huso into 

Acipenser (Brandt & Ratzeberg 1833, Fitzinger & 

Heckel 1836, Dúmeril 1870). While Huso is now recognized 

as an independent genus (defined by 

Brandt 1869), its diagnostic characters (Tatarko 

1936, Antoniu-Murgoci 1936a, b) remain untested. 

At a higher level, Huso has remained paired with 

Acipenser-within the subfamily Acipenserinae (sensu 

Bonaparte 1838), and the shovelnose sturgeon 

genera Scaphirhynchyus and Pseudoscaphirhynchus 

are universally accepted individually and composing 

the subfamily Scaphirhynchinae (Scaphirhynchini 

of Bonaparte 1846). However, anatomical 

characters accepted as defining genera or subfamilies 

have never been examined rigorously. 

In this study, I use comparative osteology and cladistics 

to survey for and test skeletal characters relevant 

to acipenserid phylogeny. Previous studies of 

acipenserid systematics focused on external features 

that are significantly variable and pose problems 

for a phylogenetic analysis. The only studies 

emphasizing the skeleton were made by Antoniu- 

Murgoci (1936a, b, 1942), but her analysis only included 

Rumanian species and only examined portions 

of the skeleton. Comparative osteology can 

develop numerous phylogenetic characters and notably 

allows use of fossil taxa as outgroups (e.g., 

Nielsen 1949, Patterson 1973, 1982, Gardiner 1984). 

Cladistic methods focus on defining characters at 

specific phylogenetic nodes to determine interrelationships 

(Hennig 1966, Wiley 1981), but also arrays 

character transformations as focal changes defining 

taxa. This provides insight into evolutionary processes 

underlying phylogeny and allowing evaluation 

of performance and behavior. Cladistics and 

comparative osteology have dramatically increased 

our understanding of actinopterygian evolution, 

but acipenserids have been neglected. Only recently 

have interrelationships within Acipenseriformes 

been convincingly defined (Grande & Bemis 1991, 

Findeis 1993, Bemis et al. 1997) recognizing outgroups 

necessary for a new examination of acipenserid 

characters (Figure I). These studies accept the 

Polyodontidae as the sister group to Acipenseridae 

(together composing the Acipenseroidei), with an 

unresolved trichotomy among the Acipenseroidei, 

†Chondrosteidae, and † Peipiaosteidae with Acipenseriformes 

(but see Grande & Bemis 1996). 

Morphological and systematic studies of acipenserids 

pose certain problems making comprehensive 

phylogenetic studies difficult. Specimens of 

many species are not readily available, so taxonomic 

coverage is difficult. Previous morphological descriptions 

are not detailed (e.g., Marinelli & Strenger 

1973) or comprehensive enough (e.g., Tatarko 

1936, Antoniu-Murgoci 1936a, b, 1942) to support 

cladistic analyses and new descriptions are needed 

(Findeis 1993). Acipenseriforms are largely cartilaginous 

and acipenseriform fossils do not show cartilage 

preservation, leaving incomplete data for 

comparison. Because of these problems, this study 

focuses on generic interrelationships within Acipenseridae. 

Although little definitive phylogenetic work has

75 

Acipenseriformes 

Acipenseroidei 

Figure 1. proposed phylogenetic relationships within Acipenseriformes: Characters defining this cladogram are from Grande & Bemis 

(1991), Findeis (1993), and Bemis et al. (1997 this volume). These characters support a monophyletic Acipenseroidei comprising Acipenseridae 

and Polyodontidae. The Acipenseroidei forms an unresolved trichotomy in Acipenseriformes with the fossil taxa †Peipiaosteidae 

and †Chondrosteidae. For outgroup comparison with Acipenseridae, all (three families are used when possible. Illustrated taxa are 

†Chondrosteus acipenseroides Agassiz 1844, † Peipiaosteus pani Liu & Zou 1965, Psephurus gladius (Martens 1862), and Huso huso 

(Linnaeus 1758). 

been made of the Acipenseridae at any level, two midwater environments. Second, classic ideas 

themes dominate evolutionary studies of the family. about acipenserids focus on paedomorphosis as the 

The first suggests that shovelnose sturgeons (Sca- dominant mechanism in their evolution (Woodphirhynchini) 

represent the primitive condition ward 1889, Goodrich 1909, Gregory 1933). These 

among acipenserids (Schmalhausen 1991, Birstein persisting hypotheses have never been examined 

1993). In this scenario, sturgeons evolved initially as rigorously and the results from this phylogenetic 

benthic predators, with Huso and the more preda- study contradict them. 

ceous species of Acipenser rising subsequently into

76 

Materialsand methods 

Phylogenetic methods 

Interrelationships among genera of Acipenseridae 

were examined using cladistic methods as generally 

espoused by Hennig (1966) and Wiley (1981). Skeletal 

features identified as potentially relevant characters 

for phylogenetic reconstruction were conipared 

with outgroup taxa to: (1) determine which 

subgroups possess or lack the character: and (2) define 

the polarity of change in character states. Polarity 

assessments were made through comparison 

with all genera of Acipenseridae, Polyodontidae 

(personal observations; Grande & Bemis 1991), 

† Chondrosteus (Traquair 1887, Woodward 1889, 

Watson 1925, 1928, Hennig 1925), †Peipiaosteus 

(Liu & Zhou 1965, Bai 1983, Zhou 1992), and multiple 

non-acipenseriform taxa such as † Mimi and 

mens were prepared with dermestid beetles resulting 

in near total loss of cartilage, but leaving intact 

dermal skeletons. Many small specimens were prepared 

by clearing and double staining (Dingerkus 

& Uhler 1977) to examine intact skeletons. Specific 

osteological structures were examined in preserved 

specimens of multiple taxa to confirm or denyputative 

characters identified from skeletons. Developmental 

series mere examined in cleared and double 

stained preparations to clarify structural interpretations 

amidst morphological variation and to interpret 

homology recognition. 

Scaphirhynchus 

Scaphirhynchus platorynchus was accepted as generally 

typical for the genus in this study. Nine newly 

collected adult specimens were hand cleaned and 

† Moythomasia (Gardiner 1984a), † Cheirolepis multiple preserved specimens were examined ex- 

(Pearson & Westoll 1979), † Birgeria (Nielsen 1949), ternally and through dissection. Two large adult 

† Saurichthys (Rieppel 1992), Polypterus, Lepisos- specimens from the Shedd Aquarium (FMNH 

teus, and Amia (personal observations). Characters 98285, 98286) were prepared with dermestid beewere 

accepted only when skeletal features were tles. An extensive developmental series ranging 

consistent within ingroups compared to outgroups from prehatching embryos to small juveniles was 

(for respective polarities). Rather than provide a cleared and double stained with addition of a larger 

matrix with proposed character states, putative syn- juvenile (AMNH 4485) with slightly more adapomorphies 

are defined and directed to specific vanced skeletal development. Scaphirhynchus alphylogenetic 

nodes. Character descriptions pro- bus was examined externally and non-invasively to 

vide information on character morphology of in- confirm skeletal characters of the genus (see Bailey 

groups and outgroups to unambiguously define & Cross 1954, Carlson 1985). No specimens of S. 

apomorphic and plesiomorphic character states. suttkutsi were available for examination, but this 

species is very similar to S. platorynchus (Williams 

& Clemmer 1991). 

Specimens and preparation 

Specimens examined included representatives of Pseudoscaphirhynchus 

all four acipenserid genera. Skeletal characters generally 

focus on bone since most taxa possess ossified Only two specimens of the dwarf morphotype of P. 

endoskeletons (and fossils are predicated on pres- kaufmanni were available for examination of the 

ervation of bone), but cartilage is dominant in the genus in this study. One was cleared and double 

acipenserid endoskeleton. Conventional tech- stained (MCZ 27653) and one was examined externiques 

of skeletal preparation can damage or de- nally with additional description from Ivanzoff 

stroy cartilage, so several techniques were used to (1887) and Sewertzoff (1926a, 1928). This species is 

assess morphology of specimens examined in this accepted as representative for the genus in this 

study. Large, newly collected specimens were hand study, although P hermanni differs markedly from 

cleaned to preserve cartilages. Several adult speci- P. kaufmannni (Berg 1948a) and is assumed to be spe-

cialized. Pseudoscaphirhynchus fedtschenkoi has 

been reported to be morphologically variable (Berg 

1948a) with distinct morphotypes that differ in varying 

degrees compared to P. kaufmanni. 

Acipenser 

I define 69 characters used to analyze interrelation- 

ships of genera within Acipenseridae. All characters 

described and analyzed here are skeletal to al- 

low outgroup comparison with the fossil acipenseri- 

form taxa †Chondrosteus (Traquair 1887, Hennig 

1925, Watson 1925, 1928), †Peipiaosteus (Liu & 

Zhou 1965, Bai 1983, Zhou 1992), and the fossil poger 

(1973) described A. ruthenus and several Eu- lyodontids † Paleopsephurus and † Crossopholis 

ropean species of Acipenser are described in Se- (Grande & Bemis 1991), as well as extant polyodonwertzoff 

(1926a, b, 1925), Tatarko (1936), and Anto- tids. Several soft tissue characters such as presence 

niu-Murgoci (1936a, b, 1942). 

of four barbels, the spiracle, and the ligaments of 

the jaws and hyoid arches may characterize specific 

nodes within Acipenseridae, but are not included 

Huso 

here. Soft tissue characters are problematic in a cladistic 

analysis of Acipenseridae because Polyodontidae 

is the only relevant extant outgroup (Bemis et 

al. 1997), leaving any putative familial level characters 

as two taxon statements (Polyodontidae vs. 

Acipenseridae). 

I examined several species of Acipenser to assess 

morphological variation within the genus to allow 

comparisons with other genera. Four adult A. brevirostrum, 

two large juvenile A. medirostris, two large 

juvenile A. oxyrinchus, and the head of an adult A. 

oxyrinchus (2.4 m total length) were hand cleaned. 

I cleared and double stained several small specimens 

of A. brevirostrum, A. transmontanus, and 

heads of A. ruthenus. Abbreviated developmental 

series of A. brevirostrum and A. transmontanus 

were cleared and double stained. Marinelli & Stren- 

77 

four genera Huso, Acipenser, Scaphirhynchus, and 

Pseudoscaphirhynchus. At higher levels, the taxa 

recognized in this study are the Husinae (comprising 

only Huso and usually referred to here with only 

the generic name), Acipenserinae (comprising Acipenser, 

Pseudoscaphirhynchus, and Scaphirhynchus), 

and Scaphirhynchini (comprising Pseudoscaphirhynchus 

and Scaphirhynchus). 

Characters and phylogeneticcomparisons 

Huso huso is the only species of the genus examined 

in this study, but is similar in morphology to H. 

dauricus by all accounts (Berg 1948a). Of three 

small juveniles, one was cleared and double stained, 

one sectioned, and one examined intact (all CAS 

37541). Two moderate sized juveniles (FMNH 

96852, 96853; each approximately one meter total 

length) were examined externally and by dissection 

to confirm character states between small and 

larger sizes. 

Terminology of acipenserid taxa 

In the description of characters, characters are 

grouped according to the levels of acipenserid taxa 

that they define. Accordingly, character descriptions 

often refer to higher level taxa defined in this 

study that are not consistent with historic usage. 

Taxa recognized within Acipenseridae include the 

Character 1. Trunk bracketed with five rows of scutes 

– Acipenseridae 

Five scute rows are present along the trunk in acipenserids 

(shown in Huso in Figure 1). The five 

rows are distinguishable as three groups: (1) the 

dorsal scute row extending from the dermal skull to 

the predorsal scale of the dorsal fin; (2) paired Clank 

scute rows bearing the trunk canal from the supracleithrum 

into the base of the caudal fin; and (3) 

paired ventral scute rows spanning the pectoral and 

pelvic fins. Shape, number, and size of individual 

scutes varies dramatically, but their position and 

presence as complete groups is consistent within

78 

Acipenseridae. Some species of Acipenser regress Character 2. DermaI bone forms a pectoral fin spine 

the ventral scutes (e.g., A. fulvescens) almost com- - Acipenseridae 

pletely (Dúmeril 1867), but the row is always present 

in juveniles and most adults. Dorsal scute mor- The pectoral fin of all acipenserids is supported 

phology has been used as a phylogenetic character along its anterior edge by a thick pectoral fin spine. 

by some workers (Antoniu-Murgoci 1936a, 1942), The fin spine is composed of dermal bone extending 

but no clear evidence of cladistically useful charac- from the Ieading edge of the propterygium to typter 

states based on scute shape has been demon- ically sheath two fin rays (Ipt1, lpt2, Figure 2a). One 

strated. 

ray is included in the weak spine of Scaphirhynchus 

In addition to scutes, acipenserids possess three platorynchus and rarely three are included in taxa 

novel and discrete series of other scales: (1) median with strong fin spines (occasionally in Acipenser oxpredorsal 

and preanal scales at the anterior bases of yrinchus). 

these fins, (2) a variable assemblage of scales ante- The base of the pectoral fin spine is an expanded 

rior to the anal fin, and (3) scales on the caudal pe- propterygium (ptg) articulating with the scapulocduncle 

(Findeis 1993). Rhombic caudal scales sup- oracoid (Findeis 1993). This enlarged propterygium 

porting the caudal fin are plesiomorphically present is also diagnostic of acipenserids and included within 

all acipenseriforms except † Peipiaosteus (Liu & in this character as an associated feature of the fin 

Zhou 1965) and are typical for palaeoniscids. spine. Dermal bone molds to the propterygium and 

Scutes and other large scales develop as bony anterior fin rays to unify the spine with its propteryplates 

with their approximate adult morphology gial base (Figure 2a). Fusion of dermal bone with 

distinct from smaller scales of the skin. Sewertzoff the fin rays is extensive and segmentation ofthe Iep- 

(1926b) suggested that scutes develop as compos- idotrichia is lost as they merge into the spine in 

ites of these trunk scales, but I find no scale assem- adults (compare lpt1 and lpt2 in Figure 2a). In large 

blages coalescing in early ontogeny of scutes or (= old) specimens, the dermal spine fuses with a 

other named scales. Scutes are the earliest scales to perichondral ossification or the propterygium (Figappear, 

and develop as series distinct from other ure 2b). 

scales. Other named scales or scale groups appear Dermal bone and their incorporated fin rays aplater 

in ontogeny, but also as discrete units. 

pear separately in ontogeny. Most authors have as- 

No large trunk scales are present in any other aci- sumed that fin rays fuse into the fin spine (e.g., Vlapenseriform 

taxa. Psephurus bears small scales dykov & Greeley 1963, Jollie 1980, Grande & Bemis 

studding the skin of the trunk and Polyodon pos- 1991), but my observations suggest that lepidotrisesses 

denticular scales restricted to the anterior chia are simply covered by the expanding dermal 

base of the median fins (Grande & Beinis 1991). bone (Figure 2b). Recognition of a dermal compo- 

†Crossopholis and † Paleopsephurus possess nent in the pectoral fin spine defines this character. 

fringed scales infiltrating the skin of the trunk Polyodontids (Grande & Bemis 1991), † Chon- 

(Grande & Bemis 1991), but they are still small, drosteus (Traquair 1887). and †Peipiaosteus (Liu & 

scattered scales. Scales in polyodontids are compa- Zhou 1965) lack a pectoral fin spine. No accessory 

rable in size and distribution to the isolated trunk dermal bone and no enlarged propterygium is prescales 

present in all acipenserids examined, but not sent in Polydon or Psephurus. Individual fin rays 

scutes or other named scales. † Chondrosteus (Tra- at the leading edge of the pectoral fin are recognizquair 

1887) possesses no known trunk scales. † Pei- able in † Chondrosteus (Traquair 1887, Hennig 1925) 

piaosteus (Liu & Zhou 1965) has thin, paired scales and † Peipiaosteus (Liu & Zhou 1965, Zhou 1992), so 

bracketing the putative trunk canal, but no other no dermal sheath could be present in these outtrunk 

scales. 

groups.

79 

a Acipenser transmontanus 

b Acipenser oxyrinchus 

Figure 2. Pectoral fin spine of Acipenseridae (Character 2): a - Illustrations of the pectoral fin spine of Acipenser transmontanus in an 

intact fin (left) and isolated (right). The fin spine supports the leading edge of the pectoral fin. At higher magnification, dermal bone 

contacts the propterygium (ptg) at the base and encompasses one fin ray completely (Iptl is exposed distally) and shows bone encroaching 

onto the second ray (arrows onto lpt2). This juvenile specimen (cleared and double stained) shows only partial development of the spine. 

but in adults the first two fin rays are fully encompassed by dermal hone. b – Illustrations of the base of the fin spine in a large A. 

oxyrinchus (2.4 111 total Iength) in posterior (left) and lateral (right) views. The propterygium is braced within the dermal spine and fused 

to the dermal bone via its perichondral ossification (arrows). The canal bearing blood vessels and nerves into the fin (pca) is a portion of 

the propterygium and shows the extent of fusion. Two fin rays are fused into this spine, but (they cannot be distinguished from the dermal 

spine at the base where (the segmented Iepidotrichia merge full) into the new bone (scc = scapulocoracoid, ra = pectoral radials and 

metapterygium).

80 

Figure 3. Jugal of representatives of all genera of Acipenseridae: The jugal defines the posteroventral margin of the orbit (top in black). 

Illustrations include lateral and ventral views for each genus. The anterior process of the jugal (atp, Character 3) extends anterolaterally 

beneath the orbit and lacks any portion of the infraorbital canal. The canal extends anteromedially within the canal process of the jugal 

(cnp) before entering a series of tube bones in all acipenserids except Pseudoscaphirhynchus (Character 57) (brb = border rostral bones).

81 

Character 3. Jugal possesses an anterior process - 

Acipenseridae 

The jugal of all acipenserids examined extends a 

prominent anterior process undercutting the orbit 

(atp, Figure 3). It is small in Huso (Figure 3a), but 

large in all species of Acipenser examined and Scaphirhynchus, 

and massive in Pseudoscaphirhynchus 

(Character 57). The anterior process extends 

anterolaterally to contact the neurocranium. 

The anterior process does not bear the infraorbital 

canal that curls anteromedially within a separate, 

smaller canal process of the jugal (cnp, Figure 

3). Thus, passage of the infraorbital canal, typical of 

the circumorbital series, docs not apply to the anterior 

process of the jugal of acipenserids. The extended 

jugal braces the dermal skull roof against 

the neurocranium anterior to the orbit (Findeis 

1993) and conforms the dermal skull to the expanded 

neurocranium of acipenserids. Ethmoid expansion 

of the neurocranium coincides with a broadened 

postnasal wall as a probable character of the 

Acipenseridae not scorable in fossil taxa, but coincident 

jugal expansion restricted to acipenserids 

suggests that ethmoid expansion is an acipenserid 

character. 

No polyodontid possesses homologizable circumorbital 

bones as the infraorbital canal is carried 

Figure 4. Antorbital of representatives of all genera of Acipenseridae: a – Huso huso, b–Acipenser oxyrinchus, c–A. brevirostrm, d - 

Pseudoscahirhynchus kaufmanni, c – Scaphirhynchus platorynchus. The antorbital lies between the orbit and oIfactory opening dorsally 

in the dermal skull (top in black; Character 4). It lacks any portion of the supraorbital canal and extends ventrally as a variably sized 

wedge-shaped process. The ventral wedge is small in Huso (a), variably sized in Acipenser (b, c), but elongate in scaphirhynchines (arrows 

in d, e; Character 46). It contacts an enlarged postrostral bone (prb) inScaphirhynchus (Character 61).

82 

Figure 5. Extrascapular bones of the posterior skull roof in † Chondrosteus and representatives of all genera of Acipenseridae: The 

median extrascapular (excm; Character 5 ) is a midline bone that bears the commissure of the occipital canal (ocll; Character 24) in all 

acipenserids. The lateral extrascapulars (excl) carry the occipital canal from the posttemporal (pt) to the median extrascapular in all 

acipenserids except Pseudoscaphirhynchus, where the lateral extrascapular series includes the origin of the occipital canal (Character 

56). Lateral extrascapulars typically form a series of canal bones or are variable in position, but are clustered in Scaphirhynchus (Character 

60). † Chondrosteus (a - redrawn from Traquair, 1887) possesses a series of extrascapulars (exc), but no distinct median and lateral 

extrascapulars. pa = parietal, st = supratemporal, op = opercle, stll = supratemporal canal, trll = trunk canal, dsl = first dorsal scute.

y tube bones independent of the skull roof Character 5. Median extrascapular bone present – 

(Grande & Bemis 1991). The infraorbital canal of Acipenseridae 

† Peipiaosteus (Zhou 1992) is similarly borne by 

tube bones rather than a dominant series of elements 

and is not comparable with acipenserids. An 

anterior process of the jugal has been reconstructed 

for † Chondrosteus (e.g., Traquair 1887, Gardiner & 

Schaeffer 1989), but it apparently bears the infraorbital 

canal unlike acipenserids. 

Character 4. Antorbital bonepresent 

- Acipenseridae 

The antorbital defines the anterodorsal corner of 

the orbit (Findeis 1993) and is present in all acipenserids 

examined. It lies dorsally between the orbit 

and olfactory capsule as a small plate that angles 

ventrolaterally onto the postnasal wall as ventral 

points (Figure 4). 

The antorbital varies in size and shape, but not 

position or presence, in Acipenseridae. Its ventral 

points are short or absent in Huso (Figure 4a) and 

variably extended in most species of Acipenser 

(Figure 4b, c), but antorbitals of scaphirhynchines 

(Figure 4d, e) possess elongate ventral processes 

(see Character 46). Antorbitals rest alongside the 

nasal, but never bear the supraorbital canal. As with 

the anterior process of the jugal (Character 3), presence 

and ventrolateral extension of the antorbital is 

consistent with the expanded neurocranium as the 

skull is covered locally by appearance of a new 

bone. 

The antorbital is not present in polyodontids 

(Grande & Bemis 1991), and has not been described 

in † Chondrosteus (Traquair 1887, Hennig 1925). 

Zhou (1992) names an antorbital in † Peipiaosteus, 

but it is a tube bone carrying the supraorbital canal 

not comparable to acipenserids. The only positionally 

comparable bone in † Mimia (Gardiner 1984a) 

and other palaeoniscids is the nasal, but the nasal 

ubiquitously bears the supraorbital canal. 

83 

The median extrascapular (excm) is a triangular 

plate present between the posterior ends of the parietals 

(pa) and anterior to the first dorsal scute 

(ds1, Figure 5). It is present in all acipenserids examined, 

and bears the commissure of the occipital canals 

(see Character 24 below). 

The median extrascapular develops extremely 

late, first appearing as splints bracketing the occipital 

canal before expanding to cover the posterior 

skull. Several bones may compose the median extrascapular 

initially, but the ossification is single in 

all adult specimens examined. Expansion beyond 

the occipital canals and consistent shape suggests 

that the median extrascapular has developed phylogenetically 

from an anamestic bone into a permanent 

bone of the skull. 

No similar median element in the posterior skull 

roof is known from any other acipenseriform. 

Grande & Bemis (1991) provisionally identified a 

Figure 6. The rostral canal and rostrum ofHuso huso: The rostral 

canal extends onto the ventral surface of the rostrum from the 

jugal (see Character 3) to converge medially before arching laterally 

around the outer barbels (Character 6). After curling 

around the outer barbels, the rostrum canals extend anteriorly in 

parallel before converging at the rostral tip.

84 

Figure 7. The opercular series of † Chondrosteus, † Peipiaosteus, and representatives of all genera of Acipenseridae: † Chondrosteus (a – 

redrawn from Woodward 1889) and †Peipiaosteus (b – redrawn from Zhou 1992) possess serial branchiostegals (bsg) supporting the 

operculum beneath the subopercle (sop). Acipenserids (c, d, f) typically possess two branchiostegals (Character 7), with a vertical, 

rectangular first branchiostegal (bsg1) and small second branchiostegal (bsg2). Scaphirhynchus (e) possesses a short, triangular first 

branchiostegal (Character 62). The subopercle of scaphirhynchines is dorsoventrally compressed with an anteroposteriorly elongate 

shape (Character 47).

85 

‘median nuchal’ in † Paleopsephurus, but the specimen 

is too poorly preserved to identify an autonomous 

element or note whether posttemporal extensions 

typical of polyodontids expand over this area. 

All other polyodontids conclusively lack a median 

extrascapular. † Chondrosteus (Traquair1887) possesses 

multiple small bones that cross the posterior 

midline of the skull roof (Figure 5a), but they are 

small bones more comparable to lateral extrascapulars. 

† Peipiaosteus (Liu & Zhou1965, Zhou1992) 

is not well described in this area, but no bone separates 

the parietals. 

Character 6. The rostral canal arches laterally – Acipenseridae 

Rostral sensory canals extend ventromedially under 

the rostrum, but then curl laterally around the 

outer barbels before recurving to parallel the rostral 

midline (Figure 6). The rostral canal develops 

with this lateral arch originally and is not displaced 

by the developing barbels. 

In extant polyodontids the rostral canals converge 

smoothly to parallel the midline to the anterior 

tip of the rostrum without disruption. Incomplete 

remains of rostral tube bones in † Crossopholis 

are consistent with this condition (Grande &Bemis 

1991), but are missing in † Paleopsephurus. 

Rostral canals of † Chondrosteus (Hennig1925, and 

Figure 8. Dermal pectoral girdle of Acipenser brevirostrum: a – Anterolateral view of an intact pectoral girdle showing the medial 

opercular wall (Character 10) rising vertically from the cleithrum (clt) and clavicle (clv), the clavicle process (cvp) binding the cleithrum 

and clavicle (Character 13), the propterygial restraining process (prp; Character 12), and the close contact between the supracleithrum 

(scl) and posttemporal (pt). b – Dorsal (left) and ventral (right) views of the supracleithrum. The anterior shelf of the supracleithrum 

(Character 9) extends as a flat, unornamented area anterior to the trunk canal (arrows). The supracleithral cartilage (sclc; Character 15) is 

bound to the ventral surface of the supracleithrum. c – Ventral view of the pectoral girdle showing the expanded clavicle and cleithrum 

forming the cardiac shield (Character 11) and the extension of the propterygial restraining process (Character 12) laterally from the 

cleithrum.

86 

indications from Gardiner & Schaeffer 1989) are 1991) support the caudal fin, leaving a gap in the peapparently 

also straight. † Peipiaosteus possesses a duncle. 

rostral canal that extends anteriorly onto the snout Polyodontids (Grande & Bemis 1991) and 

and bends dorsally to terminate in a cluster of bones † Chondrosteus (reconstruction from Woodward 

(Zhou 1992). In † Mimia (Gardiner 1984a) and Pol- 1889) possess supraneurals throughout the axial 

ypterus, the rostral canal is straight and no other skeleton. † Peipiaosteus apparently lacks supraneuoutgroups 

possess an abrupt lateral arch. 

rals in the peduncle (Zhou 1992), but † Peipiaosteus 

is small and supraneurals are difficult to identify 

and may have never ossified. Among other outgroups, 

Character 7. The opercular series includes a serial 

pair of branchiostegals – Acipenseridae 

distribution of supraneurals is variable. Pol- 

ypterus and † Pteronisculus (and several palaeoniscids; 

Gardiner 1984a) possess a complete series of 

supraneurals, but † Mimia (Gardiner 1984a), Lepisosteus, 

Amia, and neopterygians typically possess 

incomplete series. Inconsistency among outgroups 

clouds analysis of this character, but a complete supraneural 

series in polyodontids suggests that a peduncle 

gap is characteristic of Acipenseridae. This 

correlates with the flattened peduncle of acipenserids 

that presumably puts spatial constraints on the 

vertically oriented supraneurals unlike other acipenseriform 

taxa. 

The dominant opercular bone of acipenseroids is 

the subopercle, but acipenserids typically possess 

two branchiostegals that extend ventrally and then 

medially in support of the operculum (Figure 7). 

Branchiostegal one (bsg1) forms an elongate vertital 

support before branchiostegal two (bsg2) angles 

medially to undercut the head. Branchiostegal one 

is rectangular and variably elongate in Huso and all 

species of Acipenser examined (Figure 7c, d). and 

Pseudoscaphirhynchus (Figure 7f), but is stubby 

and triangular in Scaphirhynchus (Figure 7e; Character 

46). Occasionally three branchiostegals are 

present, but the third was diminutive and did not 

significantly enlarge the opercular series when present. 

Polyodontids possess a single branchiostegal separate 

from the subopercle (Findeis 1993, Bemis et 

al. 1997). The opercular series of † Chondrosteus 

(Traquair 1887, Hennig 1925) and † Peipiaosteus 

(Liu & Zhou 1965, Zhou 1992) include multiple, serial 

branchiostegals not vertically elongate (Figure 

7a, b). This condition is plesiomorphically similar to 

most palaeoniscids and suggests that reduction to 

two branchiostegals is diagnostic of Acipenseridae. 

Character 8. Loss of supraneurals in the caudal peduncle-Acipenseridae 

Character 9. Supracleithral shelf undercuts the posttemporal 

— Acipenseridae 

The supracleithrum (scl) expands anteriorly as a 

broad shelf undercutting the posttemporal (pt) in 

all acipenserids examined (Figure 8a, b). This shelf 

broadly contacts the underside of the posttemporal 

and the bones are bound tightly to unify the pectoral 

girdle and skull roof. This shelf does not bear the 

trunk canal that passes from the posttemporal to 

the supracleithrum at their surface suture (arrows 

in Figure 8b). 

Extant polyodontids possess a mobile supracleithral-posttemporal 

articulation (Grande & Bemis 

1991). Polyodon, Psephurus, and t Crossopholis 

all show slight supracleithral undercutting of the 

posttemporal with a short portion of the supracleithrum 

extending anterior to the exit of the trunk 

canal. However, length of this process is not equiv- 

Supraneurals of all acipenserids examined are serially 

present above neural arches in the thoracic 

trunk between the neurocranium and dorsal fin, but alent to acipenserids. The supracleithrum of 

absent beneath the dorsal fin and in the caudal pe- † Chondrosteus (Traquair 1887) broadly contacts 

duncle. Supraneural homologs (Grande & Bemis the posttemporal. but without an anterior process.

† Peipiaosteus lacks tight contact between these 

bones (Zhou 1992). 

Character 10. Presence of a medial opercular wall — 

Acipenseridae 

87 

scapulocoracoid with the cardiac shield supporting 

the expanded coracoid shelf (see Character 14). 

The clavicle and cleithrum of polyodontids 

(Grande & Bemis 1991), † Chondrosteus (Traquair 

1887), and †Peipiaosteus (Liu & Zhou 1965) are 

slender bones lacking shelves. The clavicles of Psephurus 

and † Crossopholis possess short posterior 

wedges smaller than the cardiac shield, but they do 

The medial opercular wall is a vertical shelf defining 

the internal surface of the opercular chamber not flare posteromedially or meet medially 

(Findeis 1993). It comprises expanded laminae (Grande & Bemis 1991). No similar cardiac shields 

curving dorsally from the cleithrum and clavicle are present in Polypterus, Amia, or other distant 

(clt, clv, Figure 8a). The medial opercular wall is outgroups. 

present in all acipenserids examined. It is not as expansive 

in Huso as in acipenserines, but the corresponding 

opercular chamber is more slender in Character 12. Presence of a propterygium restrain- 

Huso. 

ing process — Acipenseridae 

Polyodontids possess slender pectoral girdle 

bones with laterally exposed faces that never angle 

internally or form expanded laminae (Grande & 

Bemis 1991). Clavicles and cleithra of † Chondrosteus 

(Traquair 1887) and † Peipiaosteus (Liu & Zhou 

1965) arc also slender and lack internal expansion. 

No expanded opercular wall is present in Polypterus, 

Lepisosteus, Amia, or † Mimia (Gardiner the fin in all acipenserids examined. 

1984a) and other palaeoniscids. 

Character II. Presence of a cardiac shield 

—Acipenseridae 

The propterygium restraining process is a prominent, 

posteriorly curved process in Scaphirhynchus 

and extended ridge in Pseudoscaphirhynchus, but is 

less prominent in Huso and Acipenser (Figure 8a). 

It is well developed in juveniles, but is allometrically 

reduced in adults as the cleithrum thickens with 

dermal ornament obscuring the shallow ridge. 

When a distinct process is absent, this region is en- 

larged as a robust cleithral notch enfolding the base 

of the fin spine. This character tacitly includes such 

a cleithral notch that acts as a pectoral fin spine con- 

straint when the process is less obvious. 

No similar process is present in any other acipenseriform 

group. Outgroups possess no pectoral fin 

spine (see Character 2) or, among extant polyodon- 

tids, a propterygial fossa (Character 16) allowing 

frontal pivoting of the propterygium. the † Crossopho- 

lis possesses a shallow notch in the cleithrum 

aligned with the fin (Grande & Bemis 1991), but it is 

an isolated condition within Polyodontidae. 

The cardiac shield is a ventral shelf formed by expansion 

of the clavicle and cleithrum. The shield expands 

posteromedially as a flat, exposed plate that 

meets its contralateral partner at the midline (Figure 

8c). The cardiac shield covers the pericardial 

cavity and is found in all acipenserids examined. 

The cardiac shield is almost completely flat in 

Scaphirhynchus (Findeis 1993), but angles centrally 

through the anteroposterior axis in other genera, 

with a frontally flat medial region and dorsally angled 

lateral face (Figure 8c). This central angle is 

acute (up to 20°) in species with cylindrical body 

shapes (all species of Acipenser examined and 

Huso), but shallow in the flatter Pseudoscaphirhynchus. 

The cardiac shield and opercular wall of acipenserids 

meet in a sharply angled anteroventral 

edge (approximately 160°). This angle brackets the 

The propterygium restraining process extends from 

the lateral edge of the cleithrum (prp, Figure 8a, c) 

to wrap anterolateral to the propterygial fossa of 

the scapulocoracoid (see Character 16) and its articulating 

propterygium. It brackets the pectoral fin 

spine anteriorly to support and limit movement of

88 

Figure 9. Left scapulocoracoid of Acipenser brevirostrum (a) and Scaphirhynchus platorynchus (b) in lateral and anterior views: The 

ventral scapulocoracoid extends from the coracoid wall (cw) as a flat shelf of cartilage (csh; Character 14) medially in all acipenserids 

(arrows pointing left) except Scaphirhynchus, where it forms a small footprint that flares laterally (arrows pointing right; Character 68). 

Acipenserids also possess a broad propterygial fossa (ptgf) at the anterior end of the glenoid ridge where the propterygium (see Character 

2) pivots on the propterygial bridge (ptb; Character 16). The. propterygial fossa is open anteriorly in all acipenserids except Scaphirhynchus, 

where a (thin ridge encircles the fossa anteriorly (Character 67). The anterior face of the scapulocoracoid is L-shaped spanning 

the anterior process of the middle region (anp) to the propterygial bridge, then rises dorsally as the cleithral arch (cta) in most acipenserids 

(a), but is expanded as a broad cleithral wall (ctw) inScaphirhynchus (b; (Character 66). msc = mesocoracoid arch.

89 

Character 13. Clavicle process interdigitates with the 

cleithrum - Acipenseridae 

The clavicle process is a small wedge that interdigitates 

with the cleithrum in all acipenserids examined 

(cvp, Figure 8a, c). The clavicle process extends 

along the anteroventral edge of the pectoral 

girdle in Scaphirhynchus (Findeis 1993), but typically 

undercuts the clavicle slightly in other acipenserids 

(Figure 8 for Acipenser). The process interlocks 

with a opposing groove in the cleithrum to solidify 

the pectoral girdle. 

No clavicle process is present in extant polyodonlids 

or † Crossopholis (Grande & Bemis 1991). This 

character is a small feature not easily noted from 

illustrations or descriptions of † Chondrosteus (Traquair 

1887, Hennig 1925) or †Peipiaosteus (Liu & 

Zhou 1965), but their slender pectoral girdles are 

not suggestive of such an interlocking process. 

Character 14. Coracoid shelf spreads over the cardiac 

shield-Acipenseridae 

The coracoid wall (cw) extends ventrally from the 

middle region of the scapulocoracoid to spread onto 

the cardiac shield as a flat coracoid shelf (csh, Figure 

9; Findeis 1993). The coracoid shelf makes immediate 

contact with the cleithrum and spreads anteromedially 

almost to the tip of the clavicle in all 

acipenserids (Figure 9a) except Scaphirhynchus. In 

Scaphirhynchus, the coracoid shelf spreads laterally 

and is restricted to the cleithrum (Figure 9b; see 

Character 68). 

In extant polyodolitids, the coracoid wall is cylindrical 

and extends anteromedially separate from 

the cleithrum before curving anteroventrally onto 

the clavicle. Shape of this coracoid process corresponds 

to the slender dermal girdle. The scapulocoracoid 

is largely cartilaginous and not scorable in 

fossil taxa, but shape of the dermal girdle of † Crossopholis 

and † Paleopsephurus (Grande & Bemis 

1991), † Chondrosteus (Traquair 1887), and †Peipiaosteus 

(Liu & Zhou 1965) is similar to extant polyodontids, 

suggesting that a correspondingly cylindrical 

coracoid process would be consistent in outgroup 

acipenseriforms. 

Character 15. SupracleithraI cartilage present – Aci - 

penseridae 

The supracleithral cartilage lies under the supracleithrum 

(Figure 8b). It varies in shape among acipenserids 

from an elliptical, tall cartilage in some 

species of Acipenser to an elongate, shallow element 

in Huso and Scaphirhynchus. 

The supracleithral cartilage is absent in extant 

polyodontids, polypterids, lepisosteids, and amiids. 

It never ossifies and is unknown from any fossil acipenseriform. 

Lacking † Chondrosteus or † Peipiaosteus 

as outgroups clouds cladistic analysis of this 

character within Acipenseriformes, but its absence 

in extant polyodontids suggests it is restricted to 

Acipenseridae. 

Character 16. Propterygial fossa present in scapulo - 

coracoid - Acipenseridae 

The propterygial fossa is a broad, semicircular 

opening in the scapulocoracoid between the glenoid 

ridge and the propterygium restraining spine 

of the cleithrum (ptgf, Figure 9; see Character 12). It 

is bounded posteriorly by the propterygial bridge 

(ptb) and dorsally by the vertical cleithral arch (cta, 

Figure 9a) or cleithral wall (ctw, Figure 9b; see 

Character 66). The propterygial fossa opens a space 

for the rotating propterygium that articulates with 

the propterygial bridge (see Character 2) and is filled 

with pectoral musculature that pulls the pectoral 

fin spine forward. The propterygial fossa is a 

rounded notch (Figure 9a) in all acipenserids except 

Scaphirhynchus, where it forms a half circle 

(Figure 9b; see Character 67). 

The glenoid ridge extends completely to the 

cleithrum in extant polyodontids. The propterygium 

of these taxa is small and can articulate with the 

glenoid 

ridge without need for an anterior fossa. Although 

this character cannot be confirmed in fossil 

taxa, lack of a cleithral notch (see Character 12) in 

† Chondrosteus (Traquair 1887, Hennig 1925) or 

† Peipiaosteus (Liu & Zhou 1965) suggests that there 

would be no opposing opening in the scapulocoracoid. 

No propterygial fossa is present in † Mimia 

(Gardiner 1984a) and other palaeoniscids.

90 

Character 17. Basipterygial process present- Acipenseridae 

This basipterygial process extends from the ventral 

surface of the basipterygium, flaring around the anterior 

edge of the pelvic fin musculature (Findeis 

1993). It is present in all acipenserids examined. 

Extant polyodontids possess a segmented basipterygium 

different from acipenserids, but also 

lacking a ventral process. The basipterygium is cartilaginous 

in adults and unknown from fossil acipenseriforms. 

Lacking † Chondrosteus and †Peipiaosteus 

as outgroups clouds cladistic analysis of 

this character, but the pelvic plate of † Moythomasia 

(Gardiner 1984a) is complete and lacks a ventral 

process. Polypterus, Lepisosteus, and Amia possess 

differing basipterygial morphologies, but all lack a 

ventral process. 

Character 18. Palatal complex present 

- Acipenseridae 

Figure 10. Palatal complex of representatives of three genera of 

Acipenseridae: The palatal complex is a cartilaginous plate 

bound to the palatoquadrate to expand the functional surface of 

the upperjaw (top in black; Character 18). It is formed by a single 

dominant cartilage in Huso, but comprises multiple large and 

small cartilages in other acipenserids. 

The palatal complex comprises an integrated group 

of flat cartilages embedded within loose skin posterior 

to the upper jaw and opposite the ventral 

tongue pad (Figure 10). This complex is attached to 

and functionally linked with the palatoquadrate. 

Number of cartilages forming the complex and 

their individual shapes vary, but it is present in all 

acipenserids examined. 

The palatal complex is composed of several large 

plates of cartilage unified as a wedge with thin lateral 

arms in Scaphirhychus and Pseudoscaphirhynchus 

(Figure 10c). The palatal complex of all 

species of Acipenser examined is deeper and more 

rounded than in scaphirhynchines, and typically includes 

numerous small cartilages arrayed around a 

large central and paired lateral plates (Figure 10b; 

see Antoniu-Muigoci 1942). Huso possesses a 

broad, shallow palatal complex formed by one 

dominant plate with occasional thin cartilages 

along the anterior edge (Figure 10a). Number of 

cartilages forming the palatal complex has been 

used as a character within Acipenseridae (Antoniu- 

Murgoci 1936b, Sokolov 1989), but this variation 

makes it dificult to polarize character states and no

91 

tapers ventrally in Huso and all species Acipenser 

examined (Figure 11b, c) to a ventral position forming 

a flat edge in scaphirhynchines (Figure 11d; 

Character 50). The ventral end is cartilaginous, but 

the ossified core reflects the wedge by posterior 

flaring and thinning of the perichondral center. 

The hyomandibula of Psephurus is slender, with 

a ventral head tapering with a continuously curved 

posterior edge (Figure 11a). The ossified center of 

Psephurus and †Crossopholis expands ventrally 

(Grande & Bemis 1991), but not as sharply as in acipenserids 

and with a rounded posterior edge. The 

hyomandibula of † Paleopsephurus is incomplete 

and not well known (Grande & Bemis 1991, MacAlpin 

1947). The ossified cores of † Chondrosteus (Trainterpretation 

on shape or composition is made 

here. 

No palatal complex is present in other extant acipenseriforms 

or actinopterygians, but as a cartilaginous 

character its presence or absence is unknown 

in †Chondrosteus or †Peipiaosteus. 

Character 19. Posteroventral edge of hyomandibula 

forms a wedge – Acipenseridae 

The hyomandibulae of all acipenserids examined 

are expanded posteriorly to form a posterior wedge 

in the ventral cartilaginous head (Figure 11). Position 

of the wedge varies from a dorsal position that 

Figure 11. Hypomanbibula of Psephurus and respresentatives of three genera of Acipenscridae: The hyomandibula is shown in lateral view 

in all taxa and also in anterior view in Acipenser (c) and Scaphirhynchus (d). The hyomandibula of Psephurus (a) possesses a convex 

posterior edge, but is expanded posteriorly in all acipenserids examined (heavy arrow in b, c, d; Character 19). The posterior wedge is 

dorsal in Huso (b) and Acipenser (c), but ventral in scaphirhynchines (hollow arrow; Character 50). Also, the dorsal tip is board in Huso 

and Acipenser, but thin in scaphirhynchines (thin arrows; Character 49).

92 

quair 1887), † Gyrosteus (Woodward l889), and 

† Peipiaosteus (Liu & Zhou 1965) all expand ventrally 

as in all other acipenseriforms, but since this 

cartilaginous character is unpreserved in fossils 

they do not assist in assigning polarity. More distant 

outgroups lack the hyostylic jaw suspension of acipenseriforms 

and are useless in assessing this character. 

I accept Psephurus as representing the plesiomorphic 

condition. 

Character 20. Anterior ceratohyal is flat and rectangular, 

with a mandibulo-hyoid process and asymmetric 

hypohyal joint - Acipenseridae 

Anterior ceratohyals of all acipenserids examined 

are dorsoventrally flattened and rectangular in oral 

view (Figure 12). The lateral head is centrally 

grooved with a rising posterior ridge articulating 

with the posterior ceratohyal and anterolateral process 

that is the origin of the mandibulo-hyoid ligament 

(arrows, Figure 12c, d, e). The medial end is 

blunt, with an asymmetric, anteriorly displaced facet 

for the hypohyal (hh, displaced arrows of Figure 

12c, d, e). 

Anterior ceratohyals of Psephurus are cylindrical, 

hourglass-shaped elements lacking distinct processes 

and possessing a central hypohyal facet on 

the medial head (Figure 12a). The lateral end lacks 

a distinct mandibulo-hyoid ligament process or central 

groove and the posterolateral head is a blunt tip 

articulating with the posterior ceratohyal. The anterior 

ceratohyal of † Paleopsephurus is unknown, but 

that of † Crossopholis is also cylindrical based on 

shape of its ossified center (Grande & Bemis 1991). 

Anterior ceratohyals of Polyodon are flattened and 

not comparable to other taxa (Grande & Bemis 

1991). Cylindrical morphologies are inferred for 

† Chondrosteus (Traquair 1887) and † Gyrosteus 

(Figure 12b; Woodward 1889) based on their cylindrical 

core. The hyobranchial skeleton of † Peipiaosteus 

is unpreserved (Liu & Zhou 1965). 

Character 21. Anterior shelf protrudes from hypobranchial 

one – Acipenseridae 

An anterodorsal shelf expands from hypobranchial 

one (hbl) as a wedge overhanging the anterior ceratohyal 

and hypohyal (hh) in all acipenserids examined 

(arrow in Figure 13b, c). The shelf is concave 

medially, opening a gap where the hypohyal extends 

dorsally to articulate with basibranchial one 

(Figure 13b, c). The anterior shelf, in concert with 

the exposed hypohyal and anterior basibranchial, 

forms a flat anterior edge of the ventral branchial 

skeleton. This edge bears connective tissue ridges 

Figure 12. Anterior ceratohyal of Psephurus, † Gyrosteus, and 

representatives of three genera of Acipenseridae: The anterior 

ceratohyal is narrow and cylindrical in acipenserid outgroups (a, 

b; † Gyrosteus redrawn from Woodward 1889), but expanded 

centrally as a flattened rectangular element (thin arrows in c, d, 

e; Character 20). The acipenserid anterior ceratohyal also possesses 

an anterolateral process supporting the mandibulo-hyoid 

ligament (heavy arrows in c, d, e) and an asymmetric facet for the 

hypohyal on the medial tip (hh and bent arrows in c, d, e).

93 

used for prey processing opposite to the palatal consistent. Scaphirhynchines lack these scales 

complex (Character 18). (Character 54). 

Hypobranchial one of Psephurus and † Cross- Pectoral scales of fossil and extant polyodontids 

opholis is cylindrical with a flattened dorsal surface (Grande & Bemis 1991) are small, round elements 

bearing teeth (Figure 13a), but with no expanded with a single, recurved process (Figure 14a). † Peishelf 

(Grande & Bemis 1991). Polyodon possesses a piaosteus possesses pectoral scales with three prosmall 

hypobranchial one not comparable to other cesses extending from a narrow tip (Liu & Zhou 

acipenseriform taxa. 

1965), but processes of these scales fan directly from 

Hypobranchials are typically cartilaginous (al- the base and are not elevated, recurved tips that 

though a small ossification occurs in large acipense- overhang the scale (Figure 14b). Such scales have 

rids and † Crossopholis) and not known from not been described in † Chondrosteus. Individual 

† Chondrosteus or †Peipiaosteus. Anterior shelves sections of acipenserid pectoral scales (with a single 

are not present in † Mimia (Gardiner 1984a), Pol- tip) are more robust than, but similar to, the pectoypterus, 

Lepisosteus, or Amia. 

ral scales of polyodontids. 

Character 22. Hypobranchial three makes a bicontact 

joint with basibranchial one-Acipenseridae 

Hypobranchial three articulates with basibranchial 

one at two sites in all acipenserids examined. The 

anterior end is crescentic, with a short dorsal process 

articulating with the posterior tip of basibranchial 

one and a ventral prong that curls anteroventrally 

under basibranchial one (Figure 13c, inset). 

Hypobranchial three of Psephurus and Polyodon 

is slender and makes single contact with the basibranchial 

(Grande & Bemis 1991). Hypobranchial 

three of † Crossopholis (when preserved) is apparently 

similar (Grande & Bemis 1991), with a narrow 

medial end suggesting a slender tip. It is cartilaginous 

in adults and not known from † Chondrosteus 

or † Peipiasteus. Hypobranchial three of † Mimia 

(Gardiner 1984a) and Polypterus possess single 

joints with the basibranchial. 

Character 23. Pectoral scales are elongate with multiple 

toothlike extentsions – Acipenseridae 

Pectoral scales studding the inner surface of the 

opercular chamber are elongate elements with multiple 

recurved tips (Figure 14c, d). Typically, three to 

five recurved tips overhang opposing depressions 

within the scale. Morphology of these scales varies 

inAcipenser and Huso, although the basic pattern is 

Character 24. Commissure of the occipital canals - 

Acipenseridae 

In all acipenserids examined, the contralateral occipital 

canals enter the median extrascapular and 

merge as a short common canal extending anteriorly 

(Figure 5). 

Occipital canals of Polydon, Psephurus, and 

† Crossopholis are borne by tube bones that expand 

in adults but do not meet at the midline (Grande & 

Bemis 1991). Extrascapulars, and passage of lateral 

line canals, of †Paleopsephurus are unknown. A 

complete row ofextrascapulars is present in † Chondrosteus 

acipenseroides (Traquair 1887), but not in 

† C. hindenburgi (Hennig 1925). These extrascapulars 

are small (Figure 5a), and the commissure 

might be variable, but a persistent canal has not 

been described in these bones. † Peipiaosteus lacks 

extrascapulars in described specimens (Liu & Zhou 

1965, Zhou 1992). 

Character 25. Basitrabecular processes form flattened 

shelves - Huso 

Basitrabecular processes of Huso are elongate 

shelves that flare laterally under the orbit (Figure 

15a). They are flat ventrally, extending flush from 

the base of the neurocranium with little or no ventrolateral 

curvature. The groove carrying the palatine 

ramus of the facial nerve and segregating the

94 

Figure 13. Ventral hyobranchial skeleton in Psephurus and representatives of Huso and Scaphirhynchus: The skeleton is shown in oral 

view Hypobranchial three (hb3) ofScaphirhychus is also shown in lateral view in the inset of (c). The first hypobranchial (hbl) is 

expanded with an anterior shelf in acipenserids (heavy arrow in b, c; Character 21). It also possesses a posterior wedge contacting 

hypobranchial two (hh2) in scaphirhynchines (thin arrow; Character 51). Hypobranchial three (hb3) makes double contact with basibranchial 

one (bb1) through a ventral process undercutting the basibranchial (inset in c) in all acipenserids (Character 22). The unidentified 

median cartilage (ug)ofPsephurus and Huso is missing in acipenserines (Character 37). hh = hypohyal, bb = basibranchial, cb = 

ceratobranchial, hb = hypobranchial.

95 

basitrabecular process medially (Findeis 1993) is 

thin and shallow. 

This morphology contrasts with the inferred plesiomorphic 

condition of Psephurus and several species 

of Acipenser (e.g., A. ruthenus, A. transmontanus) 

with basitrabecular processes that protrude 

ventrally (Figure 15b) and are isolated by deep 

grooves medially. Basitrabecular morphology varies 

widely among other taxa. Some species of Acipenser 

(e.g., A. oxyrinchus) possess basitrabecular 

processes that curl medially over the palatine 

groove to occasionally complete a nerve canal. Acipenser 

brevirostrum possesses stubbier processes 

that flare laterally unlike other species of Acipenser 

examined (Figure 15c). Scaphirhynchines possess 

small processes and a basitrabecular cartilage (Figure 

15d, e; Character 43). Variation within Acipenser 

makes basitrabecular morphology a difficult 

character to analyze, but the morphology of Huso is 

unique. 

Character 26. No palatoquadrate-interhyal joint 

- Huso 

The interhyal (ih) ofHuso does not contact the palatoquadrate, 

articulating only with Meckel’s cartilage 

(mk, Figure 16c). It is unexpanded anterodorsally 

and the palatoquadrate lacks a corresponding 

interhyal process (Figure 16c). This character was 

described by Tatarko (1936) and has been used as a 

Huso character by other authors (e.g., Berg 1948a, 

Antoniu-Murgoci 1936b). 

All other extant acipenseriforms possess jaw-interhyal 

joints with mutual contact of the interhyal, 

Meckel’s cartilage, and palatoquadrate (Figure 16a, 

b, d, e). Osteologically, contacting extensions of the 

interhyal (ihpa) and palatoquadrate (pq) are found 

in extant polyodontids (Figure 16a, b), all species of 

Acipenser examined (Figure 16d; Tatarko 1936, Antoniu-Murgoci 

1936b), and scaphirhynchines (Figure 

16e), but ratio of Palatoquadrate/Meckel’s cartilage 

contact with the interhyal varies. Meckel’s 

Figure 14. Scales of the pectoral girdle in Psephurus, † Peipiaosteus, and representatives of Huso and Acipenser: The pectoral scales of 

acipenserids (c, d) possess multiple recurved tips overhanging an elliptical base (Character 23). Polyodontids (a - redrawn from Grande 

& Bemis 1991) possess pectoral scales with a single process and the scales of † Peipiaosteus (b - redrawn from Liu & Zhou 1965) possess 

three processes fanning from a flat base.

96 

Figure 15. Basitrabecular processes of representatives of all genera of Acipenseridae: Basitrabecular processes (btp) extend ventrally 

beneath the orbit (top in cross-hatch). Morphology varies within Acipenser (b, c), but they are flattened shelves in Huso (a; (Character 25). 

Scaphirhynchines (d, e) possess indepent basitrabecular cartilages (btc) bound to small basitrabecular processes (Character 43). 

cartilage dominates the jaw joint in polyodontids 

(Figure 16a, b) with its posterior end expanded as a 

bulb displacing the palatoquadrate (also in Huso, 

Figure 16c). Scaphirhynchines and all species of 

Acipenser examined possess jaw joints with approximately 

equal contact among elements (Figure 16d, 

e) or jaw joints with dominant palatoquadrate-interhyal 

contact (i.e. A. oxyrinchus).

Figure 16. Jaw joint of polyodontids and representatives of three genera of Acipenseridae: The jaw joint is shown with anterior facing left. 

The interhyal (ih) contacts the palatoquadrate (pq) in all extant acipenseriformes except Huso (c; Character 26) where contacting extensions 

of the interhyal (ihpa, heavy arrows) and palatoquadrate are not present. The joint with the posterior ceratohyal (chp) is anterior in 

Huso and polyodontids (arrows to left in a, b, c), but displaced posteriorly in acipenserines (arrows pointing right in d, e; Character 36). 

h = hyomandibula, mk = Meckel’s cartilage. 

97

98 

Figure 17. Ventral rostrum of Psephurus and representatives of three genera of Acipenseridae: The rostrum is thin and tapers in Psephurus 

(a) and Huso (b) with the groove for the rostral nerves (grn) opening laterally alongside the endochondral rostrum (large arrow in a, 

b). Acipenserines (c, d) possess lateral ethmoid ridges (ler, open arrows) that bracket the groove to the tip of the rostrum (Character 27). 

They are expanded as the lateral ethmoid shelves of scaphirhynchines (les; Character 39). Foramina for the nerves that innervate the 

dorsal ampullary organs (nf and arrows) indicate expansion of the lateral ethmoid shelves. The parasphenoid (pas) is exposed as it 

contacts the ventral rostral bones in Huso and polyodontids (a, b), but is covered by the central trabecular process in acipenserines (ctp in 

c, d; Character 31). tr = trabecular ridge, vrb = ventral rostral bones.

99 

Character 27. Presence of lateral ethmoid ridges - 

Acipenserinae 

Lateral ethmoid ridges form the lateral edges of the 

endochondral rostrum in scaphirhynchines (les, 

Figure 17d) and all species of Acipenser examined 

(ler, Figure 17c). They are ventrolaterally expanded 

bands of cartilage lateral to the grooves housing the 

rostral nerves (grn; Findeis 1993). These ridges extend 

seamlessly from the median rostrum and ethmoid 

region of the neurocranium without obvious 

boundaries. In acipenserines, the lateral ethmoid 

ridges support a ‘hard’ rostrum of cartilage and dermal 

bone. Lateral ethmoid ridges of Acipenser 

curve ventrally as thin ridges parallel to the median 

trabecular ridge (tr). These ridges expand into 

broad lateral ethmoid shelves in scaphirhynchines 

(see Character 39). 

Huso and extant polyodontids possess endochondral 

rostra that indent anterior to the olfactory 

bulbs (Figure 17a, b). In Huso, the ethmoid region 

possesses expanded olfactory bulbs contributing to 

the postnasal wall as in acipenserines (see Characters 

3,4), but no lateral ethmoid ridges extend anteriorly 

(Figure 17b) as the rostral grooves (grn) pass 

under the olfactory capsule (oc) and open anteriorly 

alongside the trabecular ridge (tr, Figure 17b) 

without cartilage bracketing them laterally. The 

rostrum correspondingly tapers rather than remaining 

expanded as a shield as in acipenserines. 

Psephurus and Polyodon lack a broad ethmoid region, 

with a bare olfactory capsule exposed along 

the thin endochondral rostrum (Figure 17a). In 

Huso and polyodontids, the rostral surface expands 

laterally beyond the endochondral rostrum as a 

‘soft’ rostrum supported by skin. The rostrum converges 

anteriorly in Huso and the rostral skin is not 

supposted by any bones. The rostrum expands as a 

paddle in polyodontids supported peripherally by 

an extensive series of stellate bones (Grande & Bemis 

1991). 

Character 28. Dorsal rostralseries forms an expanded 

shield- Acipenserinae 

Dorsal rostral bones in all acipenserines examined 

form a broad shield expanding anterior to the olfactory 

cavity (drb, Figure 18c, d). The dorsal rostral 

shield broadens in concert with expansion of the endochondral 

rostrum of acipenserines (see Character 

27). 

Huso and polyodontids (Grande & Bemis 1991) 

possess a narrow dorsal rostral series with consistent 

breadth along the rostrum (Figuse 18a, b). 

Lacking rostral expansion anterior to the olfactory 

bulb, there is no space for an expanded rostral 

shield in the outgroups. The expanded dorsal rostral 

series is likely linked with the lateral ethmoid 

ridges as the bones occupy the expanded rostral surface 

in acipenserines. Initially developing bones of 

the dorsal rostral series form a median row similar 

to Huso and polyodontids that ontogenetically and 

phylogenetically expands by addition of novel 

bones (Findeis 1993). 

Character. Presence of border rostral bones - Acipenserinae 

Border rostral bones (brb) are a thin series (one or 

two bones wide) of small bones along the posterolateral 

edge of the rostrum anterior to the jugal (j, 

Figure 18c, d). They are positionally separate and 

ontogenetically distinct from the dorsal rostral series 

as a novel group of rostral bones in scaphirhynchines 

(Findeis 1993) and all species of Acipenser 

examined (Figure 18c, d). Although variable in 

number, border rostral bones form a consistent assemblage. 

Spatial separation ofdorsal and border rostral series 

is typical in Acipenseroxyrinchus, A. transmontanus, 

and A. ruthenus, with an open corridor housing 

ampullary organs of the dorsal rostrum (Figure 

18c). Only in large adults ofA. brevirostrum (among 

species of Acipenser examined) did this gap partially 

close to make identification of the groups diffi 

cult. In scaphirhynchines, bones entirely cover the 

rostrum (Figure 15, 16), but by addition of ampullary 

bones between these series (Character 40). The 

multiplicity of rostral bone groups confuses character 

recognition in the dermal rostrum, but each series 

is ontogenetically discrete. 

No bones lateral to the dorsal rostral series are

100 

Figure 18. Dorsal bones of the rostrum of † Paleopsephurus and representatives of three genera of Acipenseridae: Dorsal rostral bones 

(drb) form a rectangular cover in polyodontids and Huso, but are expanded as a shield (Character 28) and accompanied by border rostral 

bones (brb) extending from the jugal (j) in acipenserines (Character 29). The dorsal rostral and border rostral series are separated by an 

ampullary field (stippled circles in c) in Acipenser, but this area is filled with ampullary bones (apb) in scaphirhynchines (d; Character 40). 

The pineal fontanelle (pf) is open between the frontal bones in polyodontids and Huso (a, b), but filled by pineal bones (pb) in acipenserids 

(Character 32). The pineal fontanelle is partially filled in juveniles of Acipenser oxyrinchus (b), but covered in other acipenserines (as 

in d). oc = olfactory capsule opening in dermal skull.

101 

face of the neurocranium without a cartilage cover 

(Figure 17a, b). These taxa also lack an ethmoid-orbital 

angle as the ventral neurocranium curves 

smoothly into the orbit in Huso (Figure 20b), Psephurus, 

and † Paleopsephurus (Grande & Bemis 

1991), or is straight in the derived polyodontids Polyodon 

(Figure 20a) and † Crossopholis. The central 

trabecular process correlates phylogenetically with 

ventral displacement of the jaws of acipenserines 

and possibly deflects them ventrally during projec- 

tion. 

present in Huso (Figure 18b). Stellate bones supporting 

the lateral rostrum in polyodontids are present 

lateral to the endochondral rostrum only within 

the skin of the paddle (Grande & Bemis 1991). 

Border rostral bones lie directly on the rostrum 

posterolaterally, while polyodontid stellate bones 

are isolated anterolaterally. 

Character 30. First ventral rostral bone in single - 

Acipenserinae 

The first ventral rostral bone of acipenserines (vrb1, 

Figure 19c, d, e) is a single bone that contacts the Character 32. Pineal bones present - Acipenserinae 

parasphenoid as the most posterior bone of the ventral 

rostral series (Findeis 1993). It is only modestly 

larger than other ventral rostral bones in all species 

of Acipenser examined, but is elongate in scaphirhynchines 

(Character 42). 

In Huso and all polyodontids (Figure 19a, b), the 

ventral rostral series possesses paired bones contacting 

the parasphenoid. These bones were named 

vomers by Grande & Bemis (1991), but they develop 

on the rostrum well anterior to the parasphenoid 

and are not present in † Chondrosteus (Traquair 

1887, Hennig 1925) or † Peipiaosteus (Liu & Zhou 

1965), suggesting that they are novel bones of the 

rostrum and rostral series of acipenseroids. 

Pineal bones develop within the pineal fontanelle 

between the frontals (pf, Figure 18b, c) in juveniles 

and typically expand to fill the space in adults (pb, 

Figure 18c, d). Number of pineal bones varies, but 

they are consistently present in all acipenserines examined. 

Pineal bones are anamestic bones that are developmentally 

constrained by bones surrounding the 

pineal fontanelle. Pineal bones fill the pineal fontanelle 

completely in Scaphirhynchus and most species 

of Acipenser, but A. oxyrinchus and A. sturio 

are often recognized by an open fontanelle (Figure 

18c; Vladykov & Greeley 1963, Magnin 1963, Magnin 

& Beaulieau 1963). However, pineal bones appear 

even in these species, but do not enlarge to fill 

Character 31. Central trabecular process present - the fontanelle except in very large adults. 

Acipenserinae 

The pineal fontanelle occasionally closes by expansion 

of the frontals. Pseudoscaphirhynchus 

The central trabecular process is a ventral cartilagi- kaufmanni shows both morphologies, with the 

nous wedge between the ethmoid and orbital re- frontals separated by pineal bones (illustrated by 

gions of the neurocranium in all acipenserines ex- Sewertzoff 1926a) or also exhibiting frontal closure 

amined (ctp, Figure 20c, d). This process protrudes posteriorly. Specimens of Acipenser mediostris and 

posterior to the trabecular ridge (tr, Figure 17) be- A. oxyrinchus also partially close the pineal fontafore 

rising sharply under the orbit as the ethmoidorbital 

angle (Findeis 1993) to open a ventral space 

for the jaws (Figure 20c, d). The central trabecular 

process covers the posterior end of the first ventral 

rostral bone and anterior extension of the parasphenoid 

(shown in Figure 17c, d). 

In Huso and extant polyodontids (Grande & Bemis 

1991), the paired first ventral rostral bones (see 

Character 30) contact the parasphenoid on the sur- 

nelle by frontal expansion. While pineal bones appear 

universally in small juveniles, frontal expansion 

occurs only in adults and all specimens showing 

frontal expansion also possess pineal bones. 

No pineal bones are present in Huso or any polyodontid 

(Grande & Bemis 1991). The pineal fontanelle 

of these taxa (when present) is narrow between 

frontals (Figure 18a, b). The fontanelle is reduced 

or absent in large juveniles of Huso, but no

102 

Figure 19. Ventral rostral bones in †Paleopsephurus and representatives of all genera of Acipenseridae: The series is shown in ventral view 

with anterior to top. The first ventral rostral bone (most posterior) is paired in polyodontids and Huso (a, b), but single in acipenserines (c, 

d, e; Character 30). This bone is elongate in scaphirhynchines (d, e; Character 42), with the remaining bones clustered at the anterior tip of 

the rostrum. 

pineal bones are present and the frontal lacks dermal 

ornament medially, suggesting that closure occurs 

by frontal expansion. There are often two 

openings in polyodontids (Grande & Bemis 1991), 

but only one in Huso. These outgroups possess 

frontals making medial contact, and the frontals of 

† Chondrosteus (Traquair 1887, Hennig 1925) and 

†Peipiaosteus (Liu & Zhou 1965) uniformly close in 

the skull roof. 

joint. Polyodon is similar, but less strikingly since its 

elongate jaws coincidentally flatten all jaw features. 

The dentary of all fossil polyodontids (Grande & 

Bemis 1991 and †Chondrosteus (Traquair 1887) is 

angled, suggesting that an angled lower jaw is plesiomorphic 

within Acipenseriformes. Zhou (1992) 

reconstructs the dentary of †Peipiaosteus with a 

slight angle and I accept an angled lower jaw as plesiomorphic 

for Acipenseridae. 

Character 33. Lower jaw is straight-Acipenserinae 

The lower jaw of all acipenserines examined is short 

and transverse under the head. Meckel’s cartilage 

curves slightly opposite the upper jaw to define the 

mouth near the symphysis, but the lateral end of 

Meckel’s cartilage and the dentary is almost entirely 

linear throughout its length (Figure 21c). 

The posterior end of Meckel’s cartilage and the 

dentary of Huso and Psephurus (Grande & Bemis 

1991) angles dorsally (Figure 21a, b) toward the jaw 

Character 34. Dermopalatine sheIf present-Acipenserinae 

The medial dermopalatine broadens as a ventral 

shelf in all acipenserines examined (Figure 22c). 

This dermopalatine shelf deepens the upper jaw as 

an anteromedial surface often opposing a protruding 

dentary shelf (Figure 21c). The dermopalatine 

shelf is consistently present, but the dentary shelf is 

not universal and not used as a character here. The 

dermopalatine shelf occurs where the dermopala-

103 

Figure 20. Lateral view of the orbit and ethmoid regions ofthe neurocranium in Polyodon and representatives of three genera of Acipenseridae: 

The ventral surface of the neurocranium is flat in Polyodon (a) and rises smoothly in Psephurus and Huso (b), but angled by the 

central trabecular process (ctp) in acipenserines (Character 31). oc = olfactory capsule, pnw = postnasal wall, btp = basitrabecular process, 

fII = foramen of the optic nerve. 

tine contacts the palatoquadrate medially and bears 

teeth in juveniles. 

Dermopalatines of Huso (Figure 22b), all polyodontids 

(Figure 22a; Grande & Bemis 1991), †Chondrosteus 

(Traquair 1887), and †Peipiaosteus (Liu & 

Zhou 1965) possess flat anteroventral edges. These 

taxa also bear teeth along the full edge of the dermopalatine, 

not in a restricted portion. Similarly, 

the lower jaws of outgroups lack a dentary shelf 

(Figure 21a, b). 

Character 35. Prearticular bones are small and thin - 

Acipenserinae 

The prearticular is a small, splinter-like bone on the 

inner surface of Meckel’s cartilage (Figure 21c). Its 

size and shape conforms to the thin, straight jaws of 

acipenserines (Character 33). The prearticular is 

absent in scaphirhynchines (Character 48). 

The prearticular of Psephurus (Grande & Bemis 

1991) and Huso (Figure 21a, b) is a flat, triangular 

bone covering the posterodorsally angled inner surface 

of Meckel’s cartilage (see Character 33). This 

bone is elongate and thin in † Crossopholis and Polyodon 

(Grande & Bemis 1991), but these taxa pos-

104 

sess thin jaws. † Paleopsephurus is not preserved 

correctly to see the prearticular. † Chondrosteus 

possesses a large, flat prearticular (Watson 1928), 

but it is apparently not present in † Peipiaosteus (Liu 

& Zhou 1965, Zhou 1992). Despite the multiplicity 

of outgroup morphologies, the acipenserine prearticular 

is characteristically reduced. 

Character 36. Interhyal-posterior ceratohyal joint 

displaced posteriorly - Acipenserinae 

The interhyal-posterior ceratohyal joint occurs on 

the posterior half of the interhyal in all acipenserines 

examined (Figure 16d, e). Precise position of 

the joint ranges from the posterior edge (chpf, Figure 

16d; e.g., A. oxyrinchus, A. transmontanus) toa 

more central position within the interhyal (Figure 

16e; e.g., scaphirhynchines, A. brevirostrum). 

Figure 21. Lower jaw and prearticular of Psephurus and representatives of Huso and Acipenser : The lowerjaw is shown in lateral view to 

the left, with the prearticular shown in oral view to the right. Meckel’s cartilage angles posterodorsally tu the jaw joint in Psephurus and 

Huso (arrows in a, b), but is straight in acipenserines (c; Character 33). Coincidentally, the flat prearticular of the outgroups (a, b) is 

reduced to a thin bone in acipenserines (Character 35) and absent in scaphirhynchines (Character 48).

105 

of all acipenserines examined includes a large basibranchial 

one and one or two small posterior basibranchials 

(Figure 13c), but no other elements. 

The posterior basibrachials are paired serially with 

ceratobranchial lour and five (e.g., bb2 associated 

with cb4 in Figure 13). 

The branchial arch skeleton of Huso and extant 

polyodontids possesses a median cartilage posterior 

to the serial basibranchials (ug). The median cartilage 

of Huso is thin and short (Figure 13b), but 

forms a plate in Polyodon and Psephurus (Figure 

13a). Grande & Bemis (1991) named it an unidentified 

median cartilage and it has no postional affinity 

with any branchial arch. This element is cartilaginous 

and not scorable in fossils, but is present in all 

extant outgroups. 

Character 38. Loss of haemal spines anterior to the 

caudal fin - Acipenserinae 

Figure 22. Dermopalatine of † Paleopsephurus and representatives 

of Huso and Acipenser: The dermopalatine is flat along the 

anteroventral edge in † Paleopsephurus and Huso (a. b). but expanded 

medially in acipenserines (arrows in c: Character 34). 

The dermopalatine (dp) and ectopterygoid (ecp1) fuse in Sca 

phirhynchus (Character 69). but are separate elements in all 

other acipenseriforms (as shown in a. b c). 

The in terhyal-posterior ceratohyal joint of Huso 

and extant polyodontids (Grande & Bemis 1991) 

occurs anteriorly on the interhyal (Figure 16a, b, c). 

This is a cartilaginous character not scorable in fossil 

acipenseriforms. but the anterior joint is consistent 

in all extant outgroups. 

Character 37. Loss of median cartilage posterior to 

branchial arches – Acipenserinae 

The ventral midline of the branchial arch skeleton 

Elongate basiventrals with haemal spines are present 

in a short span of the vertebral column entering 

the caudal fin, but are missing in the caudal peduncle. 

In all acipenserines examined, three to four basiventrals 

with haemal spines (bvh) are typically 

found anterior to the hypurals (hyp, Figure 23b) 

supporting the anterior fin rays of the caudal fin as 

an anterior shelf characteristic of Acipenseriformes 

(Findeis 1993, Bemis et al. 1997). More anterior basiventrals 

never possess haemal spines (bv, Figure 

23b). 

Polyodontids (Grande & Bemis 1991) and Huso 

(Figure 23a) possess haemal spines throughout the 

caudal peduncle and extending anteriorly over the 

anal fin. Elongate haemal spines may be dependent 

on a deep peduncle, with the flattened peduncle of 

acipenserines too spatially restricted to accommodate 

them. 

Character 39. Lateral ethmoid shelves present- Scaphirhynchini 

The lateral ethmoid ridges of scaphirhynchines are 

broad and ventrally flat, forming lateral ethmoid 

shelves (les, Figure 17d) lateral to the groove carry-

106 

ing the rostral nerves (grn). The lateral ethmoid 

shelves are penetrated several millimeters from the 

lateral edge by foramina carrying nerves to ampullary 

organs of the dorsal rostrum (nf and arrows, 

Figure 17d). Size and shape of the rostrum varies, 

but expanded lateral ethmoid shelves are present in 

all scaphirhynchines. 

In all species of Acipenser examined, the lateral 

ethmoid ridges end in a thin ventral edge (Figure 

17c). No foramina penetrate these lateral ethmoid 

ridges, suggesting that cartilage is added lateral to 

the foramina in scaphirhynchines. Since Huso and 

polyodontids do not possess lateral ethmoid ridges, 

this is a two taxon statement at the generic level, but 

1 accept the flattened morphology of scaphirhynchines 

as derived. The cylindrical head of Huso sug- 

Figure 23. Caudal fin endoskeleton of Huso huso and Scaphirhynchus platorynchus: Anterior faces to left. Hypurals (hyp) are stippled 

lightly while the more anterior basiventrals (bv) and basiventraIs with haemal spine (bvh) are dark. Basiventrals with haemal spines 

overlap the anal fin in Huso, but are restricted to the caudal fin in acipenserines (Character 38). The elongate caudal peduncle of 

Scaphirhynchus (b; (Character 64) displaces the dorsal and anal fins anteriorly, but possessing only three-four basiventrals with haemal 

spines is typical for acipenserines. The notochord and bracketing cartilages end in unison in Huso (a) and Acipenser, but a cartilaginous 

core supporting the cercus continues in scaphirhynchines (Character 53) beyond the terminus of the notochord. bd = basidorsals, sn = 

supraneural homologs.

gests that the generally cylindrical skulls and rostra 

typical of most species of Acipenser are plesiomorphic. 

Character 40. Ampullary bones present - Scaphirhynchini 

107 

lost discrete spines, but a ridge is present in photographs 

in Williams & Clemmer (1991) and probably 

represents a residual spine. When present, 

spines are present on the parietal, posttemporal, supracleithrum, 

and multiple anterior dorsal rostral 

bones. 

Spines of Scaphirhynchus are shallow and ridgelike, 

but elevate into sharp posterior points. They 

are prominent in juveniles, but become allometri- 

cally smaller in adults as dermal ornament thickens 

and obscures them. Spines of the posttemporal and 

supracleithrum are the largest in Scaphirhynchus, 

Ampullary bones compose an ossification group 

covering the endochondral rostrum between the 

dorsal rostral series and peripheral border rostral 

bones (Figure 18d). They are small, rounded (Scaphirhynchus) 

or larger, rectangular (Pseudosca- with posteriorlycurved tips identical to and in series 

phirhynchus) plates that interweave among the with the flank scutes. Spines of P.kaufmanni are 

dorsal rostral ampullary field. Ampullary bones de- large, with posttemporal and supracleithrum spines 

velop as a group well after appearance of the dorsal similar to Scaphirhynchus accompanied by huge 

rostral series (Findeis 1993) and anterior to the si- parietal and frontal spikes (see Character 55). 

multaneously developing border rostral bones Weak spines occur occasionally on the supratempo- 

(brb, Figure 18c, d) to cover the broad scaphirhyn- ral of Scaphirhynchus, but they are rarely visible 

chine rostrum (see Character 39). 

and not present in P. Kaufmanni 

The border rostral series is a putative synapo- Some skull bones of Acipenser possess central 

morphy of the Acipenserinae (Character 29) dis- ridges, but never manifest spines and anterior dortinct 

from the ampullary series. Border rostral sal rostral bones are plates without raised ridges or 

bones of Acipenser are positionally separate from spines. Huso never possesses spines or strong ridges 

dorsal rostral bones in early ontogeny and usually in in any skull bones and polyodontids possess little 

adults (Figure 18c). No interior rostral bones fill this dermal ornament on the skull roof and no discrete 

gap in small juveniles of any species of Acipenser ridges (Grande & Bemis 1991). † Chondrosteus 

examined, suggesting that the ampullary series is (Hennig 1925) and †Peipiaosteus (Liu & Zhou 1965) 

missing in Acipenser. Broadening of the rostrum in possess obvious dermal ornament, but no spines. 

scaphirhynchines (see Character 39) opens it dorsal 

surface unlike any outgroup and this area is covered 

by a novel ampullary series. 

Character 42. First ventral rostral bone is elongate - 

Scaphirhynchini 

Character 41. Central spines present on the parietal, 

postiemporal, supracleithrum, and anterior dorsal 

rostral bones – Scaphirhynchini 

Central spines are present in Scaphirhynchusplatorynchus, 

S.albus, and Pseudoscaphirhynchus kaufmanni, 

variably present in P. fedtschenkoi (Berg 

1948a), but absent in S. suttkusi and P. hermanni 

(Berg 1948a). Within Pseudoscaphirhychus, P. 

kaufmanni is most simiIar to Scaphirhynchus and 

seems to be representative for the basal morphotype 

of the genus, with presence of spines pulatively 

plesiomorphic. Scaphirhynchus suttkusi may have 

The first ventral rostral bone of scaphirhynchines is 

elongate, accounting for over two-thirds the length 

of the ventral rostral series (vrb1, Figure 19d, e). It is 

a wide, Flat bone slightly keeled centrally with additional, 

smaller bones of the ventral rostral series 

clustered anteriorly. Scaphirhynchus typically possesses 

four or five additional ventral rostral bones 

(Findeis 1993), while Pseudoscaphirhynchus kaufmanni 

can possess twice as many (nine in Figure 

19c). 

This is a qualitative character since first ventral 

rostral bones of all species of Acipenser examined 

are also the longest of the series (Figure 19c). How-

108 

ever, in Acipenser they are not as dominantly elongate 

and are thin. Similarly, Huso and all polyodontids 

(Grande & Bemis 1991) possess paired first ventral 

bones only modestly longer than other bones of 

the series (see Character 30). 

Character 43. Basitrabecular cartilages present - 


orbit and do not open dorsally. Extant polyodontids 

possess open orbits without boundaries other than 

the bare olfactory bulbs (Figure 20a). They do possess 

a broad channel dorsomedial to the olfactory 

bulb, but this is open for their protractor hyomandibularis 

muscle and is not comparable to the orbital 

notch. 

Character 45. Posttemporal processes present - Sca- 

Basitrabecular cartilages are present in all scaphi- phirhynchini 

rhynchines lateral to the small basitrabecular processes 

(Figure 15d.,e). The basitrabecular cartilage Posttemporal shelves are cartilaginous processes of 

of Scaphirhynchus is large and curved (Figure 15d) the neurocranium that interlock with the posttemalong 

the postnasal wall (Findeis 1993). It is much poral. In scaphirhynchines, they flare posteromesmaller 

in Pseudoscaphirhynchus, being barely dially as thick processes with short distal tips that 

larger than the diminutive basitrabecular process it- angle posteriorly. They possess medially angled anself 

(Figure 15d). In Scaphirhynchus basitrabecular teroventral laces that converge to the base of the 

cartilages develop as outgrowths of the basitrabec- neurocranium. The dorsal surface is rounded and 

ular processes that separate from the neurocranium indented from the surface of the neurocranium. Bein 

small juveniles. Sewertzoff (1928) identified ba- cause of their cylindrical shape, I refer to them as 

sitrabecular cartilages as outgrowths of the palato- posttemporal processes (Findeis 1993). 

quadrate and homologized them as pharyngoman- In all species of Acipenser and Huso examined, 

dibulars, but they develop distinct from the man- the posttemporal shelves have flat lateral faces that 

dibular arch. 

converge without curvature to the base of the neu- 

All species of Acipenser examined, Huso, and rocranium. The dorsal edges are also flat, extending 

Psephurus possess large basitrabecular processes smoothly from the dorsal surface of the neurocrani- 

(Figure 15a, b, c), but no independent, accessory um and the posterolateral tips are short processes 

cartilage. 

that extend linearly from the shelves. Polyodontids 

possess posttemporal shelves similar to Acipenser 

and Huso, but they are broader, flatter, and not as 

elongate. 

Character 44. Orbital notch present - Scaphirhynchini 

The orbital notch indents into the neurocranium 

from the dorsal edge of the orbit (Findeis 1993). It 

contains passage of the profundal ramus that scatters 

onto the dorsal surface of the neurocranium 

and the superficial ophthalmic ramus of the anterodorsal 

lateral line nerve. The orbital notch lies beneath 

the supraorbital canal and an ampullary field 

anterodorsal to the orbit. 

The dorsal orbit of Acipenser and Huso is semicircular, 

without indentation. Huso and all species 

of Acipenser examined possess shallow anterodorsal 

depressions in the postnasal wall homologous to 

the orbital notch, but they are restricted within the 

Character 46. Ventral process of the antorbital is 

elongate - Scaphirhynchini 

The antorbital possesses elongate ventral processes 

along the postnasal wall in scaphirhynchines (see 

Character 4). In Scaphirhynchus, it is a straight, 

rectangular process contacting the postrostral bone 

(Figure 4e; see Character 61). In Pseudoscaphirhynchus, 

the ventral process tapers with an anteriorly 

curving point (Figure 4d). The elongate ventral process 

correlates with the expanded rostrum (see 

Character 39) to cover the postnasal wall. 

The antorbital of Huso possesses a short wedge

(Figure 4a). All species of Acipenser examined possess 

a ventral point of varying size (Figure 4b, c; see 

Character 4), but none are as elongate as in scaphirhynchines. 

Character 47. Subopercle is distinctively shaped - 


The subopercle is distinctive in scaphirhynchines by 

being elongate with a prominent anterior process, 

flattened dorsal edge, and abrupt anteroventral 

notch that angles ventrally (Figure 7e, f). This shape 

is typical of Scaphirhynchus, Pseudoscaphirhynchus 

and also † Protoscaphirhynchus (Wilimovsky 

1956). one plane. 

Subopercle shape varies within Acipenseridae. 

Huso and several species of Acipenser (e.g., A. oxyrinchus, 

A. ruthenus) possess a triangular subopercle 

(Figure 7c), while other species (e.g., A. brevirostrum, 

A. gueldenstaedtii) possess circular plates 

with blunt anterior and ventral processes (Figure 

7d). No species of Acipenser examined possesses a 

subopercle as dorsoventrally compressed as scaphirhynchines. 

The scaphirhynchine subopercle 

correlates with the flattened head limiting space for 

the operculum. As a shape character, it is difficult to 

segregate subopercle areas as characters, but overall 

bone shape is unique. 

Character 48. Loss of prearticular bones- Scaphirhynchini 

Prearticular bones are generally present on the oral 

surface of Meckel’s cartilage (see Character 35), 

but are absent in scaphirhynchines. 

Prearticular bones are present in Psephurus (Figure 

21a) and †Crossopholis(Grande & Bemis 1991), 

†Chondrosteus (Traquair 1887, Watson 1925), Huso 

(Figure 21b), and all species of Acipenser examined 

(Figure 21c). Prearticulars are unknown in † Paleopsephurus 

and †Peipiaosteus (Liu & Zhou 1965), 

but otherwise ubiquitous distribution of the bone in 

outgroups suggests it is plesiomorphically present. 

109 

Character 49. Dorsal head of the hyomandibula is 

cylindrical - Scaphirhynchini 

The dorsal head of the hyomandibula of scaphirhynchines 

is cylindrical and ends in a small elliptical 

tip (Figure 11d) that articulates with the neurocranium 

as a loose joint. 

Psephurus (Grande & Bemis 1991), Huso, and all 

species of Acipenser examined possess hyomandibulae 

with the dorsal head expanded frontally (Figure 

11c). In extant polyodontids, the dorsal head is 

rectangular. In Huso and Acipenser, the head is elliptical 

with an expanded bony shaft at its base (Figure 

11c). The frontally expanded hyomandibula 

forms a restrictive joint allowing pivoting in only 

Character 50. Ventral edge of the hyomandibula is 

flat - Scaphirhynchini 

The ventral head of the hyomandibula of scaphirhynchines 

ends in a flat edge roughly perpendicular 

to the long axis of the element (Figure 11d). The 

interhyal joint opens on the anteroventral face, but 

is not isolated from the ventral edge. 

The hyomandibula of Psephurus (Grande & Bemis 

1991), Huso, and all species ofAcipenser examined 

taper ventrally into narrow anteroventral tips 

(Figure 11a, b, c) that articulate with the interhyal. 

Ventral flattening of the hyomandibula of scaphirhynchines 

correlates with overall flattening of the 

head and consequent restricted dorsoventral space 

for the hyoid skeleton. 

Character 51. Hypobranchial one contacts hypobranchial 

two - Scaphirhynchini 

In scaphirhynchines, the posterior edge of hypobranchial 

one forms a wedge contacting hypobranchial 

two (Figure 13). Contact is slight, but ligaments 

consolidate the elements as a unit. 

In Psephurus (Grande & Bemis 1991), hypobranchials 

are roughly cylindrical, without expansion of 

the oral surface (Figure 13a). Huso and all species of 

Acipenser examined possess rectangular first hypo-

110 

Figure 24. Ventral axial skeleton of representatives of Acipenser and Scaphirhynchus: Ontogeny of the haemal arch is shown in A. 

brevirostrum (a) with a small juvenile (left) possessing only slight extension of the basiventrals (bv) compared to the nearly complete 

haemal arch of an adult (right). This adult specimen possessed a complete haemal arch more anteriorly similar to that of A. oxyrinchus (b) 

with contralateral sealing of the basiventrals and interventrals (iv). Scaphirhynchines never possess a haemal arch and lack ventral 

expansion of the basiventrals even in large adults (c; Character 52). 

branchials in the tongue pad (see Character 21), but 

they lack a posterior wedge contacting hypobranchial 

two (Figure 13b). Connective tissue ridges are 

restricted to hypobranchial one in Huso and Acipenser, 

but overlap hypobranchial two in scaphirhynchines. 

Juvenile Pseudoscaphirhynchus possess 

a tooth plate on hypobranchial two (Berg 

1948a), suggesting that the functional palate is expanded 

generally in scaphirhynchines. 

Character 52. Loss of a haemal arch 

- Scaphirhynchini 

Ventral edges of basiventrals of scaphirhynchines 

end flatly with a slight ventral lip (Figure 24c). The 

basiventrals are open ventrally, lacking a haemal canal 

until reaching the caudal fin supported by haemal 

spines (see Character 38). In the peduncle, the 

basiventrals extend more ventrally to form a ventral 

groove, but never converge toward the midline.

In adults of Polyodon, Huso, and Acipenser, ventrolateral 

edges of the basiventrals curl to the midline 

to complete a haemal arch (Figure 24a, b). This 

is a problematic character because it develops late, 

only in adults by progressive elongation and merging 

of the basiventrals and interventrals (bv, iv, Figure 

24a). In the thoracic region, independent ventral 

plates also integrate into the haemal arch. Juvenile 

specimens of Acipenser are similar to Scaphirhynchus, 

but with a slightly more pronounced 

basiventral edge (Figure 24a, c). However, while all 

species of Acipenser examined close a haemal arch, 

even large Scaphirhynchus lack any expansion of 

the basiventrals. 

Character 53. Caudal fin filament present - Scaphirhynchini 

111 

Universal presence of these scales in all other acipenserids 

and their outgroups suggests that this loss 

defines Scaphirhynchini. 

Character 55. Spikes present on the frontals-Pseudoscaphirhynchus 

Spines of the frontals, parietals, and anterior dorsal 

rostral bones of Pseudoscuphirhynchus kaufmanni 

are large spikes. Spikes are always present in P. 

kaufmanni, but are lacking in P. hermanni and P. 

fedtschenkoi (Berg 1948a). Pseudoscaphirhynchus 

hermanni occasionally has weak spines on anterior 

dorsal rostral bones (Berg 1948a), perhaps suggesting 

that a morphotype possessing spines is plesiomorphicforthegenus. 

I accept P. kaufmannias rep- 

resentative for the genus, with spines as a scaphirhynchine 

character (Character 41) secondarily lost 

in other species of the genus. 

Spines of Scaphirhynchus are raised ridges simi- 

lar to, but more shallow than spikes of P. kaufman- 

The caudal fin filament (or cercus) is found in Scaphirhynchus 

and Pseudoscaphirhynchus kaufmanni 

extending from the tip of the caudal fin (Figure 

23). It is formed by a thin core of cartilage sheathed ni. This variation in morphology and presence 

by small scales. It originates posterior to the noto- among scaphirhynchinesmakes it difficult to define 

chord, developing distinctly later than the caudal distinct types of spines or spikes. While spikes of 

endoskeleton in smalljuveniles. 

Pseudoscaphirhynchus are distinct in size from the 

All species of Scaphirhynchus, P. kaufmanni, and spines of Scaphirhynchus, they are similar in shape 

certain morphotypes of P. fedtschenkoi (Berg andnot accepted as discrete shape characters here. 

1948a) possess a cercus. It is not present in P. her- Nevertheless, nospines arepresent onthefrontal in 

manni, but presumably due to secondary loss. The Scaphirhynchus, and presence of frontal spikes is 

fin filament is short in Scaphirhynchus, rarely ex- distinctive of Pseudoscaphirhynchus. 

ceeding five centimeters in length, but can reach 13 

centimeters or more in P. kaufmanni. 

No other extant acipenseriforms possess a caudal Character56. Lateral extrascapulars enclose the triradiation 

fin filament and its scalation would be visible in fossils 

of the trunk, occipital, and supratemporal 

if present. The caudal endoskeleton of outgroup canals - Pseudoscaphirhynchus 

acipenseriforms possesses dorsal and ventral sheets 

of cartilage that merge and terminate with the notochord 

(Figure 23a). 

Character 54. Loss of pectoral scales 

- Scaphirhynchini 

Pectoral scales with elevated, recurved tips typically 

found on the opercular wall of acipenseriforms 

(see Character 23) are absent in scaphirhynchines. 

The occipital canal (ocll) is carried by a lateral extrascapular 

series (excl, Figure 5e) in Pseudoscaphirhynchus 

that includes its origin separating from 

the trunk (trll) and supratemporal canals (stll). The 

lateralmost lateral extrascapular encompasses the 

tri-radiation of these canals as this series of bones 

(usually three) intrudes centrally over the posttemporal 

(Figure 5e). 

In all other acipenserids examined (Figure 5b, c, 

d), splitting of these canals occurs within the post-

112 

Figure25. Gill rakers of representatives of all genera of Acipenseridae: The gill rakers of Huso (a), primitive polyodontids, and † Chondrosteus 

are elongate. Species of Acipenser typically possess triangular rakers (b). Scaphirhynchus (c) possesses crenelated rakers with 

several paired nubs along the oral edge (Character 63). Pseudoscuphirhynchus kaufmanni possesses pronged rakers with two, orally 

pointed tips (Character 58). 

temporal as the occipital canal is carried initially by 

the posttemporal before entering the lateral extrascapulars. 

Pattern of the canals themselves is invariable 

in acipenseriforms, suggesting that the dermal 

patterning changed in Pseudoscaphirhynchus. 

Character 57. Jugal is large and lacks a canal process 

- Pseudoscaphirhynchus 

The jugal of Pseudoscaphirhynchus is huge, extending 

anteriorly to completely undercut the orbit and 

most of the olfactory opening, but lacks a canal process 

(see Character 3) enclosing the infraorbital canal 

(Figure 3d). The posteromedial jugal is expand-

113 

Figure 26. Ventral views of the dermal pectoral girdle of representatives of Huso, Acipenser, and Pseudoscaphirhynchus: The anteromedial 

edge of the clavicles (clv) meet roughly linearly (thin arrows in a, b) in all acipenserids except Pseudoscaphirhynchus where they 

angle anteriorly to form a discrete wedge (curved arrows in c; Character 59). clt = cleithrum, cvp = clavicle process. 

ed, but as an integral portion of the bone, not a process. 

This character is predicated on P. kaufmanni 

as representative for Pseudoscaphirhynchus due to 

lack of specimens of other species. 

The jugals of Scaphirhynchus and all species of 

Acipenser examined undercut the orbit, but not to 

the posterior edge of the olfactory opening (Figure 

3a, b, c). The anterior process of Huso is small and 

barely contacts the neurocranium. Relative size is a 

qualitative character, but jugals of all other acipenserids 

examined possess canal processes (Figure 3) 

missing in P. kaufmanni. 

Character 58. Gill rakers are pronged- Pseudoscaphirhynchus 

Gill rakers of Pseudoscaphirhynchus kaufmanni 

are split distally into a crescentic edge with paired 

pronged tips. These rakers split from a thin base into 

a curved outer (relative to the branchial arch) tip

114 

more elongate than a small, inner tip (Figure 25d). 

Larger rakers may possess only an outer tip, but the 

base remains expanded where the inner tip would 

protrude Gill rakers of P. fedtschenkoi are described 

as lanceolate (Berg 1948) and undescribed 

in P. hermanni, but lacking clear description, I accept 

P. Kaufmanni as diagnostic of the genus. 

Raker shape varies greatly among acipenserids. 

Rakers of Huso, Psephrirus, and several species of 

Acipenser (e.g., A. oxyrinchus) are elongate and 

lanceolate, tapering from a narrow base to a blunt 

tip (Figure 25a). Most other species of Acipenser 

(e.g., A. brevirostrum) possess triangular rakers 

(Figure 25b), but none possess rakers with pronged 

tips. The crenelated rakers of Scaphirhynchus are 

distinct (Character 63) and not comparable to Pseudoscaphirhynchus. 

varies from two to seven and they may fuse in ontogeny 

(Findeis 1993), but they collectively occupy an 

consistent area (Figure 5d). Localization of the lateral 

extrascapulars is consistent in all species of Scaphirhynchus. 

There is a significant variation in the dermal skull 

of acipenserids (Parker 1882, Jollie 1980) and position, 

size, and number of the lateral extrascapular 

bones is variable. In Pseudoscaphirhynchus (Figure 

5e; see Character 56) and Huso (Figure 5b), lateral 

extrascapulars are typically canal bones. Whereas 

Huso typically possesses only canal-bearing lateral 

extrascapulars (Figure 5b). Pseudoscaphirhynchus 

possesses multiple anamestic bones (Figure 5c). All 

species of Acipenser examined show extensive variation 

in number and position of lateral extrascapulars 

(Figure 5c). 

Character 59. Clavicles tips meet us an anteromedial 

wedge – Pseudoscaphirhynchus 

The clavicles of Pseudoscaphirhynchus converge 

medially as an anteromedial wedge (Figure 26c). 

This anterior wedge is externally visible and confirmable 

from photographs in P. hermanni (Berg 

1948a). Clavicles of Pseudoscaphirhynchus also distinctively 

possess strong central ridges running 

through the anteroposterior axis that possess three 

or four spikes in P. Kaufmannni (Figure 26c), but is a 

plain ridge in P. hermanni (Berg 1948a). 

In Scaphirhynchus, Huso, and all species of Acipenser 

examined, anteromedial edges of the clavicles 

converge more linearly to the midline (Figure 

26a, b). The clavicles typically meet in a slight anterior 

point, but this wedge is not prominent as in 

Pseudoscaphirhynchus Also, outgroups do not 

possess a robust central ridge, much less any spikes 

along the clavicle. 

Character 60. Lateral extrascupulars are clustered – 


Lateral extrascapulars form a positionally restricted 

cluster alongside the median extrascapular in 

Scaphirhynchus (excl, Figure 5d). Number of bones 

Character 61. Complete circumorbital series present 

– Scaphirhynchus 

The dermal skull roof of Scaphirhynchus is unique 

within Acipenseridae in possessing a complete circumorbital 

series with contact between the antorbital 

(see Character 46) and an enlarged postrostral 

bone of the border rostral series (prb, Figure 4e). 

With postrostral contact, the antorbital is widened 

ventrally with a flat edge. Antorbital shape and postrostral 

presence are also diagnostic of Scaphirhynchus 

chus, but correspond to completion of the circumorbital 

series and are subsumed into this character. 

Huso, Pseudoscaphirhynchus, and all species of 

Acipenser examined lack a complete circumorbital 

series,with the antorbital isolated dorsally. No postrostral 

is identifiable in these taxa as the border rostral 

series is thin without any expanded bones (see 

Figure 18c, d). 

Character 62. Branchiostegal one is short and triangular 

– Scaphirhynchus 

Branchiostegal one is a thin, triangular bone in Scaphirhynchus 

with a flat ventral edge that converges 

dorsally (Figure 7e) to contact the subopercle within 

a broad, vertical groove.

115 

In Acipenser and Huso branchiostegal one is typically 

rectangular and hourglass-shaped (Figure 7c, 

d) as it drops vertically before angling ventromedially 

under the operculum. All scaphirhynchines 

possess a flattened head with restricted vertical 

space in the operculum, but address these restrictions 

differently. Pseudoscaphirhynchus has a rectangular 

branchiostegal, but it is short and indents 

medially immediately from the subopercle. Branchioslegal 

one of Scaphirhynchus is vertical, but 

dorsoventrally compressed in shape to define this 

character. The independent branchiostegal of polyodontids 

(Grande & Bemis 1991, Findeis 1993) 

and branchiostegal series of †Chondrosteus (Traquair 

1887, Hennig 1925) and†Peipiaosteus (Liu & 

Zhou 1965, Zhou 1992) are not comparable (see 

Character 7). 

and dorsoventrally flattened with a rectangular 

cross-section. Elongation occurs suddenly and rapidly 

in small juveniles to achieve adult dimensions 

by elongation of vertebral cartilages, with individual 

vertebral segments over twice the length of typical 

vertebral segments (Findeis 1993). Total number 

of segments composing the peduncle is consistent 

with other acipenserids. †Protoscaphirhynchus 

squamosus (Wilimovsky 1956 possesses an elongate 

peduncle linking this fossil species to Scaphirhynchus. 

The caudal peduncle of all other acipenserids is 

short, with a cylindrical cross-section. Vertebral 

cartilages within the peduncle of the outgroups are 

unlengthened and retain a recognizable segmental 

organization. 

Character 65. Caudal peduncle and preanal area ar- 

Character 63. Gill rakers are crenelated – Scaphi- mored - Scaphirhynchus 

rhynchus 

Six groups of peduncle scales make mutual contact 

Gill rakers of Scaphirhynchus possess short double- with the Flank scutes and anal scale series to combranched 

nubs at regular and close intervals along pletely armor the posterior trunk from the vent and 

the oral edge (Figure 25c). Basic raker shape is a dorsal fin to the caudal scales of the caudal fin 

right triangle, with a vertical posterior edge and (Findeis 1993). †Protoscaphirhynchus possesses argradually 

descending anterior edge bearing the rays of peduncle scales similar to Scaphirhynchus, 

nubs. Scaphirhynchus albus possesses slender rak- but the specimen is too weathered to make detailed 

ers with a single pair of nubs on the first arch (Bailey comparisons. 

& Cross 1954), but rakers of other arches are similar Similar peduncle and preanal scale rows are 

to S. platorynchus 

found in Pseudoscaphirhynchus, Huso, and many 

These rakers are distinctive compared to most species of Acipenser, but they are not organized inacipenserids, 

but apparently similar to the to plates as numerous, large, or with precise interbranched 

rakers of Acipenser baerii (Sokolov & Va- digitation as Scaphirhynchus. Acipenser oxrinchus 

sil’ev 1989). They differ from the pronged rakers of is the best scaled species of Acipenser examined, 

Pseudoscaphirhynchus (see Character 58) in pos- possessing paired rows of scales preanally and on 

sessing blunt nubs and being generally triangular. the peduncle, but they remain separate rows with- 

The lanceolate rakers of Huso and several spcecies out mutual contact. Pseudoscaphirhynchus Kauf 

of Acipenser are elongate (Figure 25a) and the tri- manni possesses robust preanal scales and paired 

angular rakers of other species ofAcipenser (Figure scales on the dorsal peduncle, but ventral peduncle 

25b) are symmetric and lack nubs. scales are not organized. More typically in other 

acipenserids, peduncle and anal scales form single 

rows of variable size and separation. 

Character 64. Caudalpeduncle is flattened and elongate- 


The caudal peduncle of Scaphirhynchus is elongate

116 

Chavacter 66. Cleithral wall present 

converging posteriorly and symmetrically on the 

- Scaphirhynchus cardiac shield. 

The coracoid shelf of Pseudoscaphirhynchus, 

Acipenser, and Huso spreads anteromedially (Figure 

9a) onto the clavicle as an elongate sheet, but 

without lateral expansion (see Character 14). The 

scapulocoracoid of polyodontids extends similarly 

as a thick cylindrical process. This matches the anteriorly 

extended pectoral girdles of the outgroups 

compared to the compact pectoral girdle of Scaphirhynchus. 

The coracoid shelf corresponds to the 

dermal girdle and implicitly includes a pyramidal 

scapulocoracoid shape as a character of Scaphirhynchus. 

The cleithral wall of the scapulocoracoid is a triangular 

sheet that spreads over the cleithrum in Scaphirhynchus 

(ctw, Figure 9b). It spans the anterior 

process of the middle region (anp), the dorsal tip of 

the mesocoracoid arch (msc), and the anterior edge 

of the propterygial bridge (ptb, Figure 9b). 

The scapulocoracoid of all other acipenserids examined 

possesses a thin cleithral arch (cta) extending 

dorsally, but not expanded medially (Figure 9a). 

The anterior edge of the middle region is isolated as 

a horizontal spar extending medially from base of 

the cleithral arch (cta) to the anterior process (anp, 

Figure 9a). Thus, the anterior face of the scapulocoracoid 

of outgroups is L-shaped, with a vertical 

cleithral arm and horizontally extended anterior 

process. 

Character 67. A thin process encircles the propterygial 

fossa - Scaphirhynchus 

The scapulocoracoid of Scaphirhynchus possesses a 

thin process extending under the propterygium restraining 

process of the cleithrum (prp, Figure 8a). 

This process curls anteroventrally as a half-circle 

around the propterygial fossa (ptgp, Figure 9b). 

This process is not present in any other acipenserid 

(Figure 9a) and the propterygial fossa is open 

primitively anteriorly against the cleithrum. 

Character 68. Coracoid shelf restricted to the cleithrum 

- Scaphirhynchus 

The coracoid shelf (csh) of the scapulocoracoid in 

Scaphirhynchus spreads from the coracoid wall 

(cw) medially and laterally onto the cleithrum (arrows 

in Figure 9b). The largest portion spreads anterolaterally 

into the angle between the opercular 

wall and cardiac shields (Findeis 1993). The medial 

side slightly overlaps the clavicle, but ends in a small 

footprint. In ventral view, the coracoid shelf is 

roughly triangular, with the broad anterior edge 

Character 69. Dermopalatine and ectopterygoid 

bones fuse - Scaphirhynchus 

The dermopalatine and ectopterygoid develop as 

separate bones that fuse in adult Scaphirhynchus 

(Findeis 1991,1993). All adult specimens of S. platorynchus 

examined exhibited complete fusion, while 

all small juveniles retain separate elements, suggesting 

that fusion occurs in moderately sized juveniles. 

In †Paleopsephurus (Grande & Bemis 1991), an 

elongate process positionally similar to the acipenserid 

ectopterygoid is probably an independent 

bone (Figure 22a), but the short process of Psephurus 

and Polyodon suggests that the ectopterygoid is 

lost in these genera. In Huso, Acipenser, and Pseudoscaphirhynchus, 

the ectopterygoid is independent 

and closely contacts the dermopalatine (Figure 

22b, c), but even in large specimens of A. bvevivostrum 

and A. oxyrinchus there was never fusion between 

these bones. A small ectopterygoid process is 

present in †Peipiaosteus (Zhou 1992), but it is unclear 

if it is a separate bone or fused. †Chondrosteus 

has an independent ectopterygoid (= pterygoid of 

Traquair1887). 

Generic level phylogeny of Acipenseridae 

The character distribution from this analysis supports 

a new cladogram of genera of Acipenseridae

117 

Figure 27. Proposed interrelationships of the genera of Acipenseridae: Huso is defined by two synapomorphies forming the subfamily 

Husinae recognized as the sister group to the Acipenserinae. Acipenser is not recognized by any skeletal synapomorphies. Shovelnose 

sturgeons of Scaphirhynchus and Pseudoscaphirhynchus compose Scaphirhynchini. 

(Figure 27). The family Acipenseridae is supported 

by 24 skeletal synapomorphies (Characters 1–24). 

The genus Huso is defined by two synapomorphies 

(Characters 25,26) and is the sister group to a redefined 

subfamily Acipenserinae defined by 12 synapomorphies 

(Characters 27–38) comprising all 

other genera. Scaphirhynchus and Pseudoscaphirhynchus 

compose a monophyletic tribe Scaphirhynchini 

based on 16 synapomorphies (Characters 

39–54). Pseudoscaphirhynchus is defined by five 

synapomorphies (Characters 55–59) and Scaphirhynchus 

is defined by 10 synapomorphies (Characters 

60–69). Each node is supported by characters 

from different skeletal complexes suggestive of 

multiple evolutionary events occurring at one node 

rather than a one event affecting multiple characters. 

A remaining phylogenetic problem is the lack of 

identified synapomorphies defining the genus Acipenser, 

leaving this largest genus (17 species) as po-

118 

tentially untenable. Characters typically ascribed to 

Acipenser in the literature are plesiomorphic for 

Acipenserinae. Interspecific variability in morphological 

features within Acipenser is rampant, clouding 

the applicability of most characters used in phylogenetic 

reconstruction. It is possible that Acipenser 

is paraphyletic and closer examination of the genus 

is warranted. 

Taxonomic recommendations 

Order Acipenseriformes Berg 1940 

suborder †Chondrosteodei sensu Grande 

&Bemis1991 

suborder Acipenseroidei sensu Grande 

&Bemis 1991 

family Polyodontidae Bonaparte 1838 

phirhynchus a local remnant of the original radiation; 

and (2) the observation that scaphirhynchines 

are heavily scaled, ancient looking sturgeons 

easily interpreted as primitive. That the earliest acipenserid 

fossils are from the upper Cretaceous of 

North America (not Europe or Asia), and that putatively 

primitive aspects of scaphirhynchine morphology 

have never been examined phylogenetically 

have not impeded such hypotheses. Typically, the 

interpretation that scaphirhynchines are plesiomorphic 

within Acipenseridae is accepted a priori, 

and has driven evolutionary discussions of the family. 

A second dominant tenet to historical perspectives 

on acipenserid evolution is paedomorphosis. 

In recognizing chondrosteans with cartilaginous endoskeletons 

and a reduced dermal skeleton as secondarily 

de-ossified compared to their palaeoniscid 

ancestors (e.g., Traquair 1887, Woodward 1891, 

Goodrich 1909, Gregory 1933), early authors initi- 

ated a persistent theme presenting sturgeons as de- 

generate and primitive among extant actinoptery- 

family Acipenseridae Linnaeus 1758 

subfamily Husinae new name 

genus Huso Brandt 1869 

subfamily Acipenserinae new usage 

tribe Acipenserini undefined gians. Although acipenserids possess extensive 

taxon 

scalation, they remain perceived as paedomorphs. 

genus Acipenser Linnaeus 

The phylogeny and characters presented in this 

1758 

study allow for new interpretations about the evolution 

tribe Scaphirhynchini 

of the Acipenseridae. The cladogram sup- 

Bonaparte 1846 

ported here reverses classic evolutionary scenarios 

genus Pseudoscaphirhynchus 

for Acipenseridae, suggesting instead that acipenserids 

Nikolskii 1900 

show progressive layering of peramorphic 

genus Scaphirhynchus Heckel characters in phylogeny and have evolved into in- 

1836 creasingly benthic fishes. 

Evolutionarypatterns within Acipenseridae 

Benthic cruising as a scenario in 

acipenserid evolution 

Based on this cladogram, scaphirhynchines are derived 

sturgeons, with Huso the most phylogeneti- Based on this phylogeny of Acipenseridae, a major 

cally primitive genus within Acipenseridae (Figure trend in acipenserid evolution was to become in- 

27). This counters widely held interpretations that creasingly benthic. However, acipenserids never 

implicate scaphirhynchines as representing the achieved the extreme benthic specializations exhibprimitive 

condition within Acipenseridae (Schmal- ited by some fishes exemplified by such features as 

hausen 1991, Birstein 1993). Scaphirhynchines are flattened bodies, extensive camouflage, and stagenerally 

accepted as phylogenetically primitive for tionary behaviors. Instead, acipenserids remain cytwo 

reasons: (1) the premise that acipenserids orig- lindrical in cross-section and are relatively active 

inated in freshwater basins of Triassic northern fishes that interact with the substrate focally for 

Asia (Berg 1948b, Yakovlev 1977) with Pseudosca- predation, while developing locomotory abilities

allowing mobile benthic foraging. This proposed Feeding 

behavioral style I term benthic cruising is unique to As benthic cruisers, acipenserines forage by feeding 

Acipenseridae and incorporates a medley of ben- focally from the substrate. Hyostylic jaw suspension 

thic and non-benthic features. Benthic cruising will and resulting jaw projection is characteristic of the 

be addressed according to features that dominate Acipenseriformes, but nonacipenserid acipenseriacipenserid 

evolution including: (1) feeding, (2) re- forms universally possess jaws that lace anteriorly. 

spiration,(3) rostral expansion and head flattening, Huso also possesses large, anterior jaws that typi- 

(4) scalation, and (5) locomotion. Characters are cally extend onto the lateral surface of the head. 

examined at several phylogenetic levels to show in- These jaws are positioned to open anteriorly and 

creasing specialization within Acipenseridae. are not obviously linked to benthic feeding. 

The linchpin to this phylogeny is defining Huso as Nevertheless, acipenserids, including Huso, have 

the sister group to a redefined subfamily Acipense- modified the jaws and skull to exploit benthic prey. 

rinae. Huso is distinct from all other acipenserids Acipenserids possess ‘internal’ jaws based on the 

morphologically by lacking 12 acipenserine synapo- novel palatal complex which extends the oral surmorphies 

and ecologically as both species of Huso face of the upper jaw posterodorsally (Character 

maintain a life history style distinct compared to 18) and the sharply defined tongue pad with biting 

other acipenserids, but comparable to the polyo- ridges on the expanded first hypobranchials 

dontid Psephurus. Additionally, although Huso (Chracter 21). Double articulation of hypobranshares 

24 synapomorphies with acipenserids, many chial three with basibranchial one (Character 22) 

skeletal features plesiomorphically resemble those further consolidates the ventral hyobranchial skeleof 

Psephurus in shape of the rostrum and associated ton within the tongue pad. Functionally, the dorsal 

bones, lack of several bone groups in the dermal palatal complex shears across the tongue pad as the 

skull, and possessing anterior racing jaws compared upper jaw is projected and retracted to hold prey. 

to acipenserines. While these character states are This mechanism acts to retain prey during winnowplesiomorphic, 

similarities in life history among ing of ingested substrate and is a putative benthic 

Huso and Psephurus provide a backdrop to inter- specialization. 

preting morphological and behavioral changes in Within Acipenserinae, acipenserines possess 

acipenserid evolution. 

ventral jaws restricted beneath the orbit. The jaws 

Living Huso (e.g., Aritipa 1933, Berg 1948a) and are sequestered behind the central trabecular pro- 

Psephurus (Liu & Zeng 1988) prey dominantly on cess (Character 31) and expanded postnasal wall 

fishes, and fossil †Crossopholis occur with fishes en- (see Character 3) that form a barrier anterior to the 

closed in its remains (Crande & Bemis 1991), sug- orbit. At rest, the jaws are held entirely within the 

gesting that acipenseroids were originally piscivo- confines of the head. The jaws are short and transrous 

predators. Piscivory in itself does not contra- verse to fit ventrally, and the lower jaw is straightdiet 

a benthic feeding pattern, but midwater species ened (see Characters 33,35) opposite the upperjaw. 

included in the diet of adult Huso (Berg 1948a, Piro- During feeding, these jaws open obligately ventralgovskii 

et al. 1989), and fishes enclosed in †Cross- ly in an ideal position for benthic reeding. Posterior 

opholis, confirm that they are pelagic predators. In displacement of the interhyal-posterior ceratohyal 

contrast, most species of Acipenser and all scaphi- joint (Character 36) facilitates projection by sparhynchines 

focus on benthic prey such as molluscs, tially separating the jaws from the non-projectile 

crustaceans, and substrate oriented fishes. Second- anterior ceratohyal. 

ary characteristics such as the cylindrical body and Scaphirhynchines have essentially identical jaws, 

head shape of Huso polyodontids, †Chondrosteus but the tongue pad expands onto hypobranchial 

and Peipiaosteus futher bolster suggestions that two as it is included into the tongue pad by posterior 

nonacipenserine acipenseriforms are neither ben- expansion of hypobranchial one (Character 51). Althic 

in morphology nor in life history. 

though their rakers differ (Characters 58, 63), both 

scaphirhyncline genera possess complex rakers 

119

120 

ideal for retaining small prey (fishes and/or insect Rostrum and flattening 

larvae) that they prefer, as well as to winnow detri- Many benthic fishes are flattened to allow direct, 

tus inevitably ingested while feeding in their pre- stable interaction with the substrate. Outgroup aciferred 

habitats. 

penseriforms and Huso possess cylindrical heads 

These characters organize a feeding morphotype and trunks, but varying degrees of flattening occur 

that initially develops prey processing surfaces sup- within Acipenserinae. This is most apparent with 

portive of jaw projection in acipenserids and then expansion and flattening of the head, rostrum, and 

restricts the jaws into their benthic specific ventral trunk within Acipenseridae that develops a platorientation 

in acipenserines. 

form parallel to the substrate. 

Appearance of the jugal (Character 3), antorbital 

Respiration 

(Character 4), and median extrascapular (Charac- 

Acipenserids possess an accessory respiratory ter 5) all suggest that skull expansion occurs in Acishunt 

allowing them to pull water into the buccal penseridae. The neurocranium is broader in genercavity 

from the opercular chamber whenever the al than in polyodontids and these bones reflect this 

mouth is occluded (Burggren 1978). This shunt al- expansion dermally. 

lows acipenserids to respire when the buccal cavity The rostrum of Huso is thin and cylindrical, but 

is blocked by substrate ingested during benthic the rostrum of all acipenserines is expanded by adfeeding 

or large prey that acipenserids preferential- dition of the lateral ethmoid ridges (Character 27), 

1y feed on fill the mouth during ingestion. Juvenile broadening of the dorsal rostral series (Character 

sturgeons ingest remarkably large prey requiring 28), and appearance of border rostral bones (Charextensive 

processing before swallowing. The sub- acter 29). While the acipenserine rostrum appears 

opercle is bound to the hyomandibula and automat- flatter than in Huso, this is due more to addition of 

ically flares laterally duringjaw movements to open the lateral ethmoid ridges that broaden the ventral 

the shunt during ingestion or winnowing. 

face of the rostrum than actual dorsoventral coni- 

The respiratory shunt is predicated on a dorsal pression of the head in Acipenser. Rostrum expanopening 

in the operculum (not a character here), sion is likely associated with expansion of electrosolid 

pectoral girdle (Characters 9,13), and curved sensory ampullary fields and hydrodynamics of a 

gill filaments that direct water ventrally out of the head with ventral jaws. An indicator of skull expanbuccal 

cavity (Findeis 1989). The branchiostegals of sion in acipenserines is addition of pineal bones in 

acipenserids (Character 7) arch ventrally and then the widely opened pineal fontanelle (Character 32) 

medially to support an opercular cavity open to dor- and ventral extension of the antorbital (see Characsal 

inflow and ventral outflow. The medial opercu- ter 4). 

lar wall (Character 10) stabilizes the opercular Scaphirhynchines possess flattened rostra enchamber 

as an open, concave structure promoting Iarged by expansion of the lateral ethmoid shelves 

unimpeded water outflow. Such skeletal stabiliza- (Character 39) and dorsal coverage with the ampultion 

of the girdle is central to opening the dorsal in- lary bones (Character 40). The skull itself is wider 

current channel and then directing outflow ventral- and flatter than in Acipenser as indicated by addily. 

tional extension of the antorbital (Character 46). 

This basic morphology of the pectoral skeleton is Head flattening is not indicated by skull characters 

typical of acipenserids, and dimensional changes that simply form a shallower cover of the head, but 

among genera are not recognized as discrete char- by dorsoventral compression of the hyomandibula 

acters here. The medial opercular wall is larger in (Character 50) and operculum (Characters 47, 62) 

acipenserines than in Huso, and the girdle is more beneath the skull. 

compact in Scciphirhynchus than other genera. Further, scaphirhynchies are the only acipense- 

These changes do not reflect obvious functional rids to extensively flatten their trunk. In contrast to 

changes so much as changes in overall body flatten- the cylindrical trunk of Huso and Acipenser, the 

ing (see below). 

ventral surface of scaphirhynchines is nearly flat be-

tween the ventral scute rows. Among acipenserids, 

only scaphirhynchines make extensive contact with 

the substrate, and their highly flattened belly serves 

as an ideal resting platform as Scaphirhynchus is especially 

benthic and mobile on the substrate (see 

below). 

Initially, flattening of the head and trunk seems to 

support an expanded suite of ampullary organs as 

well as conform the skull to ventral displacement of 

the jaws. Trunk compression only occurs in advanced 

sturgeons, as Acipenser generally remains a 

genus of mobile predators while scaphirhynchines 

become obligate benthivores. 

121 

of extensive adult scalation and peduncle scalation 

in Scaphirhynchus is unclear, but correlates well 

with their benthic life history and persistent contact 

with the substrate. 

Locomotion 

Benthic cruising implies mobile interaction with the 

substrate. Acipenserids are strong swimmers with 

several features facilitating this behavior. Morphology 

of the caudal fin is not a character here due to 

variation within Acipenseridae and among acipenseriforms, 

but the hypochordal lobe is often reduced 

to allow sweeping of the tail while close to the 

substrate. More pelagic taxa (e.g., Huso, Acipenser 

Scalation 

oxyrinchus) possess deep caudal fins similar to 

Extensive scalation correlates with benthic habits those of †Chondrosteus and polyodontids, while 

in many groups of fishes, and may serve for protection 

more benthic species possess either abbreviated 

against the substrate or to counter predation. (e.g., A. brevirostrum) or obliquely folded hypo- 

While acipenserid outgroups lack any extensive chordal lobes (Scaphirhynchus). 

scalation, the most distinctive hallmark of acipenserids 

Pectoral fin spines of acipenserids (see Charac- 

is their scutes (Character 1). A precise role for ters 2,12,16) are neither sharp, nor possess serrated 

scutes is unknown, but they are prominent and edges exposed for protection. Instead, they are permanent 

sharp in juveniles as a tight assemblage covering 

lateral processes erected during swimming 

well over 50% of the trunk, suggesting that those as diving planes. Acipenserids can excellently maintain 

ages are most reliant on scalation. In fact, juvenile 

position over variable bottoms by precisely 

acipenserids prefer benthic habitats (Richmond & regulating inclination of the spines to modulate 

Kynard 1995) and even juvenile Huso huso focuses depth during swimming. Pectoral fin spines of Scaphirhynchus 

on benthic prey (Pirogovskii et al. 1989) when 

are uniquely curved and are used as 

scutes are most developed. Scutes become allometrically 

‘legs’ to shuffle along the substrate during feeding 

reduced in adults in size, roughness, and co- 

and exploration, something not done by other aci- 

hesiveness (they become well separated within the penserids. In this scenario, fin spines are locomotory 

rows) and actually regress significantly and are progressively 

stabilizers for depth control. Polyodontids lack 

covered by skin in some species (e.g., H. fin spines, but are midwater fishes not requiring the 

huso, Acipenser fulvescens, A. nudiventris). As same precision during locomotion. 

large fishes, adult sturgeons do not face serious predation 

In all cases, acipenserids show phylogenetic 

and tend to be more active above the sub- 

trends suggesting increasing abilities as benthic 

strate, and we might regard scutes as an adaptation fishes. Huso is morphologically and behaviorally 

for juveniles rather than adults in Acipenseridae. pelagic as adults, but possess underlying characters 

Scaphirhynchines retain well developed scutes in indicating an original shift to benthic behaviors in 

adults that are broader and more tightly overlapping 

Acipenseridae. This shift is likely associated with 

than other acipenserids. Also, scales on the pe- 

evolutionary success of juvenile interval in Huso 

duncle are large and organized as multiple, discrete when benthic prey (notable other acipenserids) and 

groups in Scaphirhynchus (Character 65) with the predator avoidance is most important. Huso then 

posterior trunk completely armored by overlapping rises into pelagic environments when large enough 

scales. Peduncle scales are present in all other acipenserids, 

to exploit larger prey. Regardless of the initial rea- 

but vary in number and size and never son to exploit benthic habitats in primitive acipen- 

form an extensive cover (see Character 1). Purpose serids, original opportunities afforded by the rich

122 

benthic prey fauna continued with evolution of 

preferential benthic cruising acipenserines. 

Many species of Acipenser depend on benthic 

abilities. Ventral displacement of the mouth allows 

for benthic foraging, but restricts their options to 

capture midwater prey. Unlike the piscivorous Huso 

and Psephurus, all species of Acipenser and Scaphirhynchini 

feed wholly or partially on benthic 

prey. Several species become piscivorous as adults 

(e.g., A. transmontanus A. oxyrinchus), but these 

large species still never prey consistently on pelagic 

prey to such an cxtent as Huso. Far more commonly, 

species of Acipenser are molluscivores, insectivores, 

or generalized benthic predators. While the 

focus here is on feeding, the other suites of characters 

are critical to allowing acipenserines to interact 

with the substrate and together compose a successful 

benthic cruiser. 

Scaphirhynchines are more obligate benthivores 

with the flattened trunk and head promoting stability 

and mobility along the substrate. Scaphirhynchus 

is the most derived acipenserid genus in each 

category and exemplifies character acquisitions 

pointing to sequential entry into benthic habitats 

during evolution of the Acipenseridace 

cate that loss of endochondral ossification, dermal 

cheek bones, and trunk scalation (the most obvious 

paedomorphic characters) are synapomorphies of 

Acipenseriformes and plesiomorphic to Acipenserridae. 

Thus, while reduction of the skeleton exeniplifying 

paedomorphic events are valid phylogenetic 

characters and evolutionary events. they characterize 

the origin of Acipenseriformes and define a 

morphotype underlying Acipenseridae. 

Paedomorphosis is also accepted as the primary 

process driving evolution in Acipenseriformes and 

Acipenseridae. However, ideas that paedomorphy 

dictates morphological change in acipenserifoms 

conflicts with the suggestion that selective forces for 

performance might drive evolutionary patterns 

themselves and only result in paedomorphy secondarily. 

For instance, evolution of projectile jaws 

in acipenserifoms requires loss of the dermal 

cheek to free the mobile palatoquadrate. Invoking 

paedomorphosis as a preliminary route removing 

the cheek originally ignores the possibility of precedent 

selection for jaw projection. 

In contrast to loss and reduction characters consistent 

with paedomorphosis, numerous characters 

defined in this study entail addition or enlargement 

of skeletal elements at all levels with Acipenseridae 

and suggest a progressive role for peramorphosis 

(gerontomorphosis, Balon 1983, 1985, 1989) in aci- 

penserid evolution. For the purposes of this discussion, 

peramorphic characters are simply defined as 

transformations that result in addition of new structures 

or enlargement ofpreexisting structures corn- 

pared to outgroups. A peramorphic pattern ofchar- 

acter acquisition contrasts sharply with ideas of 

Peramorphy as a mechanism in acipenserid 

evolution 

A persistent theme overshadowing studies of the 

Acipenseridae is the putative role of paedomorphosis 

dominating their evolutionary change. Paedomorphosis 

has been invoked to generally explain 

loss of ossification of the endoskeleton and loss of paedomorphy in evolution of Acipenseridae. In 

dermal elements in Acipenseridae compared to fact, basal to Acipenseridae, the Acipenseroidei 

other fossil and extant actinopterygians. Paedo- (Polyodontidae + Acipenseridae) is defined by a 

morphic themes are so pervasive that they have character complex including both paedomorphic 

possibly promoted or capitalized on the idea that (e.g., loss of the opercle, reduced branchiostegal 

scaphirhynchines are plesiomorphic sturgeons, number) and peramorphic (e.g., presence of a roswith 

the more lightly armored species of Acipenser trum) characters (see Findeis 1993, Bemis et al. 

and Huso being natural evolutionary destinations 1997). This suggests that a shift away from domwithin 

the family. 

inant paedomorphic mechanisms toward peramor- 

However, paedomorphy has focused on the well phy begins prior to evolution of Acipenseridae. 

known Acipenseridae, not the larger assemblage However, the most dominant peramorphic charac- 

Acipenseriformes. Our current understanding of ters in number and morphological results appear 

polyodontids and fossil acipenseriforms now indi- within Acipenseridae.

Acipenseridae is defined by a pervasive array of rinac; Characters 48. 52, 54 for Scaphirhynchini), 

peramorphic characters. Scutes (Character 1), the they are generally associated with shape changes 

pectoral fin spine (Character 2), the antorbital and that require reduction or loss of elements to facilmedian 

extrascapular bones (Characters 4, 5), the itate the morphological shift to benthic cruising and 

supracleithral cartilage (Character 15), and palatal are significantly outnumbered by peramorphic 

complex (Character 18) all appear without precur- characters. Many of these peramorphic characters 

sor in Acipenseridae. Many other characters are pe- are not linked and occur at all major nodes within 

ramorphic enlargements of features such as the Acipenserdae, supporting peramorphy, not paedoskull 

(Character 3), pectoral girdle (Characters 9- morphy, as a dominant influence in acipenserid evo- 

14), pelvic girdle (Character 17), hyobranchial skel- lution. 

eton (Characters 19–22), pectoral scales (Character 

23), and even the occipital canal (Character 24). 

Peramorphic characters defining Acipenserinae Conclusions 

include the expanded rostrum (Characters 2–29), 

central trabecular process (Character 31), and der- (1) Huso exemplifies a precedent primitive condimopalatine 

shelf (Character 34) that are all addition within Acipenseridae as a pelagic sturgeon 

tions to the plesiomorphic (e.g., Huso) condition. compared to other acipenserids. However, charac- 

Acipenserines are also the first level within Acipen- ters defining Acipenseridae (including Huso) apseridae 

with numerous anamestic bones in the skull pear to be linked to benthic behaviors and may inroof 

including pineal bones (Character 32) and dicate importance for benthic orientation for juveanamestic 

lateral extrascapulars. Anamestic bones nile acipenserids. Thus, many features diagnostic of 

generally lack consistent organization, filling areas acipenserids may have evolved in support of the juof 

the skull with variable numbers and sizes of venile period of life history, not for adults. 

bones between individuals and species. While they (2) Acipenserines are clearly more benthically orican 

define peramorphic characters, they may also ented than Huso. Acipenserines possess ventral 

represent general peramorphic processes beyond mouths and a broadened, somewhat flattened roscladistic 

characterization. 

trum and head. These features define a morphology 

Scaphirhynchines continue this peramorphic allowing more precise benthic foraging. 

trend with extreme expansion of the rostrum (3) Scaphirhynchus represents an ultimate benthic 

(Characters 39, 40), appearance of basitrabecular morphology within Acipenseridae. Their increased 

cartilages (Character 43), ventral expansion of the dermal armor, highly flattened head and trunk, and 

antorbital (Character 46), posterior expansion of pectoral ‘legs’ allow for stable benthic exploration. 

hypobranchial one (Character 51), and appearance Pseudoscaphirhynchus is similarly flattened, but 

of the caudal fin filament (Character 53). 

this genus lacks features that facilitate the level of 

While Pseudoscaphirhynchus is generally de- benthic behaviors characteristic of Scaphirhynchus 

fined by characters that are peramorphically neu- (4) In the scenario of benthic cruising, initial opportral, 

several peramorphic transformations occur in tunities for Huso to exploit substrate habitats were 

Scaphirhynchus. The caudal peduncle is elongate expanded upon by phylogenetically successive aci- 

(Character 64), and armored (Character 65). This penserid taxa that focused on substrate habitats and 

genus possesses a circumorbital series based on ex- prey. 

panded antorbital and postrostal bones (Character (5) Peramorphy is a dominant mechanism in aci- 

61), an expanded cleithral wall (Character 66), and penserid evolution. Appearance of new elements 

fusion of the dermopalatine and ectopterygoid and enlargements of preexisting features are typical 

(Character 69). 

for characters defined in this study. 

While putative paedomorphic characters occur 

at several nodes of the cladogram (Character 8 for 

Acipenseridae; Characters 35, 37, 38 for Acipense- 

123

124 

Future research on Acipenseridae 

with facilities, finances, and help that made field 

work rewarding and beneficial. This project was 

The most immediate problem in acipenserid phylo- supported at different times by the Lerner-Grey 

geny is alpha-level systematics of Acipenser. and Donn E. Rosen Funds of the American Mu- 

Morphological variation within and among species seum of Natural History and a National Science 

of Acipenser is a stumbling block for comparative Foundation Grant BSR-9220938. Finally, I thank 

work, but most species do possess a basic morphol- Carolanne Milligan for reading the manuscript and 

ogy definable for phylogenetic analysis. Morpho- supporting me during the writing and final preparalogical 

characters such as shape of the trunk scales, tion of this study. 

scutes and even morphometric characters might be 

fruitful for species comparisons. For instance, Acipenser 

brevirostrum and A. fulvescens are similar to References cited 

each other in these characters, but not to A. oxyrinspecies 

chus. Similar biogeographically localized groups of Agassiz, L. 1844. Recherches sur les poissons fossiles. 2 (2, 

within Acipenser are recognizable, but too 

many species are currently undescribed and all are 

necessary for a phylogenetic analysis. Recent work 

on karyological and molecular systematics suggests 

interesting patterns among the species of Acipenser 

that would be ideal starting points for a complete 

analysis of potential characters. 

At the evolutionary level, many of the hypotheses 

presented here require additional ecological information 

and functional investigation. Detailed 

ontogenetic studies on behavior and morphology, 

external and internal, will certainly define characters 

for phylogenetic analysis within Acipenser The 

cladogram presented here is a first step toward better 

understanding acipenserids, but future studies 

on several fronts are necessary to make progress in 

phylogenetic and evolutionary studies of sturgeons. 


This project is a portion of a doctoral dissertation 

completed at the University of Massachusetts. I 

wish to thank Willy Bemis and Lance Grande for 

their assistance and dialogue throughout the work. 

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Bemis and Eugene Balon for reviewing this manuscript 

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Environmental Biology of Fishes 48: 127–155,1997. 


Phylogeny of the Acipenseriformes: cytogenetic and molecular approaches 

Vadim J. Birstein 1 , Robert Hanner 2 & Rob DeSalle 3 

1 


2 

Department of Biology, University of Oregon, Eugene, OR 97405–1210, U.S.A. 

3 

Department of Entomology, American Museum of Natural History, New York, NY 10024, U.S.A. 


Key words: sturgeon, paddlefish, Huso, Acipenser, Scaphirhynchus, Pseudoscaphirhynchus, Polyodon, Psephurus, 

karyotype, chromosome, macrochromosome, microchromosome, genome, DNA content, 18S rRNA 

gene, cytochrome b, 12S mtrRNA gene, 16s mtrRNA gene, rate of molecular evolution, phylogeny, evolution 

Synopsis 

The review of the data on karyology and DNA content in Acipenseriformes shows that both extant families, 

the Polyodontidae and Acipenseridae, originated from a tetraploid ancestor which probably had a karyotype 

consisting of 120 macro- and microchromosomes and DNA content of about 3.2–3.8 pg per nucleus. The 

tetraploidization of the presumed 60-chromosome ancestor seems to have occurred at an early time of evolution 

of the group. The divergence of the Acipenseridae into Scaphirhyninae and Acipenserinae occurred 

without polyploidization. Within the genus Acipenser, polyploidization was one of the main genetic mechanisms 

of speciation by which 8n and 16n-ploid species were formed. Individual gene trees constructed for 

sequenced partial fragments of the 18S rRNA (230 base pairs, bp), 12S rRNA (185 bp), 16S rRNA (316 bp), and 

cytochrome b (270 bp) genes of two Eurasian (A. baerii and A. ruthenus) and two American (A. transmontanus 

and A. medirostris) species of Acipenser, Huso dauricus, Pseudoscaphirhynchus kaufmanni, Scaphirhynchus 

albus, and Polyodon spathula showed a low level of resolution; the analysis of a combined set of data 

for the four genes, however, gave better resolution. Our phylogeny based on molecular analysis had two major 

departures from existing morphological hypotheses: Huso dauricus is a sister-species to Acipenser instead of 

being basal to all acipenseriforms, and Scaphirhynchus and Pseudoscaphirhynchus do not form a monophyletic 

group. The phylogenetic tree constructed for the cytochrome b gene fragments (with inclusion of 7 additional 

species of Acipenser) supported the conclusion that octoploid species appeared at least three times 

within Acipenser. 

Introduction 

Although a few species of Acipenser require revision, 

usually 24–25 extant sturgeon and two paddlefish 

species, Polyodon spathula and Psephurus 

gladius, are included in the Acipenseriformes (Rochard 

et al. 1991, Birstein 1993a). The extant members 

of this order form the monophyletic sistergroup 

of all extant Neopterygii (e.g., Lepisosteidae, 

Amiidae, and Teleostei; Bemis et al. 1997 this volume). 

Most ichthyologists regard Polypteridae as 

the sister group of Acipenseriformes + Neopterygii 

(Patterson 1982). A comparison of partial sequences 

of 28S rRNAs supported this relationship (Le et 

al. 1993). In contrast to earlier works, Grande & Bemis 

(1991) concluded that paddlefishes and sturgeons 

are sister taxa, and that extinct Mesozoic genera 

such as Chondrosteus lie outside this clade.

128 

Within Acipenseriformes, all workers agree that ous occur in Central Asia (Nesov & Karnyshkin 

the Acipenseridae and Polyodontidae diverged pri- 1983). 

or the Late Cretaceous (Berg 1948a, Yakovlev 1977, The China-western American group consists of 

1986, Grande & Beinis 1991, Jin 1995, Grande & Be- Acipenser sinensis, A. dabryan us, A. medirostris, 

mis 1996, Bemis et al. 1997). Within the Acipeenser- and A. transmontanus; the external morphology of 

dae, the subfamily Scaphirhynchinae (Central the last two species is very similar (Findeis 1993). 

Asian species of Pseudoscaphirhynchus plus North All of these species seem to have common Tertiary 

American species of Scaphirhynchus) was tradi- roots (Artyukliin & Andronov 1990). The two extionally 

considered the sister group of all other stur- tant paddlefish species also indicate a trans-Pacific 

geons (Berg 1905, Vasiliev 1985). Another interpre- pattern that is strengthened by the inclusion of fostation, 

based on osteology, was proposed by Findeis sil taxa, such as Eocene Crossopholis and Paleo- 

(1993,1997 this volume), who found that Huso lacks cene Paleopsephurus (Grande & Bemis 1991, Jin 

many characters found in Acipenser, Scaphirhyn- 1995, Bemis et al. 1996, Grande &Bemis 1996). 

chus and Pseudoscaphirhynchus On this basis, he The third group includes European and Amerconsidered 

Scaphirhynchinae as a derived group ican Atlantic sturgeons (Vladykov & Greeley 1963, 

within Acipenseridae (Findeis 1997). This point of Kinzelbach 1987, Holc ∨ ík et al. 1989). Probably, the 

view was disputed since the description of the Pseu- European A. sturio has many primitive characters 

doscaphirynchus species 120 years ago (Kessler of the genus (Nesov & Kaznpshkin 1977). Once con- 

1877, Berg 1905), while other researchers consid- sidered a subspecies of A. sturio, the American Atered 

Scaphirhyninae as the oldest group within Aci- lantic sturgeons were subsequently split off as a seppenseridae 

(Bogdanov 1887). The examination of arate species, A. oxrinchus (Vladykov & Greeley 

generic relationships within Acipenseriformes us- 1963). Then, two subspecies, A. o. oxyrinchus and 

ing molecular phylogenetic methods was one of the A. o. desotoi, were described within A. oxyrinchus 

main goals of this paper. 

(Vladykov 1955, Vladykov & Greeley 1963). The 

According to Nesov & Kaznyshkin (1977), extant origin and spread of the Atlantic sturgeon probably 

species of Acipenser belong to different evolution- reflect close Tertiary links between Europe and 

ary lineages which diverged long lime ago. Artyuk- North America (Artyukhin & Andronov 1990). 

hin & Andronov (1990) and Artyukhin (1995) pro- The freshwater sturgeons of eastern North Amerposed 

that there were at least four main regions in ica, belonging to the fourth group, the lake sturwhich 

the speciation and spread of sturgeons took geon, A. fulvescens, and shortnose sturgeon, A. breplace: 

(1) the Ponto-Caspian area: (2) China-west- virostrum are possibly closely related (Vladykov & 

ern America; (3) the Atlantic area: and (4) eastern Greeley 1963) and may have originated on the East- 

North America the group of Ponto-Caspian spe- ern coast of North America (Artyukhin & Androcies 

includes most of the Eurasian species (Acipen- nov1990). 

ser gueldenstaedtii, A. persicrus, A. stellatus. A. ruth- Evidence for monophyly of these four groups reenus, 

A. nudiventris Huso huso, A. baerii; Berg mains uncertain, and the relationships among them 

1948b, Holc ∨ ík et al. 1989, Pirogovsky et al. 1989, are unknown. Recently, Artyukhin (1995) publish- 

Shubina et al. 1989, Vlasenko et al. 1989a, b, Soko- ed a first phylogenetic tree based on general data of 

lov &Vasilev 1989a–c, Ruban 1997 this volume), as morphology, biogeography and karyology (but not 

well as Amur River endemics (A. schrenckii and the DNA content) of Acipenser. Atryukhin’s 

Huso dauricus; Artyukhin 1994, Krykhtin & Svir- scheme is the first modern attempt to reconstruct 

skii 1997 this volume), and, possibly, an Adriatic relationships within the genus Acipenser (see Bespecies 

A. naccarii (Tortonese 1989, Rossi et al. mis et al. 1997, for a history of the 19th century at- 

1991). The origin of Ponto-Caspian species might tempts to subdivide Acipenser into subgenera). 

have been associated with brackish-water deriva- Artyukhin & Andropov (1990) wrote: ‘It is quite 

tives of the Tethys Sea. The oldest extinct forms of evident that methods of biochemical genetics and 

the Ponto-Caspian group from the Upper Cretace- karyology, as well as paleontological data and cur-

129 

Table 1. Chromosome numbers and DNA content in the Acipenseriformes, Lepiaosteiformes, and Amiiformes 1 . 

Species Chromosome DNA content in Ploidy, n Reference 

numbers Pg (according to the 

DNA content) 

Order Aciperiseriformes 

family Polyodontidae 

North America 

Polyodon spathula 

Tennesse River, Alabama 120 – – Dingerkus & Howell (1976) 

Kentucky – 3.9 2 4 Tiersch et al. (1989) 

Missouri – 4.89 2 4 Blacklidge & Bidwell (1993) 

Moscow Aquarium, Russia – 3.17 2 4 Birstein et al (1993) 

family Acipenseridae 

subfamily Aciperiserinae 

Europe 

Acipenser gueldenstaedtii 

Volga River 250 ± 8 – – Birstein & Vasiliev (I 987) 

7.87 2 8 Birstein et al. (1993) 

Caspian Sea 247 ± 8 – – 

Vasilev (1985) 

Sea of Azov 250 ± 8 – – Vasiliev ( 1985), Areijev (1989a) 

Italy, cell culture 250 ± 8 – – Fontana et al. (1995) 

A.naccarii 

Italy 239 ± 7 – 

– Fontana & Colombo (1974) 

246 ± 8 – – Fontana (1994) 

Italy, cell culture 246 ± 8 – – Fontana et al. (1995) 

A. nudiventris 

Black Sea 118 ± 2 – 

– Arefjev (1983), Vasiliev (1985) 

Aral Sea, Uzbekistan (Central Asia) – 3 90 2 4 Birstein et al. (1993) 

A. percius 

Caspian Sea > 200 – – Fashkhami (pers comm.) 

A. ruthenus 

Volga River 118 ± 2 – - Vasiliev (1985), Birstein & Vasiliev 

(1987) 

- 3.74 2 4 Birstein et al. (1993) 

Don River 118 ± 3 – – Arefjev (1989b) 

Danube, Yugoslavia 116 ± 4 – – Fontana et al.(1977) 

Danube, Slovakia 118 ± 3 – – Rab (1986) 

Italy (aquaculture) 118 ± 4 – - Fontana (1994) 

Italy, cell culture 118 ± 9 – – 

Fontana et al. (1995) 

A. stellatus 

Volga River 118 ± 2 – – Birstein &Vasiliev (1987) 

– 3.74 2 4 Birstein et al. (1993) 

A. sturio 

Italy 116 ± 4 – – Fontana & Colombo (1974) 

– 3.6 4 4 Fontana (1976) 

– 3.26 4 Mirsky & Ris (I951) 

Husohuso 

Don River 118 ± 2 – – Serebryakova et al. (1983), Arefjev 

(1989b) 

Volga River 118 ± 2 

– 

– 

3.17 2 – 

4 

Birstein &VasiIiev (1987) 

Birstein et al. (1993) 

Italy 116 ± 4 – – Fontana & Colombo (1974) 

– 3.6 4 4 Fontana (1976) 

Asia 

Siberia 


Lena River 248 ± 5 – – Vasiliev et al. (1980) 

Italy (aquaculture) 246 ± 8 Fontana (1 994)

130 

Table 1 (Continued). 

Species Chromosome DNA content in Ploidy, n Reference 

numbers Pg (according to the 

DNA content) 

Far East and China 

A. mikadoi (A. medirostris mikadoi) 

Tumnin (Datta) River [500?] 3 14.20 2 16 Birstein et al. (1993) 

A. schrenckii 

Amur River [240?] 5 – – Sereberyakova (1970) 

A. sinensis 

Yangtze River 264 ± – – Yu et al. (1987) 

Huso dauricus 

Amur River [120?] 5 

– 

– 

3.78 2 – 

4 

Serebryakova (1969) 

Birstein et al. (1993) 

NorthAmerica 

A. brevirostrum 

Florida and South Carolina, USA [360? or 500?] 3 13.08 2 12 (?) or 16 Blacklidge & Bidwell (1993) 

A. fulvescens 

Wisconsin [250?] 3 8.90 2 8 Blacklidge & Bidwell (1993) 

A. medirostris 

Washington [250?] 3 8.82 2 8 Blacklidge & Bidwell (1993) 

A. oxyrinchus desotoi 

Florida [120?] 3 4.55 2 4 Blacklidge &Bidwell (1993) 

A.o. oxyrinchus 

Halifax, cell culture (99-112) 7 – – Li et al. (1985) 

A. transmontanus 

San Francisco Bay, California, cell 

culture (230 ±) 8 – – Hedrick et al. (1991) 

– 9.55 2 8 Blacklidge & Bidwell (1993) 

Snake River, Idaho – 9.12 2 8 Blacklidge & Bidwell (1993) 

Columbia River, Washington – 9.59 2 8 Blacklidge & Bidwell (1993) 

Italy (aquaculture) 248±8 – Fontana (1994) 

subfamily Scaphirhynchinae 

Central Asia 

Pseudoscaphirhynchus kaufmanni 

Amu Darya River, Uzbekistan [120?] 3 3.47 2 4 Birstein et al. (1993) 

North America 

Scaphirhynchus platorynchus 

Illinois 112± 3.6 2 4 Ohno et al. (1969) 

Order Lepisosteiformes 

family Lepisosteidae 

North America 

Lepisosteus oculatus 

L. osseus 

68 ± 

56 

2.8 4 

– 

2 

– 

Ohno et al. (1969) 

Ojima & Yamano (1980) 

L. platostomus 54 – – Ueno (1985), cit. in Suzuki & Hirata 

(1991) 

Order Amiiformes 

family Amiidae 

North America 

Amia calva 46 ± 2.4 4 2 Ohno et al. (1969) 

2.3 6 2 Mirsky & Ris (1951) 

46 2.0 4 2 Suzuki & Hirata (1991) 

1 All species investigated karyologically so far are listed: the DNA content values for all species studied are given. 

2 Determined by flow cytometry. 

3 

Chromosome number is assumed on the basis of the DNA content. 

4 

Determined by microdensitometry of Feulgen-stained nuclei. 

5 Only macrochromosomes were counted precisely. 

6 

Determined by the biochemical Schmidt-Thankauser method. 

7 

Chromosome number was determined in cardiac tissue cell culture. 

8 Chromosome number was determined in cell cultures: the modal 2n in a spleen cell line was 219, and in a heart cell line, 237–243 (Hedrick 

et al. 1991).

131 

Table 2. Characteristics of karyotypes of several acipenseriform species 1 . 

Species Chromo- Number of Number of Number of Approximate Reference 

some large meta- large micro- arm number, 

number centrics plus telocentrics chromo- NF 

medium meta/ 

somes 

submetacentrics, 

M + 

m/sm 

1. Tetraploid species 

Family Polyodontidae 

Polyodon spathula 120 8 + 36 4 72 164 Dingerkus & Howell 

Family Acipenseridae 

Acipenser nudiventris 

Black Sea, Russia 118 ± 3 8 + 46 4 60 ± 3 172 

(1976) 

Arefjev (1983) 

A. ruthenus 

Sea of Azov, Russia 118 ± 3 8 + 50 4 56 ± 3 176 Arefjev (1989a) 

Volga River, Russia 118 ± 2 8 + 50 4 56 ±23 176 Birstein & Vasiliev 

Danube, Slovakia 118 ± 4 8 + 50 4 56 ± 4 176 

(1987) 

Rab (1986) 

Danube, Yugoslavia 116 ± 2 8 + 48 4 56 + 4 170 Fontana et al. (1977) 

A. stellatus 

Volga River, Russia 118 ± 2 8 + 48 4 58 ± 2 174 Birstein & Vasiliev 

A. sturio 

Italy 116 ± 4 8 + 48 4 56 ± 4 172 

(1987) 

Fontana & Colombo 

Huso huso 

Volga River, Russia 118 ± 2 8 + 54 4 52 ± 2 180 

(1974) 

Birstein & Vasiliev 

Sea of Azov, Russia 118 ± 3 8 + 54 4 52 ± 3 180 

(1987), Arefiev & 

Nikolaev (1991) 

Serebryakova et al. 

Italy 116 ± 54 8 + 52 4 52 ± 4 176 

(1983), Arefiev 

(1989b) 

Fontana & Colombo 

(1974) 


USA 112 ± 2 8 + 52 4 48 ± 172 Ohno et al. (1969) 

2. Octoploid species 



Lena River, Siberia, Russia 248 ± 5 16 + 42 190 308 Vasiliev et al. (1980) 

A. gueldenstaedtii 

Volga River, Russia 250 ± 8 16 + 76 155 339 Birstein & Vasiliev 

(1987) 

Sea of Arzov, Russia 250 ± 8 16 + 82 152 348 Arefjev (1989a) 

A. naccarii 

Italy (wild) 239 ± 7 16 + 76 147 331 Fontana & Colombo 

(1974) 

Italy, aquaculture 241 ± 3 16 + 74 151 331 Arlati et al. (1995) 

A. sinensis 

China 264 ± 3 16 (?) + 82 166 362 Yu et al. (1987) 

1 

A revision of data from papers mentioned as References. The numbers of m/sm, microchromosomes, and NF are given 

approximately, since it is impossible to discriminate the form and exact number of small chromosomes and microchromosomes. For 

octoploid species, the number of telocentrics and microchromosomes is given together because there is no clear size difference 

between these two kinds of chromosomes. Usually there are 2–5 middle and/or small-sized telocentric pairs in these karyotypes.

132 

rent views on paleogeography will provide useful The size of macrochromosomes in both groups is 

tools for resolving complex relationships and phy- between 2–5 µm, and the majority of macrohromologeny 

of sturgeons’. In the first part of this paper somes are the meta- and submetacentrics (Table 2). 

we review all cytogenetic data available on Acipen- One third to one half of the chromosome number in 

seriformes and make some new conclusions rele- both groups is comprised of microchromosomes of 

vant to the four groups within Acipenser mentioned a very small size (about 1 µm). Karyotypes of the 

above. In the second part we describe experimental 120-chromosome species typically consist of 4 pairs 

data on the molecular phylogeny of Acipenseri- of large metacentrics (no. 1–4), 5 pairs of large but 

formes. Because multiple gene regions have been somewhat smaller metacentrics (no. 5–9), about 20 

useful in other groups of fishes (reviews in Normark pairs of medium-sized metacentrics and/or subet 

al. 1991, Stock et al. 1991a, Meyer 1993, Patterson metacentrics of gradually decreasing size (no. 10– 

et al. 1993), we believed that they might also provide 30). one pair of comparatively large telocentrics 

reasonable character state information for acipen- (no. 30), one pair of small telocentrics, and approxiseriforms. 

Consequently we amplified and se- mately 56 ± 4 microchromosomes of different form 

quenced partial fragments of 18S rRNA, 12S rRNA, (Table 2). The difference between karyotypes of 

16s rRNA, and cytochrome b genes of a few repre- representatives of two lineages of the extant acisentatives 

of all lineages of this order. We included penseriforms, the Polyodontidae (Polyodon spaththe 

phylogenetic analysis of the combined molecul- ula) and Acipenseridae (all other 120-chromosome 

ar and morphological data for all the species we species in Table 1), as well as of the lineages within 

studied. Also, we examined relationships among the Acipenseridae (Huso huso, the 120-chromorepresentatives 

of four species groups of the genus some species of the genus Acipenser, and Scaphir- 

Acipenser recognized by Artyukhin (1995), using hynchus platorynchus), seems to be small. Evidentdata 

for a partial sequence of the cytochrome b ly, the ancestral acipenseriform karyotype was pregene. 

served in these fishes without dramatic changes 

during diverisification of the group. 

In general, few karyotypic changes are noticeable 

Acipenseriform cytogenetics: an overview 

among the species of Acipenser with 120-chromosomes 

(Table 2). The karyotype of Huso huso is 

Main karyotypic characteristics, DNA content, and 

polyploidy 

more symmetric than those of the 120-chromosome 

species of Acipenser, i.e., it contains more biarmed 

chromosomes and fewer microchromosomes (see 

Karyotypes of about half of all sturgeon species 

have been described and the DNA content in most 

sturgeon species and American paddlefish has been 

measured (Table 1). Acipenseriform karyotypes investigated 

sofar have two particular characteristics: 

(1) they are large; and (2) they consist of macro- and 

microchromosomes. According to the number of 

chromosomes (2n), the species can be divided into 

two groups: those with about 120 chromosomes 

(e.g., Huso huso, H. dauricus, Acipenser ruthenus, 

A. stellatus, A. nudiventris, A. sturio, and Polyodon 

spathula), and those with 240 chromosomes (e.g., A. 

gueldenstaedtii, A. naccarii, A. baerii, A. schrenckii, 

and A. transmontanus). By comparison to the 120- 

chromosome species, the 240-chromosome species 

are tetraploids. 

Morescalchi 1973). Also, there is a small difference 

among the 120-chromosome species in the size of a 

pair of large telocentrics (no. 30): it is small in A. 

sturio (Fontana & Colombo 1974) and A. nudiventris 

(Arefjev 1983) and it is as large as pair no. 8 or 9 

in Huso huso (Fontana & Colombo 1974, Birstein & 

Vasiliev 1987, Arefjev 1989b) and A. ruthenus (Rab 

1986, Birstein &Vasiliev 1987). 

The similarity of karyotypes of the 120-chromosome 

acipenseriforms points to a generally slow 

rate of karyological evolution. This correlates with 

a slow rate of nuclear DNA evolution: practically all 

genome fractions (both the repeated and unique sequences) 

are homologous in Acipenser ruthenus, A. 

stellatus, A. gueldenstaedtii, and H. huso, and the 

number of nucleotide substitutions in the first frac-

133 

tion is 0–2.65, and 1.5–2.7% in the second (Kedrova 

et al. 1980). These data were supported by our results 

from sequencing the 18S genes, which are almost 

invariable among acipenseriforms (see below). 

A low degree of protein evolution is usually characteristic 

of the acipenseriforms. especially the 120- 

chromosome species. A mean heterozygosity for 

three freshwater species, Polyodon spathula, Scaphirhynchus 

platorynchus and S. albus, is between 

0.010 and 0.017 (Carlson et al. 1982, Phelps &Allendorf 

1983) and is the highest (of all species investigated) 

in the anadromous Acipenser stellatus, 0.093 

(Ryabova & Kutergina 1990). All of these species 

are 120-chromosome forms. The mean heterozygosity 

for other osteichthyans is 0.051 (Ward et al. 

1992). The complete lack of genetic divergence at 

the protein level between the two species of Scaphirhynchus 

is very unusual for fishes, especially 

because freshwater fishes typically exhibit subpopulational 

differentiation significantly higher than 

that of anadromous and especially marine species 

(Ward et al. 1994). 

The DNA content (2C) of all of the 120-chromosome 

species is about 3.7–3.9 pg (in Polyodon spathula 

it is a little lower, 3.2 pg), whereas in the 240- 

chromosome species it is twice as high, 7.9–8.3 pg 

(Birstein et al. 1993, Table 1). Moreover, the same 

tendency in DNA content is present in American 

sturgeons whose karyotypes have not been investigated: 

A. oxyrinchus desotoi (2C = 4.6 pg) is evidently 

a 120-chromosome subspecies, whereas A. 

fulvescens and A. medirostris (American form) are 

240-chromosome species, 2C = 8.8–8.9 pg (Blacklidge 

& Bidwell 1993; the slightly higher DNA content 

for all American species as compared with the 

Eurasian species in Table l is due to the different 

methods used by Birstein et al. 1993, and Blacklidge 

& Bidwell 1993). DNA content in Pseudoscaphirhynchus 

kaufmanni (3.2 pg) is slightly lower than in 

the sterlet, A. ruthenus (3.7 pg), which was used by 

Birstein et al. (1993) as a standard species for comparative 

measurments due to its invariable DNA 

content. However, this difference is so small that we 

predict P. kaufmanni is a 120-chromosome species. 

The sterlet, Acipenser ruthenus, has other properties 

which attest to its genetic stability. The basic 

chromosome number in three generations of the 

‘bester’, the fertile hybrid between beluga, Huso 

huso, and sterlet, A. ruthenus, does not differ from 

that of parental species, and a gradual displacement 

of karyotypic parameters (numbers of bi- and uniarmed 

chromosomes) towards those of the sterlet 

occurs (Arefjev 1989b). The sterlet has evidently 

not only invariable DNA content, but also a dominant 

karyotype. The situation is very unusual, because, 

as a rule, the karyotypes of fish interspecies 

hybrids are more variable than karyotypes of the 

parental species (Arefjev 1991, Arefjev & Filippova 

1993). 

The Asian green (Sakhalin) sturgeon, A. mikadoi 

(or A. medirostris mikadoi as explained below), and 

the American shortnose sturgeon, A. brevirostrum, 

have even higher DNA contents than the 240-chromosome 

forms. The DNA content of A. mikadoi is 

14.2 pg per nucleus, four times higher than in the 

120-chromosome species or roughly twice that of 

the 240-chromosome forms (Birstein et al. 1993). In 

American green sturgeon, A. medirostris, it is about 

half of this value (8.8 pg, Blacklidge & Bidwell 

1993). Therefore, the American green sturgeon 

seems to be a typical 240-chromosome form, while 

the Sakhalin sturgeon might be predicted to have 

twice the number of chromosomes, or around 500. 

If so, the Sakhalin sturgeon would have the highest 

diploid number reported in vertebrates. But polyploidization 

can occur without an increase in chromosomes 

number, as in several species of sharks 

(see below), and only direct karyotypic study can 

address the chromosome number and morphology 

of the Sakhalin sturgeon. DNA content data support 

the old point of view that the Asian form of A. 

medirostris is a separate species, A. mikadoi (Hilgendorf, 

1892), or a subspecies, A. medirostris mikadoi 

(Shmidt 1950, Lindberg &Legeza 1965; in Table 

1 it is mentioned as a species, see Birstein 1993b). 

Although Blacklige & Bidwell (1993) consider A. 

brevirostrum to be an allopolyploid (12n = 360), a 

descendant of ancestral spontaneous triploids, allopolyploidy 

is unknown in other acipenserids, and it 

is more logical to propose that this is a 16n-ploid. 

An investigation of active nucleoli gave additional 

information about ploidy in the acipenseriforms. 

There are different modal numbers of nucleoli per

134 

nucleus in species investigated (Table 3): 2–4 (maxi- of four homologs, and Dingerkus & Howell (1976) 

mum 6) in the 120-chromosome species, and 6-8 divided the karyotype of 120-chromosome Polyo- 

(maximum11–12) in the 240-chromosome species of don spathula into 30 groups consisting of four chro- 

Acipenser (Birstein & Vasiliev 1987, Fontana 1994). mosomes of similar morphology. If it is taken into 

In A. ruthenus, 4n, the NORs are located in two consideration that this species has 4 active nucleoli 

pairs of small chromosomes, a pair of metacentrics per nucleus (see above), it is clear that P. spathula is 

and a pair of telocentrics (possibly no. 30; Rab 1986, a tetraploid. The same procedure of chromosome 

Birstein & Vasiliev 1987, Fontana 1994). According grouping (but with greater uncertainity) can be 

to Arefjev (1993), in octoploid A. baerii NORs are done for A. ruthenus and H. huso (Birstein & Vasilocated 

also on two pairs of chromosomes, while liev 1987). From this comparison, one can conclude 

Fontana (1994) found two quadruplets bearing that the 120-chromosome species are in reality tet- 

NORs in A. baerii, A. naccarii, and A. transmonta- raploids, while the 240-chromosome species are renus. 

The average number of nucleoli in Polyodon ally octoploids, and the ploidy of A. mikadoi and A. 

spathula is 4 (Dingerkus &Howell 1976), as many as brevivostrum possibly is 16n. 

in the 120-chromosome species of Acipenser (Table Further evidence that the 120-chromosome spe- 

3). Usually the number of nucleoli in diploid tele- cies are tetraploids comes from the existence of duosts 

is half that of the 120-chromosome acipenser- plicated loci, a common characteristic of polforms 

and equals 1–2 nucleoli per nucleus (review in yploids. A high level of duplicated loci (31%) was 

Birstein 1987). 

found in A. stellatus (Nikanorov et al. 1985, Ryabo- 

The tendency seen in 120-chromosome sturgeons va & Kutergina 1990); duplicated loci were also 

to have more nucleoli than in diploid teleosts is ap- found in Huso huso (Slynko 1976). In A. stellatus, 

parently caused by their high ploidy. Ohno et al. duplicated loci Ldh3 and Ldh4 are located at two 

(1969) arranged the first 64 chromosomes of Sca- different chromosomes (Kutergina & Ryabova 

phirhynchus platorynchus, 4n =116 ± into 16 groups 1990). In Polyodon spathula the expression of dupli- 

Table 3. Number and location of nucleolar organizer regions (NORs) in Acipenseriformes (data on Ag-staining). 

Species Chromosome Number of NORs Number of NORs-bearing Reference 

number per nuclei 1 chromosomes and NORs’ 

location 2 


Polyodon spathula 120 4 Dingerkus & Howell 

(1976) 


1. Tetraploid species 

Acipenser ruthenus 118 2–3 (1–6) Two pairs (T & m), telomeric Birstein & Vasiliev (1987) 

118 – Two pairs, telomeric Fontana (1994) 

A. stellatus 118 2–3 (1–6) Two pairs (both (?) m). 

telomeric Birstein & Vasiliev (1987) 

Huso huso 118 2–3 (1–6) Two pairs (both (?) m). 

telomeric Birstein & Vasiliev (1987) 

2. Octoploid species 

Acipenser baerii 250 4 (2–6) Two pairs (T & m) Arefjev (1993) 

250 – Two quadruplets Fontana (1994) 

A. gueldenstaedtii 250 6–8 (2–12) – Birstein & Vasiliev (1987) 

A. naccarii 246 – Two quadruplets Fontana (1994) 

A. transmontanus 248 – Two quadruplets Fontana (1994) 

1 The modal number; a variation in the number is given in the parenthesis. 

2 

T means medium-sized telocentric, and m, microchromosome: telomeric means telomeric location of NORs.

135 

Table 4. Natural hybridization of sturgeon species and their ploidy. 

Interspecies hybrids 

Intergenera hybrids 

1. Caspian Sea basin 1 

(a) Volga River 

A. ruthenus (4n) × A. stellatus (4n) 

H. huso (4n) × A. gueldenstaedtii (8n) 

A. stellatus (4n) × A. ruthenus (4n) 

H. huso (4n) × A. ruthenus (4n) 

A. nudiventris (4n) × A. gueldenstaedtii (8n) 

A. gueldenstaedtii (8n) × A. ruthenus (4n) 2 

A. gueldenstaedtii (8n) × A. stellatus (4n) 

A. gueldenstaedtii (8n) × A. persicus (8n) 3 

(b) Kama River 

(c) Ural River 

A. nudiventris (4n) × A. stellatus (4n) 

A. stellatus (4n) × A. nudiventris (4n) 

(d) Kura River 


A. stellatus (4n) × A. nudiventris (4n) 


(e) Sefir-Rud River 



(f) Caspian Sea 

2. Sea of Azov basin 4 

Don River 


3. Black Sea basin 5 

(a) Danube 


A. ruthenus (4n) × A. nudiventris (4n) 

A. stellatus (4n) × A. ruthenus (4n) 

A. ruthenus (4n) × A. gueldenstaedtii (8n) 

A. stellatus (4n) × A. gueldenstaedtii (8n) 


A. sturio (4n) × A. gueldenstaedtii (8n) 

(b) Black Sea 

A. gueldenstaedtii (8n) × A. sturio (4n) 

A. gueldenstaedtii (8n) × A. nudiventris (4n) 

4. Siberian rivers 

Huso huso (4n) × A. nudiventris (4n) 

H. huso (4n) × A. gueldenstaedtii (8n) 

H. huso (4n) × A. stellatus (4n) 

A. ruthenus (4n) × H. huso (4n) 


H. huso (4n) × A. nudiventris (4n) 

H. huso (4n) × A. persicus (8n) 

A. gueldenstaedtii (8n) H. huso (4n) 

A. stellatus (4n) × H. huso (4n) 

A. nudiventris (4n) × H. huso (4n) 


Main rivers (Yenisey, Lena, Ob, Kolyma) 6 Amur River 7 

A. baerii (8n) × A. ruthenus (4n) 

Huso dauricus (4n) × A. schrenckii (8n?) 

5. Central Asia 8 

Amu-Darya River 

Pseudoscaphirhyncus kaufmanni (4n) × P. hermanni 

6. North America 9 

Missouri and Mississippi Rivers 

Scaphirhynchus albus (?) × S. platorynchus (4n) 

1 

Data from Berg (1911,1948b), Kozhin (1964), Kozlov (1970), Legeza (1971), and Keyvanfar (1988). 

2 

In the early 1950s, this hybrid was the most numerous (46% of all hybrids caught; Konstantinov et al. 1952). 

3 

Data from Vlasenko et al. (1989b). 

4 

Data from Berg (1948b) and Kozhin (1964). 

5 

Data from Antipa (1909), Antoni-Murgoci (1946), Banarescu (1964), and Berg (1948b). 

6 

Data from Berg (1948b). 

7 

Data from Berg (1948b), Wei et al. (1996), and Krykhtin & Svirskii (1996). 

8 Data from Nikolskii (1938) and Berg (1948b). 

9 

Data from Carlson et al. (1985).

136 

cated loci is much lower, only 6% (Carlson et al. 

1982). Why this is so is unknown. In this species duplicated 

loci for insulin, glucagon and glucagon-like 

peptide were found (Nguyen et al. 1994). 

As for the 240-chromosome octoploid species, it 

is evident that two forms of vitellogenin monomers 

in American A. transmontanus (Bidwell et al. 1992) 

and two forms of growth hormones in Russian A. 

gueldenstadtii (Yasuda et al. 1992) are a result of 

polyploidization. A higher ploidy level seems to be 

a reason for a higher heterozygosity in A. gueldenstuedtii 

compared to the 120-chromosome species of 

Acipnser from the same geographic area (Slynko 

characters studied, 9 deviated toward the maternal 

species (beluga), and 18 deviated toward the paternal 

species (sterlet) (Krylova 1981). The meristic 

characters (the number of dorsal, lateral, and ventral 

scutes) deviated toward the maternal species 

(beluga ). The case of hybridization of sturgeon species 

allowed to show the maternal inheritance of 

some behavior characters of sturgeons (Marshin et 

al. 1969). 

Problem of the ancestral karyotype 

1976, Keyvanfar 1988, Kuzmin 1991). Possibly, a Data presented above support the hypothesis of the 

high level of ploidy causes a high variation in the tetraploid origin of 120-chromosome acipenserimean 

heterozygosity of American octoploid A. forms from a 60-chromosome ancestor before the 

transmontanus (0.014–0.069, Bartley et al. 1985). radiation of this order (Dingerkus & Howell 1976, 

Hemoglobin, the only protein examined in the 16n- Carlson et al. 1982). The karyotypes of Lepisosteiploid 

A. mikadoi is more heterogeneous (11 elec- dae (gars) and Amiidae (bowfins) are relevant to 

trophoretic fractions) than in tetra- (8–9 fractions) understanding the proposed acipenseriform ancesor 

octoploid (7–8 fractions) species of Acipenser tral karyotype. Gars have approximately 60 chro- 

(Lukyanenko & Lukyanenko 1994). 

mosomes (Table 1), but it seems that many karyo- 

Polyploidization is a relatively uncommon genet- logical changes have occurred during their evoluic 

mechanism in vertebrates, occurring only in lam- tion. The karyotype of Lepisosteus oculatus, 2n = 

preys, elasmobranchs, acipenseriforms, some 68, consists of many meta- and acrocentric macrogroups 

of teleosts (salmonids, cyprinids, and catos- chromosomes, as well as many microchromosomes 

tomids), amphibians (anurans), and lizards (review (Ohno et al. 1969), while the karyotype of L. osseus, 

in Birstein 1987). To date, polyploidization is un- 2n = 56, lacks microchromosomes (Ojima & Yamaknown 

in birds or mammals. It seems that the pol- no 1980). Tho karyotype of Amia calva is even more 

yploid state, and karyotypic and genomic similarity reduced,2n = 46, but it still includes microchromoof 

different acipenseriforms contribute to easy in- somes (Ohno et al. 1969, Suzuki &Hirata 1991). The 

terspecific and even intergeneric hybridization cellular DNA content of gars and Amia ranges from 

within the Acipenseridae. 

2.0 to 2.8 pg per nucleus, which is approximately 

The Acipenseridae is the only group among ver- half that of the 120-chromosome acipenseriforms. 

tebrates all members of which can hybridize with Therefore, it is quite possible that the common aneach 

other in the wild if their spawning grounds cestor of acipenseriforms and neopterygians had a 

overlap (Table 4). The unique easiness of hybrid- karyotype of about 60 chromosomes consisting of 

ization of acipenserids was described by Russian micro- and macrochromosomes, with a DNA conichthyologists 

more than 100 years ago (Ovsyanni- tent about 2.0 pg per nucleus. 

kov 1870, Zograf 1887). Some hybrids (such as the Extant polypterids. which are the living members 

artificially obtained‘bester’, H. huso × A. ruthenus, of the basal actinopterygian group Cladistia, have 

and its reciprocal hybrid, Nikolyukin 1970), have 36 bi-armed chromosomes (except Polypterus 

the desirable characteristics of last growth and high weekesii, 211 = 38; reviews in Vervoort 1980, Suzuki 

viability, are fertile (which is also unusual for ver- et al. 1988,1989). The DNA content in polypterids is 

tebrate hybrids) and are widely used in aquaculture considerably higher than in the acipenseriforms, 2C 

(Williot et al. 1993). Besters inherit a phenotype in- = 12–13 pg per nucleus (Vervoort 1980). It is evident 

termediate between the parental species. Of 29 that the polypterids are a cytogenetically advanced

Cytogenetic data and phylogeny of the Acipenseri- 

formes 

group. Molecular data also support this conclusion: 

the 18S rRNA sequences in the species of the genera 

Polypterus and Erpetoichthys are very similar to 

each other, but both arc highly divergent from those 

of other gnathostomes (Stock et al. 199la). 

The karyotypes of chondrichthyans are more informative. 

Chondrichthyans are mostly tetraploids, 

4n = 90–104 (reviews in Schwartz & Maddock 1986, 

Asahida et al. 1988,1993, Asahida & Ida 1989,1990, 

Stingo et al. 1989, Stingo & Rocco 1991), and karyotypes 

contain macro- and microchromosomes. According 

to cellular DNA content and DNA re-association 

kinetics data (Olmo et al. 1982, Ida et al. 

1985), the ploidy level of a few species of sharks is 

higher, and in these cases polyploidization occurred 

without a change in the chromosome number (phenomenon 

known as cryptopolyploidy; Wagner et al. 

1993). The only extant chondrichthyan which possibly 

retains a diploid karyotype is the spotted ratfish 

Hydrolagus colliei: it has the lowest chromosome 

number among elasmobranchs, 2n = 58, and 

the lowest DNA content, 2C = 3.0 pg (Ohno et al. 

1969). But this could be a derived condition, for insufficient 

taxa have been studied to draw any conclusion. 

Moreover, changes in DNA content occur 

even during ontogenesis of this species: about 10% 

of the genome is eliminated in somatic tissues as 

compared with the germ cells (Stanely et al. 1984). 

In contrast to Acipenseriformes, the reduction of 

chromosome number through fusion of micro- and 

small chromosomes into macrochromosomes was 

the main evolutionary karyotypic trend in chondrichthyans 

(Schwartz & Maddock 1986, Stingo et 

al. 1989). As a result, the karyotypes of advanced 

chondrichthyans consist of a smaller number of 

mainly bi-armed chromosomes, 2n = 50–70. Another 

considerable difference is that acipenseri- 

137 

teristics of the karyotypes of spotted ratfish, gars, 

and sturgeons, Ohno (1970) and later Dingerkus 

(1979) proposed that the ancestral karyotype of 

gnathostomes consisted of approximately 50–60 

macro- and microchromosomes. 

Recently a karyotype consisting of macro- and 

microchromosomes was described in another living 

fossil fish, the coelacanth Latimeria chalumnae 

(Bogart et al. 1994). It appears to include 16 pairs of 

macro- and eight pairs of microchromosomes. This 

karyotype resembles to a high extent that of one of 

the most primitive living frogs, Ascaphus truei, but 

this resemblance could be coincidental. 

Karyotypes of acipenseriforms generally resemble 

karyotypes of primitive amphibians, not anurans 

as in L. Chalumnae, but, instead, urodeles belonging 

to the family Hynobiidae. With several exclusions, 

the karyotypes of hynobiids, 2n = 56–62, 

consist of a few large and middle-sized pairs of biarmed 

macrochromosomes, a few pairs of telocentric 

macrochromiosomes. and 15–20 pairs of microchromosomes 

(Morescalchi et al. 1979, King 1990, 

Kohno et al. 1991). It seems that the ancestral karyotype 

of these amphibians consisted of 60 macro- and 

microchromosomes. Because the karyotypes of hynobiids, 

as well as those of acipenseriforms, include 

a large number of bi-armed macrochromosomes, 

they should be considered derived (as compared, 

for instance, with those of the most ancient forms of 

chondrichthyans). 

It is impossible to infer generic interrelationships 

within the Acipenseridae from cytogenetic data. 

forms have numerous bi-armed macrochromo- Divergence of the three lines within the family ocsomes, 

whereas the most generalized, plesiomor- curred without polyploidization, and the ancestors 

phic elasmobranchs have only 2–3 pairs of bi-armed of all three lineages within the acipenserids seem to 

rnacrochromosomes, and up to 50 pairs represented have been tetraploids, 4n = 120. If the genus Huso 

by small telocentrics or by microchromosomes originated as the first outshoot within the Acipen- 

(Schwartz & Maddock 1986, Stingo & Rocco 1991). seridae (as proposed by Findeis 1993, 1997), then 

Moreover, the average DNA content in elasmo- this event was not accompanied by a substantial kabranchs 

is much higher than in acipenseriforms (re- ryotypic change. The ancestral karyotype seems to 

views in Schuartz & Maddock 1986, Birstein 1987, have been retained without significant modifica- 

Asahida et al. 1988,1993). Based on general charac- tion, since the karyotype of Huso huso is only slight-

138 

Figure 1. A schematic representation of changes in ploidy in Acipenseriformes. M = macro-, m = microchromosomes 

ly more symmetric than karyotypes of other acipen- content data) and l6n-ploid (according to DNA 

serids. A schematic course of possible cytogenetic content data) species. The octoploid 240-chromoevolution 

within the Acipenseriformes is presented some sturgeon species seem to have originated inin 

Figure 1. 

dependently in different regions. The closely relat- 

Cytogenetic data are helpful for understanding ed A. gueldenstaedtii and A. persicus may have a 

some relationships within the genus Acipenser, common origin and a common octoploid ancestor. 

where polyploidization was one of the main genetic Molecular data point to the close relatedness of A. 

mechanisms of speciation. The diversification of dueldenstaedtii to A. baerii (see below). 

this genus was accompanied by an appearance of Acipenser medirostris and A. transmontanus 

octoploid (according to the karyotypic and DNA have many similar characteristics in morphology,

iology, and ecology, as well as overlapping ranges character in cladistic terms) to the hypothetical 

in western North America (Hart 1973, Scott & grouping of species within the genus Acipenser 

Grossman 1973). Moreover, according to Artyuk- based on the species morphology, ecology, biogeoghin 

& Andronov (1990), some ecological and bio- raphy and possible area of origin (Artyukhin & Anlogical 

characteristics are common to these two spe- dronov 1990, Artyukhin 1994, 1995). 

cies and the Chinese sturgeon, A. sinensis. All three Among fishes, an analogous mode of speciation 

species areoctoploid (Table 1). Possibly, tetraploi- through multiple independent tetraploidization 

dization occurred in the ancestor of all three spe- events is characteristic of only one group of teleosts. 

cies. If the difference between the karyotype of A. the family Cyprinidae (review in Buth et al. 1991). A 

sinensis and A. transmontanus (8n = 264 ± 3 and 230 tetraploid ancestor of two species, Cyprinus carpio 

± or 248 ± 8, respectively is real, then it means that and Carassius auratus, appeared through tetraploiat 

least two polyploidization events took place in dization about 16–20 million years ago ( Risinger & 

the ancestral 120-chromosome form. The next step Larhammar 1993, Larhammar & Risinger 1994). 

of polyploidization which occurred in the 240-chro- Hexaploids in Eurasia and Africa (reviews in Vasimosome 

ancestor of A. medirostris and A. mikadoi, liev 1985, Buth et al. 1991, Golubtsov & Krysanov 

resulted in the formation of the genome of A. mika- 1993), as well as a l6/20n-ploid Asian species Dipdoi 

(which is, therefore, the youngest in this group tychus dipogon (Yu & Yu 1990) also were formed 

of species). The Amur River sturgeon, A. schren- within Cyprinidae. Moreover, as a result of a tetrackii. 

also seems to be an octoploid (but these data ploidization event which occurred approximately 

are preliminary, see Table 1), as the species of the 50 million years ago an ancestor of another family, 

trans-Paci fic A. sinensis-A medirostris-A. trans- Catostomidae, appeared within this group (Uyeno 

montanus group, and lives in a close geographic & Smith 1972). Catostomids are considered to have 

area. According to Artyukhin (1994, 1995), A. been tetraploid since then (Ferris & Whitt 1979, Ueschrenckii 

is closely related to the Ponto-Caspian no et al. 1988,Tsoi et al. 1989). Tetraploids were also 

species A. nudiveritris and A. ruthenus 

formed in another family closely related to Cyprin- 

It is difficult to draw any conclusions concerning clae, the Cobitidae (review in Vasiliev 1985). Only 

the ancestor of A. brevirostrum. the species with the one other group of teleosts, the Salmonidae (which 

second highest level of DNA content. The other includes three subfamilies, Coregoninae, Thymallispecies 

of the Eastern Coast of North America, A. nae, and Salmoninae, sensu Nelson 1994) also origoxyrinchus, 

is closely related to the European 120- inated from a tetraploid ancestor (Cold 1979, Alchromosome 

Atlantic sturgeon, A. sturio, and, ac- lendorf & Thorgaard 1984). By contrast with the 

cording to the DNA content, has the same ploidy acipenseriforms, cyprinids, and catostomids, a de- 

(Table 1). Possibly, A. brevirostrum is also related to crease in chromosome number through centromersome 

European sturgeons (A. nidiventris; see be- ic fusion was characteristic for different lineages of 

low), and originated from these European-related salmonids (Vasiliev 1985, Buth et al. 1991). Thereancestors 

through polyploidization. Because of its lore, a gradual increase in chromosome number 

high ploidy level, A. brevirostrum might be a young through polyoidization has occurred a few times 

species among East American repesentatives of during the history of actinopterygians. 

the genus Acipenser. As for another American species, 

the freshwater lake sturgeon, A. fulvescens, 

which is also an octoploid like A. oxyrinchus (according 

Molecular phylogeny of the Acipenseriformes 

to its DNA content), its origin and relation- 

ships with the other species are still unclear, although 

it is morhologically similar to A. brevirosrum 

(Vladykov & Greeley 1963, Findeis 1993). 

Therefore, the cytogenetic data provide additional 

information (ploidy level can be considered as a 

Our first objective was to search for molecular synapomorphies 

of Acipenseriformes and its major included 

clades using representatives of all extant 

genera (except the Chinese paddlefish, Psephurus 

gladius, due to our inability to obtain suitable tis- 

139

140 

sue). Our data were polarized using other Actinop- found (Brown et al. 1992b, 1993). Fifty percent ofA. 

terygii, Polypterus and Amia. We also attempted a mediostris studied were also heteroplasmic; D- 

synthesis of morphological, karyological and mole- loops of these individuals included from one to four 

cular characters as related to relationships among repeats (Brown et al. 1996). The average size of 

Acipenseriformes. Finally, we examined interrela- mtDNA of the lake stugeon, A. fulvescens is aptionships 

among representatives of Artyukhins spe- proximately the same as that of white sturgeon, 

cies groups proposed for Acipenser (see above). 16.6-16.9kb (Guènette et al. 1993, Ferguson et al. 

Whereas our examination of acipenseriform taxa 1993) or 16.1–16.5 kb (Browm et al. 1996). Noheteroconcentrated 

on comparisons of species belonging plasmy was detected in A. fulvescens and A. oxyrinto 

different genera or species within the gems Aci- chus (Brown et al. 1996). All individuals of A. fulpenser 

most previous workers have concentrated vescens studied had one of five possible mtDNA 

on intraspecies structure using the control region size variants which closely corresponded to A. 

(D-loop) of the mtDNA. Buroker et al. (1990) transmontanus with one to five repeat units. In A. 

showed that in the American white sturgeon, Aci- oxyrinchus, nearly every individual was fixed for 

penser transmontanus, mtDNA size varies between mtDNA roughly equivalent in size to the smallest 

16.1 and 16.7 kb depending on the number of tan- repeat found in the other species. Restriction analydemly 

repeated 82 nucleotide sequences in the con- sis of mtDNA (Bowen & Avise 1990, Avise 1992) 

trol region of the mtDNA. Nearly 50% of the indi- and partial sequencing of the control region (Miraviduals 

studied by Brown et al. (1992a) were hetero- sle & Campton 1995, Ong et al. 1996, Wirgin et al. 

plasmic (i.e., had multiple copies of different 1997 this volume) were used for inferring relationmtDNA 

types within an individual) lor length vari- ships between subspecies and populations of , A. oxyation, 

with six different mt DNA length variants 

Table 5. List of sturgeon species and blood samples studied. 

Species Species Geographical region Number of blood (or Collector 

number 

tissue) samples 

1. Acipenser baerii 1 Lena River, Siberia, Russia 

(Moscow Aquarium) 2 V. Birstein 

2. A. brevorustrum Connecticut River, MA,USA (eggs) B. Kynard 

3. A. gueldenstaedtii 1 Volga River, Russia (Moscow 

Aquarium) 2 V. Birstein 

4. A.Mediostris Columbia River, OR,USA 1 J. North 

5. A. mikadoi Tumnin River, Russia 2 (fragments of muscles) E. Artuykhin 

6. A. nacarri Ferrara, Italy (Aquarium) 2 F. Fontana 

7. A. nudiventris 1 Aral Sea, Uzbekistan (Moscow 


8 A. oxyrinchus oxyrinchus Hudson River 2 (fragments of muscles) J. Waldman 

9. A. rutthenus 1 Volga River, Russia (Moscow 


10. A. stellatus Volga River, Russia (Moscow 


11. A. transmontanus Columbia River, OR, USA 2 J. North 

12. Huso dauricus Amur River, Siberia, Russia 


13. Pseudoscaphirhynchus kaufmanni 1 Amu-Darya River, Uzbekistan 


14. Scaphirhynchus albus Yellowstone River, MT, USA 2 M. Bollig 

15. Polyodon spathula Moscow Aquarium 1 V. Birstein 

1 

These samples were used for the DNA content measurements in Birstein et al. (1993); see Table 1 above.

inchus Both subspecies. A. o. oxrinchus and A. 

oxyinchus desotoi, exhibited low mtDNA diversity. 

The order and transcriptional polarity of three 

mitochondrial genes in A. transmontanus (genes for 

cytochrome b, threonine and proline tRNAs) are 

identical to those of other vertebrates (Gilbert et al. 

individuals used for DNA content measurements 

by Birstein et al. (1993). Also, we isolated DNA 

from alcohol-Fixed samples of muscles of Amia calva 

and Polypterus senegalus provided by Paul Vrana 

(American Museum of Natural History, New 

York). 

1988. Brown et al. 1989, Buroker et al. 1990). The 

whole sequence of the cytochrome b gene for A. 

transmontanus as well as partial sequences of the DNA extraction, amplification, and sequencing 

same gene for Scalp hirhync chus platoryn ch us and 

Polyodon spathula were published recentely DNA was isolated from each sample using a stan- 

(Brown et al. 1989, Normark et al. 1991). Partial se- dard phenol preparation (Hillis et al. 1990, DeSalle 

quences of the same gene for A. brevivostrum, A. et al. 1993). We examined partial sequences of three 

oxyrinchus, Scaphirhynchus albus, and S. suttkusi ribosomal genes (two mitochondrial and one nuclewere 

submitted by W. Schill into GenBank under ar) and a partial sequence of cytochrome b. PCR 

numbers Z22822, L35111, L35110, and L35112, re- products were prepared for DNA sequencing in 

spectively. Although acipenseriforms were includ- several ways. In all cases the nuclear 18S rDNA 

ed in a higher level phylogenetic analysis based on fragments were GeneCleaned (BIO 101 ; Palumbi et 

cytochrome b sequence (Normark et al. 1991), no al. 1991) and directly sequenced. PCR products of 

direct evidence on the utility of other gene regions the mitochondrial genes (12S, 16S, and cytochrome 

for phylogenetic analysis is available. b) were either GeneCleaned and directly se- 

Because phylogenetic divergence within the Aci- quenced or cloned into the TA vector (INVITROpenseriformes 

is potentially broad, based on the GEN) and sequenced (in such cases, at least two 

fossil record (e.g., Grande & Bemis 1991, Bemis et clones for each taxon were used to establish the seal. 

1997), no single gene region can be assumed to be quence). We used the following primers: in the 18S 

adequately broadly informative on all phylogenetic gene region, 18sai0.7 (5' -ATTAAAGTTGTTGClevels 

as a source of characters. Consequently we GGTTT-3') and 18sai0.79 (5'-TTAGAGTGCTYchose 

to examine several gene regions as potential AAAGC-3') (Wheeler et al. 1993). in the 12S gene 

sources of characters, including well characterized region, 12SA (5' -GGTGGCATTTTATTTTATTgene 

regions from mitochondrial DNA (16S rDNA, AGAGG-3' ) and 12SB (5' CCGGTCTGAACTC- 

12S rDNA, and cytochrome b) and one nuclear AGATCACGT-3') (Kocher et al. 1989, Hedges et 

al. 1993b), in the 16S gene region, 16SA (5' -CG- 

CCTGTTTACCAAAACAT-3’) and 16SB (5’-CC- 

GGTCTGAACTCAGATCACGT-3') (Palumbi et 

al. 1991), and in the cytochrome b region, H15149 

gene region (18S rDNA). Below we discuss each of 

these four gene regions. 

Materials and methods 

Specimens 

Species used in this study and location of the fishes 

are listed in Table 5. With three exceptions (Acipenset, 

brevirostrum, A. mikadoi and A. oxyrinchus), 

blood samples were taken, mixed with buffer (100 

mM Tris, 100 mM EDTA, and 2% SDS; 0.5ml of 

blood and 5 ml of buffer), and the blood cells lysed 

in this solution were kept in a freezer at –70°C. 

Most Russian specimens examined were the same 

141 

(5' -AAACTCCAGCCCCTCAGAATGATATT- 

TGTCCTCA-3') (Kocher et al. 1989) and L14724 

(5' -CGAAGCTTGATATGAAAAACCATCG- 

TTG-3') (Meyer et al. 1990). All sequencing, g was 

performed using the Sequenase system (U.S. Biochemicals) 

and double stranded templates. The sequences 

reported in this paper have been deposited 

in the EMBL Nucleotide Sequence Database (accession 

no. X95003–X95061).

142 

DNA sequence alignment and phylogenetic analysis 

We used equal weights for all nucleotide positions 

in all analyses. When multiple parsimonious trees 

were obtained for a particular analysis, successive 

weighting based on the retention index was used to 

choose among these multiple parsimonious trees 

(Carpenter 1988). DNA sequences for the mitochondrial 

16S and 12S rRNA regions and the nuclear 

18S rRNA regions were aligned using the program 

MALIGN (Wheeler & Gladstein 1993). Gap 

costs were varied in order to explore the effects of 

alignment parameters on phylogenetic inference 

(the results of varying alignment parameters on 

phylogenetic inference are discussed in detail in 

Fitch & Smith 1983, Gatesy et al. 1993, Hillis et al. 

1994, Wheeler 1995, Wheeler et al. 1995). In most 

cases our alignments were extremely stable (i.e., 

Figure 2. A phylogenetic tree for a combined (18sai0.7 plus 

18sai0.79; 229 bp) region of fishes: eight acipenseriform species alignment columns did not change by altering gap 

studied, Polypterus senegalus, Amia calva; four chondrich- costs) and this stability suggests a low level of ‘alignthyans, 

Notorynchus cepedianus (Hexanchiformes, Hexanchi- ment ambiguity’ (Gatesy et al. 1993). Consequently, 

dae; Bernardi & Powers 1992), Echinorhinus cookei (Squali- the methods of ‘culling’ (Gatesy et al. 1993) and 

fomes, Squalidae; Bernardi & Powers 1992, Bernardi et al. 1992, 

‘eliding’ (Wheeler et al. 1995) were not applied to 

M91179, GenBank), Squalus acanthoides (Squalifomes, Squalidae; 

Bernardi &Powers 1992, Bernardi et al. 1992, M91181, Gen- infer alignment. It was trivial to align cytochrome b 

Bank), and Rhinobatos lentiginosus (Stock & Whitt 1992, sequences, which were also performed using MA- 

M97576, GenBank); Latimeria chalumnae (Stock et al. 1991b, LIGN with a gap cost of 8. Parsimony trees for each 

L11288, GenBank); and two teleosts, Fundulus heteroclitus (cy- of the four individual gene regions were generated 

prinodontiformes, Fundulidae; Bernardi et al. 1992, M91180, 

GenBank), and Sebastolobus altivelis (Scorpaeniformes, Scorpaenidae; 

separately using the PAUP 3.1 program (Swofford 

M91182, GenBank). Squalus acanthias and Rhinoba- l993) to examine the signal inherent in each gene 

tos lentiginosus were used as outgroups. region. Sequence alignments using a gap cost of 8 

were arbitrarily chosen and were combined (Kluge 

Outgroup choice 

1989, Ernisse & Kluge 1993) into a single data matrix. 

Phylogenetic hypotheses were generated from 

We chose Polypterus senegalus, a representative of this combined data matrix using PAUP The degree 

a lineage often considered to be the sister group of of support for particular nodes in these trees was 

Acipenseriformes plus Neopterygii (Patterson examined using the Bremer support index (Bremer 

1982), as our outgroup. Because the use of multiple 1988, Donoghue et al. 1993, Kallersjo et al. 1993). 

outgroups is recommended in phylogenetic analyses 

(Watrous & Wheeler 1981), we also used Amia 

calva (Amiidae), generally regarded as the living Results and discussion 

sister species of teleosts (see Patterson 1973), as an 

outgroup. In the analysis of the partial sequence of Gene regions 

the 18S gene we used two chondrichthyan species, 

Squalus acanthias and Rhinobatos lentiginosus 18S rDNA 

(Bernardi et al. 1992, M91179; Stock & Whitt 1992, 

M97576), as outgroups. 

The 18S rRNA gene is relatively slowly evolving in 

vertebrates and has been useful at higher taxonomic 

levels (e.g., Stock et al. 1991a). We used two se-

quencing primers in our analyses, 18sai0.7 and there are three nucleotides, TCG, whereas in tele- 

18sai0.79. These primers are in a region of the 18S osts there are 7 nucleotides, TTCTCCT or 

gene that varies in insects and other organisms TCTTTCT, and in species studied by us, only a part 

(Wheeler et al 1993). The 18sai0.7 sequences were of the latter sequence, CCT. 

invariant in all acipenseriform species investigated, 

whereas the 18sai0.79 fragment was variable at sev- 16S mitochondrial rDNA 

eral positions. A low degree of 18S rRNA sequence We obtained sequences for two parts of this gene: 

divergence between Scaphirhynchus and Polyodon (1) a 147 nucleotide sequence using the 16SA primer 

was reported previously (Stock et al. 199la). 

(146 nucleotides for Amia calva and Polypterus se- 

The phylogenetic tree for combined data sets for negalus), and (2) a 169 nucleotide sequence with the 

both fragments of the 18S gene for all fish species 16SB primer (164 nucleotides in Amia culva). Both 

investigated so far is presented in Figure 2. Species regions were highly conserved, although there were 

used and origin of the sequences are explained in differences in the 3' -part of the 16Sb fragment. 

the legend to this figure. Echinorhinus cookei and 

Rhinobatos lentiginosus were chosen as outgroups. 12S mitochondrial rDNA 

The tree statistics are shown in Table 6. 

Two overlapping short stretches of 12S mtrDNA, 

There is a high degree of similarity between the 12SA and 12SB, were sequenced. The final contiggene 

fragments under consideration in all four uous sequence consisted of 183 nucleotides in Huso 

chondrichthyans and Latimeria chalumnae and dauricus and Pseudoscaphirhynchus kaufmanni, 

they differ from these fragments in actinopteri- 184 nucleotides in Polyodon spathula, A. medirosgyans. 

There are two putative synapomorphies of tris, A. baerii, Scaphirhynchus albus, and Amia calacipenseriformes 

in the 18sai0.7 region: (1) all aci- va, and I85 nucleotides in Polypterus senegalus. The 

penserids and Polyodon spathula had an insertion 12S region is more variable than the 16S regions and 

of A between 684 and 685 comparatively to the ho- yields several phylogenetically informative characmologous 

sequence of L. chalumae, and (2) a T ters for examining higher level relationships (see 

between positions 773 and 774 relative to L. cha- below). Extremely low levels of variability, howlumnae.Also, 

a change of A to Tin position 771 (L. ever, exist within the genera Acipenser and Huso. 

chalumnae) seems to be synapomorphic for all acipenseriform 

species. The most variable region of Cytochrome b 

18sai0.79 region in all groups of fishes examined so The amplified region consisted of 270 base pairs, 

far lies between T and G in position 851 and 855 (L. from the 7th to 97th codons according to Normark 

chalumnae). In chondrichthyans and L. chalumnae et al. (1991). Most variation occurs at the third posi- 

Table 6. Tree statistics. 

Gene Numberof Apomorphies Number of Number of Number of Consistency Retention 

characters totalnumber phylo- trees steps index index 

genetically 

informative 

characters 

(I18sai0.7+ I8sai0.79) fragment 241 39 24 6 47 0.94 0.98 

12S gene fragment 189 51 10 6 61 0.71 0.67 



Cytochrome b gene fragment 270 163 56 3 187 0.62 0.54 

Combined molecular characters 1006 300 96 1 354 0.65 0.59 

Cytochrome b with additional 

species of Acipenser 270 163 56 2 216 0.54 0.52 

143

144 

tions of codons. For comparable lengths of the 16S 

and 12S sequences, the cytochrome b gene for the 

species examined by us has from three to four times 

more nucleotide changes. 

Generic relationships within Acipenseriformes 

Alignment and phylogenetic inference 

First, we examined phylogenetic signal in the individual 

gene character sets by constructing separate 

cladograms for each of the four genes studied. Second, 

due to the small number of apomorphic characters 

for each gene, we used a combined approach 

(Miyamoto 1985, Kluge 1989, Ernisse & Kluge 1993) 

to infer phylogenetic relationships. 

We used aggressive alignment parameters for the 

program MALIGN (build; treeswapping; random 

sequence addition; Wheeler & Gladstein 1993) in 

our computer searches. We avoided rearranging 

computer generated alignments based on eye judgment 

because of the arbitrary aiid inherently nonrepeatable 

nature of this approach and because the 

choice of gap:change cost ratios in DNA sequence 

alignment can greatly affect final alignment (Fitch 

& Smith 1983, Waterman et al. 1992, Gatesy et al. 

1993). We performed several alignments with varying 

gap:change ratios, and found alignments for all 

three rRNA were very stable. There were few alignment 

ambiguities as judged by comparing alignments 

generated at gap:change costs of 2,4,8 or 16. 

The phylogenetic hypotheses generated by these 

various alignments were congruent, further supporting 

our notion that the alignments are very stable. 

IIndividual gene trees 

We report three consensus gene trees from sequences 

aligned using a gap:change ratio of 4 for the 

three rRNA genes (Figure 3). As noted above, cytochrome 

b sequences were aligned with a gap cost of 

8 and the resulting gene tree is also shown in Figure 

3. The tree statistics for each of the gene trees, including 

the number of apomorphies and phylogenetically 

important characters, is given in Table 6. 

The phylogenetically informative characters and 

Figure 3. Consensus trees for individual gene regions examined 

for the 12S mtrDNA (189 bp), 16S mtrDNA (318 bp), 18S rDNA 

(229 bp), and cytochrome b genes (270 hp). Amia calva and Polypterus 

senegalus are outgroups. The tree statistics are in Table 6. 

their positions in the sequences for each gene are 

shown in Figure 4. 

In general, each gene tree alone showed low levels 

of resolution (Figure 3). Successive weighting of 

tlie individual character sets did not result in the 

choice of a single or fewer trees. Although character 

congruence was high as indicated by the relatively 

high consistency and retention indices, the 

number of informative characters for each character 

set was so low (Figure 4) that resolution of only a 

few nodes in each single gene tree was demonstrated. 

One general observation, however, is that Acipenser 

was not found to be monophyletic in any of 

the four gene trees (Figure 3). For 12S mtDNA, Huso 

dauricus clustered with A. ruthenus and no characters 

were found that hypothesized the remaining 

species of Acipenser as a group. For 16S mtDNA, 

Polyodon spathula clustered with the four species 

of Acipenser surveyed, and no character was found

145 

Figure 4. Phylogenetically informative characters (nucleotide composition at variable sites) for four gene regions studied. Numbers 

above the sequences refer to base pair position from the first base in the amplified fragments. The first position for the amplified fragment 

for 12S (No. 35) corresponds to No. 570 in the published 12S sequence for Latimeria chalumnae (Hedges et al. 1992), in 16S (No. 30) 

corresponds to No. 176 for L. chalumnae (Hedges et al. 1992), in 18S (No. 33) corresponds to No. 682 for L. chalumnae (Stock et al. 1991b), 

and in cytochrome b gene (No. 6) corresponds to No. 25 for L. chalumnae (Normark et al. 1991). 

uniting Acipenser as monophyletic. In the 18S 

rDNA tree, there was again no evidence of monophyly 

of Acipenser. Finally, the cytochrome b tree 

groupedA. medirostris,A. transmontanus,A. ruthenus 

and A. baerii with Huso dauricus. Acipenser medirostris 

and A. transmontanus shared apomorphies 

in the 18S rDNA and cytochrome b trees, and such a 

grouping was not ruled out by either of the other 

two trees. Pseudoscaphirhynchus and Scaphirhynchus 

emerged as monophyletic in only one tree 

(16S, Figure 3). 

Combined molecular tree and comparison to existing 

morphological hypothesis 

The DNA sequence characters for the four gene regions 

were combined into a data matrix and each 

character was given equal weight. One parsimony 

tree was obtained using this combined molecular 

data matrix (Figure 5, Table 6). 

Findeis (1993,1997) used osteological characters 

for constructing a morphological phylogenetic hypothesis 

which focused on generic relationships 

among Acipenseriformes. Only a single parsimony 

tree resulted from his data set. He examined six species 

of acipenseriforms not included in our molecular 

survey (Scaphirhynchus platorynchus, A. brevi-

146 

Figure 5. The single parsimony tree obtained for the combined 

set of molceular characters. Amia calva and Polypterussenegalus 

arc outgroups. Decay indices (Bremer 1988, Donoghue et al. 

1993) are shown at each node. Numbers above the branches represent 

bootstrap values computed by 1000 replications. The tree 

statistics are given in Table 6. 

rostrum A. fulveescens A. oxyrinchus. and Huso huso). 

He did not examine the osteology of three species 

studied by us (A. baerii, H. dauricus, and S. 

albus). Thus. there is incomplete overlap of taxa 

surveyed by the two phylogenetic approaches. 

morphological and molecular. A further complication 

is that Findeis (1993, 1997) does not provide 

evidence that Acipenser is monophyletic. whereas 

our total molecular data set does (Figure 5). 

Comparison of the osteological and molecular 

trees shows two major differences: (1) the placement 

of Huso dauricus and (2) the sister relationship 

of Scaphirhynchus and Pseudoscaphirhynchus 

Findeis (1993, 1997) found that Huso is basal to the 

other Acipenseridae, and that the clade including 

all other sturgeons was well supported by ostcological 

characters. Our combined molecular data. however, 

suggest that Huso dauricus is a sister-species 

to the genus Acipenser (Figure 5). Perhaps. this conflict 

between the molecular and morphological in- 

formation results from the small number of molecular 

characters that are pertinent to the Huso-Aci- 

A. medirostris 

penser sister group hypothesis. It is interesting, 

A. transmontanus however, that many 19th century systematic studies 

placed Huso within Acipenser and that Huso was 

A. ruthenus 

not elevated to a separate generic status until 

Brandt (1869). Later the generic status of Huso was 

A. baerii 

still debated (for instance, Nikolukin 1970, Artyukhin 

1995). Evidently, Huso warrants new attention 

H. dauricus 

from systematists. 

The sister relationship of Scaphirhynchus and 

P. kaufmanni 

Pseudoscaphirhynchus is strongly supported by the 

morphological data (Findeis 1993,1997),but it is not 

S. albus supported by our molecular characters. In Figure 5 

Scaphirhynchus emerged as the sister taxon of all 

Polyodon other sturgeons, and Pseudoscaphirhynchus 

emerged as the sister taxon of Huso and Acipenser. 

Amia 

This is an interesting difference between the two 

phylogenies because conventional pre-cladistic 

Polypterus 

ideas about relationships within Acipenseridae suggest 

that Scaphirhynchus plus Pseudoscaphirhynchus 

are basal members of the family (e.g., Zograf 

1887). The fact that Pseudoscaphirhynchus and Scaphirhynchus 

did not group together is supported in 

Our combined tree by relatively high decay indices 

(4 and 3 at the pertinent nodes in Figure 5) and 

bootstraps. We suspect that the traditional idea of 

this monophyly may be incorrect. 

Relationships within flip genus Acipenser 

For this investigation we used partial sequences of 

the cytochrome b genes of eight Eurasian and four 

American species of the genus Acipenser. This data 

set includes 7 species absent in the previous molecular 

analysis because we did not sequence the ribosomal 

genes for these taxa. Taxa chosen represent 

all four specics groups proposed by Artyukhin 

(1995, see above). The result of phylogenetic analysis 

is presented in Figure 6, and tree statistics, in Table 

6. 

Two parsimony trees were obtained. In the cytochronic 

b analysis, Acipenser is not monophyletic, 

and two main clades of species are seen in both 

trees. Two western American species, A. medirostris 

and A. transmontanus, group together and are a

147 

(n) 

Species Croup of 

Acipenser 

8 2 

8 2 

16 2 

4 1 

4 1 

8 1 

4 1 

4 3 

4 

8 1 

8 1 

16 4 

4 

4(?) 

4 

2 

2 

(n) 

8 2 

8 2 

16 2 

4 1 

4 1 

8 1 

4 1 

4 3 

4 

8 1 

8 1 

16 4 

4 

4 (?) 

4 

2 

2 

Species Croup of 

Acipenser 

Figure 6. The two parsimony trees based on partial sequences (270 bp) of the cytochrome b gene regions from 11 species of Acipenser 

(representatives of all groups of species in Table 5), Huso dauricus, Pseudoscaphirhynchus kaufmanni, Scaphirhynchus albus, and Polyodon 

spathula. As in the previous analyses, Amia calva and Polypterus senegalus were used as outgroups. The ploidy of fishes and the group 

number for species Acipenser are given to lhe right of species names. The tree statistics is shown in Table 6. 

sister-group to A. mikadoi, whereas A. ruthenus is 

basal to all these species. Except for the freshwater 

A. ruthenus all other species of the clade are typically 

anadromous sturgeons. The difference in the 

cytochrome b gene sequences between A. mikadoi 

and A. mediotris supports the previous assumption 

based on DNA ploidy that A. mikadoi is a separate 

species in spite of the fact that it is morphologically 

indistinguishable from A. mediostris (Birstein 

et al. 1993, Birstein 1994b). Unexpectedly, the 

ancestral form of this group seems to be related to 

A. ruthenus 

The sccond group is also unexpected. It consists 

of two clades. The first clade includes the European 

A. nudiventris grouped with the eastern American 

A.oxyrinchus (and Huso dauricus, see discussion 

above). Their sister-group consists of the European 

A. gueldenstaedtii, Siberian A. baerii, and an eastern 

American species A. brevostrum These relationships 

suggest that: (1) the Atlantic group of species 

is related to the Ponto-Caspian A. nudiventris; 

(2) a Ponto-Caspian European A. gueldenstaedtii is 

closely related to a Ponto-Caspian Siberian A. baerii; 

(3) both Ponto-Caspian A. gueldenstaedtii and 

A. baerii are related to the eastern North American

148 

A. brevirostrum; and (4) both clades show transat- 1991a, Hedges et al. 1993a). One surprising result of 

lantic relationships for the species. 

our study is the general lack of variability in the 

The position of a small clade consisting of A. stel- gene regions studied as compared to other animal 

latus and A. naccarii, is unresolved: in the first tree it groups, including teleosts (reviews in Meyer 1993, 

is grouped with the first main clade, whereas in the Meyer et al. 1993, Patarnello et al. 1994), some amsecond 

tree it clusters with the second main clade phibians, most mammals and insects (for instance, 

(Figure 6). Traditionally, the octoploid A. naccarii Irwin et al. 1991, Hedges et al. 1993b, Wheeler et al. 

was considered to be closely related to the octo- 1993). The slow rate of molecular evolution in aciploid 

A. gueldenstaedtii (e. g., Tortonese 1989, Rossi penseriforms may be correlated with slow karyoet 

al. 1991, Artyukhin1995), but not to the tetraploid typic evolution in these fishes (see above). 

A. stellatus. The other group of fishes with a low rate of evolu- 

According to the tree in Figure 6, ploidization oc- tion in 18S and mitochondrial genes is Chondrichcurred 

at least three times within the Acipenser: two thyes (Bernardi & Powers 1992, Martin et al. 1992, 

octoploid ancestral forms were formed independ- Martin & Palumbi 1993). Slow evolution of the 18S 

ently in A. mikadoi-A. medivostris-A. transmonta- genes, as in acipenseriforms (see Figure 2), could be 

nus, A. gueldenstaedtii-A. baerii-A. brevirostrum, related to polyploidy (cryptoploidy) in these fishes 

and in A. stellatus-A. naccarii; two polyploidization (reviews in Schwartz & Maddock 1986, Birstein 

events followed resulting in the appearance of A. 1987, Stingo & Rocco 1991). But the nucleotide submikadoi 

and A. brevirostrum. These data support stitution rate in the cytochrome b gene in sharks is 

our assumption (see above) that ploidization one sixth that of primates (Martin et al. 1992, Martin 

played a significant role in speciation within the & Palumbi 1993), and this characteristic cannot be 

Acipenser, but contradict a simple scheme of hypo- attributed to ploidy differences. Perhaps, it is 

thetical relationships of the species of Acipenser caused by differences in the rate of accumulation of 

published by Artyukhin (1995, see also Bemis et al. silent transversions (Martin & Palumbi 1993), but 

1997). Except the close relatedness of A. transmon- this remains a peculiar problem. It is interesting 

tanus and A. medirostris, which is supported by that the sequence of the region of the 18S gene unother 

molecular data (Brown et al. 1996), the other der discussion in sharks is more similar to that in the 

relationships in Artyukhin’s tree (Artyukhin 1995) coelacanth than to that in acipenseriforms (Figure 

are not supported by our molecular data. 2). 

We caution that the trees in Figure 6 are prelimi- It is evident that the molecular data (at least 

nary ones. Evidently, additional data should be ob- those presented here), as well as the cytogenetic datained 

for better resolution of relationships among ta (see above), have restrictions in application to 

the species. We have already sequenced longer re- the phylogeny of Acipenseriformes at the generic 

gions of the cytochrome b gene, as well as other level. Low levels of variability of the genes comgenes 

(Birstein & DeSalle 1997). Our data do show, monly used as phylogenetic tools (12S, 16S, 18S, and 

however, that phylogenetic relationships within the cytochrome b) suggests that some other, rapidly 

Acipenser can be reconstructed using even a partial evolving gene regions such as the mitochondrial 

sequence of the cytochrome b gene. 

control region (D-loop, Shedlock et al. 1992) or 

larger portions of the cytochrome b or other mitochondrial 

structural genes (Normark et al. 1991) 

General lack ofmolecular variability among the genem 

of Acipenseriformes 

might be helpful for examining relationships among 

the genera of Acipenseridae. 

In the meantime, our results suggest that the cytochrome 

We initially chose the gene regions described above 

because of the high degree of variability shown in 

other taxa of comparable divergence times (Meyer 

& Wilson 1990, Normark et al. 1991, Stock et al. 

b gene could be used for investigation of 

relationships among species of Acipenser. The cytochrome 

b data suggest that Acipenser is not monophyletic 

(due to the insertion of Huso dauricus into

this group), as considered before. We hope that future 

analyses involving longer regions of the cytochrome 

b gene and, possibly, some other protein 

coding genes will help to establish mono- or polyphyly 

of this genus. 

Conclusions 

(1) Little cytogenetic change has occured during the 

evolution of Acipenseriformes. Polyodontidae and 

Acipenseridae presumably originated from a tetraploid 

ancestor whose karyotype consisted of 120 

macro- and microchromosomes with a DNA content 

about 3.2–3.8 pg per nucleus. Tetraploidization 

of the 60-chromosome ancestor possibly occurred 

at the early times of evolution of the Acipenseriformes, 

probably, during the origin of this group in 

the Mesozoic. 

(2) No conclusions regarding interrelationships 

within Acipenseridae among Huso, Acipenser, Scaphirhynchus, 

and Pseudoscaphirhynchus can be 

made based on cytogenetic data. Divergence of 

these lineages of sturgeons occurred without polyploidization. 

(3) Diversification within Acipenser was accompanied 

by appearence of octoploids (according to 

karyotypic and DNA content data) and 16n-ploids 

(according to DNA content data). The octoploid 

240-chromosome sturgeon species have about 240 

chromosomes and may have originated independently 

in different geographic areas. The two 16n- 

149 

1993, 1997): Huso dauricus was a sister-species to 

the genus Acipenser instead of being basal to all acipenseriforms, 

and Scaphirhynchus and Pseudoscaphirhynchus 

did not form a monophyletic group. 

(6) A partial sequence of the cytochrome b gene 

(270 bp) was used to examine relationships within 

the genus Acipenser. Seven additional species of 

Acipenser were included in this part of the study 

(A. brevirostrum, A. gueldenstaedtii, A. mikadoi, A. 

naccarii, A. nudiventris, A. oxyrinchus, and A. stellatus). 

The data support the hypothesis that octoploid 

species appeared at least three times within 

the Acipenser. Also they show close relationships 

between the Eurasian A. ruthenus and the Pacific A. 

mikadoi-A. medirostris-A. transmontanus, between 

the European A. gueldenstaedtii, Siberian A. baerii, 

and American A. brevirostrum, between two European 

species, A. stellatus and A. naccarii, as well 

as a possible trans-Atlantic relationship between 

the Eurasian A. nudiventris and American A. oxyrinchus 

suggesting limited utility of geographic locality 

as an indicator of relationship. 


We are very grateful to all colleagues who helped us 

to collect blood and tissue samples: Serge Gamalei 

(Moscow Aquarium, Moscow), Boris Goncharov 

(Institute of Developmental Biology, Russian 

Academy of Sciences, Moscow), Evgenii Artyuk- 

hin (Central Laboratory of Regeneration of Fish 

ploid species, A. mikadoi and A. brevirostrum, may Resources, St. Petersburg), Francesco Fontana 

be the youngest species within the genus. 

(University of Ferrara), Herb Bollig (US Fish and 

(4) A study of partial sequences of genes from mi- Wildlife Service, South Dakota), Boyd Kynard (Natochondrial 

DNA (16S rDNA, 315 bp; 12S rDNA, tional Biological Survey, Massachusetts), John 

189 bp, and cytochrome b, 270 bp) and of one nucle- North (Department of Fish and Wildlife, Oregon), 

ar gene region (18S rDNA, 230 bp) demonstrated and John Waldman (The Hudson River Foundavery 

low levels of variability in the eight acipenseri- tion, New York). We are also indebted to Paul Vraform 

species surveyed (Polyodon spathula, Huso na for his kind permission to use his collection of 

dauricus, four species of Acipenser, Scaphirhynchus tissue samples. We are extremely thankful to Willy 

albus, and Pseudoscaphirhynchus kaufmanni). This Bemis for his patient reading of the manuscript and 

low variability is unusual for these genes, which are his important notes which allowed us to improve 

commonly used as phylogenetic tools. 

the manuscript immensely. 

(5) The molecular tree based on combined data 

from all four genes had two major departures from 

the existing morphological hypothesis (Findeis,

› 

150 


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155

Portraits of a juvenile Huso huso 23 cm TL from the Ryal Ontario Museum collection (given originally as Caspian Sea fish to Montreal 

Expo 1967) above the head of Acipenser schrenckii 81 cm TL from the Amur River stock held at the Propa-Gen International, Komadi, 

Hungary. Originals by Paul Vecsei, 1996.

Environmental Bioiogy of Fishes 48: 157–163, 1997. 

© 1997 Kluwer Academic Publishers. Printed in the NetherIands. 

How many species are there within the genus Acipenser? 

Vadim J. Birstein 1 & William E. Bemis 2 

1 The Sturgeon Society, 331 West 57th Street, Suite 159, New York, NY 10019, U.S.A. 

2 

Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, 

Amherst, MA 01003, U.S.A. 

Receiv ed 23.4.1996 Accepted 17.5.1996 

Key words: Acipenser baerii, A. brevirostrum, A. dabryanus, A. fulvescens, A. gueldenstaedtii, A. medirostris, 

A. mikadoi, A. naccarii, A. nudiventris A. oxyrinchus, A. persicus, A. ruthenus, A. schrenckii, A. sinensis, A. 

stellatus, A. sturio, A. transmontanus, Huso huso, H. dauricus 

In their paper in this volume Bemis et al. (1997) ask: ‘How many valid species of Acipenser should we recognize?’Although 

a partial answer to this question is presented in their Table 5, we discovered in the course of 

preparing this volume that sonic additional commentary is needed. In fact, there are two questions: (1) how 

many species should be recognized? and (2) what scientific names should be used for some of the species? The 

sympatric distributions of most species of sturgeons set the stage for much confusion about species boundaries, 

but the situation is actually much more complicated. Confusion about the number of species of sturgeons 

living within the same basin can result from the often close morphological and meristic similarities of certain 

species of Acipenser, particularly during juvenile period. Moreover, we still have remarkably inadequate 

knowledge of the comparative anatomy of the species of Acipener: no modern study has ever attempted a 

comprehensive examination of all species, and it is impossible to rely on literature for the sorts of comparisons 

that must be made (for more on this general problem, see Grande & Bemis 1991,1997). Most classical descriptions 

and comparative anatomical studies relied upon small sample sizes. Voucher specimens of large sturgeons 

are especially rare in most historical collections, and type specimens (if available at all) are seldom 

prepared in ways that are suitable for making detailed anatomical comparisons (e.g., many skins are simply 

overstuffed with straw, so that all internal structures are lost). Intraspecific morphological and meristic polymorphisms 

occur in all species of acipenserids, and in most cases we have very poor knowledge of differences 

that develop during ontogeny, particularly changes in such features as the shape of the rostrum (Bemis et al. 

1997). Another problem is the ease of hybridization between different species of sturgeons (reviewed in 

Birstein et al. 1997 this volume). In many of these cases, it is not easy to discriminate between parental species 

and the hybrids. 

Two opposite tendencies appeared in the literature 

on the genus Acipenser. (1) Recognizably different 

species have been considered to be the same species. 

This situation is illustrated below by two species 

pairs, A. gueldenstaedtii and A. persicus and A. 

mediostris and A. mikadoi (2) Some authors elevated 

many forms to the rank of species. For instance, 

Duméril (1870) described six subgenera of 

Acipenser with more than 30 species Acipenser in 

five of them (he considered Huso as the sixth subgenus 

of Acipenser). Most of the species described 

by Duméril (1870) have long since been recognized 

as conspecific with other well-known species. 

We still do not know the number of species of 

Acipenser, and may never know it because of overfishing 

and habitat destruction in Europe and Asia,

158 

which have quickly eliminated sturgeons from certain 

river basins (see discussions in this volume by 

Bacalbasa-Dobrovici 1997, Khodorevskaya et al. 

1997, Krykhtin & Svirskii 1997, Wei et al. 1997). 

Therefore, we probably have already lost forever 

the opportunity to study some species of Acipenser. 

In the meantime, it is clear that genetic and molecular 

phylogenetic approaches are increasingly crucial 

for the recognition of sturgeon species and their 

relationships (for discussion, see Birstein et al. 1997 

this volume). 

In Eurasia, the genus Acipenser is centered upon 

three main basins: (1) the Black Sea and Sea of 

Azov, (2) Caspian Sea, and (3) the Aral Sea. Each of 

three main species of Acipenser, A. gueldenstaedtii 

Brandt, 1833, A. stellatus Pallas, 1771, and A. nudiventris 

Lovetsky, 1828 were described as having 

subspecies or forms in these basins (see Berg 1948, 

Shubina et al. 1989, Sokolov & Vasilev 1989a, Vlaclature 

of species discussed by Holcík & Jedlicka 

senko et al. 1989a). If we follow the view on nomen- 

∨ 

∨ 

(1994), then the concept of subspecies and trinomial 

nomenclature is inefficient. Therefore, we consider 

all intraspecies forms and subspecies of A. gueldenstaedtii, 

A. stellatus, and A. nudiventris invalid until 

detailed molecular and morphological studies of 

different forms within these species can be performed.1 

The same is true for A. ruthenus Linnaeus, 

1758, for which a few intraspecies forms were described 

by different authors (see Berg 1948, Sokolov 

&Vasilev 1989b). 

An example helps to illustrate the taxonomic 

frustration of sturgeon biologists. Acipenser persicus 

was described as a valid species by Borodin in 

1897 (Borodin 1897, 1926), but it was later considered 

to be a subspecies (Berg 1934), and, still later, 

again regarded as a valid species (see Vlasenko et al. 

1989b, Birstein & Bemis 1997 this volume, for discussion). 

Moreover, Artyukhin &Zai-kua (1986) described 

two subspecies within A. persicus: the population 

inhabiting the Caspian Sea they named as A. 

persicus persicus Borodin, 1897, and the population 

inhabiting the Black Sea, as A. persicus colhicus 

Marti, 1940. Although some Russian authors follow 

this nomenclature (Pavlov et al. 1994), additional 

support from genetic and molecular data is desirable. 

The validity of some Asian species and subspecies 

of Acipenser is questionable. For example, Ruban 

(1997 this volume) reviewed and presented new data 

on the Siberian sturgeon, A. baerii Brandt, 1869, 

which has an extremely wide range. Ruban’s new 

work supports the traditionally recognized subspecies 

(A.b. baerii, A. b. baicalensis and A. b. stenorrhynchus, 

e.g., Sokolov & Vasiliev 1989c). No genetic 

study on the subspecies of A. baerii is yet available. 

The three far eastern Asian species, A. schrencki 

Brand, I869 of the Amur River, and A. dabryanus 

Duméril, 1868, and A. sinensis Gray, 1834 of the 

Yangtze River are certainly valid (see Krykhtin & 

Svirskii 1997, Wei et al. 1997, Zhuang et al. 1997, all 

this volume). Chinese sturgeon, A. sinensis, from the 

Pearl River differ morphologically from those of the 

Yangtze River, but whether this difference warrants 

separate species status is not clear (Wei et al. 1997). 

The nomenclature and species status of the socalled 

‘green sturgeon’ and ‘Sakhalin sturgeon’ of 

the Pacific Northwest of America and northeastern 

Pacific in Asia has been particularly confusing. 

Ayres (1854) described the American green sturgeon. 

A. mediostris. Nearly 40 years later, Hilgendorf 

(1892) described an Asian species caught in the 

northern waters of Japan as A. mikadoi, and 

Schmidt (1904) soon thereafter referred a sturgeon 

caught in the Aniwa Bay of Sakhalin Island to A. 

mikadoi . However, Berg (1911, 1948) considered this 

Sakhalin sturgeon to be conspecific with the American 

green sturgeon, A. medirostris. Schmidt (1950) 

eventually reconsidered his 1904 view, and named 

Sakhalin sturgeon as a subspecies of A. mediostris, 

A. mediostris mikadoi (Schmidt, 1950). Therefore, 

three names coexisted in the literature for the Sak- 

halin sturgeon: A. mikadoi (Okada & Matsubara 

1 In the literature on genetics, molecular phylosenetics and systematics, 

the taxonomic unit subspecies is often preserved 

(Avise 1994 Mallet 1995). Avise & Ball 1990 and Avise (1994, p 

253) suggested that we recognize ‘by the evidence of concordant 

phylogenetic partitions at multiple independent genetic attributes’. 

When phylogenetic concordance is exhibited across genetic 

characters solely because of extrinsic barriers to reproduction, 

subspecies stalus is suggested’. It is evident that according 

to these terminology, populations of the same species of sturggeon 

in disjunct sea basins (e.g., Caspian and Black seas), could 

be considered as subspecies.

159 

2 

Since the description of the species, the name A. oxyrinchus has 

changed a few times. Mitchill described this species in 1815 under 

the name A. oxyrinchus (Mitchill, 1815). Later, the name was 

changed to A. oxyrhynchus and an incorrect date of publication 

(1814) began to be cited widely (e.g., Vladykov & Greely 1963). 

Also, A. oxyrinchus desotoi was first described under the name 

A. oxyrhynchus de sotoi (Vladykov 1955). In this volume we fol- 

low Smith & Clugston (1997) and use the names A. o. oxyrinchus 

and A. oxyrinchus desotoi. 

1938, Matsubara 1955), A. medirostris (Berg 1948, 

Andriyashev & Panin 1953, Masuda et al. 1984, 

Houston 1988, Artyukhin & Andronov 1990, Pavlov 

et al. 1994), and A. medirostris mikadoi (Lindberg & 

Legeza 1965, Shilin 1995). Recently Birstein (Birstein 

et al. 1993, Birstein 1993) noted the difference 

in ploidy between the Sakhalin sturgeon and American 

green sturgeon, and suggested that they should 

be considered different species, A. mikadoi Hilgendorf, 

1892, and A. medirostris Ayres, 1854, respectively. 

Molecular data on three mitochondrial genes 

presented in this volume (Birstein & DeSalle 1997) 

also show great differences between these two species. 

Other molecular data obtained show a close genetic 

relationship of A. medirostris to another 

American Pacific sturgeon species, A. transmontanus 

(Brown et al. 1996. Birstein et al. 1997). Therefore, 

A. mikadoi and A. medirostris should be considered 

as morphologically similar, but genetically 

different, species. The Sakhalin sturgeon inhabits 

the Sea of Japan up to the Korean Peninsula and waters 

to the north from Hokkaido Island (Berg 1948, 

Lindberg & Legeza 1965). It occurs in the mouths of 

small rivers of the Asian far east and Korean Peninsula, 

as well as the Amur River, and rivers of the 

Sakhalin Island. Now it spawns in the Tumnin (Datta) 

River in the Russian far east (Artuykhin & Andronov 

1990), and historically it also spawned in the 

Ishikari and Teshio rivers of Hokkaido Island (Okada 

1955). Acipenser medirostris ranges from the Gulf 

of Alaska to southern California (Houston 1988), 

with three known spawning rivers: the Sacramento 

and Klamath rivers in California and the Rogue River 

in Oregon (Moyle et al. 1994). 

Two other species of sturgeons are usually mentioned 

in descriptions of the fish fauna of Japan, A. 

kikuchii Jordan & Snyder, 1901, and A. multiscutatus 

Tanaka, 1908 (Okada 1959–1960, Masuda et al. 

1984, Rochard et al. 1991). Only one specimen of A. 

kikuchii is known (Jordan & Snyder 1901, l906) and 

this species was re-identified as A. sinensis (Takeuchi 

1979). Only a few specimens ofA. multiscutatus 

were described (Tanaka 1908, Fowler 1941, Matsubara 

1955). It seems that these specimens are morphologically 

similar to A. schrenckii (Lindberg & Legeza 

1956) and are probably conspecific with A. 

schrenckii. It is most improbable that a sturgeon spe- 

cies could be restricted only to Japan and not inhabiting 

Asian continental waters (Artyukhin & Andronov 

l990). There are no new reports on the catch 

of A. multiscutatus in Japanese literature (see a 

compilation of data in Honma 1988) since the review 

of Okada (1959-1960). Therefore, A. multiscutatus 

is most probably a synonym of A. schrencki. 

It is easy to distinguish the second Pacific North 

American species, A. transmontanus Richardson, 

1836, the freshwater North American A. fulvescens 

Rafinesque, 1817, and one of the two Atlantic North 

American sturgeons, A. brevirostrum Le Sueur, 

1818 (Vladykov & Greeley 1963, Scott & Crossman 

1973, Lee et al. 1980). Molecular data on the structure 

of the control region of mtDNA not only supported 

close relationships of two Pacific North 

American sturgeon species, A. medirostris and A. 

transmontanus, but also showed a significant genetic 

difference between these species, A. fulvescens, 

and the second Atlantic North American species, 

A. oxyrinchus (Brown et al. 1996). 

American and the European Atlantic sturgeon 

were long considered to be one species, A. sturio 

Linnaeus, 1758. In this older terminology, the 

American Atlantic sturgeon was regarded as subspecies 

A. sturio oxyrinchus, with the European Atlantic 

sturgeon being known as A. sturio sturio (see 

Smith 1891, Vladykov & Greeley 1963). Magnin & 

Beaulieu (1963) suggested elevation of these subspecies 

to species ranks, with the European form retaining 

the name A. sturio Linnaeus, 1758, and 

American form named A. oxyrinchus Mitchill, 1815. 

Two subspecies, the Atlantic sturgeon, A.o. oxyrinchus, 

and the Gulf coast sturgeon, A.o. desotoi, 

were described within A. oxyrinchus (Vladykov 

1955, Vladykov & Greeley 1963). 2 These two subspecies 

of A. oxyrinchus are morphologically similar, 

with the most significant known difference be-

160 

ing the length of the spleen (in A.o. oxyrinchus the 

spleen is statistically smaller than it is in A.o. de 

sotoi, Wooley 1985). Molecular data are more informative 

for the discrimination between subspecies. 

Comparison of the control region of mtDNA sequences 

of both subspecies showed three fixed nucleotide 

changes in that region (Ong et al. 1996). 

Bowen & Avise (1990) suggested that there is genetic 

structuring among A. oxyrinchus from various 

drainages of the North American Atlantic coast. 

Recently, analyses of the control regions of mtDNA 

supported this hypothesis: Atlantic sturgeon populations 

in the Saint Lawrence and Saint John rivers 

(Canada), the Hudson River (U.S.A.), and rivers of 

Georgia (U.S A.) are genetically distinct (Waldman 

et al. 1996a,b). 

Unpublished results of Birstein & DeSalle on the 

sequences of three more genes of mtDNA (cytochrome 

b, 12S rRNA, and 16S rRNA) also show a 

genetic difference between the two subspecies of A. 

oxyrinchus (one fixed nucleotide change in cytochrome 

b gene). The analysis of these genes demonstrated 

that the European A. sturio is the only sturgeon 

species closely related to A. oxyrinchus. Moreover, 

it appeared that there is a significant genetic 

differentiation within A. sturio. Birstein & DeSalle 

studied samples from two specimens of A. sturio 

caught in the Gironde estuary system (Dorgonne 

and Garonne rivers) and in the North Sea. The genetic 

difference between two individuals of A. sturio 

(6 nucleotide changes in the region of cytochrome 

b analyzed) was even more than the difference 

between subspecies of A. oxyrinchus (one 

change). These data seem to support the difference 

in some meristic characters between specimens 

from the Baltic Sea, from one side, and specimens 

from the Atlantic Ocean, Mediterranean and Black 

seas, from the other (Marti 1939, Magnin 1963, Ni- 

∨ 

nua 1976, Holcík et al. 1989). Because A. sturio has 

∨ 

almost disappeared in the wild (Holcík et al. 1989), 

more work should be done in museum collections 

on the comparison of specimens from different 

populations. This is especially important in terms of 

recovery projects for this species (Hochlethner 

1995, Williot et al. 1997, this volume). 

The last species in the genus Acipenser is the 

Adriatic sturgeon, A. naccarii Bonaparte, 1836. It is 

restricted to the Adriatic only and resembles A. 

gueldenstaedtii in meristic characters (Tortonese 

1989). 

Since Berg (1904), Huso huso Brandt, 1869 and 

H. dauricus Georgi, 1775 were considered as representatives 

of a distinct genus Huso, not Acipenser as 

they were usually considered in the 19th century (also 

see Findeis 1997, this volume). Results of recent 

molecular studies, however (see Birstein et al. 1997 

this volume) showed that the two species of Huso 

do not form a separate monophyletic group, but are 

inserted among species of Acipenser. This result reactivates 

the old discussion on the validity of the genus 

Huso. In the absence of detailed work on this 

problem, it makes sense for now to regard Huso as a 

genus based on morphological and anatomical data 

(Findeis 1997 this volume). Also, a few subspecies 

were described within H. huso (reviewed in Pirogovskii 

et al. 1989). For instance, some authors still 

consider the Sea of Azov population of H. huso as 

Huso huso maeoticus Salnikov & Myatskii, 1934 

(Pavlov et al. 1994). Until genetic differences can be 

shown in combination with morphology, we recommend 

the name H. huso for the Mediterranean, 

Black, Azov, and Caspian sea populations of beluga. 

In conclusion, we recognize 17 valid extant species 

within Acipenser. For the moment, we accept 

that two species (A. baerii and A. oxyrinchus) contain 

subspecies. Further genetic and molecular 

studies will generate new data for correction of our 

contemporary knowledge about some of the species, 

including A. sturio. 

A final note regarding the names of sturgeon species 

concerns the need to return to the originally 

published spellings for names of genera and specie 

3 . In addition to two recent clarifications on the 

correct spelling of species names for Siberian (A. 

baerii see Ruban 1997, this volume) and American 

Atlantic sturgeon (A. oxyrinchus, see Gilbert 1992), 

we note the following correct spelling for two other 

3 

Such decisions to use the originally published spellings of 

names, regardless of subsequent practices, are based on the International 

Code of Zoological Nomenclature (Ride et al. 1985). 

For a specific explanation of rules, see Chapters 31 and 33 of the 

International Code of Zoological Nomenclature. 1985, 3rd ed. 

International Trust for Zoological Nomenclature, London.

161 

species of Acipenser The scientific name of the 

Russian sturgeon should be spelled Acipenser gueldenstaedtii 

Brandt, 1833, and the scientific name of 

the Amur River sturgeon should be spelled Acipenser 

schrenckii Brandt, 1869. 


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∨ ík (ed.) The Freshwater Fishes of Europe. Vol. 1, Pt. II, General 

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of the New York Bight Atlantic sturfeon fishery based on 

analysis of mitochondrial DNA. Trans. Amer Fish. Soc. 125: 

364–371. 

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differentiation of three key anadromous fish populations of 

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Lepage & P. Elie. 1997. Biological characteristics of the European 

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restoration program in France. Env. Biol. Fish. (this volume). 

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in taxonomic separation of Gulf of Mexico sturgeon, Acipenser 

oxyrhynchus desotoi. pp. 97–103. In: F.P. Binkowski & S.I. 

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Part 2: Biology and status reports on sturgeons and paddlefishes 

Huso huso juvenile ca. 37 cm long above a large adult 380 kg in weight (about 5 m long) from Antipa (1909, plate 24, fig. 120 and 123).

An early print of Polyodon spathula and Scaphirhynchus platorynchus from Wood (1863, p. 201).



Sturgeon rivers: an introduction to acipenseriform biogeography and life 

history 

William E. Bemis 1 & Boyd Kynard 1,2 

1 Department of Biology and Graduate Program in Organismic and Evolutionary Biology, University of 


2 National Biological Service, Conte Anadromous Fish Research Center, 1 Migratory Way, Turners Falls, 

MA 01376, U.S.A. 


Key words: †Chondrosteidae, †Peipiaosteidae, Polyodontidae, Acipenseridae, Holarctic, anadromy, 

potamodromy 

Synopsis 

We present an overview of the global distribution of all 27 living species of Acipenseriformes in an attempt to 

understand their biogeographic history and the range of life history patterns displayed by different species. 

Our biogeographic analysis (based on the most recent phylogenetic analysis including fossil Acipenseriformes) 

suggests that Acipenseriformes originated in Europe, and that early diversification took place in 

Asia. Acipenseriformes do not have a common life history; variation within and between species is the rule 

rather than exception. The few relatively well-known case studies (e.g., Caspian Sea sturgeons, European 

Atlantic sturgeons in the Gironde system, and shortnose and North American Atlantic sturgeons in rivers of 

the east coast of America) greatly influence what we think we know about sturgeon biology. Our present level 

of phylogenetic understanding does not allow us to determine whether anadromy or potamodromy is the 

plesiomorphic life history pattern for Acipenseriformes. We propose that rivers in which spawning occurs 

must be the central unit for biogeographic analysis of living Acipenseriformes. After mapping these rivers, we 

recognized nine biogeographic provinces for acipenseriforms. Some repeated historical patterns emerge from 

this analysis, but, again, we are limited by our current understanding of phylogenetic relationships within the 

genus Acipenser in particular. Distribution and biogeographic data are central to deciding where to make new 

efforts to update existing status information for acipenseriform species. We single out a widely ranging and 

highly variable species, Acipenser ruthenus, as particularly intriguing, for it spans three of our nine biogeographic 

provinces, and apparently has different life history patterns in different river systems. Finally, we 

note new areas in need of basic research, particularly the need for more detailed descriptions and analyses of 

life histories of different populations of sturgeons. 

Introduction 

This paper attempts a new approach to the global 

biogeography of Acipenseriformes, although we 

admit from the outset that this is daunting topic because 

in its most comprehensive form, such an analysis 

concerns the history of the entire Holarctic region 

for the last 200 million years. Still, this topic is 

important because it lies at the interface between 

basic research on Acipenseriformes and practical

168 

steps needed to plan for sturgeon and paddlefish terns have certainly influenced the biogeography of 

conservation (e.g. Rochard et al. 1990). Our review Acipenseriformes although at present, we can do 

has several explicit purposes. 

little more than catalogue them, because no one un- 

First, although Acipenseriformes has long been derstands the genetic bases or adaptive significance 

regarded as a biogeographically interesting group, of these patterns. An important but still neglected 

the phylogeny necessary to study this question has approach to studying the evolution of different life 

yet to be assembled. Comprehensive phylogenetic history patterns of Acipenseriformes are ideas of Baundertanding, 

particularly concerning relation- Ion (I990 and references therein) that emphasize 

ships within the genus Acipenser, still eludes us. the importance of altricial or precocial patterns of 

Complicating factors include high levels of ontoge- development. This is likely to prove a productive 

netic and individual variation, hybridization, and approach, for size and yolk content differences are 

extirpation of many populations within the historic known for different species of sturgeons, though 

ranges of certain species (Bemis et al. 1997b this vol- they have not yet been correlated with different 

ume) Some key intergeneric relationships are patterns of life history. 

equally problematic. Results from karyological and Fourth, we want to introduce the remaining pamolecular 

phylogenetic approaches (Birstein & pers in the status part of this collection (Bemis et al 

DeSalle 1997) place the two species of Huso within 1997a), which detail aspects of life history and bio- 

Acipenser (as sister taxa to A. ruthenus) whereas os- geography for many of the extant species of Aciteological 

data place Huso as the sister taxon of all penseriformes. One need that emerges immediateother 

sturgeons (Findeis 1997 this volume). Future ly is for more detailed river surveys and life history 

updating of our interpretations is inevitable as our studies of virtually all species of sturgeons, particphylogenetic 

insight into Acipenseriformes im- ularly those from geographically remote regions in 

proves. 

Asia and northern North America. These surveys 

Second, a detailed understanding of the geo- need to be done with the most advanced technolgraphic 

distribution of acipenseriforms is compli- ogies available, including in particular telemetry of 

cated by the wide ranges historically reported for individuals to determine life history patterns (Kyadults 

of certain species, so that a more restrictive nard 1997 this volume) and molecular based identiand 

useful definition of species ranges is required. fication of populations within and between river 

We explicitly propose the concept that rivers in systems (Wirgin et al. 1997 this volume). 

which spawning occurs should be the central unit of 

analysis for interpreting the biogeographic ranges 

of acipenseriform species (and other groups containing 

Basic background 

anadromous species). We provide a global 

summary of these rivers, but given the scope of the Biogeographic observations 

question (i.e., identify all rivers in the world in 

which sturgeons or paddlefish historically We begin with three general biogeographic obserspawned) 

it is certain that more exhaustive analyses vations: 

will yield additional rivers. It may also be necessary 1. With the exception of the Pearl River in China, 

to find nore restrictive ways to define our concept all spawning rivers used by Acipenseriformes lie 

of spawning rivers, and perhaps we will succeed in entirely within the north temperate zone of Asia, 

provoking such a response. 

Europe or North America, although individual 

Third, Acipenseriformes exhibit a broad array of adults have been taken at sea south of the Tropic 

spawning and feeding migratory patterns, with of Cancer. All known fossil Acipenseriformes 

some species utilizing fresh water exclusively, are also from north temperate localities (Grande 

others fresh water and estuarine environments, & Bemis 1991, Jin 1995, Bemis et al. 1996 this volwhile 

others span the range from fresh water to fully ume, Grande & Bemis 1997). The absence of 

marine environments. Different life history pat- Acipenseriformes from tropical rivers is proba-

› 

› 

bly related to themal requirements for matura- Life history observations 

tion and early development, which generally 

need temperatures below 20° C (e.g., Artyukhin We make seven general observations about acipen- 

1988, Dettlaff et al. 1993). seriform life history and spawning biology: 

2. With the exception of Acipenser ruthenus, which 1. Acipenseriformes spawn repeatedly, but most 

lives in both Europe and Asia, no species within females do not spawn annually. This pattern re- 

Acipenseriformes is known to spawn in rivers on sembles that for anadromous fishes such as shad 

two continents and few species spawn in more (Alosa; e.g., Leggett 1976) but is different from 

than two of the biogeographic provinces that we that typical for Pacific salmonids (Orcorhyndefine 

below. This situation is unlike that, for ex- chus; see Groot & Margolis 1991). 

ample, for salimonids of the North Pacific Ocean, 2. All Acipenseriforms spawn in freshwaters of low 

several of which spawn in both North American salt content (0–0.1‰) even though adults of 

and Asian rivers (e.g., chum salmon. Oncorhyn- some species may migrate to feed in estuarine or 

chus keta spawns in rivers along the east and brackish waters (approximately 14 to 27‰, 

north coast of Asia as well as the west coast of Pearse & Gunter 1957) or seawater (35‰). 

America, Salo 1991). Our interpretation con- 3. The timing of spawning for Acipenseriformes is 

cerning sturgeons and continents is subject to highly variable, equaling or exceeding the variafalsification, 

but all detailed work to date sug- bility round in any other group of fresh water or 

gests that this pattern will hold true. For instance, diadromous fishes. They spawn in all seasons 

Acipenser medirostris (west coast of North and in highly variable conditions of water flow 

America) and A. mikarioi (Sea of Okhotsk and and temperature. 

Sea of Japan) were at various times considered 4. Characteristics of spawning migrations vary 

to be conspecific, but recent genetic and mole- greatly among Acipenseriformes in total discular 

data confirm that they are distinct species tance migrated, the distance upstream from salt 

(Birstein 1993b, Birstein et al. 1997 this volume). water, etc. Several evolutionary scenarios and 

3. Much of the historic work concerning the distri- sets of terminology have been proposed to debution 

of different species of sturgeons (e.g., scribe these variations in spawning migration 

Berg 1948a, 1948b, 1959) predates contemporary pattern (reviewed below). 

concepts of continental drift. More recent ac- 5. The few studies done to date indicate that the 

counts (e.g., Berra 1981, Hocutt & Wiley 1986, availability of suitable spawning habitat is crit- 

Banarescu 1990, 1992, 1995) predate contempo- ical to reproductive success. Spawning sites are 

rary phylogenetic interpretations of acipenseri- characterized by areas with hard substrate of 

forms. If one restricts analysis to †Chondrostei- gravel to boulder size rocks containing many 

dae, †Peipiaosteidae, Polyodontidae and the crevices. The water velocity near the bottom is 

tribe Scaphirhynchini, all of which are small typically moderate (Kynard 1997 this volume). 

groups with intriguing but fairly simple biogeo- 6. Annual spawning success and recruitment is 

graphic distributions (Grande &Bemis 1991, Jin highly unpredictable, and may be zero if river 

1995, Bemis et al. 1997b), then historical bioge- flows are too high during the brief reproductive 

ography is easy to contemplate. The widely rang- window of females. High flows, whether caused 

ing genus Acipenser, however, imposes many by natural phenomena or controlled releases by 

difficult biogeographic questions, which is why it dams, can create high bottom velocities that preis 

a focus in our present analysis. 

clude or greatly reduce spawning success (Kynard 

1997 this volume). 

7. A particular spawning site is usually used from 

year to year. Such site fidelity might derive either 

from the particular characteristics of the site or 

from homing. Sturgeons are believed to have 

169

170 

Figure1. Tree suggesting possible evolutionary relationships among fossil and recent acipenseriforms. See text for explanation and 

discussion. Biogeographic areas are keyed to the map in Figure 3, and our scheme of provinces is explained in the biogeography section of 

the text. Fossils are preceded by dagger symbols; continents from which fossils were recovered are indicated. Life history pattern is keyed 

as follows: A- anadromous; P-potamodromous; FWA-freshwater amphidromous. These terms are defined in the life history section of 

the text. Data for relationships among acipenserines (Acipenser plus Huso) based on preliminary analyses by Birstein & DeSalle (1997).

strong homing capabilities, although direct evidence 

for this is only recently available, and the 

subject needs additional research (Waldman et 

al. 1996a,b, Wirgin et al. 1997 this volume). If 

homing proves to be as important as currently 

expected, then it might be the proximate explanation 

for the existence of different morphs or 

races within species, which is a particularly common 

pattern in the family Acipenseridae. 

Species and evolutionary relationships 

171 

tionships within Polyodontidae also are well understood 

(Grande & Bemis 1991, Bemis et al. 1997b). 

Other aspects of the tree in Figure 1 have been 

recently proposed on the basis of molecular sequence 

data (Birstein et al. 1997 this volume) and 

still others are decidedly controversial. A close 

comparison of formal phylogenetic hypotheses proposed 

by various current authors will reveal major 

differences in branching pattern within Acipenser 

as well as the placement of Huso. The largely unresolved 

pattern of relationships within Acipenser 

that we show in Figure 1 is derived from ongoing 

analyses of a growing molecular phylogenetic data 

set that is the basis for a separate formal phyloge- 

netic analysis (Birstein & DeSalle 1997). A special 

problem is indicated on the tree by the dotted lines 

leading to Huso huso and H. dauricus. Based on a 

phylogenetic analysis of osteological and other 

morphological characters, Findeis (1997 this vol- 

ume) proposed Huso as the sister taxon of all other 

species of Acipenseridae, and this is the placement 

Figure 1 presents a tree of the well-preserved fossil 

and all living species of acipenseriforms. It includes 

†Birgeria, which was considered to be a closely related 

outgroup for Acipenseriformes by Bemis et 

al. (1997b this volume). Next to each extant taxon in 

Figure 1, we list the biogeographic province(s) in 

which it occurs and its supposed life history pattern 

(biogeographic provinces and life history patterns 

are described further below). For extinct taxa in we show in Figure 1. Birstein & DeSalle (1997), 

Figure 1 (indicated with dagger symbols), we identi- however, reported molecular characters that link 

fy the continents from which the fossils were reco- Huso with Acipenser ruthenus (also see Berg 

vered. Life history cannot be assessed with certain- 1948a,b). 

ty in fossils. 

Our goal in presenting the tree in Figure 1 is not 

to present a single preferred hypothesis of relation- Time and the biogeography of fossil acipenseriships 

among acipenseriform taxa but rather to orga- forms 

nize biogeographic and life history information. It 

should be regarded as a heuristic synthesis of formal Many relatively well-known Earth historical factors 

phylogenetic analyses presented in this volume have impacted Acipenseriformes during their long 

(Bemis et al. 1997b, Findeis 1997, Birstein et al. (circa 200 Ma) history. Our intent is not to review 

1997) and elsewhere (Artyukhin 1995, Jin 1995, these in detail but to outline the scope and time 

Grande & Bemis 1996). Some nodes in this tree are course of the changes. Divergence times are necescorroborated 

by all contemporary phylogenetic sarily uncertain, given the relative paucity of wellanalyses. 

For example, we are now very confident preserved fossil taxa. To date, no one has used moleabout 

the placement of †chondrosteidae as the sis- cular phylogenetic data to estimate the times of diter 

taxon of all other Acipenseriformes (Grande & vergence for major lineages within Acipenseri- 

Bemis 1996). Both Polyodontidae and Acipenseri- formes. 

dae are now considered to be monophyletic fam- The outgroup for Acipenseriformes, †Birgeria, is 

ilies (contrary to the view of Gardiner 1984; see known from the Triassic of Europe, North America 

Grande & Bemis 1991), and all available data sup- and Madagascar (Nielsen 1949, Lehman 1952, 

port our concept of Acipenseroidei, a group con- Schwarz 1970). Two families of Acipenseriformes 

taining Polyodontidae and Acipenseridae (see known only from fossils (†Chondrosteidae and Pei- 

Grande & Bemis 1991, Bemis et al. 1997b for de- piaosteidae) are important for understanding the 

tailed comments on the strength of this node). Rela- biogeography of the entire order (see discussion of

172

← 

Figure 2. Paleocoastline maps and the distribution †Birgeriidae and Acipenseriformes. On the map representing the Late Triassie/ 

Early Jurassic, the distribution of †Birgeria is indicated by solid squares, and the distribution of †Chondrosteidae is indicated by solid 

circles. On the map representing the Late Jurassic/Early Cretaceous, the distribution of †Peipiaosteidae is indicated by open circles, and 

the locality for the oldest fossil paddlefish, †Protopsephurus, is indicated by a solid triangle. On the map representing the Late Cretaceous/Early 

Tertiary, the distribution of three additional genera of paddlefishes (†Paleopsephurus,†Crossopholis and Polyodon) in western 

North America is indicated by solid triangles, and a few localities for fossil species assigned to Acipenser are marked with open squares. 

the role of fossils in biogeographic studies in not been the subject of recent comprehensive re- 

Grande 1985). Several fossil Polyodontidae and views, generic level distinctions suffice for current 

Acipenseridae are known. With the exception of purposes. 

the Green River paddlefish, †Crossopholis magni- We organize our comments on the biogeography 

caudatus, from the Early Eocene Green River For- of fossil Acipenseriformes around three paleocoasmation 

in southwestern Wyoming, the localities in tline maps and a time scale (Figure 2; base maps 

which fossil paddlefishes and sturgeons occur lie were redrawn and simplified from Smith et al. 

within the historic ranges of the extant families. 1994). The lowest map shows a reconstruction of 

Some additional data about these fossil taxa are the continents and their coastlines in the Late Triassummarized 

in tabular form in Bemis et al. (1997b sic/Early Jurassic, with the localities of the outgroup 

this volume) and Jin (1995). All well-preserved fos- taxon, †Birgeria, plotted in solid squares in Europe, 

sil genera of Acipenseriformes are included in the North America and Madagascar. Also plotted on 

present study, but because species level distinctions the lowest map (solid circles) are localities for 

within these genera are often problematic and have †Chondrosteus and †Strongylosteus, from the Early 

173 

Figure3. Major rivers, lakes, seas and oceans of the Holarctic relevant to the biogeographic ranges of recent Acipenseriformes. Base map 

redrawn from Bond (1996: Fig. 30–3); data used to assemble this figure are derived chiefly from secondary sources (Anonymous 1980, 

∨ 

Vladykov & Greeley 1963, Scott & Crossman 1973, Hart 1973, Trautman 1981, Lee et al.1980, Holcík1989). Key: 1 - Gulf of Alaska; 2 – 

Fraser R.; 3 -Columbia R.; 4 – Rogue & Klamath R.; 5 – Sacramento R.; 6 -Hudson Bay; 7 - Churchill R.; 8 – Nelson R.; 9 -Albany R.; 10 

-Moose R.; 11 -Rupert R.; 12 -Hamilton Inlet; 13 -Great Lakes (Superior, Huron, Michigan, Eric, & Ontario); 14 – L. Winnebago, Fox 

R., & Menominee R., 15 – St. Lawrence R., 16 – Ottawa R., 17 – St. Maurice R, 18 - Gulf of St. Lawrence;19 -St. John R.; 20 - Kennebec/ 

Androscoggin R. & Merrimack R.; 21 – Connecticut R.; 22 – Hudson R.; 23 – Delaware R.; 24 – Chesapeake Nay system (includes 

Potomac & Susquehanna); 25 – Santee R.; 26 – Savannah R. & Altamaha R.; 27 – St. John’s; 28 – Gulf of Mexico; 29 - Suwanee R. & 

Apalachicola R.; 30 – Alabama R.; 31 -Mississippi R. (includes Missouri, Ohio, & Tennessee rivers); 32 -Baltic Sea; 33 – Neva R., Nara 

R., & Luga R.;34 -Wista R.;35 -Oder R.; 36 -North Sea;37 -Elbe R.;38 -Rhine R.;39–Bay of Biscay; 40–Gironde Estuary (Garrone 

& Dorgonne R,); 41 – Douro R. & Guadiana R.: 42 – Guadalquivir R.; 43 – Mediterranean Sea; 44 -Adriatic Sea; 45 -Po R.; 46 – Black 

Sea; 47-Danube R.;48-Dnestr R.;49 -Dniepr R.;50 -Don R.;51 -Kuban R.;52 -Rioni R.;53 -Caspian Sea; 54-Volga R.; 55-Ural R.; 

56–Gorgan R.;57-Qezel Owzan R.; 58 -Kura R.;59–Terek R.;60-Aral Sea;6l -Syr Darya R.;62–Amu Darya R.;63–L. Balkash;64– 

White Sea; 65–Severnaya-Dvina R.; 66 - Kara Sea; 67 -Ob R. (inclucles Irtysh R.); 68 – Yenesei R.; 69 – L. Baikal; 70 – Laptev Sea; 71 – 

Khatanga R.; 72–Lena R.;73–East Siberian Sea;74–Yana R.; 75 -Indigirka R.;76–Kolyma R.;77–Sea of Okhotsk;78–Amur R.;79– 

Tumnin R.; 80 – Ishikari R.; 81 – Sea of Japan; 82 – East China Sea; 83 – Yangtze R.; 84 – South China Sea; 85 – Pearl R.

174 

Figure 4. Nine biogeographic provinces for recent Acipenseriformes discussed in text. Also see Table 1. Key: NEP – North Eastern 

Pacific; GL - Great Lakes, Hudson Bay & St. Lawrence R., NWA – North Western Atlantic; MGM -Mississippi R. & Gulf of Mexico; 

NEA - Northeastern Atlantic, including White, Baltic & North seas, PC – Ponto-Caspian Region, including Mediterranean, Aegean, 

Black, Caspian & Aral seas; SAO – Siberia & Arctic Ocean; ASJ – Amur R., Sea of Okhotsh & Sea of Japan; CH – China. 

Jurassic of England and Germany, respectively. 

These are the diagnosable genera in the family 

† Chondrosteidae. 

The middle map in Figure 2 shows a reconstruction 

of the continents and coastlines in Late Jurassic/Early 

Cretaceous times, with the localities plotted 

for the earliest known paddlefish, †Protopsephurus 

(solid triangle), and all four genera of the 

extinct family †Peipiaosteidae (†Peipiaosteus and 

†Yanosteus in China, †Stichopterus in Trans Baikal 

and Mongolia, and †Spherosteus in Kazakhstan indicated 

by open circles). The range of †Peipiaosteidae 

is restricted to Asia (Grande & Bemis 1996). 

The top map in Figure 2 shows a reconstruction 

of the continents in Late Cretaccous/Early Tertiary 

times. Localities are plotted for three fossil paddlefishes: 

†Paleopsephurus from the Late Cretaceous 

Hell Creek Formation of Montana, †Polyodon tuberculata 

from the Early Paleocene Tullock Formation 

of Montana and †Crossopholis from the Early 

Eocene Green River Formation in Wyoming. A 

scaphirhynchine sturgeon, †Protoscaphirhynchus 

occurs in the Late Cretaceous Hell Creek Formation 

of Montana (and in fact was recovered from the 

same hadrosaur stomach as was the paddlefish †Paleopsephurus). 

Fossils assigned to the genus Acipenser 

are, for the most part, fragmentary, and have 

never been comprehensively reviewed or compared 

with the living species. For establishing the 

presence of Acipenser in North America, we plot in 

Figure 2 the locality of †Acipenser albertensis from 

the Late Cretaceous of Alberta and other fossil species 

assigned to Acipenser from the Early Eocene of 

England and Miocene of Virginia. 

Biogeography of living acipenseriforms 

Figure 3 maps selected major rivers of the world in 

which acipenseriforms spawn. The rivers, lakes and 

seas relevant to our analysis are coded by number to 

the list in the caption. Given the global scope of our 

survey, we followed a standard rule concerning the 

nomenclature of streams: we only name the relevant 

river that enters a particular ocean or sea basin. 

For example, the Mississippi River (# 31) is named 

in Figure 3 but not its major tributaries, which include 

the Missouri and Ohio rivers. Anadromous 

acipenserids are absent from the Mississippi River, 

and some acipenseriform species occur only in its 

upper tributaries (e.g., Scaphirhynchus albus lives 

in far upstream reaches of the Missouri River), but 

for purposes of our survey, the only river noted is 

the Mississippi. We also simplified many river systems 

and omitted many smaller rivers from our diagram. 

We also found it convenient to define nine biogeographic 

provinces with which acipenseriforms are 

associated (Figure 4). Table 1 lists the provinces and 

species of acipenseriforms that currently live in 

each. Although some species occur in more than 

one province, we defined them for and primarily 

use them to discuss the biogeography of Acipenser 

and Huso. Most provinces are based on drainages 

feeding into distinct oceanic basins. Discrete geo-

175 

sible to make meaningful comparisons based on 

such speculations. Thus, we restrict the analysis of 

life history patterns shown in Figure 1 to extant species. 

Acipenseriforms migrate for two basic reasons: 

feeding and reproduction, and we illustrate some 

possible life history patterns in Figure 5. Downstream 

migrations of sturgeons are always associated 

with feeding. The interfaces between freshwater 

and saltwater or between rivers and large lakes can 

be nutrient rich, with abundant food. The shallow 

(< 100 m), near-shore continental shelf regions in 

which some species of sturgeons feed at sea are similarly 

productive environments. Sturgeons are not 

known to utilize deep environments while at sea, 

and do not in general make extensive offshore migrations. 

Upstream migratiom are usually associatgraphic 

boundaries currently limit emigration of 

sturgeons from some of these provinces to adjacent 

provinces (e.g., around the lower one half of Florida 

there are no suitable spawning rivers). In other 

cases, the provinces are readily distinguishable 

based on geological history (e.g., the Mediterranean 

basin connected to the North Eastern Atlantic 

through the strait of Gibraltar in the Messinian; see 

Hsu 1972). 

Life history 

This section explains the life history patterns scored 

on the tree in Figure 1. Although some authors comment 

on evidence for anadromy in fossil Acipenserforms 

(e.g., Bai 1983), we consider that it is not pos- 

Table 1. Occurrence of species of acipenseriforms in nine biogeographic provinces (mapped in Figure 4). 

NEP - North Eastern Pacific 

GL - Great Lakes, Hudson Bay & St. Lawrence River 

NWA - North Western Altantic 

MGM - Mississippi R. & Gulf of Mexico 

NEA - Northeastern Atlanlic, including White, Baltic & North seas 

PC - Ponto-Caspian Region, including Mediterranean, Aegean, Black, Caspian & Aral seas 

SAO- Siberia & Arctic Ocean 

ASJ - Amur R., Sea of Okhotsk & Sea of Japan 

CH - China 

Acipenser medirostris 

Acipenser transmontanus 

Acipenser fulvescens 

Acipenser o. oxyrinchus 

Acipenser brevirostrum 

Acipenser o. oxyrinchus 

Polodon spathula 

Acipenser oxyrinchus desotoi 

Scaphirhynchus albus 


Scaphirhynchus suttkusi 

Acipenser ruthenus 

Acipenser sturio 

Acipenser gueldenstaedtii 

Acipenser nudiventris 

Acipenser naccarii 

Acipenser persicus 


Acipenser stellatus 


Huso huso 

Pseudoscaphirhynchus fedschenkoi 

Pseudoscaphirhynchus hermanni 

Pseudoscaphirhynchus kaufmanni 



Acipenser mikadoi 

Acipenser schrenckii 

Huso dauricus 

Acipenser dabryranus 

Acipenser sinensis 

Psephurus gladius

176 

Figure 5. Concepts of anadromy, amphidromy and potamodromy in acipenseriforms. These terms are defined and further explained in 

the text. Patterns of spawning migrations used by fish employing these different life history patterns are indicated in text below each 

condition. Once a spawning migrant enters a river, it typically follows one of three spawning migration patterns. These are keyed to the 

drawing as follows: one step - short or long migration, spawning; short two step - migration, overwintering, short migration, spawning; 

long two step - migration, overwintering or oversummering (or both), long migration, spawning. See text for additional explanation. 

ed with spawning activities, although in many cases, 

anadromous sturgeons may re-enter estuaries or 

even freshwater reaches of rivers during summer 

months to feed and amphidromous sturgeons may 

move from one riverine or estuarine foraging site to 

another. Fish with mature gonads that migrate upstream 

during the spawning season are commonly 

referred to as spawning fish or spawners, regardless 

of whether they successfully complete spawning. 

The age at first spawning migration is an important 

life history parameter for all species of sturgeons, 

although it is unknown in many cases. Emigration

efers to an individual that leaves its river basin and 

migrates via a sea or lake. Emigrants may return to 

their natal river to spawn or colonize a new river 

basin (non-natal emigrants). 

Thanks to McDowall (1987, 1988, 1992), other 

terms necessary to accurately describe migrations 

of Acipenseriformes have widely accepted definitions, 

which are: 

Diadromous/diadromy – Fishes that migrate between 

salt water and fresh water (Myers 1949, 

McDowall1988,1992). Many, but not all, acipenseriforms 

are diadromous. 

ishes (Polyodontidae) are potamodromous, for the 

few reports of Polyodon taken at sea seem to represent 

rare individuals, and all fossil polyodontids are 

from freshwater deposits (Grande & Bemis 1991, 

Bemis et al. 1997b this volume). The only possible 

exception is the Chinese paddlefish, Psephurus gladius, 

which was historically captured near the 

mouth of the Yangtze River and from the East China 

Sea, but which now is so rare that its true life 

history pattern will probably remain unknown. 

Based on the few data available, we think that it is 

probably fresh water amphidromous, because juve- 

Anadvomous/anadromy – Diadromous fishes nile Chinese paddlefish were historically taken in 

that spend most of their lives at sea but return to 

fresh water to breed (Myers 1949, McDowall1988, 

1992). Most species in the genus Acipenser are anadromous, 

as are both species in the genus Huso. 

Surprisingly limited information is available about 

the physiological mechanisms that underlie anadromy 

in acipenseriforms (McEnroe & Cech 1985, 

1987) 

177 

the estuary of the Yangtze River (see Wei et al. 1997 

this volume). Some species of Acipenser, such as A. 

ruthenus, are commonly considered to be potamodromous, 

such as the populations in upper reaches 

fishes whose migration from fresh water to the salt 

water, or vice-versa, is not for the purpose of breeding 

although it occurs regularly at some point(s) in 

the life cycle (McDowall 1988, 1992). McDowall 

(1992) defined two types of amphidromy: freshwater 

amphidromy, in which spawning is in fresh water 

and growth occurs during migrations into salt water, 

and marine amphidromy, in which spawning occurs 

in salt water and growth occurs during migrations 

into fresh water. All acipenseriforms spawn in 

fresh water, so that only freshwater amphidromy is 

relevant for the group. Only a few cases convincingly 

document freshwater amphidromy for any species 

of Acipenseriformes, because this requires detailed 

knowledge of the movements of individuals 

which can only be obtained from tagging and recapture 

or telemetric studies. The best documented of 

these species is the shortnose sturgeon. Acipenser 

brevirostrum (Bain 1997 this volume, Kynard 1997 

this volume). 

Potamodromous/potamodromy - Fishes that migrate 

within a river system to breed and forage 

(McDowall 1988, 1992). All shovelnose sturgeons 

(tribe Scaphirhynchini, Scaphirhynchus and Pseudoscaphirhynchus) 

are potamodromous. Paddlef- 

∨ 

of the Danube River described by Hensel & Holcík 

(1997 this volume). Recent information suggests 

that A. ruthenus may prove to be amphidromous, 

because juveniles are commonly captured in salt 

Amphidromous/amphidromy – Diadromous water at the mouth of the Danube River. Other species, 

such as A. schrenckii, may be facultatively potamodromous, 

with some populations in upper 

reaches of the Amur River apparently never venturing 

near the estuary (Krykhtin & Svirskii 1997 

this volume). Some authors refer to such populations 

as residents, meaning that the individual fish 

do not migrate to the sea. Poorly understood are 

other cases demonstrating the type of facultative 

potamodromy that occurs when dams obstruct passage 

of a formerly anadromous or amphidromous 

species, a condition referred to as damlocked (Kynard 

1997 this volume). By itself, potamodromy can 

only provide negative evidence concerning a species’ 

ability to cross large ocean basins. 

In those marine coastal rivers that have sturgeons, 

usually at least two species (and sometimes 

as many as six) are present. If only two species are 

present, one is always anadromous, and the other is 

usually potamodromous (or amphidromous; see 

comments on the difficulties of detecting amphidromy 

above). Two clear examples of this are found 

in the Hudson River, which has Acipenser oxyrinchus 

(anadromous) and A. bvevirostrum (amphidromous), 

and the Yangtze River, which has A. sinensis 

(anadromous) and A. dabryanus (amphidro-

178 

mous or potamsdromous). If only one species is Gerbilskiy 1957, Kazansky 1962, Artyukhin 1988). 

present, it is usually anadromous. The Northeast Some of the terms and discussions are contradicto- 

Atlantic region (Figure 4) has a high frequency of ry and difficult to follow, particularly because it is 

rivers, particularly in western France and the Iber- not always possible to link migration times, spawnian 

Peninsula, that have only one anadromous spe- ing sites and specific migrants. Also, the terminolcies, 

A. sturio The absence of a second species in ogy does not easily translate to conditions in North 

these rivers is not due to anthropogenic effects, but American rivers, many ofwhich are shorter, smaller 

instead reflects the historical 

∨ 

situation Holcík coastal streams than are the major rivers of the 

1989). It is unclear why the pattern that is so com- Black and Caspian Sea basins for which the termimon 

elsewhere is not followed in the northeast At- nology was originally developed. The simplified 

lantic region. 

scheme summarized in the box in Figure 5 draws 

In Figure 1, most taxa are scored with either an ‘A’ primarily from Kynard (1997) and Gerbilskiy 

for anadromy or ‘P’ for potamodromy; only one (1957). It classifies spawning migrations as having 

species (A. brevirostrum) is marked ‘FWA to indi- one or two steps, with a variable length of time becate 

freshwater amphidromy because without bet- tween the actual migration and the time of spawn 

ter telemetric and tagging studies, we cannot know ing. This scheme can be readily used to describe 

how inany seemingly freshwater species actually either anadromous, amphidromous or potamodrouse 

patterns of freshwater amphidromy. Future nious acipenseriforms and individual variation 

work will almost certainly change some of our ‘P’ within populations. 

scores to ‘FWA’ scores. In some cases, a species may One step spawning migrations are those in which 

be potamodromous in one river basin and anadro- fish move directly upstream to the spawning site, 

mous in another; in such cases, we scored the spe- spawn, and return downstream. Depending on the 

cies‘A’. 

bioenergetic reserves of the fish, the migration may 

be short or long, and occur in winter or spring. This 

is usually thought to be the most common pattern 

Patterns of spawning migrations 

for living acipenseriforms, although the few data 

available (mostly catch records) are conflicting. It 

Within acipenseriforms, variations in the pattern of 

spawning migration are found at the species, popdation, 

and individual levels. The genetic basis of 

spawning migration characteristics is well established 

for salmoniforms, for which extensive selection 

experiments have been done (also see papers in 

Groot &Margolis 1991). Virtually nothing is known 

about the heritability of spawning migration characteristics 

of acipenseriforms, but we expect a similar 

genetic basis to that known for salmonids. The 

existence of different spawning migration patterns 

in sturgeons has been discussed by many authors, 

including Berg (1934, 1959), Artyukhin (1988) and 

Kynard (1997 this volume). Berg (1934) introduced 

the terms vernal and winter races to describe groups 

of anadromous fishes migrating into rivers for 

spawning in the same year (vernal races) or next 

year (winter races). These terms stimulated a long 

discussion in the Russian literature concerning Eurasian 

sturgeons (reviewed by Barannikova 1957, 

corresponds to Gerbilskiy’s (1957) migrant type I, 

in which the oocytes have reached their final size 

and spermatogensis is finished by the time migration 

starts. Fat deposits in connective tissue and 

muscles arc depleted, and the stomach and digestive 

tract are empty and inactive indicating that 

feeding stopped some time before migration. Such 

migrants typically use spawning sites in the lower or 

middle reaches of rivers. 

Short two step spawning migrations involve upstream 

migration, usually in the fall, followed by 

overwintering near the spawning site, followed by a 

very short migration to spawn the following spring. 

This pattern enables fish to use bioenergetic reserves 

gained during summer foraging for their initial 

long upstream migration. This corresponds 

roughly to Gerbilskiy’s (1957) migrant type II, in 

which late stages of oogenesis are in progress, and 

the oocytes are still embedded in fatty tissue. Spermatogenesis 

is in the ‘first wave’ of divisions. There

Some have asserted (e.g., Yakovlev 1977) that Aci- 

penseriformes originated in northeastern Asia in 

the Triassic. This argument, however, cannot be 

based on either the earliest known occurrence of 

fossils or the greatest current diversity of taxa but 

must instead be consistent with the ranges of out- 

group taxa (Nelson & Platnick 1981). Based on 

available phylogenetic and biogeographic evidence 

(Figure 1), the most plausible place and time of ori- 

gin for Acipenseriformes is the Triassic of western 

Europe, for this is consistent with the range of †Bir- 

geria (Europe, North America, and Madagascar) as 

well as with the range of †Chondrosteidae, which is 

interpreted by Grande & Bemis (1996) to be the siscies 

of sturgeons in the Ponto-Caspian region that ter taxon of all other Acipenseriformes (Figure 2). 

inhabit lowland rivers, whereas spawning during The localities of Late Jurassic/Early Cretaceous 

the summer is associated with rivers having a higher members of Peipiaosteidae in Central and Eastern 

gradient. Kynard (1997 this volume) proposed a Asia suggest (but do not provide definitive evibioenergetic 

explanation of migratory patterns. As dence for) early diversification of Acipenserinoted 

above, spawning migratory patterns can be formes in central Asia. If true, this seem consistent 

variable within species or populations, and before with the greatest current species diversity of Aciconclusions 

are reached, it seems necessary to de- penseridae in the Ponto-Caspian region and the relvelop 

better understanding of sturgeon life histo- atively much later appearance of the group (Late 

ries. Factors such as spawning site fidelity and be- Cretaceous) in North America (Figure 2). We 

havior between successive spawnings need to be 

is abundant fat in connective tissue and dorsal muscles, 

and the hepatocytes are large because of lipid 

inclusions. Food remains in the stomach and digestive 

tract indicate that feeding took place just prior 

to the start of migration. These fish typically spawn 

in middle to upstream reaches of many rivers, such 

as the Volga, Ural, Danube, Hudson or Connecticut. 

Long two step spawning migrations refer to fish 

that make an initial upstream migration, followed 

either by overwintering, oversummering, or both, 

then followed by a long upstream migration to the 

spawning site. Fish with this pattern may be in fresh 

water without feeding for 12 to 15 months, which effectively 

precludes this option for small to medium 

sized species because they lack sufficient bioenergetic 

capacities. Only very large species, such as Huso 

huso and Acipenser sinensis seem likely candidates 

for this pattern. This corresponds more or less 

to Gerbilskiy’s (1957) migrant type III, which is 

characterized by late stages of oogenesis, and intermediate 

levels offat in the ovary, connective tissues, 

and muscles at the start of migration. This type of 

migration is characteristic of some individuals of 

large species in the longest rivers, such as the Danube, 

Volga, Amur or Yangtze. The only place in 

North America where this pattern may have been 

present is the Columbia River, where very large 

white sturgeon, A. transmontanus, historically 

spawned in headwaters. 

Explanations that have been offered concerning 

the adaptive significance of different spawning migratory 

patterns include river length, river gradient, 

temperature at the spawning site, and bioenergetics. 

For example, Artyukhin (1988) concluded that 

spawning in the spring is characteristic of most spe- 

179 

broadly investigated across acipenseriforms, as well 

as the genetic bases of supposedly different stocks 

of the same species in particular river systems (Wirgin 

et al. 1997 this volume). Until then, it is safest to 

regard the three patterns of spawning migration as 

descriptive tools, rather than interpretive explanations 

far particular migration patterns, and we have 

not attempted to score the migratory patterns of 

species in Figure 1. 

Discussion 

Several events in Holarctic history stand out as influencing 

the contemporary distribution of sfurgeons 

and paddlefishes. A complete review is far 

beyond our scope, so we note only a few highlights. 

Place of origin of acipenseriformes and their early diversification

180 

should expect to find new acipenseriform fossils in 

Mesozoic deposits across Europe and Asia. 

Were early acipenseriforms potamodromous or 

anadromous? 

McDowall (l993) considered that sturgeons (and by 

extension, acipenseriforms in general) are unlikely 

to have had a recent marine ancestry, a conclusion 

that all fossil data and contemporary phylogenetic 

analyses support. This does not answer, however, 

whether anadromy originated within Acipenseriformes 

or was a plesiomorphic feature of the group. 

Unfortunately, we can only speculate about the answer, 

because we can never hope to understand 

much about the life history of †Birgeriidae, †Chondrosteidae 

or †peipiaosteidae, and more distant 

outgroups are not helpful (Bemis et al. 1997b this 

volume). From the analysis in Figure 1, either potamodromy 

or anadromy could be the ancestral condition, 

because each condition appears twice on the 

tree (potamodromy in most or all species of Polyodontidae 

and Scaphirhynchini; anadromy in Huso 

and most species of Acipenser). If Huso is eventually 

nested within Acipenser (e.g., Birstein et al. 

1997), then perhaps anadromy will emerge as a derived 

character of some clade that includes Acipenser 

and Huso. This would be very interesting, because 

anadromy seems likely to be linked to the 

great diversity within Acipenser. 

Comments on biogeography of extant species 

The Ponto-Caspian region currently has the greatest 

species diversity of Acipenseridae. Some sturgeons 

of the Ponto-Caspian region have striking 

morphological distinctions from all other species, 

such as the very elongate rostrum found in adult 

stellate sturgeon, Acipenser stellatus. There are 

some intriguing links of this Ponto-Caspian region 

both to the North Eastern Atlantic (A. sturio) and 

to the Amur River district (Huso huso and H. dauricus). 

One of the most intriguing links of the Ponto- 

Caspian region is to the Mississippi-Gulf of Mexico 

region in North America indicated by the scaphir- 

hynchine sturgeons. All six extant species of Scaphirhynchus 

and Pseudoscaphirhynchus are considered 

to be potamodromous, and we know that 

Scaphirhynchini was present in North America in 

the Late Cretaceous (Figure 2). (A comparably intriguing 

and old link dating from at least the Late 

Cretaceous occurs between China and the Mississippi-Gulf 

of Mexico region as indicated by Polyodontidae; 

Grande & Bemis 1991.) 

The Ponto-Caspian region has been very unstable 

over the last 150 million years, the period in 

which we suppose Acipenseridae has diversified. 

Some indication about the magnitude of the Earth 

historical changes in the Ponto-Caspian region is 

apparent in the diagrammatic maps in Figure 2, 

which represent only a small window on this part of 

the world (see Smith et al. 1994 for additional geographical 

and geological detail). The changes include 

major sea level variation, conversions of large 

bodies of water such as the Black Sea from freshwater 

lakes to marine environments, merging of island 

arcs with the southern continental borders of 

Europe and Asia, and major shifts in drainage patterns 

as mountain building occurred. The Black Sea 

has repeatedly been connected and disconnected 

with the Caspian and Aral seas. It is tempting to link 

the current diversity of acipenserids in this region to 

its extremely complex history. 

Around the Pacific rim, we defined three biogeographic 

regions (NEP, ASJ, and CH, Figure 2) that 

together have six species of Acipenser. Based on the 

available phylogenetic interpretation (Figure 1), 

the five anadromous species (A. transmontanus, A. 

medirostris, A. mikadoi, A. schrenckii and A. sinensis) 

appear to form a monophyletic group. Acipenser 

dabryanus, a potamodromous and potentially 

amphidromous species believed to be restricted to 

the Yangtze River, lies outside the group of species 

from around the Pacific rim (see Wei et al. 1997 this 

volume and Zhuang et al. 1997 this volume for discussion 

of the ranges of sturgeons in China). One 

point concerning sturgeons of the Pacific rim is that 

we are unaware of any spawning in rivers north of 

the Fraser River, British Columbia. The explanation 

for this pattern in the Pacific is unknown, although 

other taxa of acipenserids, such as A. fulves-

› 

› 

› 

› 

› 

› 

cens in North America and A. baerii in Siberia. 

spawn in rivers at higher latitudes. 

Some biogeographic patterns may be related to 

continental movements, such as the sister group relationship 

between Acipenser sturio in Europe and 

A. oxyrinchus in North America. These two species 

are anatomically similar and were long considered 

to be conspecific (Vladykov & Greeley 1963). They 

also share molecular sequence similarities (Birstein 

et al. 1997 this volume). Although these species live 

on opposite sides of the North Atlantic Ocean, and 

are presumably blocked from most interbreeding, 

we suspect that the separation between these taxa is 

actually much younger than the North Atlantic 

Ocean. 

Species of acipenseriforms directly impacted by 

Pleistocene glaciation presumably include boreal 

taxa such as A, baerii (Ruban 1997, this volume). 

This species occurs in many of the northward flowing 

rivers of Siberia (SAO region, Figure 4). Although 

the extent of glaciation in Siberia during the 

last glacial maximum (18000 years bp) was not as 

extensive as one might suppose (Starkel 1991), A. 

baerii was certainly prevented from entering the 

Arctic Ocean. The location of its glacial refugia is 

181 

in Birstein & DeSalle 1997). We also thank Vadim 

for extensive discussions of the main ideas presentcd 

here. In spite of a few minor differences of opinion, 

this paper would not exist were it not for his 

extremely helpful input. Paul Morris read and criticized 

a draft of the manuscript and helped with paleogeographic 

questions. 


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Sturgeons of the western and eastern Atlantic: a– the shortnose sturgeon, Acipenser bvevirostrum 143 cm TL from the outlet of Washademoak 

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Museum, Bucharest. Originals by Paul Vecsei, 1996.

Environmental Biology of Fishes 48: 185–200, 1997. 

© 1997 Kluwer Academic Publishers. Printed in the Netherlands 

Past and current status of sturgeons in the upper and middle Danube River 

Karol Hensel 1 ∨ 2 

& Juraj Holcík 

1 

Department of Zoology, Faculty of Natural Sciences, Comenius University, Mlynská dolina B-I, 842 15 Bratis 

lava, Slovakia 

2 Department of Ichthyology, Institute of Zoology, Slovak Academy of Sciences, Dúbravská cesta 9, 842 06 

Bratislava, Slovakin 


Key words:Huso huso, Acipenser nudiventris, A. stellatus, A. gueldenstadtii, A. ruthenus, anadroiny, Romania, 

Serbia, Croatia, Hungary, Slovakia, Austria, Germany 

Synopsis 

Of the six species of sturgeons native to the Danube basin, five occurred in the upper and middle Danube. 

Among anadromous sturgeons were the large winter races of beluga, Huso huso, Russian sturgeon, Acipenser 

gueldenstaedtii, and stellate sturgeon, A. stellatus which ascended the middle, and sometimes also the upper 

Danube, to spawn. Due to overfishing, followed by severe habitat alteration including damming and pollution, 

these anadromous sturgeons are critically endangered or extirpated from the upper and middle Danube. 

Acipenser gueldenstadtii and A. nudiventris are represented only as resident non-migratory races with very 

small populations. The most abundant and widely distributed species is the sterlet, A. ruthenus although it is 

presently limited to the middle Danube. Its population increased in some sections of the middle Danube 

during the past 15 years, presumably because of improving water quality, but this species remains at risk 

because of continuing habitat degradation. 

Introduction 

Six species of sturgeons historically occurred in the 

Danube River and some of its tributaries. The European 

Atlantic sturgeon, Acipenser sturio, was the 

rarest, and it only occasionally entered the Danube 

estuary. Beluga, Huso huso (Linnaeus, 1758), ship 

sturgeon, A. nudiventris Lovetski, 1828, stellate 

sturgeon, A. stellatus Pallas, 1771, Russian sturgeon, 

A. gueldenstadtii Brandt, 1883, and sterlet, A. ruthenus 

(Linnaeus, 1758), however, were common to 

abundant (also see Bacalbasa-Dobrovici 1997 this 

volume). Anadromous populations, especially winter 

races (= autumnal races of some authors; see 

Birstein & Bemis 1997 this volume, for discussion of 

this terminology) of beluga and Russian sturgeon, 

moved from the Black Sea into the Danube, ascending 

the middle and sometimes even the upper Danube 

and larger tributaries. Freshwater resident 

populations of some species of sturgeons also existed. 

Because sturgeons had such great economic importance, 

many historical records are available. 

However, overfishing and habitat alteration caused 

populations to collapse (Rochard et al. 1990, Birstein 

1993). In particular, construction of the Derdap 

I Dam (= Iron Gates Dam I) at the village of Sip 

(Iron Gate, river kilometer 942) in 1969 and later 

construction of the Ðerdap II Dam (= Iron Gates 

Dam II) at Kusjak (river km 863) in 1984 blocked 

further upstream migration of anadromous sturgeons, 

and most species are now extirpated from 

the middle and upper Danube.

› 

› 

186 

Figure 1. The Danube River basin showing rivers inhabitated by sturgeons (Acipenseridae). Original figure by K Hensel. 

Geographically the Danube is divided into three Huso huso - beluga or great sturgeon 

parts (Figure 1). The lower Danube (shared by Ukraine, 

Moldova, Romania, Bulgaria and Serbia) ex- Vernal races (= spring races of some authors; see 

tends from the estuary up to the mouth of the Cerna Birstein & Bemis 1997 this volume for terminology) 

River (river km 955) in the Iron Gates region. The and winter races of this anadromous species anmiddle 

Danube (shared by Romania, Serbia, Croa- nually ascended the Danube River in large numtia, 

Hungary and Slovakia) runs from the Cerna up bers (Figure 2). Although migrations of beluga conto 

the mouth of the Morava River (river km 1880), tinued year round, two peak periods were regularly 

and the upper Danube flows through Austria and observed, one for the winter and the second one for 

Germany (Balon et al. 1986). 

the spring strain. Upstream migration of the winter 

This paper summarizes the history and status of strain usually started in August and culminated in 

five species of sturgeons in the middle and upper October or November. Migration of the spring 

Danube. We report sizes as total length (TL, the dis- strain lasted from January until April (Banatance 

between the anterior tip of the rostrum and 

the tip of the caudal fin) and weight (BW, total body 

weight). Data on catches of particular species are 

from proceedings of the JCIAFD. 1,2 We report locations 

of capture at either towns or particular river 

kilometers from the mouth. 

2 Anonymous. 1983. Appendix pp. 207–229. In: Documents 

trom the 24 session ot the Joint Commission of the International 

Agreement on the Fishing in the Danube River between the governments 

ot the Soviet Union, People Republic of Bulgaria, Peo 

ple Republic of Hungary, Socialistic Republic of Romania, Czechoslovak 

1 

Joint Commission of the International Agreement on Fishing 

Socialistic Republic and Socialistic Federative Re- 

in the Danube River. 

public of Yugoslavia. Moscow (in Russian).

Figure 2. Distribution of the beluga, Huso huso, in the Danube drainage system. Regular (continuous black area) and occasional (black and white area) occurrence at present; 

regular (continuous white area) and occasional (striped white area) occurrence in the past. Original figure by K. Hensel. 

187

188 

Figure3. Distribution of the Russian sturgeon, Acipenser gueldensraedtii, in the Danube drainage system. Regular (continuous black area) and occasional (black and white area) 

occurrence at present; regular (continuous white area) and occasional (striped white area) occurrence in the past. Information on distribution was compiled from Grossinger 

(1794), Fitzinger & Heckel (1835), Heckel & Kner (1858), Kornhuber (1863), Siebold (1863) Herman (1887), Ortvay (1902). Antipa (1909), Vutskits (1913), Munda (1926), Kähs- 

∨ 

bauer (1961), and Holcík (1995). Original figure by K. Hensel.

› 

› 

189 

rescu 1964, Manea 1966, Kirilyuk & Rovnin 3 ). The 

winter strain overwintered in the river and spawned 

in the following spring. Winter beluga ascended up 

to Bratislava (= Presburg, Preßburg or Pozsony, see 

Gesner 1575), rarely also entered the Austrian part 

of the Danube (Fitzinger & Heckel 1835) and occasionally 

even the Bavarian stretch up to Straubing 

(river km 2320; Siebold 1863). The main spawning 

grounds of beluga were located in the contemporary 

Slovak - Hungarian stretch of the river in the 

∨ 

Zitný Ostrov reach below Bratislava (river km 

1766-1866).The major fishery for beluga was concentrated 

in the Little Danube (which is the northern 

branch of the Danube River) near the mouth of 

the Váh River at the village of Kolárovo, see Figure 

1) and in the Danube proper between Komárno and 

∨ 

Sap (=Palkovicovo, see Balon 1967). 

Beluga also entered other tributaries of the Danube, 

including the lower course of the Morava 

3 Kirilyuk, M.M. & A.A. Rovnin. 1983. The status of the brood 

stock, age structure and breeding conditions ofsturgeons in 1981. 

pp. 28–36. In: Materials of the 24th Session of the joint Commis- 

sion of the International Agreement on the Fishing in the Danube 

River between the Governments of tlie Soviet Union, Peoples 

Republic of Bulgaria, Peoples Republic of Hungary, Socialistic 

Republic of Romania, Czechoslovak Socialistic Republic 

and Socialistic Federative Republic of Yugoslavia, Moscow (in 

Russian). 

(= March) River (Jeitteles 1864), where a 2 m TL 

∨ 

∨ 

specimen was caught at Lanzhot (Zboril & Absolon 

1916). In the Váh River, beluga ascended up to 

Trnovec nad Váhom (Herman 1887) and exception- 

∨ 

ally even up to Trencín (Kornhuber 1861). Beluga 

∨ 

also occurred in the Zitava River up to Nesvady 

∨ 

(Holcík1995), the Drava (= Drau) River (Taler 

1953), the Tisa (= Tisza or Tysal) River (Heckel & 

Kner 1858) up to Trakany (Anonymous 1975) and 

its tributaries the Zagyva River, Körös (= Cris) River 

(Vutskits 1913) and Maros (= Mures) River 

(Heckel & Kner 1858) where it occurred even at 

Hunedoara (Banarescu 1964). In the Sava River, 

beluga were recorded at Zagreb (Glowacki 1896) 

and also in the Sava River’s tributary, the Kupa River 

(Taler 1953). Beluga also entered the lower 

course of the Velika Morava River (Vutskits 1913) 

and the Olt River (Heckel & Kner 1858). 

Beluga was among the most abundant of Danubian 

anadromous fishes, and it was the most valuable. 

Due to overfishing of brood fish during spawncatches 

of beluga started to decline after the 16th 

ing migrations Heckel 1851, Heckel & Kner 1858, 

century (Balon 1967, 1968). Beluga were taken by 

means of special nets and particular hooks, called 

‘samolov’; however the most effective method was 

the catching weir (Rohan-Csermák 1963). Because 

most of the fish migrating to spawn for the first time 

Table 1. Specimens of Acipenser gueldenstaedtii recorded in Slovak and Hungarian segment of the Danube River since 1900 1.2 . 

1932: 

1949: 

1960: 

1962: 

1964: 

1965: 

1967: 

1968: 

1970: 

1980: 

lower stretch of the Morava River between its confluence with the Danube and Suchohrad (a 35 km long segment); 7 kg BW, 

estimated TL 950 mm 

mouth of the Little Danube at Komárno; 20.4 kg B.W, estimated TL 1118 mm. 

confluence of the Little Danube with the Nitra River, TL 375 mm, estimated BW 0,4 kg 

Danube al Zlatná na Ostrove (river km 1779); TL 850 mm 10.5 kg BW. 

Danube at Vel’ké Kosihy (river km 1787); two specimens 10.2 and 10.6 kg BW, estimated TL 1072 and 1085 mm. 

same locality ar above (Gunda 1966, erroneously writes ‘Danube at Malé Kosihy’ however the latter village is on the right bank 

of the Ipel’River, where this species was never found); 10.4 kg BW, estimated TL 1079 mm 

Danube at Radvan ∨ 

nad Dunajomi (river km 1749): 355 mm esstimated BW 331 g: this specimcn seems to be an anadromous form 

as its calculated TL (295 mm) is substantially higher than that of the resident form 190 mm according to Lukin 1937). 

Danube at Radvan ∨ nad Dunajom. 424 mm TL; this was a hybrid between A. ruthenus and A. gueldenstaedtii (Hensel 1969). 

Danube at Paks (river km 1827); 400 mm TL. estimated BW 643 g. 

Tisza River at Tiszafüred; estimated TL 852 mm 5 kg BW. 

∨ 

1 

Sturgeons caught in the Danube at Stúrovo in 1937 and 1957, BW 12 and 18 kg, respectively, where A. guendelstaedtii and not H. huso as 

said by Kux & Weisz (1962) because H. huso only matures at BW > 20 kg (Chugunov & Chugunova 1964). Moreover, beluga of such low 

weight have never been caught in the middle Danube (Khin 1957). 

2 

Lengths or weights calculated from the GM regression: BW = 0.000003994 × TL 3.10452 ; where BW = weight in grams, and TL = total 

∨ 

length in mm (Holcík 1995).

190 

Figure 4. Distribution of the sterlet, Acipenser ruthenus, in the Danube drainage system. Regular (continuous black area) and occasional (black and white area) occurrence at 

present; regular (continiuous while area) a occasional (striped white area) occurrence in the past. Information for this map was completed from Grossinger (1753), Kornhuner 

1986, Siebold (1863), Jeitteles (1861), Herman (l877), Moscáry (1877), Chyzer (1882), Malesevics (l892), Glowacki (1896), Antipa (1909), Vutskits (1913), Munda (1926), Mahen 

∨ 

(l927), Vladyltov (1931), Mihályi (1954), Kux (1956), Sedlár (1959,1960, 1969), Zitdan (1963. 3965), Holcík (1968), Anonymous (1975), Sedlár et al. (1989), Sokolov & Vasil’ev (1989) 

∨ 

and Holcík (1995). In the following list, towns or locations in parentheses give the farthest uper record. Right hand tributaries include: the Isar River (Landshut), Inn River and 

its tributary Salzach River (Laufen), Siò River (Lake Balaton), Rába (= Raab) River, Drava River (Maribor), Mura River (Graz), Sava River (Sevnica) and its tributaries Kupa 

∨ ∨ 

River (Karlovac) and Lonja River. Left hand tributaries include: the Morava River (Moravská Nová Ves), Váh River (Trencin, exceptionally Liptovský) Svätý Mikulás) and its 

tributaries Nitra (Lándor) and Z ∨ itava rivers. Hron River (Kameica andHronom), Ipel’ (= Ipoly) River, Tisa River (Sighetul Marmatie) and its tributaries Bega River, Mures 

∨ 

River (Auid), Zagyva River and Bodrog River (Brehov) with tributaries Latorica River, Laborec River and Uh (=Uz) River, Somes River (Dej), Tamis ∨ (= Temes, Timis) River. 

Original figure by K Hensel.

191 

Figure 5. Unusually large specimen of Acipenser ruthenus captured 

among over 100 sterlets in one seine haul on 9.6.1993 in the 

∨ 

Danube River at Cenkov (river km 1730). Photograph by K. 

Hensel. 

were caught, mortality surpassed recruitment. Beluga 

has a long life span and late sexual maturation 

(Pirogovskii et al. 1989), and the Danube population 

began to decrease rapidly (Rohan-Csermák 

1963). Weir fishing disappeared from the middle 

Danube at the end of the sixteenth and from the Tisa 

River at the end of the seventeenth century, but 

Serbian fishermen employed it up to World War I at 

the Iron Gate, near the village of Sip. In the 17th and 

18th centuries the last remnants of the beluga populations 

were so severely undermined that in the 

19th century only a few beluga were caught in the 

foothills and in the lower Danube The last beluga 

recorded in the Slovakian – Hungarian stretch of 

the Danube was a female, 3.l m TL and l50 kg BW, 

∨ 

taken at Stúrovo in 1925 (Khin 1957). According to 

Kornhuber (1901), Ortvay (1902) and Khin (1957), 

only 16 beluga were taken in this segment of the Danube 

between 1857 and 1957, of BW between 78 to 

500 kg, and TL estimated to range from 2.2–7.4 m. 4 

Beluga lose weight after the 1700 km migration up 

the Danube, as do other anadromous fishes (Nikol’skii 

1974). 

Construction of the Ðerdap Dams (= Iron Gates 

Dams) greatly impacted the remaining beluga. Jankovic' 

(1993) reported that catches of beluga and 

Russian sturgeons (separate data sets for the two 

species are not available) peaked during the five 

year period after construction of Iron Gates Dam I. 

In the period from 1972 to 1976, catches amounted 

to 115.7 metric tons, which is 23.1 tons higher than in 

the five years before construction of the dam. The 

higher catch was due to mass gathering of individuals 

below the dam, which allowed intensive fishing 

(see Wei et al. 1997 this volume for similar impact of 

construction of Gezhouba Dam on Yangtze River 

sturgeons). However, by a later five year period 

(1980 to 1984), the combined catch decreased to 

78.2 tons. In the period from 1985 to 1989, the five 

years following construction of the Iron Gates Dam 

II the combined catch dropped to 37.3 tons. Beluga 

only exceptionally overcome the dams via shiplocks: 

a male 3 m in TL weighing 181 kg was caught 

in Hungary at Paks (river km 1526–1528) on 16 May 

1987, and this individual must have negotiated the 

locks at both dams (Pintér 1989). 

According to the JCIAFD, the annual catch of 

beluga in the Danube between 1958 and 1981 varied 

from 19.7 to 240.4 tons, with a decrease in the last 

four years of the period. Most fish were taken by 

Romania (59.1%) and the former Soviet Union 

(30.7%) and the remainder were shared by Bulgaria 

and former Yugoslavia. Beluga is now extirpated 

from the upper Danube, critically endangered in 

the middle Danube and vulnerable in the lower Danube. 

4 

The TL of these fish was estimated by Holcík (1994) using data 

∨ 

from 9 specimens recorded by Khin (1957) to calculate a lengthweight 

regression: BW = - 101975.47 + 81.69821 TL (BW in 

grams TL in mm). This regression differs from that for beluga in 

the Sea of Azov calculated by Chugunov & Chugunova (1964; 

BW = – 4.41087 + 2.78706 log TL).

192 

Figure 6. Distribution of the stellate sturgeon, Acipenser stellatus, in the Danube drainage system. Regular (continuous black area) and occasional (black and white area) occurrence 

at present; regular (continuous white area) and occasional (striped white area) occurrence in the past. Original figure by K. Hensel.

› 

› 

Acipenser gueldenstaedtii - Russian sturgeon 

This is the largest Danubian species of the genus 

Acipenser, and was the most widely distributed anadromous 

species in the Danube River (Figure 3). 

According to Kornhuber (1863), Banarescu (1964) 

and Manea (1966), the largest specimens reached 

2–4 in in TL, with estimated BW of 70-600 kg. Anadroinous 

Russian sturgeons weighing 60–90 kg regularly 

migrated upstream to Bratislava (river km 

1569) and spawned in this section of the middle Danube 

in May and June. They rarely reached Vienna 

(river km 1925) and Regensburg (river km 2381). 

In northern. or ‘left bank’ tributaries of the middle 

Danube, Russian sturgeons occurred in the Morava 

River (at Suchohrad). Vah River, Tisza River 

(up to Versényi) and its tributaries, the Szamos 

(= Somes) River, Zagyva River, Koros River, and 

the Mures River (up to Mihalt). It occasionally entered 

the tributaries ol the lower Danube, including 

the Olt River, the Jiu River (up to Transylvania), 

the Prut River, and the Siret River. It occurrcd in 

southern, or ‘right bank’ tributaries of the Danube 

including the Drava River (and its tributary the Mu- 

193 

in the Danube near Bratislava one angler caught 

two large sturgeons, each about 1 in TL. Both specimens 

were released, but according to the description, 

these must have been A. gueldenstaedtii. Unverified 

records of Russian sturgeon exist also from 

the Hungarian stretch of the river (Pintér 1991). 

According to the JCIAFD, annual catches from 

1953 to 1981 varied from 7.1 to 42.3 metric tons (24.9 

metric tons average). The greatest catch was recorded 

in Bulgaria (45% of the total) followed by 

former Yugoslavia (33.6%). former Soviet Union 

(13.1%) and Romania (3.3%). As already noted under 

the description of H. huso the combined catch 

of beluga and Russian sturgeon dropped after cow 

struction of the dams at the Iron Gates (see Jankovié 

1993). The Russian sturgeon is critically endangered 

in the Danube Basin. 

Acipenser ruthenus - sterlet 

The sterlet is the smallest species among Danube 

sturgeons. It is a potamodromous resident species. 

Tagging performed by Unger (1953) and Ristic 

ra (= Mur) River, via which Russian sturgeon (1970a) revealed maximum migration distances in 

reached as far inland as Austria) and the Sava River the Danube of 322 km. In the Danube, stcrlet reguup 

to Litija (as well as its tributary the Kupa River, larly occurred up to Vienna, frequently to Linz, Pasup 

to Karlovac). sau and Regensburg, and even up to Ulm (Figure 4; 

In the Volga River of Russia, A. gueldenstaedtii Fitzinger & Heckel 1835, Heckel & Kner 1858, Sieoccurred 

as both resident, non-migratory form and bold 1863). It was very abundant in the Danube 

an anadromous migratory Corm (Lukin 1937). near Bratislava (Kornhuber 1863 Ortvay 1902). Ac- 

Heckel & Kner (1858) first noted that Russian stur- cording to Kinzelbach (1994), the large sterlet popgeon 

also occur in the Danube throughout the year, ulation in the upper Danube between Regensburg 

and the resident non-migratory form still occurs and Passau was autochthonous and not the result of 

both in the lower (Manea 1966) and middle Danube migration as generally been thought. Sterlet also as- 

(Sedlár 1960, Sedlár et al. 1989, Gunda 1966, Balon cended or occurred in some of the Danube’s trib- 

∨ 

1968a, Hensel 1969, Hárka 1980, and Holcík 1995). utaries (Figure 4). 

Table 1 lists all specimens of A. gueldenstaedtii re- Sterlet now has a very limited distribution in the 

corded in the Slovak and Hungarian segment of the middle and upper Danube. The species is extirpated 

Danube River since 1900. 

from the German section of the Danube (Reichen- 

∨ 

Holcík (1995) reported that until 1939, 10 to 15 bach-Klinke 1968, Balon et al. 1986), endangered in 

Russian sturgeon weighing 2 to 3 kg were caught the Austrian section (Jungwirth 1975, Schiemer & 

annually in the lower course of the Morava River. Spindler 1989), and greatly diminished in the Slova- 

In the middle Danube, especially between river km kian section. Between 1962 and 1978, sterlet gener- 

1749 and 1987, 3 to 4 specimens were caught annual- ally contracted in the Slovakian section to the 

∨ 

∨ 

∨ 

ly until 1953. At present, this species is extremely 82 km stretch from Stúrovo to Cícov to (Balon 1964, 

rare in the middle Danube. In 1957 we learned that 1968b), and only occasionally was it found at Gab-

194 

Figure 7. Distribution of the ship sturgeon, Acipenser nudiventris, in the Danube drainage system. Regular (continuous black area) and occasional (black and white area) occurrence 

at present; regular (continuous white area) and occasional (striped white area) occurrence in the past. Original figure by K. Hensel.

› 

› 

∨ 

∨ 

cíkovo Holcík et al. 1981). It disappeared from the 

Hron River (Sedlár et al. 1983). and now occurs only 

in the mouth of the Váh River. It also disappeared 

f'rom the lower course of the Morava River some- 

∨ 

time after 1966 Holcík 1995). However, since 1975, 

water quality has improved and slerlet began to re- 

∨ 

appear above river km 1820(Gabcíkovo, Slovakia). 

It is again found at Bratislava and in the lower 

course of the Morava, where 2 to 3 specimens have 

been caught annually by commercial fisherman 

∨ 

since 1980 (Holcík 1995). Catches of sterlet are high- 

∨ 

est between river km 1749 and 1762(Radvan nad 

∨ 

Dunajom - Iza), at Zlatná na Ostrove (river km 

1778–709), at Vel’ké Kosihy (river km 1786–1789) 

∨ 

and lowest at Cenkov (river km 1732–1733; but see 

∨ 

Balon 1995a, b, figure 5) and Stúrovo (river km 

1717). Population increases were presumably due to 

increasing water quality (Sedlár 1985, Sedlár et al 

1989) and stocking of juveniles from the Hungarian 

side of the Danube (Jaczó 1974, Tóth 5 6 7 ). At the 

beginning of the 1980s, as many as 300 specimens of 

sterlet were caught by Slovak fishermen in one haul 

of a 300 m beach seine. Increases in sterlet catch in 

the Hungarian part of the Danube started in 1971 

195 

(Toth 8 ). presumably caused by its emigration from 

the Tisza River where upstream migrations to 

spawning grounds were halted by dams. In the Serbian 

stretch of the Danube, the most abundant pupulation 

of sterlet occurs near Belgrade and in the 

upstream section near Vojvodina, as well as in the 

lower (Serbian) parts of the Sava and Tisa rivers 

(Jankovic' 1993). In the Slovak– Hungarian stretch 

of the Tisza River. the sterlet does not migrate (Hol- 

∨ 

cík 1995). Its continuing presence was also recorded 

in the Rába River (Sokolov &Vasi’lev 1989), the 

Drava River (up to Carinthia, Honsig-Erlenburg & 

Schultz 1989), the Sava River (up to Sevnica), the 

∨ 

Mura River (up to Mursko Sredisce) ' and the Kupa 

∨ 

(= Kolpa) River up to Krasinee (see Povz & Sket 

1990). 

Annual catches of sterlet in the Danube hetween 

1958 and 1981 varied between 36–117 metric tons 

(average 63.5 metric tons). The highest catches 

were former Yugoslavia (57.5%). followed by Bulgaria 

(28.0%). Romania (10.5%), Hungary (3.5%) 

and former Czechoslovakia (0.5 %) The catch in 

the former USSR was so low that the JCIAFD did 

not record it. The Ðerdap Dams are blamed for decreasing 

the catch of sterlet by 50% (Jankovic' 

1993). 

∨ 

Ongoing construction activities of the Gabcíkovo 

hydropower station further threaten sterlet in the 

uppermost part of the middle Danube and the lower 

course of the Morava River. Tagging performed 

by the second author between 1992 and 1994 re- 

∨ 

∨ 

5 

Tòth, J. 1978. Information of the Hungarian part. pp. 278–287. vealed that the barrages constructed at Cunovo 

In: Materials of the 19th Session of the Joint Commission of the 

lnternational Agreement on the Fishing in the Danube River 

between the Governments of the Soviet Union, Peoples Republic 

of Bulgaria, Peoples Republic of Hungary, Socialistic Repubthe 

ol Romania, Czechoslovak Socialistic Republic and Socialistic 

Federative Republic ol Yugoslavia, Moscow (in Russian). 

6 

Tóth, J. 1979. Information of the Hungarian part. pp. 125–150. 

In: Materials of the 19th Session of the Joint Commission or the 

International Agreement on the Fishing in (the Danube River 

between the Governments or the Soviet Union, Peoples Republic 

of Bulgaria, Peoplca Republic of Hungary, Socialistic Republic 

of Romania, Czechoslovak Socialistic Republic and Socialistic 

Federative Republic of Yugoslavia, Moscow (in Russian). 

7 

Tóth J. 1980. A Magyar fél tájekoztatója (Information of the 

Hungarian part) pp. 129–147. In: Materiály z 22. zasadania 

Zmiesanej komisie pre uplatnnovanie dohody o rybolove vo vodách 

Dunaja. Bratislava. 

∨ 

(river km 1840) and Gabcíkovo (river km 1820) are 

insurmuontable obstacles for the upstream migration 

of any fishes, including sterlet. 

Acipenser stellatus- stellate sturgeon 

The stellate sturgeon was always rare in the middle 

8 

Tóth. J. 1979b. Catch results changes ol the sterlet (Acipenser. 

ruthenus L.) in the Hungarian Dainube pp. 151–157. In: Materials 

of the 19th Session of the Joint Commission of the International 

Agreement on the Fishing in the Danube River between the 

Governments of the Soviet Union, Peoples Republic of Bulgaria, 

Peoples Republic of Hungary, Socialistic Republic of Romania, 

Czechoslovak Socialistic Republic and Socialistic Federative 

Republic of Yugoslavia, Moscow (in Russian).

196 

Danube (Figure 6). It ascended upstream to Komárno 

(Grossingcr 1794, Fitzinger & Heckel 1835. 

Kornhuber 1901). Bratislava (Kornhuber 1863, Orvay 

1902), the Austrian part of the Danube (Fitzinger 

& Heckel 1835), and occasionally even reached 

the Bavarian stretch near Straubing (Gesner 

1575) and the lsar River (Siebold 1863). During 

spawning migrations, stellate sturgeon entered tributaries 

of the lower Danube, such as the Prut, Siret, 

Olt and Jiul rivers (Antipa 1909); it was encountered 

also in some tributaries of the middle Danube. 

such as the Tisza River up to Tokaj (Heckel & Kner 

1858) and in the lower courses of its tributaries the 

Maros and Körös rivers, in the mouth ofthe Zagyva 

River (Herman 1887) and in the lower course of the 

Drava and Sava rivers (Heckel & Kner 1858, Glowacki 

1896, Vutskits 1913). Mahen (1927) mentioned 

stellate sturgeon from the mouth of the Morava 

River. However, this seems doubtful, as it has 

only rarely been recorded in the adjacent stretch of 

the Danube. 

We consider A. stellatus to be extirpated not only 

from the upper Danube but also from the upper 

stretch of the middle Danube (the Slovakian and 

Acipenser nudiventris - ship sturgeon 

The ship sturgeon forms both anadromous and resi- 

dent populations, but in the Danube River, only the 

resident strain occurred (Banarescu 1964, Manea 

1966). This species was recorded in the lower Da- 

nube (occasionally in the Danube delta) and in the 

Hungarian section). The last known specimen from middle Danube. upstream to Bratislava (Figure 7, 

this section was caught at Komárno on 20 February Kornhuber 1863). Only exceptionnally did it mi- 

1926. The head of this specimen, measuring grate to the Austrian segment of the river (Fitzg- 

325 mm, is at the Slovak National Museum in Bra- inger & Heckel 1835). Ship sturgeon also occurred 

∨ 

tislava (Holcík 1959) and is estimated to be from a in some tributaries: the lower course ofthe Váh Riv- 

∨ 

specimen 1282 mm TL and 9.8 kg BW Holcík er (Heckel & Kner 1858, Herman 1887), the Tisza 

1995). The last stellate sturgeon in Hungary (100 cm River at Mándok (Mihályi 1954), the Sava and Dra- 

TL) was caught in the Danube at Mohács in 1965 va rivers (Heckel & Kner 1858, Vutskits 1913, Mun- 

(Pintér1991). 

da 1926), the Maros River (Hankó 1931), and also 

Construction of the Iron Gates dams blocked from two tributaries of the lower Danube, the Prut 

most migration of stellate sturgeon to the middle and Siret rivers (Banarescu 1964). 

Danube, as few individuals succeed in passing Ship sturgeon was never abundant in the lower 

through the shipping locks (Djisalov 9 ). Jankovic' Danube (Manea 1970), although, as Pintér (1991) 

(1993) analyzed catch of stellate sturgeon in the Ser- noted, it is difficult to verify this based on historical 

bian section of the Danube: from 1967–1970, the an- documents, particularly because fishermen did not 

always distinguish larger ship sturgeon from Rus- 

9 

Djisalou. N.1983. Analysis of the migratory sturgeon fishery in sian sturgeon, and small ship sturgeon were conthe 

Yugoslavian part ofthe Danube in 1981 pp. 150–157. In:Materials 

ofthe 24th Session of the joint Commission of the International 

Agreement on the Fishing in the Danube River between 

the Governments of the Soviet Union. Peoples Republic of Bul- 

garia, Peoples Republic of Hungary Socialistic Republic of Romania, 

Czechoslovak Socialistic Republic and SociaIistic Federative 

Republic of Yugoslavia. Moscow (in Russian). 

nual catch was around 1.4–2.0 tons but, in 1971, 

when the first dam was finished, the catch dropped 

to 184 kg. During the next 8 years this species was 

not recorded in the catch. except in 1975 when 

284 kg was caught. In 1980, a catch of 80 kg was reported, 

but after construction of Iron Gates Dam II, 

the stellate sturgeon disappeared from the middle 

Danube catch. At present stellate sturgeon is only 

seldom taken, with an estimated annual catch < 

100 kg. This species was never economically significant 

in the middle Danube, with a mean annual 

catch of only 7.8 tons in 1958–1981. Of this, 34.2% 

was shared by Bulgaria, 22.7%, by the former 

USSR, 22.5% by former Yugoslavia and 20.6% by 

Romania (data from JCIAFD). 

› 

› 

fused with sterlet. The ship sturgeon is now very 

rare in the Danube, and only occasionally found in 

the catch of Romania and Serbia (Manea 1970, Bacalbasa-Dobrovici 

1991, Stamenkovic' 

1991. Jankovic' 

1993). Ship sturgeon completely disappeared 

from the Austrian and Slovak segment of the Da- 

› 

›

the first draft of this paper and to D. Matichova for 

technical assistance. Two anonymous reviewers 

provided helpful comments, and W.E. Bemis extennube, 

and in the Hungarian section it is extremely 

rare. The largest specimen recorded (170 cm TL 

and 32 kg BW) was taken at Ercs in 1932 (Pintér 

1989). sively revised the text. 

From tributaries of the middle Danube, ship sturgeon 

is known only from the Tisza and Drava rivers. 

Vásàrhely (1957) reported many juveniles of ship 

sturgeon from the upper segment of the Tisza River 

at the Tiszalök Dam and suggested that adults are 

rare. Pintér (1991) recorded one specimen caught in 

August 1975 (about 70 cm in TL) in the Tisza River 

near Kiskör and other two specimens taken in the 

Tisza River at Tiszalök (however, their identification 

is questionable). From the Drava River one 

male 147 cm in TL, 20.5 kg BW was taken at Heresznye 

in August 1989 (Pintér 1991,1994). The ship 

sturgeon in the Danube River basin is Critically endangered. 

Conclusions 

Anadromous populations of beluga, Russian sturgeon 

and stellate sturgeon, represented by winter 

races, were heavily damaged by overfishing during 

previous centuries, and were then completely elim- 

inated from the middle and upper Danube by con- 5–121. 

struction of Ðerdap I and Ðerdap II dams (Iron 

Gates Dams I and 11). Small stocks of the resident 

races of ship and Russian sturgeons occur in the 

middle Danube and some of its tributaries. The 

most abundant sturgeon in the Danube is the sterlet, 

but this species also experienced population declines. 

It disappeared from almost all of the upper 

Danube, where single specimens are now found 

only in its Austrian part. At present the sterlet is 

limited to the middle Danube and to lower courses 

of some tributaries. 


We thank Vadim Birstein, John Waldman and Robert 

Boyle for arranging for one of us (Hensel) to 

travel to participate in the International Conference 

on Sturgeon Biodiversity and Conservation. 

Special thanks to E.K. Balon for his comments on 

197 


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Environment Biology of Fishes 48: 201-207, 1997. 

©1997 Kluwer Academic Publishers. Printed in the Netherlands. 

Endangered migratory sturgeons of the lower Danube River and its delta 

Nicolae Bacalbasa-Dobrovici 

University ‘ Dunarea de jos’ Galati, Str. Domeneasca 47, 6200 Galati, Romania 


Key words: Acipenser, Huso Black Sea, anthropogenic factors, Iron Gates Dam I, Iron Gates Dam II, 

eutrophication, hypoxia, Mnemiopsis 

Synopsis 

Historically, five acipenserid species migrated from the Black Sea into the Danube River: beluga Huso huso, 

Russian sturgeon Acipenser gueldenstaedtii, stellate sturgeon A. stellatus, ship sturgeon A. nudeventris and 

perhaps European Atlantic sturgeon A. sturio. The freshwater sterlet A. ruthenus thrived in the Danube and 

its tributaries. Presently, only three anadromous species occur in the Romanian part of the Danube, Huso 

huso, A. gueldenstaedtii and A. stellatus, while A. ruthenus lives in the Danube and its tributaries. Extreme 

depletion in the number of sturgeons was caused by many, primarily anthropogenic, factors which affected the 

Danube and the Black Sea shell during recent last decades. Measures necessary for saving anadromous sturgeon 

species in the lower Danube are recommended. 

Introduction 

The Danube is the second longest river in Europe 

(2857 krn). It is divided into three main regions: the 

upper Danube from the source to Vienna (890 km 

river length), the middle Danube from Vienna to 

Iron Gates Darn I (993 km river length), and the 

lower Danube from Iron Gates Dam I to the mouth 

(942 kin river length). Thirty-five dams have been 

constructed on the upper Danube. The middle Danube 

was cut off from the lower Danube by construction 

of Iron Gates Dam I, built in 1970 (Figure 

1). In 1984, the lower Danube was divided by the 

Iron Gated Dam II, located 80 km downstream 

from Iron Gates Dam I. 

Until quite recently, five anadromous species of 

sturgeons migrated lrom the Black Sea into the Danube 

for spawning: the beluga, Huso huso, Russian 

sturgeon, Acipernser gueldenstaedtii, stellate sturgeon 

or sevruga, A. stellatus, ship sturgeon, A. nudiventris 

and perhaps Atlantic sturgeon, A. sturio 

∨ ∨ 

(Antipa 1916,1933, Banarescu 1964, Bacalbasa-Dobrovici, 

1989). In the 19th century, sturgeons swam 

upstream to Bavaria (Terofal1980). The exclusively 

freshwatcr sterlet, A. ruthenus, also thrived in the 

∨ ∨ 

Danube and its tributaries(Banarescu 1964, Bacalbas-Dobrovici 

1989). Presently, only Huso huso 

A. gueldenstaedtii and A. stellatus occur in the Romanian 

part of the Danube and their populations 

are impacted greatly by the dams and other installations 

(Bacalbasa-Dobrovici 199la, b). Acipenser 

ruthenus now lives priinarily in the middle Danube 

and its tributaries. This paper reviews the depletion 

of populations of anadromous acipenserids in the 

lower Danube and discusses factors causing decreases 

in sturgeon populations in the Danube and 

Black Sea. The status of sturgeons in the upper and 

middle Danube is described by Hensel & Holcík 

∨ 

(1997 this volume).

202 

Figure 1. Map of the lower and portions of the middle Danube River and some major tributaries to show features related to sturgeon 

populations and migrations. 

Sturgeon fisheries from ancient times to the 20th Dravo, Sava, Tizsa, Muresh, Siret, and Prut rivers 

century (Figure 1). 

In the 12–15th centuries, sturgeons were exported 

From ancient times, sturgeons had great economic from the Danube area to Poland (Giurescu 1964). In 

importance in the Danube River region and were 1409, Mircea the Great (prince of Vallachia) orthe 

basis of the population’s wealth. Sturgeons of dered all inhabitants of the villages located along 

the Danube were mentioned by ancient Greek writ- the Danube to catch sturgeons three days a year for 

ers, Herodotus (484? – 425? B.C.) and Strabo (63? the court. The Italian monk Niccolo Barsari, who 

B.C. – 21? A.D.). Strabo wrote: ‘In the Scythian visited Moldavia in 1633–1639, mentioned that fishnorth, 

sturgeon are caught and they are as big as emen brought 1000–2000 sturgeons to Chilia every 

dolphins’ (translation from Strabo 1853). In Histria day. From here they were exported to Constantino- 

(a Greek port which existed 2200 years ago) the in- pole, Poland, and Hungary. In 1690, the Austrian 

habitants were allowed to fish in the Danube mouth general Marsigli wrote that about 50–100 beluga 

and to export salted fish to Greece and Rome with- were caught every day near Adakaleh Island (now 

out charge. Most of the exported fish were beluga submerged). In 1762, the French consul Peysonnel 

and Russian sturgeon. 

reported that about 25 000 beluga were caught an- 

In the Middle Ages and until the end of the 18th nually in Chilia (Giurescu 1964). 

century, sturgeons were an inexhaustible resource Beginning in the 16th century. the town of Galati 

of the river (Giurescu 1964). Beluga were caught all on the lower Danube was an important sturgeon 

along the Romanian part of the Danube (from the fishing and market center. An Italian monk, Barsi, 

mouth to the Iron Gates), in the middle Danube mentioned Galati as having a great abundance of 

and upstream up to Bavaria. Sturgeons thrived also different sturgeons and caviar. In 1646, another Italin 

tributaries of the lower Danube including the ian, Bishop Bandini, wrote: ‘Large beluga are

203 

caught here. You would not believe it if you have 

not seen it with your own eyes’ (Giurescu 1964). In 

1652, the traveler Robert Bargrave also noted that 

‘sometimes they catch such a big fish that they need 

6–8 oxen to lift them together with a trap’. 

Since the Middle Ages, sophisticated gear has 

been used for catching sturgeons and beluga in the 

lower Danube. Methods included fences made of 

wooden branches and provided with small gates for 

ships to pass through and big cage-like traps for 

sturgeons. The fence was attached to wooden poles 

placed into the river bed. Each installation lasted 

about seven months and was remade each spring 

because ice destroyed the fence and traps. Each site 

was operated by a team of 100-200 persons who 

lived nearby on special platforms. 

Fourteen such installations near Chilia caught 

1000-2000 sturgeons daily. In the 16th century, additional 

installations were located near the town of 

Ismail in the Danube delta (92 km from the mouth. 

Chilia Branch), in tlie Borcea Branch (from 248 to 

370 km upstream), and in the Hungarian part of the 

river. In the Iron Gates zone sturgeons were caught 

by traps and iron baskets (Bacalbasa-Dobrovici 

1971). 

Because of intensive fishing, declines in the populations 

of sturgeons were reported beginning in 

the early 19th century. In 1835. J. de Hagemeister 

wrote that beluga were much less abundant in the 

Danube (Giurescu 1964). In the 20th century, the 

catch of sturgeons in Romania (the lower reaches of 

tlie Danube River) chopped catastrophically and 

now the harvest is extremely small (Figure 2): only 

11.5 metric tons in 1994 compared to about 200 metric 

tons per year in the 1960s (Bacalbasa-Dobrovici 

1991b). Not only the size, but also the structure of 

sturgeon populations in the Danube River changed 

dramatically. Individuals are much smaller and 

younger than in the past. Acipenser sturio disappeared 

from the sea catch, and there is a noticeable 

decrease in the numbers of Huso huso, A. guelden 

staedtii and especially A. nudiventris Also, the populalion 

size of A stellatus has decreased. Besides intensive 

fishing, other aspects of human activities 

have negatively impacted Danube River sturgeons, 

including deforestation, construction of hydrotechnical 

installations and dams, and pollution. 

Figue 2. Decrease in the sturgeon catch in Romanian part of the 

Danube River. Data for 1960s through 1980s are from Bacalbasa- 

Dobrovci (1991b). 

Anthropogenic factors in the 20th century decline 

of Danube sturgeons 

Deforestation 

During the Middle Ages, forests located on the 

banks of the Danube River regulated the water level, 

and floods were rare. At the end of the 18th century, 

logging was officially encouraged, and persons 

who cut the trees were allowed to cultivate the 

cleared land. As a result, forested areas in Romania 

diminished from 55–60% in 1830 to 27% in 1930. 

Similar processes occurred in neighboring countries: 

in the Czech and Slovak Republics, only 34%, 

and in Bulgaria, only 29% of the historically forested 

areas now exist (Botzan 1984). Deforestation increased 

alluvial deposits, and water turbidity, which 

affected the sand, gravel and rock bottom of sturgeon 

spawning grounds. 

Dikes and dams 

Flood plains of the Danube changed drastically 

when dikes were built. Historically, the lower Danube 

flood plain included areas adjacent to the river 

(573 000 ha) and the delta (524 000 ha). At present, 

about 85% of the flood plains have been diked 

(Botzan 1984). The delta was diked to a lesser extent, 

and this stopped after the collapse of the communist 

regime (1989) for ecological reasons.

204 

About 300 reservoirs in the Danube Basin were threaten to further alter the flow of the lower Daformed 

by damming. These lakes retain some allu- nube. Fortunately, of all proposed projects (i.e., Levial 

deposits, especially large particles, and affect vintov 1988), only the Rhine-Main-Danube Canal 

water levels in the Danube, which is 0.6 m higher has been constructed. This canal uses water 

than in historical times, and water velocity, which is pumped into it from the Danube. 

slower in the riverine lakes region. In 1970, completion 

of the Iron Gates Dam I located 862 km upstream 

from the Danube mouth prevented sturgeons 

Diminishing role of the Danube Delta as a biofilter 

from reaching their historic spawning sites. 

Iron Gates Dam II, 80 km below the first project, 

shortened the possible migration to 862 km A joint 

Bulgarian-Romanian dam at Turnu Magurele-Nicopol 

is planned, which would reduce the possible 

sturgeon migration to 265 km. 

Pollution 

Water pollution by heavy metals and pesticides in 

the lower Danube is very high (Oksiyuk et al. 1992) 

and it affects the entire biota (Pringle et al. 1993). 

No specific data are available on its impact on sturgeons, 

however. 

lrrigation and gravel excavation 

Water quality in the lower Danube is degraded by 

massive irrigation schemes. In Rumania, three million 

hectares of irrigated land decreases river flow 

and increases pollution by fertilizers and pesticides. 

Eutrophication now impacts the northwestern area 

of the Black Sea. Irrigation pumps kill fish larvae 

and juveniles. Sand and gravel taken from the Danube 

bed for construction work in the area near 

Calarasi (373 km) has destroyed sturgeon spawning 

grounds. 

The Danube Delta is an essential biofilter for the 

entire region. Also, it is the area of the contact of 

fresh riverine water with the brackish water of the 

Black Sea. Changes in water flow and circulation 

modified the whole ecosystem of the Danube Delta 

and affected its biofiltcr abilities. Poorly planned 

aquaculture and agriculture projects damaged the 

delta. Formerly, the Danube Delta was the largest 

area of reeds in Europe (almost 300 000 ha), a major 

component of its biofilter capacity. Unfortunately, 

13.4% of the delta area (61 604 ha) was transformed 

into agricultural land during the communist regime 

(1948–1989). Attempts to cultivate reeds in a part of 

the delta created more problems because the heavy 

equipment which was used destroyed rhizomes of 

the natural reeds causing decreases in their area. Illconceived 

attempts at fish aquaculture on 53 000 ha 

of the delta failed, adding negative impacts on the 

biofilter capacity of the delta. 

As a result of all these changes, eutrophication 

and turbidity increased in the delta, while biodiversity 

decreased, which in turn adversely affected the 

shelf area of the Black Sea. This shelf is crucial for 

sturgeons in the northwestern part of the Black Sea 

because this is where sturgeon live during the marine 

period of their life cycle. 

Changes in the Black Sea 

Water losses due to hydrotechnical constructions 

Brackish water areas in the mouth of the Danube 

River and the northwestern part of the Black Sea 

depend primarily on flow in the Danube River, but 

natural flow is decreased by dams and irrigation. 

Other projects, such as shipping canals and junctions 

between different river branches in the delta. 

Geologic origin 

The Black Sea has a long geological history, which 

has greatly impacted acipenserids. Originally a part 

of the Tethys Sea during the Upper Miocene (circa 

20 MYBP), the Black Sea later, together with the 

Sea of Azov, Caspian and Aral seas, formed the Sarinatic 

(or Paratethys) Sea which covered the area

205 

from the Vienna basin to the Ural Mountains. In the 

Pliocene, the Samnatic Sea was reduced to the 

smaller Pontic Sea, which included the three contemporary 

basins, the Aral, Caspian, and Black 

seas. During the Quaternary, these three basins separated. 

In the Pliocene (about 5 MYBP) the Strait 

of Gibraltar opened, and water from the Atlantic 

refilled the Mediterranean, which had been dry for 

about 1–2 million years. Eventually, the Mediterranean 

became reconnected with the Black Sea. 

At present, water in the Black Sea is only half as 

salty as the Mediterranean Sea. The Black Sea water 

is divided into two strata. Due to the lack orvertical 

circulation, the lower stratum is abiotic. Within 

the surface stratum, the northwestern area is greatly 

impacted by three rivers: the Danube (which provides 

more than a half of the fresh water flowing 

into the Black Sea), the Dniester, and the Dnieper 

(together with the Bug River). This highly productive, 

low salinity zone is a good environment for the 

marine life of sturgeons. 

The northwestern shelf of the Black Sea 

Sturgeons migrating into the Danube River spend 

most of their life on the northwestern shelf of the 

Black Sea. The shelf is characterized by shallow watcr 

and a relatively flat bottom. Young sturgeon live 

and grow in this area, and adults return there after 

spawning in the Danube. Beluga feed mostly on 

fishes, while Russian and stellate sturgeons eat benthic 

invertebrates. During the last three decades, 

major changes in the biological equilibrium of the 

Black Sea occurred, affecting primarily the biota of 

the northwestern shelf. 

Pollution 

Pollution in the Black Sea is from tens to hundreds 

of times higher than that in the Atlantic or Pacific 

oceans and it is even higher than in the Mediterranean: 

20 000 and 3775 kg km –3 of polluting agents in 

waters of the Black and Mediterranean seas respectively 

(Zaitsev 1992, 1993). Worse still, pollution is 

essentially perilittoral due to the perilittoral current 

in the Black Sea. 

Eutrophication 

Eutrophication of coastal waters had a serious inpact 

on the Black Sea. Between the 1950s and the 

1980s, the quantity of nutrient and organic substances 

brought by the Danube, Dnestr and Dnepr 

rivers into the Black Sea increased 400–500% (Table 

I; see also Zhuravleva &Grubina 1993), causing 

intensive growth of phytoplankton from 670 mg m –3 

(1950s) to 30 000 mg m –3 (Zaitsev 1991, 1993). The 

biomass of the jellyfish Aurellia aurita increased 

enormously from 1 million metric tons in the 1960s 

to 300–500 million metric tons in 1980. A simultaneous 

decline in the number of large planktonic crustaceans 

and planktophagous fishes occurred. Eutrophication 

also diminished water transparency by 

50 to 80 percent and caused a drastic change in the 

benthic flora (Zaitsev 1992). 

Effect of fish trawling 

Bottom trawling devastated main areas of sturgeon 

habitat in the northwestern shelf and the Danube 

mouth. Over a 50 year period beginning in the 

Table 1. Input of nutrient chemicals from the rivers entering into the northwestern part of the Black Sea (all values in parts million –1 data 

froin Zaitsev 1992). 

Danube River Dnestr River Dnepr River 

1950 1986 I950 I986 I950 1986 

Organic substances 2000 9800 100 246 250 664 

Phosphates 13.00 50.00 0.14 1 .00 0.80 4.00 

Nitrates 97 238 2 13 55 89

206 

1930s, the macrozoobenthic fauna near the Crimea 

decreased from 38 to 11 species, and their density 

diminished from 245 to 99 individuals m –2 (Zaitsev 

1992). 

Temporary hypoxic areas in the northwestern shelf 

Sturgeon survival in the lower Danube and Black 

Sea: the social context 

Since 1878 (the year of the Berlin Peace agreement) 

the lower Danube and the Danube Delta 

have been under the control of the Romanian state. 

For a long time, overfishing of sturgeons in this area 

was extensive. During the communist regime 

(1948–1989), the centralized economy did not con- 

sider ecological criteria in the sturgeon fishery. The 

situation, however, has not yet improved in the 

post-communist period. Moreover, fishing permits 

have increased, resulting in a lack of information 

about the extent of the catch, which is now extreme- 

ly extensive in Romania. The Danube Delta Bio- 

sphere Reserve (Gâistescu 1993), in which fish har- 

vest is controlled, is a lucky exception to the generally 

uncontrolled situation. It is very difficult to or- 

ganize protective measures for sturgeons in the 

lower Danube, and all species, especially Huso huso 

Eutrophication caused a new phenomenon, the appearance 

of temporary hypoxic areas, first noticed 

in August–September 1973. This hypoxic area affccted 

3500 km 2 between the Danube Delta and the 

Dnestr estuary (Zaitsev 1991,1993). Since then, hypoxia 

has occurred periodically in the 10–40 m 

depth regions. Biological losses due to hypoxia between 

1973 and 1990 were estimated at 60 million 

metric tons, including 5 million metric tons of fishes 

(Zaitsev 1993). Because of this destruction and perodic 

repopulation of the northwestern shelf area, 

molluscs and other benthic rood organisms are represented 

by mostly young individuals. Besides and Acipenser gueldenstaedtii should be considthreatening 

the survival of young sturgeons, hypox- ered as threatened or endangered in Romania. 

ia caused changes in populations of prey species in- Considering all of the negative conditions for 

habiting their feeding grounds. 

sturgeons migrating into the Danube River, the following 

conservation measures are recommended: 

(1) an end to fishing in the lower Danube: (2) research 

on the survival of young sturgeons in the 

Explosive growth of the ctenophore Mneimiopsis leidyi 

contemporary conditions of the lower Danube and 

the Black Sea: (3) restocking of the endangered 

sturgeon species; (4) conservation (cryopreservation) 

of genetic materials of sturgeons from the Danube 

populations. 1 

The American comb jellyfish Mnemiopsis leidyi (or 

M. maccradyi according to Zaika & Sergeeva 1990) 

seems to have been introduced into the Black Sea in 

1982 with the ballast water from ships: before this, it 

inhabited the North American Atlantic waters (Vinogradov 

et al. 1989, Travis 1993). In such an isolated 

marine basin with a depauperate fauna as the 

Black Sea, M. leidyi does not have competitors and 

its biomass grew very fast so that in August–Scptember 

1989 there were 800 million metric tons of 

this predator, which feeds on zooplankton, pelagic 

fish eggs, embryos and larvae (Zaitsev 1992). The 

abundance of M. leidyi produced a complete collapse 

of the anchovy fishery in the Sea of Azov in 

1989. Changes in the faunal structure and distribu- 

1 

Since this paper was written a new five year project entitled 

‘RecoveryProgram of the Danubian Anadromous Migratory 

Sturgeons’ began in 1995 funded by the Romanian Ministry of 

Research . . and Technology and a grant of the Global Environment 

Trust Fund administrated by the World Bank [The Edi- 

tors]. 

tion of invertebrates caused by M. leidyi (Kovalev 

et al. 1994) indirectly impact sturgeons. 


I thank Vadim Birstein and John Waldman for inviting 

me to participate in the International Conference 

on Sturgeon Biodiversity and Conservation. 

Two anonymous reviewers commented on my original 

draft. The English text was substantially revised

and improved by Vadim Birstein and William E. 

Bemis, who also drew the map and figure. 


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Sturgeons from the Danube river (Black Sea) collection at the ‘Grigore Antipa’ Natural History Museum, Bucharest: a – Acipenser 

gueldenstaedtii146 cm TL from Antipa’s personal working depository assembled at the turn of the century. Note the rare lack of medium 

sized denticles in the dorso-lateral region. b–A. nudiventris 104 cm TL, and c – A. stellatus 109 cm TL from 1940 in the same collection (all 

wet preserved). Originals by Paul Vecsei, 1996.



Present status of commercial stocks of sturgeons in the Caspian Sea basin 

Raissa P. Khodorevskaya, Galina F. Dovgopol, Olga L. Zhuravleva & Anatolii D. Vlasenko 

Caspian Fisheries Research Institute, 1 Savushkina st., Astrakhan 414056, Russia 


Key words: beluga sturgeon, Huso huso, Russian sturgeon, Acipenser gueldenstaedtii, stellate sturgeon, Acipenser 

stellatus, population size, artificial propagation, pollution, poaching 

Synopsis 

Catches for the last 25 years are analyzed for beluga Huso huso, stellate sturgeon A. stellatus and Russian 

sturgeon Acipenser gueldenstaedtii, which are the three commercially important species of sturgeons found in 

the Caspian Sea Basin. Population sizes for generations born between 1961 and 1970 are estimated, and found 

to depend on natural reproduction and the number of young fish stocked annually from sturgeon hatcheries 

located in the Volga River Delta. A ban on sea fishing from 1962 to 1991 positively impacted the number and 

total biomass of commercial stocks. Sturgeon growth rates depend on water levels in the Caspian Sea. In order 

to preserve Caspian Sea sturgeon populations, it will be necessary to coordinate efforts of all countries surrounding 

the Caspian Sea to achieve rational harvests, preserve juveniles, and produce at least 100 million 

juveniles annually from hatcheries. 

Introduction 

Recently, 80 to 90 percent of the world’s sturgeon 

catch was taken from the Caspian Sea Basin, mainly 

from the Volga River (Barannikova et al. 1995). The 

Volga River and Caspian Sea are home to three 

commercial species, the beluga (Huso huso, see Pirogovskii 

et al. 1989), Russian sturgeon (Acipenser 

gueldenstaedtii, see Vlasenko et al. 1989a), and stellate 

sturgeon (A. stellatus, see Shubina et al. 1989), 

in the Russian (northern) part of this basin. A 

fourth commercial species, the Persian sturgeon (A. 

persicus, see Vlasenko et al. 1989b), inhabits mostly 

the southern (Iranian) part of the Caspian Sea and 

the rivers entering into it. Acipenser persicus is not 

discussed in this paper because of lack of data. 

The natural reproduction of commercial sturgeon 

species decreased in the Volga River after the 

Volgograd Dam was built between 1958 and 1960 

(Figure 1). The dam prevents sturgeons from reaching 

their main spawning grounds. At present, the 

Ural River is the only large river entering the northern 

part of the Caspian Sea in which natural reproduction 

still occurs. Sturgeons no longer use the Kura 

and Terek rivers, where spawning previously occurred 

(Berg 1948). In this paper, we report on population 

changes in sturgeon stocks in the Caspian 

Sea from the early 1960s until 1994 based on data 

published in Dyuzhikov (1960), Shilov (1966), Khoroshko 

(1967,1970), VIasenko (1979,1990), Slivka et 

al. (1982), Khodorevskaya (1986,1992), Veshchev & 

Novikova (1988), Veshchev (1991a, b), Veshchev et 

al. (1992), Raspopov (1992, 1993), Dovgopol et al. 

(1993), Novikova (1993), Raspopov et al. (1994), 

Khodorevskaya et al. (1995), and Levin (1995). Also, 

the present status of natural reproduction in the 

Volga and the Ural rivers is described.

210 

Figure1. Map showing lower portions of the Volga and Ural rivers, northern part of the Caspian Sea, and adjacent regions referred to in 

text. Other river systems historically used by the three commercially important species of sturgeons (Huso huso, Acipenser stellatus, and 

A. gueldenstaedtii) are labeled. 

Harvest trends during the last 40 years 

Prior to 1951, commercial sturgeon fishing concentratedin 

the Caspian Sea (Korobochkina 1964). Following 

recommendations to concentrate harvest to 

only the lower reaches of the Volga River (Derzhavin 

1947), a ban on sea harvest was instituted. The 

only sturgeon taken in the Caspian Sea were as a 

by-catch to other fishes. The introduction of plastic 

nets in the late 1950s for harvest in the Caspian Sea 

greatly increased in the number of young sturgeons 

caught as by-catch. In 1957, of the total 2.6 million 

sturgeons harvested in the northern Caspian Sea, 

1.8 million were young sturgeons, and in 1959–1961, 

the by-catch of young sturgeons reached 2-3 million 

(Korobochkina 1964). From 1962 until 1991, 

sturgeons were not harvested legally in the northern 

part of the Caspian Sea. 

For the last 35 years, natural and artificial reproduction 

contributed to the total commercial sturgeon 

stock in the Caspian Sea (Barannikova 1995). 

Sturgeon population sizes also depend on the volume 

of harvest, the construction and operation of 

dams, water consumption for irrigation and industry, 

and impacts of pollution. All three commercially 

important species of sturgeons now have fewer 

spawning fish migrating into the Volga and Ural rivers 

than in the past. Russian and beluga sturgeons 

no longer use the Kura, Terek and Sulak rivers, although 

small runs of stellate sturgeons still enter into 

the Terek and Sulak rivers to spawn. 

The Volga River and its delta are the most important 

areas in terms of commercial harvest. About 

75% of the total sturgeon catch in the Caspian Sea 

basin comes from this area, with Russian sturgeon 

providing 60–70% of this total. Until recently, stellate 

sturgeon made up about 30% of the catch in the 

Volga River. Beluga constituted 5.0–6.0% of the 

catch. Between 1976 and 1981, Russian sturgeon 

were taken about four times more frequently than

211 

Population changes and status 

Beluga 

Figure2. Sturgeon catch in the northern part of the Caspian Sea 

in thousands of metric tons. Catches for stellate sturgeon (Acipenser 

stellatus) and Russian sturgeon (A. gueldenstaedtii) 

peaked in the 1970s. when catches of beluga (Huso huso) were 

already in decline. 

beluga and stellate sturgeons, whereas in the early 

1960s, this was only one and one half times. Harvest 

figures (in thousands of metric tons) are shown for 

selected years for each of the three species (Figure 

2). 

Historically, beluga were harvested more intensively 

than were Russian and stellate sturgeons (Korobochkina 

1964). For the last 35 years, the number of 

spawning adult beluga has decreased. In the early 

1970s, about 25 000 individuals with a total weight 

2600 metric tons migrated into the Volga River. In 

recent years, the number of spawning fish harvested 

did not exceed 11 700 individuals weighing a total 

750 metric tons. Commercial catch of beluga decreased 

from 2000 metric tons in the early 1970s to 

less than 500 metric tons at present. In the early 

1970s, 21% of spawning beluga sturgeon migrating 

into the Volga River reached the spawning grounds. 

In 1976, 36–40% of spawning beluga reached the 

spawning grounds, but the number of fish reaching 

the grounds remained at 4000–6000 individuals. 

Declines in the number of belugas occurred after 

construction of a series of hydroelectric damson the 

Volga River in the late 1950s (Frantsuzov 1960). Beluga 

no longer can reach their historic spawning 

grounds because their movements are blocked by 

the Volgograd Dam (Figure 1). Beluga now spawn 

downriver from the city of Volgograd, in reaches in 

which they did not spawn previously. In the past, the 

migration distance for juveniles was much longer 

(originating from spawning grounds far above Volgograd), 

and juveniles grew to a larger size in the 

Figure 3. Releases of sturgeon juveniles produced by hatcheries located in the northern part of the Caspian Sea.

212 

212 

Figure 4. Estimated numbers of sturgeons in the Northern Caspian Sea from the Volga and Ural river populations. 

river than they do now. These changes resulted in 

decreases in natural reproduction in the Volga River 

and in changes in the population structure of this 

species. 

In response to this decline in natural reproduction, 

the Soviet government began a program in the 

early 1960s to enhance sturgeons through artificial 

propagation (Barannikova 1995). Throughout the 

1960s, more than 3.9 million beluga juveniles were 

released from hatcheries annually. In the 1970s, the 

annual release reached more than 12.9 million 

young, and by the early 1980s, the average number 

of the young belugas released into the Volga River 

was 19.4 million (Figure 3). At present, practically 

all beluga (96.3%) in the Volga River consist of 

hatchery propagated fish (Khodorevskaya 1986, 

1992). However, artificial propagation does not 

completely compensate for the loss of natural reproduction 

of beluga in the Volga River. The population 

of beluga continues to decline even though 

the number of beluga harvested does not exceed 

0.1% of the number of individuals released. 

Spawning sites for beluga in the Ural River remain 

intact and the Ural River stock of beluga is 

replenished by natural reproduction. Until the late 

1970s, the number and biomass of beluga migrating 

into the Ural River was considerably smaller than 

that migrating into the Volga River (Figure 4).

However, since 1979, the number of beluga entering 

the Ural River has exceeded the number entering 

the Volga River. The ban on sturgeon harvest from 

the Caspian Sea enacted in the 1960s contributed 

greatly to the increase in the number of spawning 

beluga that migrate into the Ural River. 

The biomass of beluga from the 1952 through 

1976 generations, which took part in spawning during 

the years 1978 through 1987, grew from 2800 to 

4000 metric tons. In 1990, about 14000 individuals 

migrated into the Volga River from the sea. Approximately 

35% were females and males which 

were spawning for the first time (11–17 years old), 

60% of the fish were spawning for the second time 

(18–30 years old), and the remaining 5% were 31–52 

year old individuals (Table 1). The present commercial 

catch targets 14–22 year old individuals from 

1966 to 1974 spawnings. Catches in the near future 

will be based on fish spawned between 1970 and 

1978. 

The size of the beluga population in the Caspian 

Sea is small, and the number of fish migrating into 

the Volga River is low. The commercial catch of beluga 

is expected to remain low because conditions 

in the Caspian Sea are unfavorable (see below). 

Stellate sturgeon 

213 

number of stellate sturgeon harvested varies from 

194 000 in 1967 to 884 000 in 1986. From 85 000 to 

388 000 individuals (20–44% of the total number of 

spawning stellate sturgeons migrating into the Volga 

River) reached the spawning grounds below the 

Volgograd Dam. Many stellate sturgeon reached 

spawninggrounds in1978,1979,1983, and1985–1988 

(616 000–884 000 individuals. Figure 4). Harvests 

varied from 3870 metric tons in 1960 to 4550 metric 

tons in 1986. 

The spawning stock of stellate sturgeon migrating 

into the Volga River in the late 1980s consisted 

of fish either spawned after regulation of the Volga 

River flow or from fish released from hatcheries. At 

present, the generations hatched between 1972 and 

1978 dominate the catch. The largest stock reported 

consisted of 15.7% first-time-spawners, 72.9% second-time-spawners, 

and 11.4% older individuals 

(Table 1). An increase in the number of spawning 

stellate sturgeon migrating into the Volga River in 

the late 1980s could be due to stabilization of natural 

reproduction in this species. 

From the late 1960s until 1985, fewer stellate sturgeon 

have entered the Volga River (approximately 

500 000 on average) than the Ural River (800 000- 

1300 000, Figure 4). The number of stellate sturgeon 

decreased in the Ural River because of overfishing 

and insufficient annual recruitment, and between 

1986 and 1992, stocks have declined sharply 

Stellate sturgeon still have natural spawning in both rivers. In 1992, the Ural River population 

grounds below the Volgograd Dam, and 60% of was only one-third of the number observed in 1986. 

their historic spawning sites remain intact. The 

Table 1. Changes in the percent composition of spawning populations of sturgeons in the Volga River during the last 35 years. 

Species and characteristics 1965 1980 1985 1991 

Beluga sturgeon 

1st-time-spawners 30 34 41 35 

2nd-time-spawners 67 60 50 60 

Older individuals 3 6 7 5 

Stellate sturgeon 



Older individuals 10 16 22 37 

Russian sturgeon 



Older individuals 28 12 14 12

214 

The number of spawning fish in the Ural River is 

critical for the survival of this population. 

Russian sturgeon 

The tonnage of Russian sturgeon harvested from 

the Volga-Caspian stock increased from 1961 to 

1977. The increase in harvest followed the 1962 ban 

on sturgeon fishing in the Caspian Sea. The number 

of Russian sturgeon harvested increased from 

480 000 in 1950 to 3 746 800 in 1974, and tonnage increased 

more than 8 times. For 20 years, from 1966 

until 1985, the number of spawning fish harvested 

remained more than one million individuals. During 

that period, the catch was based on fish hatched 

between 1935 and 1961, before Volga River flow became 

regulated by dams. Beginning in 1978, the 

number of fish harvested decreased to 766 600 (Figure 

4c) and their tonnage declined to 16 300 metric 

tons. The decline followed a sharp decrease in natural 

reproduction, because as much as 80% of the 

spawning grounds for Russian sturgeon became unavailable 

to the fish after the Volgograd Dam was 

built in 1958–1960. The number of individuals harvested 

from the 1959–1960 generations was 691 500– 

730 000, and that from the 1965–1968 generations 

was 461 000–600 000. 

The age structure of the fish migrating in the Volga 

River has also changed (Table 1). In the early 

1960s, the run consisted of 8–l2% first-time-spawners, 

62–75% of second-time-spawners, and l6–28% 

of older fish. During peak years (1966–1985), second-time-spawners 

(68–78%) and older individuals 

(10–18%) prevailed. This phenomena continued 

until the early 1990s (Table 1). At present, older individuals 

dominate the run (approximately 50%), 

while first time spawning fish constitute around 

11%. 

Natural reproduction plays an important role in 

the formation of the present Russian sturgeon 

stock. After the Volga River flow became regulated 

in 1959, natural reproduction decreased from 7500 

metric tons in 1960 to 3000 metric tons in 1981–1985. 

In the early 1990s, natural reproduction decreased 

to 830 metric tons because of the low number of 

sturgeons reaching the spawning grounds. 

Factors affecting sturgeon stocks 

Effects of sea level on sturgeon growth 

Fluctuations in water levels in the Caspian Sea and 

consequent changes in salinity impacted sturgeon 

stocks. Fluctuations impact accessibility to feeding 

sites, the abundance of food organisms at these 

sites, and the concentration and distribution of sturgeons 

in the sea. We used the rate of weight gain to 

estimate the effect of sea level fluctuations. 

Changes were seen in beluga that returned to rivers 

to spawn. Beginning in 1970, the sea level decreased 

until, in 1977, it reached a minimum at 29 m, 

a previous lowest level which also occurred in 1936– 

1937. Starting in 1972, the relative rate of weight 

gain in beluga began to decrease. The relative 

weight gain decreased more in males than in females. 

Once sea level began to rise in 1978, beluga 

spawners continued to show a decrease in relative 

weight. In the early 1970s, the average weight of beluga 

females was 110 kg, and in 1990–1991, it was 

only 57 kg. The sex structure of the spawning stock 

of beluga also has changed, with females now (1991) 

constituting 21 to 24% of the stock as opposed to 

twice that percent in the 1960s. 

The rise in sea water level since 1978 was correlated 

with an increase in the growth rate of stellate 

sturgeon. A sharp drop in growth rate in 1989 may 

be due to high levels of pollution in the Volga River 

and the Caspian Sea. The discharge of toxic chemicals 

caused deaths of stellate sturgeon in the river 

and negatively impacted sturgeon feeding in the 

Caspian Sea (Khodorevskaya et al. 1995). 

Russian sturgeon are less tolerant of high water 

salinity than are stellate sturgeon. Optimal conditions 

for growth of Russian sturgeon are: salt concentration 

of not more than 10, an abundance of 

brackish water prey organisms, and extended opportunity 

for juveniles to live in the river. Between 

1967 and 1978, the relative rate of growth of Russian 

sturgeon returning as spawners decreased sharply 

with minimum weight gains from the 1970-1980s. 

Lukyanenko et al. (1986) considered that the relative 

increase in salinity negatively impacted the 

growth rate of Russian sturgeon in the 1970s.

215 

Influence of dams on natural reproduction 

construction of a series of hydroelectric dams in the 

middle reaches of the Volga River in the 1950s 

blocked sturgeons from reaching their primary 

spawning sites. Only 372 from a total of 3390 ha of 

suitable spawning area is left intact (Khoroshko 

1970). The success of natural reproduction depends 

on the volume of water during spring flood, runoff 

during the summer, water temperatures during the 

spawning, amount of suitable spawning grounds 

available, the condition of the substrate of the 

spawning grounds, the number of fish reaching the 

spawning grounds, and the quality or condition of 

spawners reaching the spawning grounds. As a result 

of new fishery rules introduced in 1986 in the 

Volga River Delta, the period of legal harvest in the 

river was shortened to increase the number of 

spawning fish reaching the spawning grounds. This, 

and favorable ecological conditions (i.e., an increase 

in water levels in the river and the Caspian 

Sea), allowed natural reproduction to increase in 

the late 1980s. However, levels of poaching in the 

Caspian Sea and in the Volga River have increased 

immensely in the last few years, which has decreased 

the efficiency of natural reproduction of all 

three commercial sturgeon species. 

Artificial propagation 

The Volga River sturgeon hatcheries are situated 

next to the river and began to release juveniles into 

the Volga River first in 1957; trends since then are 

shown in Figure 3. Juveniles are released into the 

river at age of 30–50 days (Lukyanenko et al. 1984). 

The number of beluga juveniles increased from 0.5 

million in 1959 to 16.0 million in 1970. However, we 

found that this did not increase the number of beluga 

harvested in later years. The release of stellate 

sturgeon juveniles, along with a ban on sturgeon 

catch from the sea in 1962, resulted in increases in 

the number of stellate sturgeon caught. In the late 

1980s, 30% of the stellate sturgeon harvest was 

from hatchery produced fish. Unfortunately, increases 

in the number of juveniles released from 

hatcheries did not seem to affect the number of 

spawning beluga or stellate sturgeon, that later entered 

the river. 

The number of Russian sturgeon juveniles released 

from sturgeon hatcheries increased from 0.7 

million in 1955 to 20–40 million in 1980–1983. However, 

these numbers also failed to stabilize the size 

of the Russian sturgeon population in the Volga 

River and Caspian Sea. Artificial reproduction of 

Russian sturgeon has not compensated for stock 

losses caused by overfishing, pollution and other 

anthropogenic factors. As previously mentioned, 

decreases in water levels in the Caspian Sea in the 

1980s may also have negatively impacted both 

growth and survival of juveniles in the Volga River 

delta during their first winter, while fish are adapting 

to more saline conditions. To offset a continuing 

decrease in the size of stock, 40 to 60 million juvenile 

Russian sturgeon were released annually from 

1986 to 1990 (Figure 3). In the late 1980s, hatchery 

propagated fish represented an estimated 25–30% 

of the catch. 

Water pollution and illegal harvest as threats 

In 1984, specimens of Russian sturgeon with degenerated 

muscles began to appear in the Volga River 

and the Caspian Sea. In 1987, muscle degeneration 

was noted on a massive scale in all three commercial 

sturgeon species covered in this paper (Altufev et 

al. 1989, Lukyanenko 1990). The phenomenon was 

called ‘muscle atrophy’ and was intensively studied 

from 1987 through 1992 (Evgeneva et al. 1990, Altufev 

et al. 1992, Kuzmina et al. 1992). Results indicated 

that fibrils of the striated muscle tissues degenerated 

and were replaced by fat and connective tissues. 

It was suggested that muscle atrophy was 

caused by cumulative toxicosis resulting from increasing 

pollution levels in the Caspian Sea basin 

(Altufev et al. 1989, Lukyanenko 1989). Volga River 

water pollution also was extremely high by the late 

1970s. In 1979, the concentration of the pesticide 

hexachlorane ranged between 0.0003 mg 1 –1 in the 

Volga River delta and 0.0025 mg 1 –1 near the city of 

Volgograd (Lukyanenko 1990). Water pollution has 

increased since then. Recent experiments support 

the hypothesis of pollution-caused etiology of mus-

216 

cle atrophy. The most common oil products, diesel 

fuel, and hexachlorocyclohexane, are known to 

cause anomalies in muscles of juvenile Russian 

sturgeon and beluga that are similar to those seen in 

sturgeons with muscle atrophy (Altufiev 1994). 

Accumulation of heavy metals and pesticides in 

gonads, livers, and muscles was discovered recently 

(Anclreevet al. 1989, Gapecva et al. 1990, Golovin et 

al. 1990, Kirillov et al. 1990, Moroz 1990, Paveleva et 

al. 1990). Since the late 1980s, high levels of tumors, 

abnormalities in gonad development and gametogenesis, 

and disturbances in the morphogenesis of 

organs have been found in all three species of sturgeons 

(Romanov et al. 1989, Romanov & Sheveleva 

1992, Romanov & Altufev 1990). In 1990, 100% of 

eggs taken from females of all three species of sturgeons 

caught in the lower reaches of the Volga River 

showed ahnormalities and 100% of the embryos 

were nonviable (Shagaeva et al. 1993). Therefore, 

the impact of pollution on present populations of 

sturgeons in the Volga River and Caspian Sea is very 

high and its effect will intensify in the near future. 

Another serious threat to survival ofsturgeons in 

the Caspian Sea basin is uncontrolled overfishing 

and an enormously increased level of poaching. After 

dissolution of the Soviet Union in 1991, sea harvest, 

which had been prohibited for 30 years (since 

1962) under Soviet law, began again. The absence of 

common fishery agreements among the states bordering 

the Caspian Sea (Russia, Azerbaidjan, Turkmenistan, 

Kazakhstan, and Iran) 1 aggravated the already 

grave situation of the commercial species of 

sturgeons. Political and economic instability in Russia, 

along with inflationary pressures in the region, 

caused a sharp rise in poaching in the Volga River 

during the early 1990s, concentrated at feeding and 

spawning areas. Unfortunately, the unprecedented 

scale of poaching in the Volga River occurred simultaneously 

with decreases in efforts to replenish 

sturgeon stocks by stocking of artificially reared juveniles. 

Together, these factors threaten the survival 

of commercial sturgeon species in the northern 

part of the Caspian Sea basin. 

1 

On 14 November 1996. Russia, Azerbaijan, Turkinmistan, and 

Iran signed an agreement to ban all sturgeon fishery in the Caspian 

Sea in 1997. Under the apgreement, sturgeon fishery will only 

be allowed in the deepest waters of the Volga and Ural rivers 

(Editors’ note, February 1997). 

Dynamics of the loss of Caspian Sea sturgeon fisheries 

(1) Before Volga River flows were regulated in 

1958, sturgeon stocks in the Volga-Caspian system 

were supported by natural reproduction only. Between 

1950–1958, returning spawning populations 

consisted of about 20 000 individuals of beluga, 

400 000 stellate sturgeon, and 700 000 Russian sturgeon. 

(2) From 1959 through 1972, recruitment was 

mostly natural. A ban on the catch of sturgeon from 

the Caspian Sea in 1962 had a positive effect on returning 

stocks. Also, beginning in 1957, sturgeon 

hatcheries began to release juveniles to maximize 

the size of sturgeon populations. The number of 

surgeons returning to the Volga River to spawn was 

from 5700 to 11 000 beluga, from 600 000 to 907 000 

stellate sturgeon, and from 334 000 to 450 000 Russian 

sturgeon. All three commercial species were 

cut off from their historic spawning areas by construction 

of dams in 1958–1960, and the length of the 

migration path was reduced. This initiated a gradual 

decrease in natural reproduction so that by the 

1970s the beluga stock was consisted primarily of 

hatchery propagated fish. 

(3) The period of 1973 through 1977 saw a sharp 

reduction in natural reproduction, a worsening environmental 

situation caused by a drop in the sea 

level which increased water salinity, decreased the 

area of feeding grounds, and reduced the deltaic arca 

where juveniles overwinter. This period was particularly 

critical for the survival of juveniles of all 

three species, especially for the Russian sturgeon, 

and many eggs laid on spawning grounds did not develop. 

(4) From 1978 through 1989, environmental conditions 

changed. Water levels rose in the Caspian 

Sea and salinity decreased. The number of juveniles 

released in the delta of the Volga River increased to 

19 million beluga juveniles, 18 million stellate sturgeon. 

and 45.7 million Russian sturgeon. But, beginning 

in 1985, high levels of water pollution began 

to affect sturgeons, and their natural reproduction 

decreased sharply. The recruitment of individuals 

from these generations have not been estimated yet 

since these fish are still too young to be caught.

217 

(5) Since 1990, declines in sturgeon populations 

have occurred due to poaching and overfishing in 

the Volga River and Caspian Sea. The number of 

juveniles released from hatcheries decreased sharply 

because of a worsening economic situation in 

. In order to preserve sturgcon stocks in the 

northern Caspian Sea, an international agreement 

is needed on fishery regulations and control of fishing 

in the sea. Strict measures against illegal fishing 

are urgently needed. It will be necessary to restore 

the propagation efforts of hatcheries and improve 

the technology for artifial reproduction of sturgeons. 

1 


We are grateful to Vadim Birstein, John Waldman 

and Robert Boyle for inviting one of us (Anatolii 

Vlasenko) to present our paper at the International 

Conference on Sturgeon Biodiversity and Conservation. 

We thank Vadim Birstein, Kent Keenlyne. 

Todd Georgi and William Bemis for editing our 

manuscript to improve the English. William E. Bemis 

drew the map and figures. 


Altufiev, Yu. V. 1994. Morphofunctional state of muscle tissue 

and liver of Russian sturgeon and beluga juveniles in euperi- 

1 

In 1995, the prospects for the three commercial sturgeon species 

of the Volga River worsened. Only 35 female beluga were 

captured for artificial breeding at the hatcheries located in the 

delta, and only 86 female beluga were legaly taken in the entire 

northern area of the Caspian Sea (in the 1960s, about 2000 female 

beluga were caught annually in the same region). Practically 

all Russian and stellate sturgeons migrating to spawning 

grounds below the Volgograd Dam were harvested in 1995 by 

poachers, who operated between Astrakhan and Volgograd (see 

Figure I). Fewer than five of the sturgeon hatcheries in the Volga 

Delta produced juveniles for stocking during 1995, a great decrease 

from the more than 12 hatcheries operated historicaly 

Juveniles from the hatcheries were released directly into the Volga 

River, where predation losses are high, instead of being relensed 

directly onto sturgeon feeding grounds in the Caspian 

Sea, the preferred method used throughout the 1980s (editor, 

note, February 1996). 

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227 (in Russian. English translation J. Ichthyol. 31: 76–83). 

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of the Volga River stellate sturgeon, Acipenser 

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27: 801–808 (in Russian, English translation J. Ichthyol. 

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Dorsal view of a head of Acipenser gueldenstaedtii 71 cm TL from the Black Sea Danube stock above the dorsal and side views of 

Acipenser persicus 54 cm TL, caught wild in the eastern Black Sea 16 km off the coast at Sochi, both now maintained alive in ponds of the 

Propa-Gen International, Komadi, Hungary. Originals by Paul Vecsei, 1996.


© 1997 Kluwev Academic Publishers. Printed in the Netherlands. 

Species structure, contemporary distribution and status ofthe Siberian 

sturgeon, Acipenser baerii 

Georgii I. Ruban 

A. N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, 117071, Russia 


Key words: Ob River, Lena River, Yenisey River, Kolyma River, Indigirka River, Lake Baikal, taxonomy, 

subspecies, range, pollution, histological anomalies 

Synopsis 

A detailed analysis of the historical and contemporary range of the Siberian sturgeon, Acipenser baerii, shows 

that the contemporary status of its populations and forms can be described as threatened or endangered. 

Recently, the abundance of the nominal subspecies, A. b. baerii, which inhabits mainly the Ob River basin, 

decreased sharply. Due to construction of hydroelectric dams, up to 40% of the spawning grounds became 

inaccessible for migrating sturgeon of this subspecies. The Lake Baikal subspecies, A. baerii baicalensis, is 

extremely rare and was included in the Russian Federation Red Data Book in 1983. The abundance of the east 

Siberian subspecies, A. baerii stenorrhynchus, inhabiting the basins of the east Siberia rivers, has also significantly 

decreased during the last few years. Its range in the Yenisey and Lena River basins is gradually being 

reduced. Gametogenesis is anomalous in a high number of females from all populations of this subspecies (in 

the Kolyma and Indigirka river stocks 80–100% of females were anomalous in 1987–1989). These anomalies 

seem to be caused by high levels of water pollution. 

Introduction 

The range of Siberian sturgeon, Acipenser baerii, is 

very large. However, because the rivers it inhabits 

are not easily accessible to researchers (it lives in 

practically all large Siberian rivers, many of which 

are difficult to reach) and because of its low abundance, 

studies of the Siberian sturgeon are few. Recent 

intensive anthropogenic impact on the north 

Siberian water bodies (fisheries, construction of 

dams, and pollution) makes it necessary to evaluate 

the contemporary status of different forms and 

populations of this species. Moreover, until recently, 

the populations of A. baerii from the northeastern 

part of its range were little known and were not 

included in the recent review on this species (Sokolov 

& Vasiliev 1989). This paper offers a revision of 

the information on the range of A. baerii, including 

its taxonomy, and evaluation of the contemporary 

status of different subspecies and populations. The 

northeastern populations are the primary focus. 

Historic and contemporary range of Acipenser 

baerii 

The range of the Siberian sturgeon extends in the 

meridional direction from 73–74°n.1. (Lena River, 

Ob Bay) to 48–49°n. 1. (Chernyi Irtysh and Selenga 

rivers) (Dryagin 1948a, Votinov et al. 1975), and in 

the longitudinal direction from the Ob River basin 

to the Kolyma River, up to 97° (Dryagin 1948a). The

222 

data on the range of A. baerii are included in Table 1 

and Figure 1, and a detailed description of the range 

is given below. 

In thc Ob-Irtysh basin, the northern boundary of 

the Siberian sturgeon range is located at the Ob Bay 

near thc Drovyanoy Cape (Dryagin 1948b. 1949). 

The sturgeon occurs in thc Ob River within its entire 

length, 3680 km from the confuence of the Biya 

and Kalun rivers (which form the Ob River), to its 

delta. Sturgeon migrate upstream to the Katun River 

for 50–70 km and were found in the mouth of the 

Biya River (Dryagin 1949, Pctkevich et al. 1950). 

They were also caught in Lake Teletskoe (Berg 

1948). Inaddition, the Siberian sturgeon inhabited 

the tributaries of the Ob River: the Chulym, Charysh, 

Nadym, and Irtysh rivers; sometimes they were 

found in the mouth of two other large tributaries, 

the Polui and Synya rivers (Dryagin 1948b, 1949). 

Sturgeon ranged throughout the entire length of 

the Trtysh River, up to Zaisan Lake and Chernyi Irtysh 

River (Sedelnikov 1910, Bogan 1939, Dryagin 

1948b,1949,Petkevichetal.1950,Votiiiov1963,Votinov 

et al. 1975). Siberian sturgeon were also 

caught in the Chinese part of the Trtysh River 

(Tehernyi Irtysch River) up to the Kren River. Acipenser 

baerii inhabited also the Trtysh River tributary, 

the Tobol River, and its tributaries, the Tura 

and Tavda rivers (Dryagin 1948b 1949). 

Table 1. Ranges of the subspecies of the Siberian sturgeon, Acipenser baerii 

Main rivers or lakes 

Tributaries 

a. Acipenser baerii baerii 

(I) Ob River, from the Ob Bay (the northern boundary) up to the 

confluence of the Biya and Katun rivers (3680 km); Teletskoe Lake 

(2) Taz River (300 km upstream) and Taz Bay 

(3) Pur Kivcr ( 100 km upstream) 

(4) Gyda and Yuribey rivers and Gyda Bay 

b A. baerii stenorrhynchus 

(1) Yenisey Rivcr, from the Yenisey Gulf (the northern boundary) up to 

the city of Krasnoyarsk (2450 km, upstream the contemporary southern 

boundary) or the Oznachennaya village (3100 km upstream, historical 

range). 

(a) migrating stock (throughout the whole river length); 

(b) non-migrating stock (historically, from thc city of Igarka up to the 

Oznachennaya village; 2300 km upstream) 

Chulym, Charysh, Nadyrn, and Irtysh rivcrs 

Messo-Yakha, Anti-Payula, Ader-Payuta rivcrs 

(a) Tuba and Abakan rivers (historically); 

(b) Angara, Podkamennaya and Nizhnyaya Tunguska 

rivers (non-migrating populations); 

(c) tributaries of the Nizhnyaya Tunguska River: the 

Kochechumo, Vivi, and Tutokchan rivers 

(2) Pyasina River Pyasina River basin lakes, Lama Melkoe 

(3) Khatanga River (up to the confluence of the Kheta and Kotui rivers) Kheta River (350–460 km up from the confluence with the 

Kotuy River) 

(4) Anabar River (a) Vitim Kivcr (860 km upstream); 

(b) Olekma River (30 km upstream); 

(c) Aldan River and its tributary, the Amga River; 

(d) Vilyuy River and its tributaries, the Chona, Chirkuo, 

and Akhtaranda rivers 

(S) Olenek Rivcr (1020 km upstreasm) 

(6) Indigirka River (850 km upstream) 

(7) Alazeya River Bor -Yuryakh River 

(8) Kolyma River (1500 km upstream) 

c. A. baerii baicalensis 

Baikal Lake and its trubutaries 

Korkodon and Ozhogina rivers 

(a) Selenga Kiver (1000 km upstream) and its tributaries, 

Chikoy and Orhon rivers; 

(b) Tula and Delger-Muren river; 

(c) Barguzin River (300 km upstream); 

(d) Verkhnyaya Angara (100–150 km upstream) and 

Kichera rivers

223 

Figure 1. The range of the Siberian sturgeon, Acipenser baerii. Areas where sturgeon are still common, rare, or extinct are indicated by 

shading. 

Sturgeon became cut off from approximately Bay tributaries: the Messo-Yakha, Anti-Payuta, 

40% of their spawning grounds in the Ob River af- and Ader-Payuta rivers. It inhabits the lower 

ter the Novosibirsk hydroelectric dam was con- reaches of the Pur River up to 100 km from the 

structed in 1957, and in the Irtysh River after build- mouth (Chupretov &Slepokurov 1979). Historicaling 

the Ust-Kamenogorsk hydroelectric dam in ly, Siberian sturgeon also occurred in the Gyda Bay 

1952 (Votinov et al. 1975). The situation became and Gyda and Yuribey rivers (Burmakin 1941, 

even worse after the Shulbinsk hydroelectric dam Dryagin 1949). 

was constructed in 1985 on the Irtysh River down- The Shirokaya bay of the Yenisey Gulf is the 

stream from the Ust-Kamenogorsk dam. The mi- northern boundary of the Siberian sturgeons range 

grating form of the sturgeon cannot swim to the in the Yenisey River basin, while Oznachennoe vilspawning 

grounds located upstream. 

lage was considered as the southern boundary of 

In the Taz River, the Siberian sturgeon was found the range before construction of the hydroelectric 

upstream up to 300 km from the mouth. It also oc- dam. The distance between these two geographic 

curs throughout Taz Bay and in the mouths of Taz points is more than 3100 km (Podlesnyi 1955,1958,

224 

1963). It was assumed that the non-migrating form 

lived in the Yenisey River over 2300 km from the 

Oznachennoe village to the city of Igarka (Podlesnyi 

1955). Sturgeon did not, apparently, migrate upstream 

from the Yartsevo village (1759 km from the 

river mouth) (Podlesnyi 1955) or the town of Yeniseysk 

(Podlesnyi1958). They were caught rarely upstream 

from the city of Krasnoyarsk (2454 km from 

the Yenisey mouth) (Podlesnyi 1963). In the past, 

sturgeon migrated to the near-mouth parts of tributaries 

of the middle Yenisey River, the Tuba and 

Abakan rivers, but now, according to the information 

received from local people, it is completely absent 

upstream from the Krasnoyarsk hydroelectric 

dam (built in 1967). Therefore, the sturgeon range 

in the Yenisey River has been reduced, and its 

southern boundary moved to the north by 500–600 

km. 

In the large Yenisey tributaries,such as the Angara, 

Podkamennaya and Nizhnyaya Tunguska rivers, 

therewere smallpopulations of non-migrating sturgeon 

(Podlesnyi 1955,1958);the upper boundary of 

its range in the two latter rivers has not been determined. 

The sturgeonoccurred also in the lower tributaries 

of the Nizhnyaya Tunguska River, the Kochechum, 

Vivi, Kuchumdek, and Tutokchan rivers 

(Dryagin 1949). It was also found in the Kureika 

River in the 19th century (Tretyakov 1869). 

In the Angara River the sturgeon inhabited an 

areafrom the mouth up to the estuary of the Belaya 

River (Dryagin 1949). Also, juveniles were caught 

several times near the Angara River source and 

near the city of Irkutsk (Yegorov 1941,1961). The 

sturgeon occurred in the Angara River tributaries, 

the Taseyeva (and its tributary Chuna) and Oka rivers 

(Yegorov 1963). 

In Lake Baikal, Siberian sturgeon were most 

abundant in the area near the delta of the Selenga 

River, aswell as in the Barguzinskii and Chivyrkuiskii 

bays. Sturgeon moved from these main habitat 

regions along the coast in the shallow-water zone of 

the lake to the mouths of the large tributaries of the 

lake, from which they migrated into these tributaries. 

They were rare in the northern part of Lake Baikal 

at the mouth of the Verkhnyaya Angara and 

Kichera rivers. They migrated into the Selenga River 

up to 1000 km, including its tributaries Chikoy 

and Orhon rivers (Yegorov 1961), as well as into the 

Tula and Delger-Muren rivers (Sokolov & Shatunovsky 

1983). Also, they migrated into the Barguzin 

River more than 300 km upstream, and into the 

Verkhnyaya Angara River, up to 100–150 km (Yegorov 

1961). Siberian sturgeon were also found in 

smaller tributaries such as the Turka River. 

In the Pyasina River Siberian sturgeonwere rather 

rare (Dryagin 1949).They were not caught in the 

Pyasina Bay (Ostroumov 1937), but were found in 

the Pyasina basin lakes, the Lama and Melkoe (Belykh 

1940,Logashov 1940). 

In the Khatanga River basin sturgeon were found 

both in the estuary (Tretyakov 1869, Berg 1926) and 

upstream from the Khatanga River to the confluence 

of the Kheta and Kotuy rivers, which form 

the Khatanga River. In the Kheta River, they were 

caught over 460 km from the mouth to Volochanka 

village, although their main habitat in this river is 

from the mouth to 350 km upstream (Lukyanchikov 

1967). Sometimes sturgeon were noticed in the 

flood plain lakes of the Kotuy River, where they migrated 

with the spring water. Sturgeon were found 

in the middle and low reaches of the Anabar River 

(Kirillov 1972). 

In the Olenek River the sturgeon was a rare fish 

(Kirillov 1972). Usually it migrated upstream up to 

the Pur River mouth and, exceptionally, to the 

mouth of the Chemudakh brook located 1020 km 

from the river mouth. 

Siberian sturgeoninhabited the Lena River basin 

up from the river mouth and the Neyelova Bay 

(Dryagin 1948a, 1949). During high-water years 

they migrated into the Tiksi Bay and coastal regions 

of the Bulunkan and Sogo bays (Kirillov 1950). 

Within the Lena River, sturgeon moved up to the 

Korshunovo village (Borisov 1928, Dryagin 1933, 

1949, Karantonis et al. 1956, Dormidontov 1963, Kirillov 

1972), and the total length of its range was approximately 

3300 km in this river. The town of Kirensk 

is considered as the southern boundary of the 

sturgeon range in the Lena River. Earlier, in the 

1840s, the southern boundary was at Makaryevskoe 

village located upstream from the town of Kirensk 

(Maak 1886). At the end of the 19th century, sturgeon 

also inhabited the right tributary of the Lena 

River, the Kirenga River (Borisov 1928). Therefore,

225 

the Siberian sturgeon range in the Lena River was 

reduced during the last 150 years by 300 km at the 

expense of the upper reaches of the river (Figure 1). 

The Siberian sturgeon also occurred in some Lena 

River tributaries: the Vitim, Olekma, Aldan, and 

Vilyuy rivers (Dryagin 1949, Karantonis et al. 1956, 

Kirillov 1972). In the Vitim River they were found 

both in the lower (Kirillov 1972) and upper reaches 

from the Tsipa River mouth (860 km upstream from 

the Vitim mouth) (Kozhov 1950), and sometimes 

even farther upstream, up to the mouth of the Kalakan 

River (Kalashnikov 1978). Sturgeon were also 

found in the Olekma River (Dryagin 1949, Kirillov 

1972). According to my own observation, sturgeon 

now migrate upstream the Olekma River approximately 

30 km. 

In the Aldan River, sturgeon inhabited the lower 

and middle reaches and they were especially abundant 

in the left tributary, the Amga River (Kirillov 

1964). The upper boundaries of the range in the Aldan 

and Amga rivers are not known. According to 

information from local people, sturgeon occur in 

the Aldan River up to Ust-Mil village (Sokolov et 

al. 1986). In the Vilyuy River sturgeon were found 

from the mouth up to the Vava River, and they migrated 

into its tributaries, the Chona, Malaya and 

Bolshaya Botuobiya, Tyung, and Markha rivers 

(Kirillov 1972). Before the flow regulation in the 

late 1960s, it was most abundant in the Chona, Chirkuo, 

and Akhtaranda river mouths. After the impoundment 

of the Vilyuy water reservoir (the Vilyuyskaya 

dam was built in 1965), the sturgeon moved 

upstream (Kirillov & Solomonov 1979). 

In the Yana River, sturgeon occurred from the 

delta up to the Verkhoyansk settlement (Kirillov 

1972). In the Indigirka River they were caught upstream 

up to the Krest-Maior settlement (850 km 

upstream) and some individuals were found up to 

the Zashiversk settlement (Kirillov 1953, 1972). 

Only single specimens were caught in the Alazeya 

River; they migrated to the mouth of its right tributary, 

the Bor-Yuryakh River (Dryagin 1933). 

In the Kolyma River, sturgeon occurred from the 

delta region up to the Seimchan settlement (Dryagin 

1933), i.e., within 1500 km, but mainly up to the 

Verkhnekolmsk settlement (Dryagin 1948a). In 

1988–1989 we found that sturgeon were abundant in 

the Kolyma River upstream from this town, near 

the mouth of the Popovka River (1085 km from the 

Kolyma River mouth) (Ruban & Akimova 1993). 

Sturgeon were caught only in two tributaries of the 

Kolyma River, the Korkodon and Ozhogina River 

(Dryagin 1948a). 

Taxonomy and species structure of A. baerii 

The first description of the Siberian sturgeon, Acipenser 

baerii Brandt 1869, was based on specimens 

caught in the Ob and Lena rivers (Brandt 1869). According 

to Chapters 31 and 33 of the International 

Code of Zoological Nomenclature (1988) 1 , the initial 

spelling of this species name should be preserved 

and the widely used name A. baeri (for instance, 

Sokolov & Vasilev 1989) is incorrect (Ruban 

& Panaiotidi 1994). Nikolskii (1896) described the 

sturgeon from the Yenisey River as A. stenorrhynchus, 

and a form from Lake Baikal as a variety of 

this species, A. stenorrhynchus var. baicalensis. Later 

Menshikov (1947) reduced the species, A. stenorrhynchus, 

to the rank of subspecies, A. barerii sternorrhynchus. 

According to Chapter 45 of the International 

Code of Zoological Nomenclature, the Baikal 

variety of the sturgeon described by Nikolskii 

(1896) should be considered as a subspecies, A. baerii 

baicalensis Nikolsky, 1896 (Ruban & Panaiotidi 

1994). 

The taxonomic status of another subspecies, the 

Yakut sturgeon, A. baerii chatys Dryagin, 1948a, remained 

unclear until recently (see, for instance, Sokolov 

& Vasilev 1989). This form inhabits the rivers 

of Yakutiya 2 from the Khatanga River in the west to 

the Kolyma River in the east. Many ichthyologists 

did not consider this form as a subspecies (Nikolskii 

1939, Berg 1948, Andriyashev 1954). Comparative 

analysis of morphological characters in large nunber 

of individuals from the Yenisey (A. baerii ste- 

1 

International Code of Zoological Nomenclature, 1988, 3rd ed. 

Nauka Press, Leningrad. 202 pp. (in Russian). 

2 

Yakutiya (now sometimes referred to as Saha) is a huge north 

central Siberian automomous republic within Russia which is 

roughIy bounded by the Anabar River on the west, the Kolyma 

River on the east and the upper Lena and Aldan rivers at the 

south.

226 

Figure 2. Siberian sturgeon catches in the 1980–1990s in the Ob. Yenisey, and Lena rivers. Data from Kirillov (1972). Yegorov (1988), 

Gundrizer et al. (1983), Votinov et al. (1975), Dryagin (1949) and own. 

norrhynchus) and Lena (A. baerii chatys) rivers 

showed that differences between the fish from 

these populations do not reach a subspecific level 

(Ruban & Panaiotidi 1994). Comparison of our results 

with previous data obtained by the other authors 

(Menshikov 1947, Dryagin 1948b, Podlesnyi 

1955, Sokolov & Vasilev 1989, Ruban 1989, 1992) 

points to clinal variation in a number of meristic 

characters of Siberian sturgeon (Ruban & Panaiotidi 

1994). Usually it is considered that when the geographic 

variation within a species is clinal, it is not 

appropriate to name such forms as a subspecies 

∨ 

(Mayr 1969, Holcík & Jedlieka 1994). Therefore, it is 

not right to consider A. baerii chatys as a subspecies 

of the Siberian sturgeon and this form should be included 

in the subspecics A. baerii stenorrhynchus 

described by Menshikov (1947) for the fish from 

populations of the Yenisey, Lena, and Kolyma rivers 

(Ruban & Panaiotidi 1994). Additionally, because 

of the absence of sturgeon specimens from 

the Ob River basin in museum collections, the 

problem of A. b. stenorrhynchus also cannot be 

solved definitively. At present one can consider the 

Siberian sturgeon to consist of three subspecies: the 

nominal A. baerii baerii Brandt. 1869 from the Ob 

River basin, A. baerii baicalensis Nikolsky, 1896 

from the Lake Baikal basin, and A. baerii stenorrhynchus 

Nikolsky, 1896 from other Siberian waters. 

Contemporary status of A. baerii 

As described above, the range of the Siberian sturgeon 

is constantly being reduced; the number of individuals 

in each population is also decreasing. Depletion 

is caused by three main factors: the elimination 

of spawning grounds after the construction of 

dam, overfishing, and water pollution. 

Fishing 

Although the catch of Siberian sturgeon has always 

been relatively small and never exceeded 1769 metrie 

tons per year, its impact on the status of different 

populations was devastating. The highest catches 

were recorded in the Ob-Irtysh and Yenisey rivers

227 

basins: 1401 and 504 metric tons per year, respectively 

(Figure 2). In other Siberian rivers the sturgeon 

catch was much smaller and there was no specialized 

sturgeon fishery. The highest catch in the 

Lena River was 189.9 metric tons in 1943. The populations 

of two sturgeon subspecies, the nominal A. 

baerii baerii of the Ob River basin and the East-Siberian 

A. baerii stenorrhynchus of the Yenisey River, 

were especially affected by fishing. The third subspecies, 

A. baerii baicalensis, is at present extremely 

rare and has been included in the Red Data Book of 

the Russian Federation (Kolosov 1983). 

Histrological data on the effect of pollution 

Disturbances in the reproductive system are often 

correlated with worsening conditions of the environment, 

especially high levels of chemical pollution. 

Our long-term histological studies (methods in 

Roskin & Levinson 1957) on the development and 

functioning of the reproductive system in Siberian 

sturgeon inhabiting East Siberia showed abnormal 

gametogenesis in individuals from the Lena, Indigirka, 

Kolyma, and Yenisey rivers. 

Between 1964 and 1977, only single cases of degeneration 

of oocytes during the period of cytoplasmic 

growth were reported in females of the Lena 

River population (Akimova & Ruban 1993). But in 

1986 the number of females with such defects was 

close to 59% (23 of 39 females studied). New types 

of anomalies appeared in these females: some of 

them had many unspawned eggs, and amitotic division 

of sex cells and degeneration of the nuclear 

membrane in oocytes during vitellogenesis were 

characteristic for many females (Akimova & Ruban 

1995). 

Similarly, but in a shorter period of time and to a 

greater extent, the state of the reproductive system 

in females of the Indigirka River population also 

changed (Ruban & Akimova 1991, Akimova & Ruban 

1993). The percent of females of different ages 

with partially degenerated oocytes during the period 

of cytoplasmic growth increased within four 

years (1984–1987) from 77 to 100%. In some females 

degeneration occurred repeatedly. The growth period 

of the oocytes was characterized by asynchro- 

nous development (which is uncommon for sturgeons), 

decreases in the strength of their membranes, 

and by degeneration of 15% of the germ 

cells. Simultaneously, the remaining oocytes undergoing 

cytoplasmic growth continued to degenerate. 

In the Kolyma River population up to 81–83% of 

all females had various defects in germ cells in 1988 

and I989 (Akimova & Ruban 1993, Ruban & Akimova 

1993). Just as in the Indigirka population, degeneration 

of some oocytes was observed during 

the period of cytoplasmic growth, in some females 

repeatedly, and amitotic divisions of oocytes were 

also found. Degeneration of oocytes at the time of 

growth was higher (up to 20% of oocytes) in females 

of the Kolyma River population than in females 

of other populations. Defects in oocyte membranes 

resulted in 50–100% of mature eggs having a 

deformed, angular shape. The gelatinous envelopes 

contained inclusions of uncertain content, which 

were absent in egg envelopes of sturgeon from the 

Lena and Indigirka populations. In some females of 

the Kolyma River population, destruction of the 

nuclear membrane was observed in still immature 

oocytes. This destruction caused the disintegration 

of the nuclei. 

Some oocytes had evidently degenerated during 

the period of cytoplasmic growth in females from 

the Yenisey River population. Also an amitotic division 

of oocytes, which caused the degeneration of 

the dividing cells, was observed. In some females 

the oocyte envelopes became locally thinner during 

the period of growth in almost 50% of oocytes. We 

also observed extensive deformation oocytes, appearance 

of cavities with foreign body inclusions 

under the oocyte envelopes and among yolk granules, 

and mass resorption of mature eggs in some 

females. Unspawned eggs were present in gonads of 

some females after spawning. In general, the discovered 

abnormalities of gametogenesis in the Yenisey 

population were not so numerous as in the 

Kolyma or Indigirka River populations. This enabled 

us to declare this phenomenon as an initial 

state of pathological development and functioning 

of the reproductive system (Akimova et al. 1995). 

Disturbances in gametogenesis of females from the 

Yenisey River are probably caused by a high level of

228 

water pollution, especially, by pesticicles (Tchuprov 

1986). 


Vadim Birstein, John Waldman and Robert Boyle 

invited me to the International Conference on Sturgeon 

Biodiversity and Conservation. I am thankful 

to Vadim Birstein and anonymous reviewers for 

their editorial notes on the draft of the manuscript 

and to William E. Bemis for drawing the map and 

figure. 


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©1997 Kluwer Academic Publishers. Printed in the Netherlands 

Endemic sturgeons of the Amur River: kaluga, Huso dauricus, and Amur 

sturgeon, Acipenser schrenckii 

Mikhail L. Krykhtin & Victor G. Svirskii 

Pacific Research Institute of Fisheries and Oceanography, 4 Shevchenko Alley, Vladivostok 690600, Russia 

Received 2.8.1994 

Accepted 8.3.I996 

Key words: anadromy, population, hybridization, endangered species, poaching 

Synopsis 

General biological characteristics and the contemporary status of the kaluga, Huso dauricus, and Amur sturgeon, 

Acipenser schrenekii, are described. Both inhabit the Amur River basin. Kaluga is the largest freshwater 

fish in this river system reaching inore than 5.6 m in length and inore than 1000 kg in weight. We recognize four 

populations of kaluga: the f'irst is from the estuary of the Amur River and coastal brackish waters of the Sea of 

Okhotsk and Sea of Japan. the second is from the lower Amur River, the third is from the middle-Amur. and 

the fourth occurs in lower reaches of the Zeya and Bureya rivers. Freshwater and brackish water morphs exist 

in the estuary population, with the freshwater morph predominating in number. The number of individuals in 

the lower Amur River population at age 2 or greater was recently estimated to be 40 000, and in the middle 

Amur, 30 000. The population will continue to decline because of rampant overfishing. The Amur sturgeon is 

represented in the Amur River basin by two morphs: brown and gray. Brown morphs occur in the middle and 

lower parts of the Amur River: they grow more slowly than the gray ones, Today, the lower Amur River 

population of Amur sturgeon is made up of 95 000 fish at age 2 or greater and is approximately half as large as 

the population in the middle Amur River. Populations of kaluga and Amur sturgeon in the Zeya and Bureya 

rivers are extremely small and on the verge of extinction. 

Introduction 

The Amur River in the Russian far east is home to 

four species of the family Acipenseridae, kaluga 

Huso dauricus, Amur sturgeon Acipenser schrenckii 

Salihalin sturgeon A. mikadoi, and sterlet A. 

ruthenus. Only kaluga and Amur sturgeon are endemic 

to this river (Berg 1948, Nikolslkii 1956). Sakhalin 

sturgeon was recorded in the Sea of Okhotsk 

from the Amur River estuary to northern Japan and 

the Korean Peninsular (Berg 1948, Artyukhin & 

Andronov 1990, Shilin 1995). and five to ten Sakhalin 

sturgeon are caught annually in the Amur 

River estuary. Sterlet was introduced into the Amur 

River from the Ob River in 1956–1959, and since 

then only a few sexually mature individuals have 

been caught in the Amur. 

Historically, kaluga and Amur sturgeon were 

commercial species. In 1891,595 metric tons of kaluga 

and 607 metric tons of Amur sturgeon were 

caught in the Amur River, constituting 42.5% of the 

total catch of all fishes in the Amur River that year 

(Kryukov 1894). As in many other places, the survival 

of sturgeon populations in the Amur River became 

problematic after the turn of the 20th century. 

By 1909, the catch of kaluga decreased to less than 

one third and that of the Amur sturgeon to about 

one fifth of 1900 levels. From 1915 until 1917, Rus-

232 

Figure 1. Map of the Amur River System showing the upper, middle and lower reaches of the Amur River. The Ussuri River is known as 

the Wusulijang, and the Sungari River is known as the Songhuajing in Chinese. The upper Amur is a portion of the river above Blagoveshchensk, 

the middle Amur extends from Blagoveshehensk to Khabarovsk, and the lower Amur extends to the mouth. Only tributaries 

currently or historically important for acipenserids are shown. 

sian authorities prohibited fishing of sturgeons during 

the spawning period. In 1923, authorities issued 

a ban on the catch of sturgeons across the USSR; 

this ban was withdrawn in 1930. Three years after 

the second world war in 1948, 61 metric tons of kaluga 

and 4.2 metric tons of Amur sturgeon were 

caught, i.e., the catch of kaluga was one tenth of the 

1891 level, whereas that of the Amur sturgeon was 

less than one-hundredth of the 1891 level (Svirskii 

structure of these species have not been studied extensively 

(but see Wei et al. 1997 this volume). This 

paper describes general characteristics and the contemporary 

status of both species. 


Fishes were collected during government surveys of 

1071). In 1958, USSR authorities banned the catch the Amur River estuary, where 30–40 tons of kaluga 

of kaluga and Amur sturgeon. A ban is formally still were caught annually, as well as in the upper and 

in effect. Both species are on the IUCN Red List middle reaches of the Amur River. Data on devel- 

(1994), with H. dauricus considered rare and A. opment were obtained at the hatcheries located in 

schrenckii vulnerable. the lower (1962–1968) and middle (1992–1993) 

Although aspects of morphology of kaluga and reaches of the Amur River. Live fish were observed 

Amur sturgeon have been described before (Berg at the Vladivostok Oceanarium. Standard methods 

1948, Nikolsky 1956), the biology and population

233 

Figure 2. Acipenserid fishes of the Amur River: a- kaluga, Huso dauricus, b -Amur sturgeon, Acpenser schrenckii,c-ventral surface of 

the head of kaluga. H. dauricus, d - ventral surface of the head of a kaluga/Amur sturgeon hybrid, and e - ventral surface of the head of 

Amur sturgeon, A. schrenckii. Note difference in head and mouth shape of H. dauricus and A. schrenekii. 

of measuring morphological characters and determining 

age were used (Romeis 1954, Pravdin 1966). 

General characteristics of the Amur River 

The Amur River is formed by the confluence of the 

Argun and Shilka rivers (Figure 1). It enters into the 

Amur estuary of the Tatar Strait. The Amur estuary 

is 48 km long and I6 km wide at the mouth of the 

river. The Amur River is 4092 km long if its longest 

tributary, the Shilka River, is included. The total 

size of the basin is 1 856 000 km 2 . For much of its 

length, it forms the border between Russia and China. 

According to the structure of its valley, bed and 

flow characteristics, the Amur River can be divided 

into three parts (Figure 1). The upper reach of the

234 

Amur extends down to the city of Blagoveshchensk 

(upper Amur, 883 km); the middle reach continues 

down to the mouth of the Ussuri River, opposite the 

city of Khabarovsk (middle Amur, 975 km); and the 

lower reach continues down to the estuary (lower 

Amur, 966 km). Its hydrology is characterized by 

spring floods. The difference between the highest 

and lowest (winter) water levels is different in various 

parts of the river: about 10 m in the upper Amur, 

11 m in the middle Amur, 7–8 m in the lower Amur, 

and up to 3m near the estuary. The current velocity 

ranges from 0.5 to 2.0m sec –1 . During the Quaternary, 

there were times when the Amur River bed 

was either elongated 1.5–2.0 times, or when sea water 

penetrated deeply into the continent, reaching 

the area of Khabarovsk. Therefore, a seawater 

body with a different gradient of salinity existed at 

the location of the contemporary lower Amur and 

estuary. These environmental changes evidently affected 

sturgeon populations during their history in 

this region (Svirskii 1968). 

Kaluga sturgeon 

Biology and population structure 

Kaluga is the largest freshwater fish in the Amur 

River basin, reaching more than 5.6m in length, 

more than 1000 kg in weight, and an age of more 

than 80 years (Figure 2a, c). It inhabits the Amur 

River Basin from the estuary to its upper reaches, 

including several large tributaries and lakes (Nikolskii 

1956). Young kaluga have been caught at the sea 

during summer in coastal waters of the Sea of Okhotsk 

(Kostarev & Tyurnin 1970, near the northeastern 

part of Sakhalin Island (Gritsenko & Kostyunin 

1979), in the northern part of the Tatar Strait 

(Krykhtin 1984a,b), and in the Sea of Japan near the 

islands of Hokkaido (Amaoka & Nakaya 1975) and 

Honshu (Honma & Itano 1994). During the last 

decade, the number of young fish increased considerably 

in coastal waters of the northern part of the 

Tatar Strait and in the southwestern part of the Gulf 

of Sakhalin. 

We recognize four populations of kaluga in the 

Amur River basin. The first lives in the estuary and 

coastal brackish waters of the Sea of Okhotsk and 

Sea of Japan, the second lives in the lower Amur, 

the third in th middle Amur, and the fourth in the 

lower reaches of the Zeya and Bureya rivers. We 

know more about the estuary population than we 

do about the other three, and most of our observations 

in this paper concern this group. Two ecological 

morphs exist in the estuary population, which 

we term the freshwater and brackish water forms 

(Lukyanenko et al. 1979, Krykhtin 1985). The freshwater 

morph predominates, making up 75–80% of 

the estuary population. They feed only in fresh water. 

The brackish water form spends winter in the 

river or estuary and, in late June-early July, migrates 

downstream to the brackish water of the estuary 

and northern part of the Tatar Strait, as well as 

to the southwestern part of the Sakhalin gulf, to salinities 

of 12–16‰. 

In autumn, when the salinity of the estuary increases, 

brackish water kaluga return to the river, 

where they overwinter together with freshwater kaluga. 

If storms rapidly fill the estuary with cold sea 

water from the Sea of Okhotsk in late Novemberearly 

December, then some of the brackish water 

individuals, mostly juveniles, cannot reach the fresh 

water zones and die in the sea water at salinities of 

about 29–30‰ and water temperatures below 0°C 

(Krykhtin 1984a). 

Kaluga consume mostly invertebrates in the first 

year of life, later switching to juveniles of pelagic 

fishes such as chum salmon, Oncorhynchus keta. At 

age three to four years, kaluga start to feed on adult 

fishes. In estuaries and coastal sea regions kaluga 

catch saffron cod, Eleginus gracilis, and ocean 

perch, Sebastes alutus. Cannibalism is frequent. Kaluga 

do not feed during winter nor do broodstock 

eat during spawning migrations (Soldatov 1915, 

Yukhimenko 1963, Svirskii 1971, Krykhtin 1979, 

Krykhtin & Gorbach 1986). 

Maturation, spawning migration, and breeding 

Males from the estuary population spawn for the 

first time at age 14–21 years, and females, at age 17– 

23. Water temperature affects the time of maturation 

of females: during warm years, females of the

235 

same generation mature and spawn a year earlier 22° C (Svirskii 1971). Free embryos and larvae of the 

than they would during cold years. Males spawn estuary drift downstream from the spawning 

once every three to four years, and females, every grounds to the lower reaches of the Amur River and 

four to five years (Svirskii 1971, Krykhtin 1986). To- estuary. Some juveniles from the estuary populatal 

degeneration of previtellogenic oocytes (40–470 tion remain in the lower reaches until age two to 

µm in diameter) was observed in a few adult fe- five years, where they feed together with juveniles 

males at age 18–24years (Svirskii 1979). Maturation from the population of the lower Amur. 

in these females can be delayed for two years and Kaluga from the lower Amur population spawn 

intervals between spawnings may increase to six to at the same spawning grounds and at the same time 

eight years. 

as individuals from the estuary population. These 

Fecundity in 411 females ranging from 16 to 30 fish migrate from the lower Amur to the spawning 

years from the estuary population ranged from grounds from May to the first half of June. The pro- 

186 000 to 4 225 000 eggs (mean = 977 465 ± cess of maturation and intervals between successive 

23 692). Relative fecundity was 3300 to 15 100 eggs spawnings appear to be similar in both populations. 

kg –1 of body weight. In some females, the coelenter- Individuals from the lower Amur population grow 

ate parasite PoIypodium hydriforme caused a de- more slowly and are probably adapted to the higher 

crease in individual fecundity by 19% (Svirskii water temperature of the lower Amur. 

1984). Gonads of most of the future spawners were The middle Amur River population of kaluga exat 

stage IV of maturation (according to the stages of tends approximately 900 km from the river mouth 

Nedoshivin 1928). In autumn and early winter, most and includes the upper part of the lower reach of the 

of these future spawning fish migrate from the estu- Amur River and lower part of the middle reach of 

ary into the Amur River, where they spend the win- the Amur River. Many individuals of the middle 

ter in preparation for spawning during the next Amur population reach sexual maturity much earlispring 

(Krykhtin 1986). A smaller group (about er than do those of the estuary population. From 

5%) of all of the spring spawners migrates into the 1988 to 1992, 11–16 year old females constituted up 

Amur River during the spring, spawning soon after to 25% of the females migrating to spawning 

migration. Thus, there are two seasonal forms of ka- grounds from the lower region of the middle reach 

luga in the estuary, which we call winter and spring. of the Amur. Such early maturation was never ob- 

The winter form predominates. 

served in the estuary population. Individual fecun- 

Most of the mature fishes from the estuary pop- dity varied from 238 000 to 4 868 000 eggs in 126 

ulation spawn 50–150 km upstream from the town females studied at 11–16 years of age. Their relative 

of Nikolayevsk-na-Amure, while a small portion fecundity varied from 5000 to 11 000 eggs kg –1 body 

spawns on sites located less than 500 km upstream weight . 

from the mouth of the river. Some individuals mi- Major spawning grounds of the middle Amur 

grate as far as Khabarovsk, nearly 1000 km from the River population of kaluga are located in the lower 

mouth, and spawn in the middle Amur. 

region of the middle reach of the Amur. Smaller 

Spawning takes place during a small increase in spawning grounds are located in the Sungari and 

the water level, from the end of May until the begin- Ussuri rivers. The spawning migration of the midning 

of July, when the water temperature ranges dle Amur population takes place from May to the 

from 12 to 21°C. The peak of spawning usually oc- first half of June. Their free embryos drift downcurs 

in the middle of June. Pebble deposits in the stream from the spawning grounds to the regions 

main river bed and some large side channels serve with well-developed flood plains. 

as spawning grounds (Svirskii 1976a). After spawn- The Zeya and Bureya populations are now repreing, 

the fish return to the estuary to feed. 

sented by rare individuals in the upper region of the 

Embryonic development until hatching lasts 82– middle reach of the Amur, in the upper reach of the 

I12 h, and development of free embryos until the Amur, and in the lower regions of the Zeya, Shilka, 

transition to active feeding takes 7.5–14 days at 14– and Argun rivers. They migrate to spawning

236 

grounds located in the upper Amur River and in a 

region 250 km long downstream from Blagoveshchensk, 

in the second half of May and early June. 

Spawning takes place in June. The biology of this 

populationhas not been studied. 

Contemporary status 

The statusof kaluga populations in the Amurbasin 

has changed since 1900. At the end of the 19th century, 

when the highest catches were recorded (more 

than 595 metric tons per year), the middle Amur 

population was the most abundant.This is evident 

from the analysis of absolute and relative catches 

throughout the Amur River. According to data for 

1891, fish from the middle Amur population constituted 

87% of the annual kaluga catch in the Amur 

River Basin. Fish from the estuary and lower Amur 

populations, however, constituted 2% of the catch, 

with remaining 11% coming from the Zeya and Bureya 

population (Kryukov1894). 

At present, the estuary populationis most abundant. 

Due to the strictly limited catch since 1976, the 

total number of fish in the estuary population increased 

by approximately one third, and the number 

of large fish of more than 100 kg in weight increased 

by 2.5 times in comparison with the early 

1970s (Krykhtin 1979), so that there were about 

70 000 fish greater than one year old at the end of 

1980s. Approximately 5000 of these fish weighed 

morethan 100kg andwerepotentially sexuallymature. 

However, by 1993, as a result of an illegal fishery 

in the lower Amur during the spawning migration, 

the number of sexually mature fish in the estuary 

population was reduced by approximately 30–35%. 

The current population of kaluga consists predominantly 

of young fish, with only 2–3% of the population 

weighing more than 100 kg and classified as 

adults. Thus, according calculations using the area 

method and based on irregular control catches in 

the lower and middle Amur, the number of individuals 

older than 2 years in the lower Amur population 

is approximately 40 000 and in the middle 

Amur population, 30 000. The decrease in the kaluga 

population which appeared at the end of the 

1960s continues. Further decrease in population 

size should be expected, especially in the middle 

part of the Amur River. The size of the Zeya and 

Bureya population, if evaluated on the basis of the 

very low catch in the Amur River within the Amur 

district (0.09–1.03 metric tons), is so small that the 

populationis on the verge of disappearing. 

Theefficiency of naturalbreeding of kalugaisvery 

low,as can be seen from the slow rate of restoration 

of the estuary population: until the beginning 

ofthe 1990s,its size increasedonly35%,orless than 

2% per year. 

Amur sturgeon 

Biology and population structure 

The Amursturgeon (Figure 2b,d) is representedin 

the Amur River basin by two morphs: brown and 

gray.Young and adults of the brown morph inhabit 

the middle and lower reaches of the Amur River. 

Brown morphs are rare and grow more slowly than 

do the gray ones, with females maturing96–117 cm 

long and weights of 3.5–5.6 kg, whereas female gray 

morphs are 125–142 cm long and weigh 8.3–16.4 kg 

by maturity at age 12 years. There are a few small 

local concentrations of brown morph in the Amur 

River. 

The maximum length of the gray morph is about 

3 m, and the weight is 190 kg at an age of more than 

60 years. The distribution, mode of life, and population 

structure of the gray morph resemble those 

of kaluga, but they do not enter the sea. They feed 

on benthos and cannibalism rarely occurs. Freshwater 

mollusks and larvae of the Arctic lamprey, Lampetra 

japonica, are usually present in the stomachs 

of the gray morph individuals (Yukhimenko1963, 

Svirskii 1971). 

Maturation, spawning migration, and breeding 

Most gray morph individuals mature at an age of 

10–14 years, being 105–125 cm in length and weighing 

6.0–18.5 kg. Females reproduce at least every 

four years. If previtellogenic and vitellogenic oo-

cytes degenerate, then the age of the first maturation, 

The rest of the catch (8%) was taken upstream from 

as in kaluga, can be delayed by two to four Ekaterino-Nikolslaya village. Differences in the 

years (Svirskii 1979). Total fecundity of Amur sturgeons 

is approximately one-fourth that of kaluga: in 

317 females 8 to 45 years old, the mean fecundity per 

female was 287 780 ± 24 489 eggs (from 41 000 to 

1 057 000 eggs in 388 females). The relative fecundity, 

however, is much higher than that of kaluga, 

from 4600 to 17 300 eggs kg –1 of body weight. 

Both morphs begin to migrate to the spawning 

grounds in autumn. During winter, the gonads of 

80% of the future spawners have not yet reached 

stage IV. A few sexually immature fish migrate from 

the estuary into the Amur River, where they live 

catch were due mostly to regional differences in the 

abundance of sturgeons. 

Now, the lower Amur population of the Amur 

sturgeon comprises about 95 000 fish greater than 

age two years and is approximately half as large as 

the population in the middle Amur. The Zeya and 

Bureya population of the Amur sturgeon is extremely 

small and on the verge of extinction. 

lf the decrease in Amur sturgeon populations 

continues, then the survival of this species is in 

doubt, especially the population inhabiting the middle 

Amur. 

until the completion of sexual maturation. They return 

to the estuary only after spawning, one or two 

years later. 

Amur sturgeon migrate to the spawning grounds 

General comments on the status of kaluga and 

Amur River sturgeon 

in small groups of 3–5 fish. Spawning takes place in 

the spring within 25–30 days at all spawning Since the fall of the Soviet Union, poaching in the 

grounds of the lower Amur. Gray morphs of the Amur River has increased enormously. Fishermen 

Amur River spawn at the same spawning grounds catch fish now not only for food but also for sale. In 

as kaluga, and during spawning, a small number of the lower Amur, intensive fishing of kaluga and 

kaluga - Amur sturgeon hybrids are produced Amur sturgeon migrating to spawning grounds 

(2–5% of all larvae; Figure 2d). The hybrids are pre- started in 1991. The catch increased both on the 

dominantly males (up to 79%). Some hybrids may Russian and Chinese banks of the Amur River, dereach 

1.9 m in length and 70 kg in weight. spite the ban on fishing issued in 1958. 

The embryo period lasts from 83 to 295 hours at The middle Amur populations of both kaluga 

24 0 C and 12° C, respectively (about the same time and Amur sturgeon are especially overfished duras 

kaluga). The transition of free embryos to active ing their spawning migrations and on the spawning 

feeding takes 8.5 days at 18–20°C, i.e., 1.0–1.5 days grounds. In the upper region of the lower Amur 

earlier than in kaluga (Svirskii 1976a). Amur stur- River, illegal fishing is carried out not only by single 

geon survive early development two or three times 

more successfully than do kaluga. 

Comtemporary status 

The current size of the estuary population of Amur 

sturgeon is relatively low: about 3000 fish are older 

than 2 years in the estuary. In 1891, when the catch of 

the Amur sturgeon in the Amur River Basin reach 

ed 607 metric tons, the fish caught in the lower 

Amur and estuary constituted only about 3% of the 

whole annual catch (kryukov 1894). Most fish 

(89%) were caught in the middle Amur, from Ekaterino-Nikolskaya 

village to Tambovskaya village. 

237 

fishermen but also by organized groups. Chinese 

fishermen alone caught approximately 410 metric 

tons of kaluga and Amur sturgeon in 1989, and 170 

metric tons in 1993, taking migrating kaluga and 

Amur sturgeon at the prespawning state. Caviar 

produced was exported to the United States and 

other countries. There is no agreement between 

Russia and China regarding sturgeon fishing in the 

Amur River. Russians started a sturgeon fishery in 

the lower region of the middle Amur in 1991, and by 

1993, had taken more than 200 metric tons of kaluga 

and Amur sturgeon migrating into the middle reach 

of the Amur River for spawning, although official 

records indicated 64.4 metric tons in 1991,62.6 metric 

tons in 1992, and 47.8 metric tons in 1993. In the

238 

near future this type of uncontrolled fishery will 

decimate kaluga and Amur sturgeon populations in 

the estuary and the lower Amur. Contamination of 

the Amur River and its tributaries with heavy metals, 

oil products, phenols, organic substances, and 

other pollutants is a potential but unknown threat. 

Because they spawn on the river bed, the low water 

level in the Amur River during some years does 

not apparently affect the breeding of sturgeons. 

Most young and adult fish also feed in the same area 

of the river. Juveniles migrating for food to the 

small tributaries of the Amur River will not overwinter 

in these areas and, therefore, are not affected 

by the low water levels during autumn-winter perigeon 

juveniles that sometimes was observed in the 

ods. The mass death of the kaluga and Amur stur 

Amur River estuary (due to cold, saline water) affected 

only the estuary populations. Predation on 

kaluga and Amur sturgeon eggs and juveniles in the 

Amur River did not increase within the last two 

decades but was, on the contrary, markedly reduced. 

Kaluga and Amur sturgeon populations in the 

Amur River seem to be in better shape than do be- 

luga and sturgeon populations in the European part 

of Russia (Khodorevskaya et al. 1997 this volume). 

Taking into consideration the existing and expected 

status of the kaluga and Amur sturgeon populations, 

their very low rate of breeding and low efficiency 

of natural reproduction in the Amur River 

basin, we consider it neccessary to build hatcheries 

for artificial breeding and restocking of these species 

1 . 


We thank Vadim Birstein and John Waldman for 

the invitation to participate in the International 

Conference on Sturgeon Biodiversity and Conservation. 

Two anonymous reviewers commmented on 

1 

In 1995. sturgeon poaching from the Russian and Chinese 

banks of the Amur River and its tributary, the Ussuri River, intensified.Increasingly, 

poaching in the Russian part of the lower 

Amur is carried out by well-organized and well-equipped groups 

(editors’ note, February 1996). 

our original draft. The English text was substantially 

revised and improved by Vadim Birstein. Williaim 

E. Bemis drew the map. 


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J. Ichthyol. 30: 11–21). 

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at the Propa-Gen International, Komadi, Hungary. Although both are nearly the same size the bottom individual has a prominent row of 

denticles in the dorso-lateral region. Original by Paul Vecsei, 1996.


© 1997 KIuwer Academic Publishers. Printed in theNetherlands 

Biology, fisheries, and conservation of sturgeons and paddlefish in China 

Qiwei Wei 1.2 , Fu’en Ke 2 , Jueming Zhang 3 , Ping Zhuang 2 , Junde Luo 2 , Rueqiong Zhou 2 & Wenhua Yang 2 

1 State Key Laboratory of Freshwater Fish Germplasm Resources and Biotechnology, Shashi 434000, China 

2 

Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shashi 434000, China 

3 Amur River Fisheries Research Institute, ChineseAcademy of Fishery Sciences Harbin 150070, China 


Key words: Acipenseriformes, Acipenser, Huso, Psephurus, Yangtze River, Amur River, Gezhouba Dam, 

Three Gorges Project, spawning areas 

Synopsis 

This paper reviews five of the eight species of acipenseriforms that occur in China, chiefly those of the Amur 

and Yangtze rivers. Kaluga Huso dauricus and Amur sturgeon Acipenser schrenckii are endemic to the Amur 

River. Both species still support fisheries, but stocks are declining due to overfishing. Acipenseriformes of the 

Yangtze River are primarily threatened by hydroelectric dams that block free passage to spawning and feeding 

areas. The Chinese paddlefish Psephurus gladius now is rare in the Yangtze River system, and its spawning 

activities were severely limited by completion of the Gezhouba Dam in 1981. Since 1988, only 3–10 adult 

paddlefishes per year have been found below the dam. Limited spawning still exists above the dam, but when 

the new Three Gorges Dam is complete, it will further threaten the paddlefish. Artificial propagation appears 

to be the only hope for preventing extinction of P. gladius, but it has yet to be successfully bred in captivity. 

Dabry’s sturgeon A. dabryanus is a small, exclusively freshwater sturgeon found only in the Yangtze River 

system. It is concentrated today in reaches of the main stream above Gezhouba Dam. The fishery has been 

closed since 1983, but populations continue to decline. Acipenserdabryanus has been cultured since the 1970s, 

and holds promise for commercial aquaculture; availability of aquacultural methods offers hope for enhancing 

natural populations. The Chinese sturgeon A. sinensis occurs in the Yangtze and Pearl rivers and seas of 

east Asia. There is still disagreement about the taxonomy of the Pearl and Yangtze River populations. The 

Yangtze River population is anadromous. Adults begin spawning at about age 14 years (males) and 21 years 

(females), and adults spend over 15 months in the river for reproduction. Spawning sites of A. sinensis were 

found every year since 1982 below the Gezhouba Dam, but it seems that insufficient suitable ground is available 

for spawning. Since 1983, commercial fishing has been prohibited but more measures need to be taken 

such as establishing protected areas and characterizing critical spawning, summering and wintering habitats. 

Introduction 

Eight species of Acipenseriformes are native to 

China. Kaluga Huso dauricus and Amur sturgeon 

Acipenser schrenckii are shared with Russia in the 

Amur River system, and Siberian sturgeon A. barerii 

and sterlet A. ruthenus with Kazakhstan and Russia 

in the lrtysh River. Acipenser nudiventris occurs in 

the Ili River, which is a tributary of Lake Balkhash 

in Kazathstan. The remaining three species, Chinese 

sturgeon A. sinensis, Dabry’s sturgeon A. dabryanus 

and Chinese paddlefish Psephurus gladius, 

are endemic to China, particularly the Yangtze River 

and China Sea. In 1988, North American paddle-

242 

Figure 1. Map of China and adjacent countries showing the Amur, Yellow, Yangtze and Pearl rivers and current ranges of sturgeons and 

paddlefish. Much of the Amur River forms the border between China and Russia. The Amur is traditionally divided into upper, middle 

and lower reaches. Most of our data for this system concerns conditions in the middle reach, which we in turn divide into upper middle 

reach and lower middle reach as shown. The Wusulijiang is also known as the Ussuri River and the Songhuajiang is also known as the 

Sungari. Also see Krykhtin & Svirskii (1997) for additional details on Amur River acipenserids. The Yangtze River is also divided into 

upper, middle and lower reaches. Most of our data concern sturgeons and paddlefish of the middle reach, near Gezhouba Dam. Also see 

Zhuang et al. (1997) for additional details on Yangtze River Acipenseriformes. 

fish, Polyodon spathula, were introduced in Hubei 

Province, China, where they are being successfully 

reared in ponds. 

Documentation of sturgeon in China dates to at 

least 1104 BC, when sturgeon were described as 

‘wang-wei’, which means ‘king of fishes’. More than 

ten ancient Chinese books mention sturgeons, including 

descriptions of morphology, habits, distribution, 

fishing and utilization (Anonymous 1988). 

These early descriptions did not distinguish between 

sturgeons and paddlefish. Sturgeons were 

depicted as fishes related to god, such as the sturgeon 

dragon in Guangdong China, and as precious 

fishes, they were sent to emperors as a tribute. 

Many parts of sturgeons were considered to have 

medicinal value. 

We still have relatively poor knowledge of the 

biology of Chinese sturgeons and paddlefish. Until 

the 1970s, most research and publications concerned 

taxonomy. Between 1972 and 1979, we studied 

sturgeon biology and fisheries on the Chinese 

side of the Amur River (Zhang 1985), and in 1988, 

established a propagation station for Huso dauricus 

and Acipenser schrenckii at Qingdeli, Heilongjiang

243 

Province. Also starting in the 1970s were two long 

term investigations of the two species of sturgeons 

and the paddlefish in the Yangtze River. The first 

project was done between 1972–1975, directed by 

the Yangtze River Fisheries Research Institute 

(Anonymous 1988). The second project began in 

1980, prompted by the construction of Gezhouba 

Dam (Fu 1985, Ke et al. 1984,1985). These research 

programs provide the basis for fisheries management 

and conservation of the three species of Acipenseriformes 

native to the Yangtze River. So far, 

A. baerii, A. ruthenus and A. nudiventris from Xingjiang 

Province in northwestern China have hardly 

been studied. 

In the last thirty years, all stocks of sturgeons declined 

due to overfishing, construction of hydroelectric 

dams, and pollution. The Pearl River population 

of A. sinensis and populations of A.dabryanus 

and Psephurus gladius in the Yangtze River 

have been severely impacted. This paper reviews 

the sturgeons and paddlefish in the Amur and 

Yangtze rivers, and discusses conservation strategies. 


Investigations on sturgeons of the Amur River 

were conducted from 1978 to 1979. Studies on the 

Yangtze River were made each fall (October and 

November) from 1981 through 1993, and in the 

spring of 1984. Sturgeons are caught by fishermen in 

accordance with our requirements. In the Amur 

River, the fishermen use three-layer gill nets (see 

Zhang 1985 for description). In the Yangtze River, 

sturgeons are taken using row hooks (Deng et al. 

1991). Chinese paddlefish are caught incidentally in 

gill nets set for copperfish, Coreius heterodom. Our 

main sampling location for Acipenser sinensis is in 

reaches just below the Gezhouba Dam (Figure 1). 

Specimens were measured to the nearest cm (total 

length, TL, body length, BL, fork length, FL) and 

weighed to the nearest 0.25 kg (body weight, BW). 

Since 1983, we have taken Chinese sturgeons, A. 

sinensis, from the Yangtze River for artificial propagation 

and population analysis. We removed the 

pectoral fin rays, clavicles and cleithra for age determination, 

and examined the condition of the gonads. 

Each aging method was read at least twice, 

and the results were usually in agreement (Anonymous 

1988, the age based on annular counts of the 

first pectoral fin ray was used in cases of disagreement). 

Methods used to determine the degree of 

gonadal development were taken from Anonymous 

(1988) and Deng et al. (1991). Several specimens 

in each sample collected since 1982 exhibited 

abnormally developed gonads, and we calculated 

gonadosomatic indices (GSI = gonadal weight/BW) 

to study this. We identified the time and general location 

of spawning for Chinese sturgeon by exam- 

Table 1. Composition of spawning stock of Acipenser schrenckii in the middle reach of the Amur River as related to river location. 

1 From Heihe to Luobei; see Figure 1. 

2 

From Zhaoxing to Qingdeli; see Figure 1. 

SD = standard deviation. 

N = number of samples (individuals).

244 

ining stomachs of copperfish, Coreius heterodom, 

for the presence of sturgeon eggs (Deng & Xu 1991). 

Hydrologicaldata were provided by local monitoring 

stations. Catches were determined from our 

censusor by local fisheries managers. All data were 

analyzed using SAS and MSA (Beijing University 

1993) software. 

Results and discussion 

Amur River 

The Amur River (also known as the Heilong Jiang) 

arises from the confluence of the Shilka and Argun 

rivers. From there, it flows nearly 3000 km to its entry 

into the Sea of Okhotsk. For about one third of 

its length, the Amur River forms the border between 

China and Russia. Geographers distinguish 

three portions of the Amur River usually referred 

to as upper, middle, and lower Amur. Our studies 

focus on the sturgeons of the middle Amur, a section 

of river about 1005km long, that we subdivide 

into upper and lower middle reaches (Figure l), 

with the uppermiddle reach extending between the 

towns of Heihe and Luobei and the lower middle 

reach extending from Zhaoxing to Qingdeli. Additional 

information about the Amur and its sturgeons, 

particularly populations from the lower 

reach and estuary of the Amur River, is given by 

Krykhtin & Svirskii (1997 this volume). Two species 

of sturgeons are native to the middle reach of the 

Amur River. 

Amur sturgeon, Acipenser schrenckii 

TheAmur sturgeonis mostly restricted to the main 

channel of the Amur River from the upper middle 

reach to the mouth (Figure 1). It also occurs in the 

Wusulijiang River (also known as the Ussuri River), 

a tributary to the Amur River, but it is now severely 

depleted in the Songhuajiang River (also 

known as the Sungari River). The species consists 

of a few distinct populations. In general, there is a 

gradient of increasing mean total length (TL) and 

body weight (BW) of spawning stocks from the upper 

to the lower middle reaches (Table 1). Males 

first spawn at age 7 to 8 years, at sizes of about 103 

cm TL and 4 kg BW. First spawningfor females occurs 

at age 9 to 10 years, at about105cmTLand6kg 

BW. Spawning individuals in the lower middle 

reach are older than those in the upper middle 

reach. In the lower middle reach, 72.6% of fish were 

between age 15 and 28 years, whereas in the upper 

middle reach, 75.3% of fish were between 13 and 24 

years of age (Table 2). The oldest individualwas 45 

years. The sex ratio also varied between reaches, 

with a skewed sex ratio in the lower middle reach 

(2.0 : 1, N=251). Betweenlate May and early June, 

we examined gonads of 24 fish aged 15to 38 years. 

The GSI of these specimens ranged from 12.7% to 

34.7%, averaging 23.5 ± 5.6%. Fecundity ranged 

from 114 000 to 1 292 000 with mean of 385 000. The 

number of eggs per gram of body weight ranged 

from 31.0 to 64.4, with a mean of 44.6. Fecundity was 

positively correlatedwith total length and age. Ripe 

eggs ranged from 3.0 to 3.5 mm in diameter. 

Kaluga, Huso dauricus 

The kaluga is a large freshwater sturgeon found 

only in the Amur River. They tend to be solitary 

and non-migratory. Fisheries exist throughout the 

mainstream of the middle reach of the Amur River. 

Kaluga ranged from 160 to 400 cm TL in the lower 

middle reach. Fish between 200 and 320 cm TL ac- 

Table 2. Age composition of spawning stock of Acipenser schrenckii in the middle reach of the Amur River. 

H-L = upper middle reach from Heihe to Luobei: Z-Q = lower middle reach from Zhaoxing to Qingdeli: Nt = total number of samples; 

Nm = number of males; Nf = number of females; and values = individuals.

245 

counted for 87.4% near Zhaoxing,whereas fish between 

180 and 300 cm TL accounted for 87.4% near 

Qingdeli (Table 3). Body weight ranged from 40- 

501kg. In a sample of 79 specimens,74.7% were between 

40 and 165 kg BW. Females tended to be 

larger than males. In a sample of 53 females, 52.8% 

ranged from 90kg to 190kg, and 41.5% ranged from 

190 kg to 501 kg. The spawning population ranged 

from 12 to 54 years of age (Table 4). Age is positively 

correlataed with length and weight. Theoldest individual 

(54 years) was also the largest at 390 cm TL 

and 501 kg BW. Sex ratios differed between the upper 

and lower middle reaches. Theratio of males to 

femaleswas1.4:1nearZhaoxing(N=113) and3.7 :1 

near Qingdeli (N = 48). The average GSI for females 

was 13.9% in May (maximum of 17.3%); by 

June, the GSI was 14.1% (maximum of 18.4%). Fecundity 

ranged froma 383 400 to 3 280 000 (N = 22; 

224–390 cm TL). Mean fecundity was 600 000, 

1500 000, and 3 000 000 for individuals with TL 

224–274 cm, 281–327 cm and 350–390 cm, respectively. 

The number of eggs per gram of body weight 

ranged from 27.8 to 53.0, with a mean of 41.4. Ripe 

eggs ranged from 2.5 to 3.5 mm. 

Reproduction. – Both Amur sturgeon and kaluga 

usually spawn between May and July when water 

temperatures range from 15° to 20°C. Spawning 

habitat is characterized by calm water and sand and 

gravel substrates. Kaluga spawn at a depth of 2 to 3 

m. Appropriate spawning habitat is available from 

the upper to the lower middle reaches of the Amur 

River. Known spawning sites are located at the 

mouth of the Pingyanghe and Xueshuiwen rivers in 

Xunke County,in the Yadanhe and Zhaoxing rivers 

within Luobei County, and in the Qingdeli and Xiabaca 

rivers within Tongjiang County. We have not 

found any spawning sites in the Songhuajiang and 

Wusulijiang rivers. 

Natural hybridization occursbetween kaluga and 

Amur sturgeon in the Amur and Songhuajiang rivers 

(Ren 1981). Historically, the hybrids were considered 

a distinct species (Gong 1940). They have 

intermediate characteristicsand resemble artificially 

produced hybrids (Krykhtin & Svirskii 1986, fig. 

2d). 

Fisheries. –Thepullnets and rowhooks used to capture 

sturgeons in the Amur River until the 1950s 

were replaced by three-layer gill nets. Fishing impact 

on sturgeons was low before the 1970s because 

few people lived along the Amur River. However, 

with increasing population and the high profit of 

sturgeon fishing, catches increased. There are now 

2 to5 sturgeonfishing boats per kilometer along the 

mid reaches of the Chinese side of theAmur River, 

and annual exports of caviar increased from 3 metric 

tons in the 1970s to 12 tons in 1990. Separate catch 

data for the two species are not available. Incomplete 

statistics from 9 sites show that the annual 

catch from 1952 to 1956 and 1959 was commonly 70 

to 80 tons year-1 in the entire middle reaches of the 

Chinese side, with a minimum of 30 tons year -1 . In 

1978, 90 tons were harvested, 141 tons in 1981,175 

tons in 1985, and 200 tons by 1987. In recent years, 

production decreased at some locations, especially 

in the upper middle reaches, despite comparable 

fishing effort. Fishing has moved to the lower part 

of the mid reaches, and harvests in these areas are 

now declining. Annual catches at Qingdeli, for instance, 

were 36.3, 31.7, 27, 26.7 and 21.6 tons in the 

years from 1985 through 1989. 

Most of the fish taken are spawning-sized adults. 

This has grave consequences for the future of the 

fishery. We sampled 256 Amur sturgeon from fishermen 

at Luobei, which included 123 young fish 

ranging from 20 to 100cm TL, and 133adults ranging 

from 100 to 180 cm TL. In another large sample 

of Amur sturgeon (407 individuals from Zhaoxing 

and Qingdeli), young fish accounted for only 5.7% 

of the total sample.For kaluga from Zhaoxing and 

Qingdeli, young accounted for 29.3% of the total 

sample. 

Conservation efforts. –The government of Heilongjiang 

Province issued specific regulations for the 

protection and management of sturgeons in the 

1950s, and renewed them in 1982. Current regulations 

are not fully implemented because of insufficient 

management. Furthermore, some regulations 

are based on insufficient understanding of the 

stocks. As the stocks declined, a propagation station 

for Amur sturgeon was set up at Qingdeli in 

1988. About 900 000 larvae (0.2 to 0.4 g BW) and

246 

168 000juveniles (1.0 to 1.5 or 20 to 30 g BW) were 

stocked into the Amur river from 1988 to 1991,and 

the number of young sturgeon in the Amur River 

seemed to be increasing through 1991 (Chen & 

Zhou 1992). 

Yangtze River 

The Yangtze (also known as the Chang Jiang) arises 

in southwestern China and flows 5500 km across the 

country to reach the East China Sea near Shanghai 

(Figure 1). Based on its outflow, the Yangtze is the 

fourth largest river in the world, surpassed only by 

the Amazon, Congo, and Indus rivers. Near the 

headwaters, the mainstream of the Yangtze is 

known as the Tongtian River; its eastward course 

toward Sichuan is known as the Jingsha River; as it 

passes through Sichuan it becomes known as the 

Yangtze. It passes through some of the most densely 

populated areas of the planet, yet it retains three 

native species of Acipenseriformes. This situation is 

now deteriorating rapidly, and all three species in 

the Yangtze River have been listed as state protected 

animals in Category I. 

Dabry’s sturgeon, Acipenser dabryanus 

Dabry’s sturgeon is a freshwater species that occurs 

only in the middle and upper reaches of the Yangtze 

River (Figure 1). It reaches at least 130 cm TL and 

16.0kg BW. Major research was done from 1972 to 

1975.This species is easily propagated, and has excellent 

commercial aquaculture potential. The native 

population, however, sharply declined in the 

last two decades. Some fish still occur in the upper 

middle reach but few occurred in reaches below the 

Gezhouba Dam in recent years. See Zhuang et al. 

(1996, this volume) for a review of this species. 

Chinese paddlefish, Psephurus gladius 

The Chinese paddlefish is characterized by its 

sword-like rostrum and several osteological features 

that distinguish it from other fossil and living 

paddlefishes (Grande & Bemis 1991,1996, Bemis et 

al. 1997 this volume). Rostral length (RL) is as much 

as 114 to 113 times the total length (TL = –17.134 + 

3.8957 RL, N=16, R = 0.9841, S=9.9181, F= 

249.366). Detailed biological investigations are impossible 

because Psephurus is now very rare. Migration 

patterns and spawning sites of the Chinese paddlefish 

are unknown, although it historically occurred 

in the East China Sea, so it is presumably 

anadromous (Anonymous 1988). It is also recorded 

from the Yellow River and Yellow Sea (Zhu et al. 

1963, Li 1965). 

Within the Yangtze River, Chinese paddlefish 

were commonly found in the mainstream, and 

sometimes in its tributaries including Tuojiang, 

Mingjiang, Jialinjiang, Qiantangjiang and Yongjiang 

rivers, and Dongting and Poyang lakes (Anon- 

Table 3. Composition of spawning stock of Huso dauricus in the middle reach of the Amur River by sex.

ymous 1988, Lin & Zeng 1987, also see Zhuang et al. 

1996 for a map of the Yangtze River). Prior to 1980, 

mature individuals only occurred in the upper 

reaches of the Yangtze River, juveniles (4 cm TL) 

occurred in the Jiangan-Fongdu section of the upper 

Yangtze River, and fingerlings (75 to 250 mm 

TL, 5 to 95 g BW) occurred in the Xupu-Chongming 

section of the lower Yangtze River (Anonymous 

1988). Juveniles ranging 80 to 530 mm TL were 

found on the eastern tidal beach of Chongming Island 

(i.e., the Yangtze estuary) from 1983 to 1985. 

No report on the population structure of paddlefish 

is available. According to Lin & Zeng (1987), the 

maximum weight is 500 kg. The total length of 17 

specimens, which were incidental-catches or carcasses 

found just below the Gezhouba Dam from 

1981 to 1986, ranged from 148.8 cm to 262 cm TL 

(Figure 2). Individuals 182 to 244 cm TL accounted 

for 88.2% of this sample. The mean weight of 11 ripe 

individuals taken in 1973 from upper reaches of the 

Yangtze River was 37.5 kg (Anonymous 1988, average 

body weight 26.9 kg, range from 13.9 to 53.5 kg). 

The relationship between TL and BW was: BW = 

1.577 × 10 –7 TL 3.5250 (N = 19, R = 0.9863, FF = 

607.702). Ages of spawning individuals ranged from 

8 to 12 years. Males with gonads at stage IV accounted 

for 75% of the sample, and the remaining 25% 

had testes at stage III (see Anonymous 1988). A single 

female found on 20 November, 1984, was 10 

years old, 244 cm TL and 41.5 kg BW, its ovaries 

were at stage IV of development. It carried 338 000 

eggs with average diameters of 2.45 mm. Yu et al. 

(1986) described a female paddlefish found just below 

the Gezhouba Dam, with gonads at stage IV 

and egg diameters ranging from 2.8 to 3.8 mm. 

247 

Chongqing (Anonymous 1988). The Sichuan Fisheries 

Research Institute (1980) reported a spawning 

ground near Yibing as evidenced by the capture of a 

female with running eggs on 6 April 1980. The mean 

diameter of the eggs, which were fully distended 

with water, was 2.8 mm. The spawning site was described 

as 500 m in length, consisting of sand in the 

upper part and gravel or cobble in the lower part. 

Spawning presumably occurred on 4 April 1980, at a 

water temperature between 18.3 and 20.0°C, surface 

water velocity of 0.72–0.94 m s –1 and at a maximum 

water depth of about 10 m. They suggested 

that the spawning period may be from late March to 

early April. We think that natural spawning still exists 

in the upper reaches of Yangtze River because 

juveniles have been found there since the construction 

of Gezhouba Dam (Liu 1992). Spawning in 

reaches below Gezhouba Dam must have occurred 

from 1983 to 1985, as evidenced by the occurrence of 

juveniles in the Yangtze River estuary in the same 

period (Zhu & Yu 1987, Yu et al. 1986). However, no 

juveniles have been found below the Gezhouba 

Dam since 1986, and we think that perhaps these 

spawning grounds disappeared after 1986. The total 

number of individual Chinese paddlefish recovered 

below Gezhouba Dam has been declining since the 

middle of the last decade (Figure 3), which suggests 

that no recruitment to this population is occurring. 

Artificial propagation of Chinese paddlefish has 

not been successful. This is in marked contrast to 

the ready availability of eggs and embryos of North 

American paddlefish, Polyodon spathula (e.g., Bemis 

& Grande 1992). We have difficulties catching 

broodstock because of the rarity of Psephurus. 

Moreover, captive ripe males and females have 

never been available at the same time. We also find 

adult Psephurus difficult to keep in captivity. 

Reproduction and present status. — The spawning 

grounds for Chinese paddlefish are unknown. They 

are probably scattered and limited to reaches above Conservation efforts. —Before 1983, it was permissible 

to take Psephurus throughout the river. The 

Table 4. Age composition of spawning stock of Huso dauricus in species has been fully protected since 1983, and pro- 

the middle reach of the Amur River. 

tected stations for Chinese sturgeon and paddlefish 

Age range 12-20 22-40 42-44 47 54 were set up along reaches in Hubei and Sichuan 

(years) 

provinces. Fishermen now usually release their incidental 

catches. Several attempts to artificially 

N 15 108 6 1 1 

Percentage 11.5 82.4 4.6 0.75 0.75 spawn paddlefish were unsuccessful, and we have

248 

Figure2. Size frequency distribution of Seventeen adult Chinese 

paddlefish. Psephurus gladius, found below Gezhouba Dam between 

1982 and 1986. 

been unable to hold brood fish for more than a 

month. 

Chinese sturgeon, Acipenser sinensis 

As presently understood, the Chinese sturgeon is 

restricted to the main channel of the Yangtze River, 

the Pearl River, and the East and South China Seas 

(Figure 1). There is still uncertainty about the taxonomy 

of the two populations in the Pearl and 

Yangtze rivers. The original specimen of A. sinensis 

(32 cm TL), collected by Reeves, may have been 

from the Pearl River (Anonymous 1988). Wu et al. 

(1963) considered the larger anadromous sturgeon 

from the Yangtze River to be A. sinensis [note that 

Zhu (1963), regarded all sturgeon in the Yangtze 

River and in the East China Sea to be A. dabrynnus, 

an opinion not shared by later workers]. It has been 

suggested that the large anadromous sturgeons of 

the Pearl and Yangtze rivers should be considered 

as two isolated species (Anonymous 1988). The 

large anadromous sturgeon from the Pearl River 

seem to differ in morphology, spawning time and 

migration pattern from those in the Yangtze River 

(Zhou et al. 1994), but much more evidence needs 

to be collected to examine this taxonomic problem, 

particularly because very little information is available 

about the Pearl River population (Zhen 1989). 

The Pearl River population appears to be even 

more endangered than the one in the Yangtze River. 

A new hydroelectric project, the Changzhou 

Dam, will block spawning migrations (Chu et al. 

1994). 

Migration of the Yangtze River population. - Adults 

with gonads approaching maturity (in early stage 

Figure3. Total number of occurrences of adult Chinese paddlefish, 

Psephurus gladius, below Gezhouba Dam from 1981 to 1993 

III), arrive from the sea in June or July at the mouth 

of the Yangtze River to ascend its main channel 

(Anonymous 1988). The adults do not feed while in 

the river. They arrive at the Jingjiang reach, not far 

below the Gezhouba Dam, in September or October, 

where they overwinter. Ripe individuals were 

formerly found as far inland as the Jingsha River 

(Figure 1) during the following October and November, 

where they spawned. Prior to construction 

of the Gezhouba Dam, the migration distance was 

as long as 2500 to 3300 km. 

Juvenile A. sinensis 7 to 38 cm TL occur in the 

Yangtze River estuary from the middle of April 

through early October. These are presumably one 

year old individuals (Wei et al. 1994, Anonymous 

1988). Juveniles weighing a few kilograms can be 

found in coastal waters near the river mouth. Individuals 

from 25 to 250 kg in weight were registered 

in some fishing grounds of East China Sea and Yellow 

Sea (Anonymous 1988). 

Structure of the Yangtze River population.– Some 

investigations on the structure of the spawning population 

have been performed (Ke & Wei 1992, Deng 

et al. 1991. Anonymous 1988, Deng et al. 1985). Females 

are larger than males (Figure 4) and the sex 

ratio is consistently about 1:1. We recorded the total 

lengths (TL) of 475 individuals taken between 1981 

and 1993, and found it to range from 189 cm to 389 

cm (mean = 273 cm). The 266 males in the sample 

ranged from 189 to 305 cm TL (mean = 242 cm), and 

the 209 females ranged from 253 to 389 cm TL 

(mean = 313 cm). Fish weighed 42.5 to 420 kg (mean 

of 213.7 kg). Males weighed 42.5 to 167.5 kg (mean 

of 85.4 kg), and females weighed 104.5 to 420 kg 

(mean of 217.3 kg). Total length is significantly cor-

249 

Figure 4. Size frequency distribution of spawning population of Chinese sturgeon. A. 

coded separately to show sexual dimorphism of this population. N = 475. 

sinensis, from 1981 to 1993. Males and females are 

related with weight: BW = 1.1969 × 10 –6 T 3.298 (N = 

269,r = 0.9452, S BW.TL = 25.58. F = 2239.39). 

From 1981 through 1993, 384 fish were used for 

age determination. This sample included 214 males, 

169 females and 1 inter-sexual. Fish ranged from age 

8 to 34 years (N = 383). The mean age of the spawning 

population was 17.0 years (14.0 years Tor males 

and 20.7 years for females, Figure 5). Males ranged 

between 8 and 27 years, with the majority between 

10 and 18 years (90.2%); females ranged between 13 

and 34 years with the majority between 16 and 27 

years (86.4%). Deng et al. (1991) reported that fish 

making an initial spawning accounted for 84% of all 

males and 76% of all females Our results differ. We 

determined whether reproductive marks occurred 

in all three structures used for aging (the first pectoral 

fin ray, the clavicle and cleithrum) in a subsample 

of 341 of the 384 specimens. Reproductive 

marks were indistinct in the remaining 43 specimens, 

in which the average ages were 14.3 years for 

males (N = 18) and 21.4 years for females (N = 25). 

The first column of Table 5 shows that individuals 

making an initial spawning run accounted for 

66.3% of males and 44.4% of females. We found 

that the first spawning mark exactly recorded the 

age of first reproductive migrations, allowing us to 

Figure 5. Age frequency distribution of spawning population of Chinese sturgeon. A. sinensis. from 1981 to 1993. N = 383.

250 

determine the age at first reproduction for the entire 

subsample of 341. The ages of individuals which 

belong to the class of initial spawners are not significantly 

different from the age of first spawning for 

repeated spawners (t = 0.485 < t 0.005 = 2.358). This 

demonstrates the validity of our determination of 

initial reproductive marks. It also suggests that the 

average age at initial reproduction of A. sinensis is 

14.3 years. Because of the blurring of structures following 

the initial spawning mark, and of insufficient 

sample, we cannot verify the time intervals between 

repeated spawning migrations. 

Chinese sturgeon exhibit different individual 

growth rates. Commonly, females are larger than 

males of the same age. For instance, 14 year old 

males had a mean TL of 248.0 cm (N = 35, SD = 

13.00, range 221-274 cm) whereas females had a 

mean TL of 289.6 cm (N = 7, SD = 11.76, range 272- 

306). By age 18 years, males had a mean TL of 256.9 

cm (N=15, SD=l4.85, range 234–285 cm) and females 

had a mean TL of 300.4 cm (N=11, SD=26.00, 

range 263–340 cm). The growth rate of A. sinensis is 

one of the highest known among the species of Acipenderifomes 

(Holcík 1989, Smith 1985). 

^ 

Some changes in age conmposition in recent years. – 

We were interested in examining age composition 

of the population as it may have changed since completion 

of the Gezhouba Dam in 1981. With very 

limited samples available. we classified them into 

four groups: group I (1981–1983), group II (1984– 

1986), group III (1987–1989) and group IV (1990– 

1993) (in I990 only 3 specimens were available). 

ANOVA shows that the differences in age are not 

significant between each group for females and also 

for males before 1990. Males in group IV, however, 

are significantly older than those in groups I, II and 

III (p < 0.01). The mean age of group IV males is 17.1 

years while those of group I, II and III are 13.0, 12.8 

and 12.6 years, respectively. Furthermore, males 

younger than 12 years are very underrepresented 

(percentages younger than 13 years were 47.1%, 

47.5%, 43.5% and 4.7% in groups I to IV, respectively). 

No fish born in 1982 and 1983 were found, 

and only two fish born in 1981 and 1984 were found. 

On the other hand, the number of repeated spawners 

was higher for group IV males (26.2, 28.6, 34.4 

and 46.5% in group I, II, III and IV, respectively) 

but did not increase for females (52.0, 69.2, 65.0 and 

42.6% in group I, II, III and IV, respectively). Taken 

together, these results suggest that recruitment of 

males to the population is declining at a dangerous 

rate. 

Gonadosomatic index and its alteration after construction 

of Gezhouba Dam. -As mentioned above, 

two groups of spawning adults can be found in the 

river at the same time, one with gonads at stage III 

(or rarely II) and another with gonads at stage IV or 

V (or rarely VI). Before completion of the Gezhouba 

Dam, females stage III gonads exhibited these 

characteristics; gonadas fat 60–70% (September 

and October) or 20–60% (November and December); 

GSI 2.8–7.1% (mean 4.8%, September and 

October) or 2.4–9.0% (mean 7.3%. November and 

December); and egg diameter 2.0–2.5 mm (September 

and October) or 2.5–3.5 mm (November and 

December; summarized from Y. Z. Leng in Anony- 

T able 5. Ages of Acipenser sinensis and repeated reproduction (1981-1993). 

1 As explained in text, this estimate compiles data from the first column in the table together with data from analysis of spawning marks 

detectcd in fish that made a subsequent spawning migration. N = number of samples, x = mean age, SD = standard deviation.

251 

mous 1988). A sample of 54 females with stage IV 

gonads had: no gonadal fat; GSI 11.77–25.95% 

(mean 19.11%); and egg diameter 4.0 x 4.2–4.5 × 5.0 

mm. However, since the damming, this situation 

has changed. In Table 6 we report data on the developmental 

status of the ovary for10 females sampled 

in October 1984.Only in individual 4 the ovary was 

in stage IV of development. For the other 9 specimens, 

GSI and egg diameter still had not attained 

conditions typical of stage IV even though the gonadal 

fat was exhausted. The shape and color of eggs 

were different, and sections showed that the yolk 

was being re-absorbed (Ke et al. 1985), so that the 

ovaries were regressing or degenerating. A similar 

phenomenon has been observed in other sturgeons 

(Kozlovsky 1968). In 1984, males also exhibited gonadal 

degeneration. Since 1984, we have investigated 

further the gonadal degeneration of spawning 

males and females (Figure 6). The absolute number 

of individuals exhibiting gonadal degeneration varies 

from year to year but the percentage of fish 

showing gonadal degeneration has decreased from 

the 1984 high. 

Spawning. – Before the damming of the Yangtze 

River by Gezhouba Dam in January 1981, spawning 

areas for A.sinensis were distributed in the section 

from the upper Yangtze above Huling to the lower 

Jingsha River below Xingshi, covering at least 800 

km of river length. At least 16 historical spawning 

sites are known (Anonymous 1988). However, only 

one major spawning site has been found below the 

dam. It is in a narrow area about 5 km long, just below 

the dam. A minor spawning site was also found 

at Huyiatan, 15 km below the dam, on 23 October 

1986 and 14 November 1987. Spawning sites are usually 

located at a bend in the river where the river 

Figure 6. Annual variation in gonadal degeneration of the 

spawning population of Chinese sturgeon, A. sinensis. 

bottom consists of gravel or rocks. Typical spawning 

sites have a complex substrate, with water depth 

ranging from 3 to 40 m, although we believe that 

shallow areas are the preferred spawning sites. In 

1993, an area 4 to 10 m deep was used for spawning 

(Kynard et al. 1995). Spawning occurs in a short period 

from middle of October to middle of November 

when water temperature is between 15.2– 

20.2°C (Anonymous 1988). In general, spawning 

occurs twice during the period. 

We documented 19 spawning that took place be- 

Table 6. Reproductive condition of ten female Acipenser sinensis from the Yichang section sampled in October 1984.

252 

Figure 7. Annual landings of the migratory population of Chinese 

sturgeon, A. sinensis, in the Yangtze River. 

low the Gezhouba Dam since it closed in January 

1981. Except in 1981, we found spawning activities 

each year in the major spawning site. Because the 

spawning population was overfished below the dam 

in 1981 and 1982 (Figure 7), few fish were available 

to spawn in 1982, and as a result, spawning activities 

were scattered and abnormal. Table 7 shows that 

spawning dates after the damming are similar to 

those before the damming. In half of the years sampled, 

spawning only occurred once at the major 

spawning site, but in 1987 we found eggs in stomachs 

of copperfish for 17 days, which we interpret as evidence 

of two spawnings during this period. We are 

not sure what factors trigger spawning, although 

some researchers consider that water level (Anonymous 

1988) or water temperature (Deng et al. 1991) 

are critical factors. Buckley & Kynard (1985) reported 

that shortnose sturgeon A. brevirostrum require 

a specific water velocity to spawn, and Chinese 

sturgeon may be similar. We believe that the 

available spawning sites are insufficient because 

ripe females can still be taken even after the spawning 

period is over. 

Harvest and stock size of the migratory population 

in the Yangtze River . -Before 1981, sturgeon fisheries 

mainly occurred in the middle and upper reaches 

of Yangtze. Fishing was unlimited, but seasonal, 

and mostly in the fall. Gear include gill nets (upper 

reach) and row hooks (middle reach). Catch data 

are not available prior to 1972. Between 1972 and 

1980, the annual mean catch of migratory adults was 

517 individuals or 77 550 kg (150 kg per individual) 

for the entire river. When the river was dammed in 

January 1981, almost all of the fish trapped in a small 

area below the dam were caught in 1981 and 1982. 

As a consequence, the catch reached a peak of 1163, 

Table 7. Hydrological characteristics of spawning areas used by A. sinensis at Yichang below Gezhouba Dam from 1983-1993. 

Water temperature (°C) Water level (m) Silt content (kg m-3) Water velocity (m s-1)2 

Date Days 1 Start Fluctuation Start Fluctuation Start Fluctuation Start Fluctuation 

7.11.83 5 17.9 17.9–17.2 43.01 42.90–43.55 0.35 0.35–0.43 0.89 0.88–1.07 

16.10.84 7 18.9 18.9–18.6 45.00 45.45–44.36 0.66 0.33–0.66 1.42 1.30–1.49 

13.11.84 5 17.1 17.1–16.8 41.71 41.69–41.90 0.10 0.10–0.08 0.81 0.80–0.84 

13.10.85 7 19.8 19.8–18.8 44.75 44.75–44.22 0.69 0.69–0.60 1.39 1.39–1.28 

7.11.85 7 17.5 17.5–15.7 43.73 44.31–43.41 0.29 0.56–0.21 1.15 1.39–1.07 

21.10.86 5 18.2 18.3–18.0 45.38 45.38–44.35 0.87 0.87–0.51 1.39 1.39–1.28 

31.10.87 17 17.2 17.4–15.8 43.00 43.29–41.49 0.44 0.44–0.09 1.16 1.16–0.90 

13.10.88 4 18.8 18.8–18.3 46.33 46.33–45.41 0.59 0.59–0.45 1.19 1.19–1.72 

3.11.88 3 18.6 18.6–18.0 43.46 43.46–42.84 0.45 0.45–0.35 1.26 1.26–1.18 

27.10.89 8 17.7 18.0–17.7 46.59 46.59–44.52 1.00 1.00–0.53 1.66 1.66–1.38 

15.10.90 7 18.9 19.0–18.8 47.29 47.29–45.49 1.32 1.91–0.67 1.98 1.98–1.49 

31.10.90 5 17.8 17.8–17.2 44.23 44.23–43.11 0.30 1.28–1.09 1.28 1.28–1.09 

23.10.91 7 19.4 19.4–18.0 44.24 44.24–43.44 0.62 1.82–1.32 1.82 1.82–1.32 

17.10.92 8 19.0 19.2–18.6 43.71 43.71–42.78 0.70 0.98–0.38 1.27 1.27–1.13 

17.10.93 6 20.0 20.0–18.8 45.20 46.31–44.70 0.83 1.24–0.79 2.07 2.20–1.81 

30.10.93 7 18.0 18.0–17.2 44.24 44.24–43.54 0.59 0.67–0.49 1.73 1.93–1.29 

1 Number of days during which sturgeon eggs were found in the stomach of Coreius guichenoti. 

2 

Mean water velocity at the Moji monitoring section; other hydrological data provided by Yichang Hydrological Monitoring Station.

including 161 from the reaches above the dam (Fig. Recommendations 

7). Commercial fishing has been closed since 1983, 

and fishing for scientific or propagation purposes Amur River 

produces annual catches of about 100 individuals. In 

addition to fishing mortality, many individuals are 

killed by the dam. and are discovered as carcasses 

below it. The number of carcasses has declined as 

the number of adult sized fish trapped above the 

dam continues to decrease. 

Stocks of Huso dauricus and Acipenser schrenckii in 

the Amur River are declining dramatically due to 

overfishing. If we ignore this situation, then we will 

loose the sturgeon fishery and perhaps even both 

species. Loss of sturgeon fisheries has occurred in 

We tagged 57 adults collected from sites at Shashi many other places (Holcík et al. 1989, Smith 1985. 

(51) and at Yichang (6) in 1983 and 1984 in order to 

estimate the stock size. By the following year, we 

had recaptured 6 individuals, including 4 from the 

areas near the release sites and 2 from the sea near 

the mouth of the Yangtze. Using Peterson's method, 

we estimated that the mean stock size of the 

spawning stock of Chinese sturgeon was 2176 (946 

Galbreath 1985, Folz & Meyers 1985, Pinter 1991). 

We recommend that the following measures be immediately 

taken: (1) modify existing regulations for 

sturgeon fishery management; (2) reduce fishing effort. 

including restrictions on the number of boats, 

the type of gear used. and the maximum allowable 

catch; (3) strictly forbid fishing juveniles and to 

and 4169 as 95% confidential intervals) in 1983 and strengthen artificial propagation; (4) strengthen 

1984. Given alternate year spawning migrations, 

the annual stock size migrating into the river was 

about 1000 individuals. 

No exact data on juveniles are available for years 

scientific investigations on the stock to establish a 

rational maximum allowable catch; (5) work out a 

joint pledge for sturgeon conservation in the shared 

waters of China and Russia. 

prior 1981. However. the stock of juveniles has decreased 

at the Yangtze estuary. In the 1960s, this 

stock supported a major commercial fishery but it Yangtze River 

has declined to about 5000 fish per year (Wei et al. 

1994). The construction of Gezhouba Dam greatly affected 

stocks of P. gladius and A. sinensis. If no mea- 

Conservation efforts. – All commercial fishing has sures are taken, paddlefish will disappear in the 

been banned since I983 and a series of protective middle and lower reaches of Yangtze in the very 

measures have been taken, including setting up pro- near future, placing the species on the verge of extection 

stations along the river and a station at Yi- tinction. Wild populations of A. dabryanus are dechang 

for artificial propagation and research. In clining despite protection. The typical anadromous 

1988. A. sinensis was listed as a state protected ani- species, A. sinensis, is increasingly threatened. As 

mal in class I. In 1983, the first successfull artificial the largest dam ever constructed, The Three Gorgspawning 

was made by the Yangtze River Fisheries es Project, nears completion (1997), the habitat for 

Institute (Fu et al. 1985). Since then, an average of both species of sturgeons and the paddlefish will be 

250 000 larvae and some juveniles have been further harmed. This huge dam will be 175m high 

stocked into the river annually. The total number and is only 47 km upstream from the Gezhouba 

stocked was 2.8 million larvae and 17 000 juveniles Dam. Furthermore, it will use 1.3 million tons of 

(size 2–10 g) from 1983 through 1993. Both the gen gravel and rocks from the reach below Gezhouba 

eral public and fishermen are now protective of Dam as construction material (Ke & Wei 1993), disturgeon, 

and willingly release incidental catches. rectly damaging the largest known existing spawn- 

For instance. in just the Yichang section. we are ing ground for Chinese sturgeon and many other 

aware of 148 incidental catches that were released commercial fishes. Despite these serious impacts. 

between 1986 and 1993. some measures can and should be taken, such as: (1) 

establishing protected areas for juvenile Chinese 

^ 

253

254 

sturgeon at the Yangtze estuary to permit effective 

recruitment of Chinese sturgeon including the Yichang 

Protected Area for spawning and the 

Chongming Protected Area Wei et al. 1994): (2) 

characterizing habitats for Chinese sturgeon including 

spawning sites, summer and winter grounds 

using telemetry and related techniques (Buckley & 

Kynard 1985) to enable agencies to protect these 

sites or, possibly. to re-create additional spawning 

areas below the dam; (3) conducting studies of paddlefish, 

particularly on artificial culture. which may 

be the only way to maintain this species. 


The Yichang Fisheries Management Station coordinated 

the field surveys, and the Bureau of East 

China Sea Fisheries Management assisted our work 

in the Yangtze Estuary. We thank Boyd Kynard for 

critical review of the initial manuscript, and James 

D. Williams, Theodore I. J. Smith, Frank M. Parauka 

and Kim Graham for providing us with valuable 

literature. We extend special thanks to Vadim Birstein, 

Robert H. Boyle and John Waldman for organizing 

the international sturgeon conference. William 

E. Bemis substantially revised the text of our 

original manuscript and drew the map and figures. 


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‘The Fresh-water Fishes of China’.



Biology and life history of Dabry’s sturgeon, Acipenser dabryanus, in the 

Yangtze River 

Ping Zhuang, Fu’en Ke, Qiwei Wei, Xuefu He 1 & Yuji Cen 

Yangtze River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shashi, Hubei, 434000, 

China 

1 

Department of Biology, Southwest Normal University, Chongqing, Sichuan, 630715, China 


Key words: Gezhouba dam, population size, conservation 

Synopsis 

Dabry’s sturgeon, Acipenser dabryanus, is a relatively small (130 cm, 16 kg) and now rare sturgeon restricted to 

the Yangtze River Basin. It behaves as a resident freshwater fish, does not undertake long distance migrations 

(except for spawning), and lives in a variety of habitats. It historically spawned in the upper Yangtze River, but 

the spawning sites are unknown. Acipenser dabryanus reaches maturity earlier than do other Chinese sturgeons, 

which gives the species aquaculture potential, and artificial spawning has been carried out. However, 

the native population in the Yangtze has sharply declined in the last two decades due to overfishing, pollution 

and habitat alteration and destruction, especially since the construction of the Gezhouba Dam, which was 

built in 1981 across the Yangtze River at Yichang, Hubei Province. Since 1981, Dabry’s sturgeon rarely occurs 

below the Gezhouba Dam because downstream movements are blocked. Clearly, conservation of Dabry’s 

sturgeon must be emphasized. Conservation methods may include protecting habitats, controlling capture 

and stock replenishment. 

Introduction 

Dabry’s sturgeon, Acipenser dabryanus, is one of 

two species of acipenserids found in the Yangtze (= 

Changjiang) River, China. The second species is the 

Chinese sturgeon, A. sinensis. More than a thousand 

years before the Christian era, external anatomy, 

general habits and characteristics, fishing methods 

and supposed medicinal value of sturgeons 

were described in ancient Chinese literature. However, 

the two species of sturgeons in the Yangtze 

River were not scientifically distinguished until the 

middle of the 19th century. Acipenser dabryanus 

was described by Duméril (1868) based on a type 

specimen collected from the Yangtze River by M. 

Dabry and now kept in the Museum National 

D’Histoire Naturelle, Paris, France (Zhang et al. 

1993). Gunther (1873), Wu (1930), Nichols (1943), 

Wu et al. (1963), and Fu et al. (1988) subsequently 

studied the morphology of this species using additional 

specimens from the Yangtze River. Until the 

1960s, there was some taxonomic confusion between 

Dabry’s sturgeon and Chinese sturgeon 

(Zhu et al. 1963, Wu et al. 1963). Now, we accept that 

Dabry’s sturgeon is a freshwater species restricted 

to the Yangtze River, whereas the Chinese sturgeon 

is an anadromous species that inhabits both the 

Yangtze and Pearl rivers (see Wei et al. 1997 this volume 

for data on the Chinese sturgeon, A. sinensis). 

Dabry’s sturgeon is also called the Yangtze sturgeon, 

Changjiang sturgeon or river sturgeon, and it 

was an important commercial fish in the middle and

258 

Figure 1. Past and present ranges of Acipenser dabryanus. Data from Nichols (1943), Wu et al. (1963), Yang (1986), Zhang (1988), Ke et al. 

(1989), He (1990), Zen et al. (1990) and the research of the authors. Names of places on the map are consistent with those used in the New 

York Times Atlas of the World, Third Revised Concise Edition. 

upper reaches of the Yangtze River (Yang 1986, 

Zen et al. 1990, He 1990). As a result of overfishing, 

pollution and habitat alteration and destruction, 

Dabry’s sturgeon populations have been declining 

for the last two decades (Wu 1990).The species now 

rarely occurs in reaches below the Gezhouba Dam, 

which was built in 1981across the Yangtze River at 

Yichang, Hubei Province (Figure 1).Commercial 

capture of Dabry’s sturgeon in the Yangtze River 

has been banned since the early 1980s when it was 

listed as an endangered species under the state’s 

special protection in Category 1. Unfortunately, this 

listing seems to have occurred too late to significantly 

impact conservation of wild populations of 

Dabry’s sturgeon. 

This paper reviews the general biology and life 

history of Dabry’s sturgeon and provides a source 

Table I. Meristic features of adult Dabry’s sturgeon (modified from Fu 1988).

259 

of pertinent information that can be quickly located 

in order to make conservation recommendations 

Description 

Dabry’s sturgeon is a freshwater fish, attaining a 

length of more than 130 cm, and weight of more 

than 16 kg. It is very similar in shape to similar sized 

Chinese sturgeon, but Chinese sturgeon achieve 

much larger sizes than do Dabry’s sturgeon. The 

body of young Dabry’s sturgeon is very rough because 

of many bony plates on the skin. This may 

provide a good distinction between young Dabry’s 

sturgeon and Chinese sturgeon (Fu 1988). In addition, 

at similar total lengths, the rostrum of Dabry’s 

sturgeon is slightly shorter than that of Chinese 

sturgeon. Adult Dabry’s sturgeon have more than 

30 gill rakers whereas Chinese sturgeon have fewer 

than 28. 

Above the lateral row of scutes. the body of Dabry’s 

sturgeon is dark gray, brown gray or yellow 

gray in color; the rest of the body is milky white in 

color. The lateral row of scutes is a distinct color 

demarcation line until the fish reaches adult size. 

Table 1 shows some meristic characteristics of 

adults. 

Distribution and habitat 

Dabry’s sturgeon is restricted to the Yangtze River 

system. Historically, under the natural, unaltered 

conditions that existed until the middle of the 20th 

century, Dabry’s sturgeon widely inhabited the upper 

and middle reaches of the Yangtze River and its 

large tributaries, including the Ming, Tuo,. Jialing, 

Xiang and Han rivers, as well as the large lakes linking 

up with the Yangtze River (Figure 1). At present, 

Dabry’s sturgeon is mainly distributed in the 

upper main stream of the Yangtze River as it passes 

through Sichuan Province. It also enters major tributaries, 

including the Ming, Tuo, and Jialing rivers. 

Occasionally, it occurs in the lower and middle sections 

of the Yangtze River. It is now rare in Dongting 

Lake (Hunan Province) and Poyang Lake 

(Jiangxi Province). although it was formerly reported 

from these places. 

Dabry’s sturgeon is a potamodromous freshwater 

fish that inhabits sandy shoals, with silt ground 

and gentle water flow. When the water level rises in 

the mainstream in the spring, the fish move into the 

tributaries to feed. Young individuals often stay in 

sandy shallows, and occur frequently in stretches 

between Luzhou and Jiangjing, Sichuan Province, 

where the current velocity is not rapid (Zhang et al. 

1988). Dabry’s sturgeon is often found in areas 

where there are drainage pipelines of waste water 

that promote growth of prey foods. Although Da- 

Table 2. Percent occurrence of different foods in different life intervals of Dabry’s sturgeon (modified from Zen et al. 1990). 

Standard length ranges (cm) 

Food category Below 10 10-15 15-40 Above 40 

Oligochacta 100.0 50.0 10.5 29.8 

Plecoptera 0.0 8.3 18.4 0.0 

Ephemeroptera 0.0 16.7 28.9 11.8 

Odonata 0.0 0.0 34.2 29.8 

Chironomidae 0.0 33.3 3 I .6 22.2 

Other insects 0.0 8.3 15.6 31.0 

Plankton 50.0 0.0 0.0 3. 87 

Bacillariophyta 50.0 8.3 5.3 0.0 

Chlorophyta 50.0 8.3 13.2 3.7 

Other plants 0.0 16.7 10.5 37.0 

Shrimps 0.0 50.0 13.2 29.8 

Gobiidae 0.0 66.7 36.8 18.5

260 

bry’s sturgeon is adaptable to a variety of habitats, 

individuals prefer sublittoral areas 10-20 m from 

the river bank, with current velocity of about 1 m s -1 , 

water depth of 8-10 m, sandy silt ground and an 

abundance of detritus and benthic organisms during 

most of the year. 

ty is calculated by the following equation: F = DW/ 

BW × 10000, where F is the feeding intensity, DW is 

the diet weight in stomach, and BW the total body 

weight. Feeding intensity varies indirectly with 

standard body length according to the following relationship: 

F=3337L-1.0213. 

Feeding habits 

Age and growth 

Feeding habits of Dabry’s sturgeon vary with age, Wc usually age specimens of Dabry's sturgeon by 

season and habitat. Their food items arc wide-rang- grinding sections of either a dorsal scute or an opering. 

Although Dabry’s sturgeon prefer living an- culum and counting the annuli. Table 3 shows the 

mal prey, seeds, leaves and stems of plant remains results of a study of individuals from upper reaches 

arc frequently found in analyses of stomach con- of the Yangtze River. In this sample. 92% of the intents. 

Dietary variation during different life stages dividuals were younger than 3 years (Fu 1988). This 

is shown in Table 2. Young fish initially feed almost is consistent with other studies that suggest that Daexclusively 

on zooplankton and oligochaetes. Ol- bry's sturgeon achieves maturity faster than other 

der individuals eat oligochaetes and small fishes, sturgeons. Three year old fish can reach 3 kg in 

such as gobies, as well as many other food items, weight. Between 3-4 years and 7-S years. growth 

including chironomids, odonates, and aquatic rates in wild populations usually decline at sexual 

plants (Zen et al. 1990). Tu (1980) reported that a 12 maturation. Males reach sexual maturity at 4-6 

cm Dabry’s sturgeon ate gobies up to 2 cm in length. years of age and females at 6-8 years of age. In pond 

From May to July, the diet is broadest. Dabry’s stur- culture, Dabry's sturgeon can grow very rapidly (up 

geon feeds throughout the winter. Typically, feed- to 3. 5 kg each year. L. Ling personal communicaing 

is more active at night than during the day. tion). Females generally grow slightly faster in 

Feeding habits of Dabry’s sturgeon are influence- length than males. and at maturity, they usually 

ced by environmental factors, such as water level weigh more than do males of the same length or age 

fluctuations. Because benthic food organisms are because of their large ovaries. 

concentrated in sublittoral areas. these arc the pre- The relationship between age (a) and length (L) 

ferred feeding grounds. 

Cor the ages contained in the data set is L = 36 + 9.9a. 

Tu (1980) studied the feeding intensity (F) of Da- This relationship does not follow the von Bertalanfbry’s 

sturgeon as a function of size. Feeding intensify growth model. The relationships between body 

Table 3. Growth of wild Dabry’s sturgeon in upper reaches of Yangtze River (modified from Zen et al. 1090 and Fu 1988). 

Age Weight (kg) Length (cm) N 

Mean Annual increase Mean Annual increase 

0 0.08 21.3 66 

1 0.65 0.55 44.1 22.8 24 

2 1.30 0.68 55.0 10.9 8 

3 3.05 1.75 68.2 13.2 6 

4 4.25 1.20 77.5 9.3 4 

5 6.60 2.35 86.5 9.3 4 

6 8.60 2.00 95.5 9.0 3 

7 11.85 3.25 101.0 5.0 3 

8 14.70 2.85 106.0 5.0 2

261 

weight (BW) and length (L) before and after sexual 

maturity are as follows: 

1gBW= 6. 005 + 2. 721gL 

(males and females before sexual maturity); 

1gBW = 6. 175 + 2. 721gL 

(males after sexual maturity): 

1gBW = 6.219 + 2.721gL 

(females after sexual maturity). 

Movement 

Dabry’s sturgeon generally behaves as a resident 

fish and does not undertake long migrations. This 

behavior resembles that of Amur sturgeon. A. 

schrenckii, in the Amur River (Nikolski 1960). Historically, 

some individuals of Dabry’s sturgeon 

reached the lower-middle section of the Yangtze 

River below Yichang (Figure l), but this was before 

the construction of the Gezhouba Dam, and such 

migrations are now impossible. Most of the available 

information about movements is based upon 

recapture of tagged fish. Zhang (1988) reported that 

a tagged fish swain 97 km downstream for 6 days 

before recapture, but this is the only report of 

movement over such a long distance. Most tagged 

individuals only moved several kilometers either up 

or downstream before recapture in 2 days to 8 

months after releasing. 

Dabry’s sturgeon swim upstream for spawning 

during spring floods. Spawning fishes do not aggregate 

to swim upstream together as a group but instead 

move individually. After spawning, the spent 

fish move slowly back downstream to the sandy 

shoals where they feed intensively. Sometime they 

enter large lakes to feed. There is a record that Dabry’s 

sturgeon was historically found far downstream 

in Anhui Province, more than 2000 km from 

the probable spawning areas (He 1990). 

Reproductive biology 

Males start to mature at 4 years, and all arc mature 

by 7 years of age. At maturity, males weigh more 

than 4.5 kg. Females usually do not mature until at 

least 6 years of age; all are mature by 8 years. Mature 

females generally weigh at least 9 kg. In natural 

populations. only 6.7% of individuals reached sexual 

maturity (4. 8% of males and 1. 9% of females. 

Zen et al. 1988). It is hard to identify the sex of the 

fish from external characteristics. When the body 

weight of female Dabry’s sturgeon reaches 2.5–5.0 

kg, the ovary can reach deelopmental stage II: by 5 

kg in weight, the ovary is at stage III (stages according 

to classification of Conte et al. 1988). The mature 

ovary accounts for 2/3 of the volume ofabdominal 

cavity and the ovary of gravid females may 

comprise 10.0–18.8% of the body weight. Gravid females 

can contain from 57 000 to 102 000 eggs. Malure 

eggs are gray to black and range from 2.7–3.4 

mm in diameter. Eggs are sticky, firmly adhere to 

stones on the bottom ofthe river after breeding, and 

are not readily eaten by other fishes. We have never 

found that copperfish and yellow catfish eat Dabry’s 

sturgeon eggs although those species usually 

eat many eggs of Chinese sturgeon during their 

spawning period. Male Dabry’s sturgeon can spawn 

annually, but most females cannot. The time required 

to develop mature eggs is unknown, but apparently 

it is longer than one year. 

Natural and artificial spawning 

Based on the capture of ripe individuals, we conclude 

that spawning occurs in the spring. although 

some individuals may spawn in the fall (Yang 1986, 

Zen et al. 1990). Since the late 1950s. researchers 

have searched for spawning sites, but they remain 

unknown despite considerable effort. Mature fish 

are unknown in the reaches below Yibin, Sichuan 

Province, whereas young are often caught in the 

reach below Yibin. Thus we infer that the spawning 

areas are in upper mainstream of the Yangtze, 

above Yibin (Figure 1). The spawning environment 

probably has a rubble, cobble and gravel bottom. 

clear water, water velocity of 1.2–1.5 m s –1 , water 

depth of 5–15 m 

Xie (1979) reported on early development (see 

Bemis & Grande I992 For SEM stages ofpaddlefishes. 

which arc very similar). At 17–18°C. the first 

cleavage occurs 3–4 hours after fertilization; the

262 

mid-gastrula stage occurs 28–30 hours after fertil- Aquaculture, fisheries, and conservation 

ization, neurulation is complete 43–45 hours after 

fertilization, and hatching occurs 115–117 hours af- Domestication of Dabry’s sturgeon started in the 

ter fertilization. Newly hatched embryos, about 4 early 1970s (Xie 1979). Because it matures rapidly, it 

mm long, swim erratically and vertically due to their was expected that the species had potential both for 

large yolksac. Three days after hatching, the larvae intensive aquaculture in ponds and for extensive 

can balance themselves. Four days after hatching, aquaculture in lakes and reservoirs by artificial 

the pectoral fin appears, with dorsal fin appearance stocking (Jia et al. 1981, Yang 1986, He 1990). How - 

on day 5 and anal fin appearance on day 6. In 10–11 ever, limited experience with production techdays, 

most of the yolk is absorbed and the mouth niques and poorly developed markets prevented 

parts are developed so the young are ready to feed. early success in this industry. Only in the last 10–15 

Yolk is depleted 12 days after hatching. Young fish years with the improvement of propagation techimmediately 

swim downstream. They can be found niques has commercial culture of Dabry’s sturgeon 

in reaches at Luxian, Hejiang and Jiangjing, about been possible (Xie 1992). 

100–200 km below the supposed spawning areas. Dabry’s sturgeon was an important commercial 

Artificial stripping of Dabry’s sturgeon was re- species in the upper Yangtze River, near Yibin, Siported 

by Xie et al. (1976) using mature fish caught chuan Province (Figure 1). In the 1960’s, landings of 

in the Jingsha River. Subsequently, Tian et al. (I986) Dabry’s sturgeon reached 10% of the total harvest 

reported artificial stripping of Dabry’s sturgeon do- of Hejiang Fishing Squad (He 1990). In the 1970s, up 

mesticated in ponds from juvenile to adult. Early to 5000 kg of Dabry’s sturgeon could be caught in a 

workers used injections of pituitary glands of Chi- spring season from the Yibin reach. Because adult 

nese or Dabry’s sturgeon to induce ovulation. In- Dabry’s sturgeon are uncommon and do not like to 

duction included two injections, with the initial (or aggregate, young individuals, weighing several 

primary) injection separated from the second (or hundred grams, made up most of the harvest. Since 

resolving) injection by 8 hours. Ovulation occurred the 1970s, however, total landings of Dabry’s sturwithin 

14–24 hours after administration of the sec- geon sharply declined, and it now seldom occurs beond 

injection. More recently, luteinizing hormone low Gezhouba Dam. 

releasing hormone analog (LHRH-A) has been Possible causes of decline in Dabry’s sturgeon 

used to induce ovulation of Dabry’s sturgeon. populations are: (1 ) Unsuitable fishing methods. 

Artificially propagated interspecific hybrids of Fishermen repeatedly have decreased the mesh size 

Dabry’s sturgeon (male) and Chinese sturgeon (le- ofnets, so that they take many small fish. This methmale) 

exhibit significant hybrid vigor, prove to be od is harmful to the small fish, especially during the 

fertile, and seem to be a promising candidate for flood season, when many young Dabry’s sturgeon 

commercial production. Hybrid progeny add concentrate to feed. As a result, the sturgeon taken 

weight much faster than do Dabry’s sturgeon, and from the Luzhou reach usually weigh less than 50 g. 

about as fast as Chinese sturgeon, before 3 years of (2) Overfishing. For example, in the Neijiang reach 

age. At 6 years of age, female hybrids weigh more of the Tuo River there were only 500 fishing boats in 

than 40 kg, much larger than Dabry’s sturgeon. Fur- 1950s, but this number increased to about 2000 by 

thermore, female hybrids reach maturity at 6 years 1985. In the Leshan Reach of the Ming River, drift 

of age, 2 years earlier than most female Dabry’s gill nets are crowded together from day to night. (3) 

sturgeon, and male hybrids reach maturity at 3 Unsuitable fishing season. The traditional busy fishyears 

of age, which is also earlier than male Dabry’s ing season in the main stream of Jingsha River is 

sturgeon. Some of the hybrids arc hermaphrodites between March and August, with more than 30% of 

(D.J. Xie personal communication). 

the catch processed in April and May. However, this 

is also spawning season of Dabry’s sturgeon in the 

main stream, so it threatens the spawning stock. 

(4) Pollution from factories and pesticides. With ec-

263 

Bemis, W.E. & L. Grande 1992. Early development of the actinopterygian 


paddlefish Polyodon spathula. J. Morphol. 213: 47-83. 

Buckley, J, & B. Ky nard 1985, Habitat use and behavior of pre- 

spawning and spanning shortnose sturgeon. Acipenser brevirostrum 

in the Connecticut River. pp. 111–117. In: F.P. Binkowski 

& S.I. Doroshov (ed.) North American Sturgeons: Biology 

and Aquaculture Potential Dr W. Junk Publishers, Dordrecht. 

Conte, F.S., S.I. Doroshov & P.B. Lutes. 1988 Hatchery manual 

for white sturgeon. University of California Press, Oakland. 

120 pp. 

Deng, Q.X. & J.S. Hu. 1988. The skeletal system of Dabry’s stur- 

onomic development, more and more factories are 

built in the Yangtze Valley. Much untreated waste 

water discharges into the river each year. For instance, 

Wenjiang district in upper Ming River pours 

out 10 million tons of industrial waste water to the 

Ming River each year. Also, many agricultural 

chemicals are used in Yangtze Valley. (5) Habitat alterations 

anddestruction. The upper Yangtze Valley 

is seriously deforested, so that vast amounts of silt 

are washed to river, muddying its waters and inpacting 

fishes and their food organisms. Perhaps 

most important are the negative impacts of hydroelectric 

projects. Since the construction of Gezhouba 

Dam in 1981, adult Dabry’s sturgeon trapped below 

the dam cannot migrate upstream to the original 

spawning areas, and no suitable spawning 

grounds have been found below the dam. Young 

fish cannot pass the dam to reach the feeding 

grounds in the middle reaches of the Yangtze River 

and the lakes linking up with it. The Three Gorges 

Dam, currently under construction, will inundate 

many habitats of Dabry’s sturgeon. Other dams 

have been built, are being built, or will be built in 

upper Jingsha River and its tributaries. These structures 

may alter the populations of Dabry’s sturgeon 

in the main stream system by restricting their naturd 

movements or by influencing spawning behavior 

(Wu et al. 1991). 

In conclusion, we propose some tactics for the 

conservation of Dabry’s sturgeon. (1) Commercial 

fishing of Dabry’s sturgeon must be strictly forbidden. 

Although Dabry’s sturgeon has been listed as 

an endangered species and is under special protection, 

net fishermen still catch them accidentally. 

Caught fish are usually hurt, cannot survive easily, 

even if they are immediately released to the river 

again (L. Ling personal communications). Small 

mesh nets and detrimental fishing methods must be 

prohibited (2) Spawning areas and feeding grounds 

need to be properly protected. When we plan hydroelectric 

projects, methods for conserving Dabry’s 

sturgeon and other fishes must be built into 

the plan. Waste water must be properly treated before 

being poured into the river. (3) Stock enhancement 

of Dabry’s sturgeon should be urgently carried 

out. Successful erforts to replenish stocks of 

other Acipenseriformes have been made in the 

United States and Russia (Graham 1986, Smith 

1990, 1991, Khodorevskaya et al. 1997 this volume). 

Perhaps Dabry’s sturgeon could also be maintained 

by artificial stocking, particularly because culture 

methods for the fish has already been developed. 

Enhancement stations could be established along 

the Jingsha River at Yibin (Sichuan Province) and 

below Gezhouba Dam at Yichang (Hubei Province) 

to release juveniles lor stock enhancement. 

(4) Research on Dabry’s sturgeon should be increased. 

Up to now, very limited information is 

available on the biology and life history of Dabry’s 

sturgeon, and many more topics need study. A particularly 

critical step in the conservation of Dabry’s 

sturgeon is to determine where the populations 

spawn so that those areas can be precisely protected. 


We thank Vadim Birstein, Robert H. Boyle and 

John Waldman for organizing the International 

Sturgeon Conference. We thank Boyd Kynard for 

constructive suggestions in preparing our draft. We 

are also grateful to Ling Ling and Mu Tianrong for 

help collecting new data on population dynamics. 

James D. Williams, Frank M. Parauka, Kim Graham 

and Theodore I. J. Smith provided valuable 

foriegn reference materials. William E. Bemis reviewed 

and substantially revised the original draft 

of our manuscript and drew the map. 

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Observations on the reproductive cycle of cultured white sturgeon, 

Acipenser transmontanus 

Serge I. Doroshov, Gary P. Moberg & Joel P. Van Eenennaam 

Department of Animal Science, University of California Davis, CA 95616, U. S.A. 


Key words: gametogenesis, neuroendocrine control, pubertal age and body size, breeding intervals 

Synopsis 

Males and females of cultured white sturgeon, Acipenser transmontanus, mature at an average age of 4 and 8 

years, respectively. However, the onset of ovarian vitellogenesis and puberty are highly asynchronous in the 

female stock. Gonadal cycles are annual in males and biennial in females, and gametogenesis is influenced by 

season. Neuroendocrine regulation of reproduction appears to involve a dual gonadotropin system controlling 

gonadal development and spawning. Labile puberty and sex-specific duration of the gonadal cycle are 

distinct characteristics of cultured and wild sturgeon. Photoperiod and temperature play a significant role in 

environmental regulation of the reproductive cycle, but further studies are necessary to elucidate the roles of 

endogenous and environmental factors in sturgeon reproduction which is critically important for both aquaculture 

and conservation of endangered wild stocks. 

Introduction 

Current development of sturgeon and paddlefish 

culture provides opportunities for studies of repro- 

Sturgeons and paddlefishes, order Acipenseri- duction in Acipenseriformes. Gametogenesis and 

formes, have attracted century-long attention of de- gonadal cycles were elucidated in cultured Siberian 

velopmental biologists (recent reviews by Dettlaff sturgeon A. baerii (Akimova et al. 1979, Le Menn & 

et al. 1993, Bolker 1993, Bemis & Grande 1992), but Pelissero 1991, Williot et al. 1991), and the hybrid 

studies of their reproductive physiology were limit- Huso huso × A. ruthenus (Burtsev 1983, Fujii et al. 

ed by the lack of cultured animals. The complexity 1991). Structure and function of reproductive horof 

the reproductive cycle of sturgeon has been re- mones have also been investigated (Burzawa-Ge- 

rard et al. 1975a, 1975b, Kuznetsov et al. 1983 Gon- 

charov et al. 1991, Sherwood et al. 1991, Lescheid et 

al. 1995, Moberg et al. 1995). Nevertheless, informa- 

tion on gonadal cycles and reproductive physiology 

of Acipenseriformes remains fragmentary. 

This paper summarizes preliminary findings on 

reproductive development in cultured white sturgeon, 

A. transmontanus. As this species is long lived 

and slow maturing, our observations are incomplete 

and investigations continue. The material was 

vealed through fishery and hatchery studies (Hol- 

∨ 

cík 1989, Barannikova 1991, Dettlaff et al. 1993). 

Hormonal induction of ovulation and spermiation 

in wild sturgeon, developed by Russian scientists, 

made hatchery propagation feasible and contributed 

to early advances in fish endocrinology (Pickford 

& Atz 1957). However, difficulties in obtaining 

experimental animals and growing them to maturity 

were major obstacles in reproductive research on 

Acipenseriformes.

266 

obtained from sturgeon broodstock raised at five 

commercial farms in Northern California and at the 

University of California, Davis research facilities. 

Broodfish and methods 

White sturgeon live along the Pacific coast of North 

America and in watersheds of the Fraser, Columbia, 

and Sacramento-San Joaquin rivers (PSMFC 1 ). 

It is a semi-anadromous species, with landlocked 

populations in freshwater reservoirs and tributaries 

of the Columbia River basin. In the wild, males 

reach first sexual maturity at age 10–12 years and 

females at 15–32 years (PSMFC 1 ). River migrations 

and spawning exhibit seasonal patterns. In the Sacramento 

River peak spawning was observed in 

April, at water temperature 14–15°C (Kohlhorst 

1976), while in the lower Columbia River major 

spawning activity occurred in May at water temperature 

12–14°C (McCabe & Tracy 1994). The commercial 

fishery and hydroconstruction at the turn of 

the century severely depleted and fragmented wild 

stocks (Skinner 2 . Semakula & Larkin 1968, Galbreath 

1985). The restricted sport fishery is currently 

the major harvester of stocks in the Columbia 

River and San Francisco Bay (PSMFC 1 ). Artificial 

propagation of white sturgeon was established during 

the 1980's (Conte et al. 1988), and the offspring 

were used by aquaculturists for raising domestic 

broodstocks and production of sturgeon for the 

rood market (Logan et al. 1995). 

The broodfish studied were 3–14 year old firsthatchery 

generations of wild sturgeon originated 

from the Sacramento and Columbia rivers. They 

were raised in freshwater tanks and fed a commercial 

salmonid diet at a rate of 0.5–2.0% body weight 

per day. Most rearing faclities were large (6–9 m 

diameter and 1.5 m depth) outdoor tanks exposed 

to natural photoperiod. In the research facility sup- 

1 

Pacific States Marine Fisheries Commission (PSMFC). 1992. 

White sturgeon management framework plan. Portland, Oregon.201 

pp. 

2 

Skinner, J.E. 1962. An historical review of the fish and wildlife 

resources of the San Franciso Bay area California Department 

of Fish & Game. Water Project Branch Report No. I. 226 pp. 

plied by irrigation water, rearing temperature fluctuated 

seasonally (10–12°C in the winter and 16– 

18° C in the summer). Commercial facilities were 

supplied by underground water with a constant 

temperature of 20°C. Ripe broodfish raised on 

commercial farms were transferred to cooler water 

(10–14º C) 3–6 months before spawning, to prevent 

ovarian atresia and testicular regression. Fish were 

held in artificially chilled tanks or transported to 

other facilities with a supply of cool reservoir water. 

To examine reproductive cycles, gonadal development 

of marked fish was monitored by tissue biopsy 

starting at age 3–4 years. Commercial broodstock 

were sampled annually in the fall, and the ripe females 

were re-sampled before spawning (March- 

May). In the experiments conducted at the university, 

fish were sampled several times per year. Animals 

were anesthetized in a 100 ppm MS-222 bath, 7 

ml of blood was drawn with a vacutainer from the 

caudal vein. centrifuged. and plasma was stored frozen 

for the analyses of reproductive hormones and 

metabolites. Gonads were biopsied (1 cm 3 fragment 

through a small abdominal incision. and tissue 

was fixed in 100% buffered formalin. As fish 

reached full sexual maturity, ovulation and spermiation 

were induced by the administration of 

mammalian GnRH analog. GnRHa ([D-Ala 6 , Pro 9 

N-Et]-GnRH, Sigma) and extracts of dried common 

carp pituitary glands (Stoller Fisheries). Although 

optimal hormonal induction protocols are 

still being investigated. the most common hormonal 

treatment Tor ovulation was a ‘priming’ dose of 10 

µg kg -1 of GnRHa followed by intramuscular injection 

of 4.5 mg kg –1 carp pituitary material 12 hours 

later. To induce spermiation. sturgeon were given a 

single injection of 1.5 mg kg –1 carp pituitary, and semen 

was collected by catheter 30–32 hours later. 

Additional procedures for hatchery breeding of 

sturgeon were described by Conte et al. (1988) and 

Doroshov et al. (1993). 

Stages of gametogenesis were examined on paraffin 

sections stained by periodic acid Schiff (PAS) 

or by hematoxylin and eosin (H&E) stains (Doroshov 

et al. 1991). The pre-ovulatory ovarian stage 

was detected by germinal vesicle migration (measuring 

distance of the nucleus from the animal pole 

of boiled and bisected eggs) and by the in vitro oo-

267 

Figure 1. Different states of gametogenesis in cultured white sturgeon male. Paraffin sections stained by H&E (scale at bottom right 0.1 

mm): a- primary spermatogonia enclosed in cysts, b -proliferation of spermatogonia. c -meiosis (primary, secondary spermatocytes, and 

spermatids), d- late meiosis and spermiogenesis, e- cysts with differentiated spermatozoa, f - postspawning testis (SG = spermatogonia, 

SC = spermatocytes, SD = spermatids, SZ = spermatozoa). 

cyte maturationresponse afterincubationwith 5 µg 

ml –1 progesteronefor 16 h at 16°C (Doroshovet al. 

1994). Relative concentrations of plasma vitellogenin 

were estimated by measuring total plasma calcium 

using atomic absorption spectrophotometry. In 

vitellogenic females, plasma calcium concentrations 

exhibiteda significantlinear relationship(r 2 = 

0.96, n = 72) with plasma vitellogenin, measured by 

an enzyme immunoassay employing polyclonal antibody 

(Linares-Casenave et al. 1994). Basal level of 

total plasma calcium in males from the samerearing 

facilities was 90 ± 0.5 µg ml–1 (mean ± s.e.m., n = 208, 

Kroll 1990). Gonadotropins (stGTH I and stGTH 

11) were measured by radioimmunoassays (RIA)

268 

Figure 2. Different states of gametogenesis in cultured white sturgeon female. Paraffin sections stained by PAS: a - early phase of 

oogenesis, oogonia and oocytes initiating meiosis, b - differentiated ovarian follicles with the oocytes in the late primary growth phase, c- 

previtellogenic follicle with differentiated granulosa layer and vitelline envelope. d - mid-vitellogenesis, deposition of yolk bodies, e - 

ripe follicle with polarized oocyte near completion of vitellogenic growth, f - ovarian tissue after ovulation, containing post-ovulatory 

follicles, atretic follicles. and new generation of oocytes (BL = basal lamina. GR = granulosa cells, ZR = zona radiata, YP = yolk platelets, 

MP = micropyle, GC = gelatinous coat, ZRE = zona radiata externa, ZRI = zona radiata interna, CG = cortical granules, ML = melanin 

granules, PF = post-ovulatory follicle, AF = atretic follicle). 

described by Moberg et al. (1991b, 1995). Briefly, the 

RIA’S were based on specific polyclonal antibodies 

to purified stGTH’s fractions. The cross-reactivity 

of stGTH I antibody with stGTH II was 2%, and 

that of stGTH II antibody with stGTH I was 9.3%. 

Minimum detectable concentrations for the stGTH 

I and stGTH II were 0.84 ng ml –1 and 1.25 ng ml –1 

respectively. Inter- and intra-assay variability was

269 

10.2 and 7.3% for stGTH I. and 9.7 and 6.1% for 

stGTHII Testosterone(Gay& Kerlan1978), estradiol-17β 

(England et al. 1974) and17α 20β-dihydroxy-4-pregnen-3-one 

(Scottet al.1982)were analyzed 

by previously described RIA procedures. 

Minimum detectable concentrationsfor these steroids 

were 0.52 ng ml -1 , 0.13ng ml -1 , and 0.10 ng ml -1 , 

respectively. 

In the following description of gonadal development 

we applied the term ‘puberty’to the gonadal 

condition or age of animals that have completed the 

first gonadal cycles. The term ‘vitellogenesis’was 

used to define a period of oocyte growth associated 

with deposition of yolk platelets in the cytoplasm. 

The three layers of the oocyte envelope were 

termed zona radiata interna,zona radiata externa 

and gelatinous (jelly) coat, following the classification 

of Dettlaff et al. (1993). 

Gonadal development and gametogenesis 

While gonadalsex differentiation in culturedwhite 

sturgeon has not been investigated in detail, our observations 

on gonadal development in domestic 

(F 2 ) offspring suggest that anatomical and cytological 

differentiation of sex glands were completed by 

the age 18 months, at fork length 58–72 cm and body 

weight 1.1–2.3 kg. The females had distinct ‘ovarian 

grooves’ on the lateral side of the ovary, with lamellae 

containing the nests of primary oogonia and the 

oocytes in meiotic prophase.The germinal portion 

of the testis was seen as a narrow layer of solid tissue 

on the dorsal part of the gonads, containing spermatogonia 

enclosed by a fibrous wall. The gonads of 

both sexes were largely composed of adipose fatty 

tissue surrounded by the peritoneal epithelium. 

Further observations at age 3–4 years, conducted 

on hundreds of marked fish on several commercial 

farms, indicated that domestic offspring had a 1:1 

sex ratio. 

Full differentiationof testicularfolliclesand proliferation 

of spermatogonia were observed at age 3 

years (Figure la. b), and were followed by meiosis 

and spermiogenesis (Figure lc, d). Cell proliferation 

was accompanied by the enlargement of the 

germinalportion of testes and by resorption of adi- 

pose tissue. Meiosis starts in October-November 

and continuesfor 3–4 months. Ripemalesthathave 

completed the first cycle of spermatogenesis are 

typically 4 years old and 10–15 kg body weight. They 

have enlarged white testes containing cysts with differentiated 

spermatozoa (Figure le). Individual cycles 

are asynchronous in a stock, but the majority of 

males mature from February to June. In summer, 

the unshed spermatozoa and remaining meiotic 

cells are reabsorbed (Figure 1f) and only primary 

spermatogonia remain in the cyst walls. Elevated 

water temperature (above 15°C) accelerates spermatogenesis 

but induces rapid testicular regression 

in the post-meiotic phase. Spontaneous spermiation 

was occasionally observed, but for scheduled 

spawning spermiation was induced by treatment 

with carp pituitary extracts. Males are capable of at 

least three consecutive spermiations at biweekly intervals, 

producing up to 200 ml of milt at each spermiation. 

As in other Acipenseriformes,white sturgeon 

spermatozoa possess an acrosome and undergo 

acrosome reaction during insemination (Cherr 

& Clark 1985). White sturgeonsperm contains the 

enzyme amidase, which is associated with sperm 

penetration through the egg envelope in non-teleostean 

vertebrates (Ciereszko et al. 1994). However, 

the functions of this enzyme and the details of 

the acrosomal reaction in insemination of eggs in 

sturgeon are unknown. 

Gonadal development of females is long and 

asynchronous, relative to individual age and body 

size (see ‘Age and body size at puberty’ below). Oocyte 

meiosis and differentiationof the ovarian follicle 

start at age 2–3 years. The narrow ovarian 

groove (formed on the lateral side of the gonad) 

contains clusters of oogonia and small oocytes surrounded 

by squamous follicular cells (Figure 2a). 

By age 4–5 years gonial mitosis appears complete, 

and the ovigerouslamellae contain only oocytes in 

the primary growth phase, reaching 100- 300 µm 

diameter and surrounded by a few granulosa cells, 

PAS-positive basement membrane and the thecal 

layer. The oocyte cytoplasm is strongly basophilic 

and contains unstained spherical vesicles in the cortex. 

Numerous small nucleoli appear in the periphery 

of the nucleus (Figure 2b). Oocytes are visible to 

the unaided eye as small transparent spheres and

270 

Figure 3. Total plasma calcium (Ca) concentrations and diameter (ED) of vitellogenic ovarian follicles in eight females repeatedly sampled 

during the first ovarian cycle. Bars are x ± se. Plasma calcium has a linear relationship with plasma vitellogenin (Ca = 98.94 – 0.015 Vg 

µg ml –1), and elevation of total plasma calcium above 100 µg ml –1 indicates the presence of vitellogenin (Linares-Casenave et al. 1994). 

Inset: SDS-PAGE of plasma from mature male (lane 1), immature female (lane 2). late vitellogenic female (lane 3), purified white 

sturgeon vitellogenin (lane 4), and molecular markers (lane 5). Vitellogenic female plasma and purified vitellogenin exhibit two polypeptides 

with an approximate molecular mass of 190 and 210 KDa. Courtesy of J. Linares-Casenave, University of California, Davis. 

arepresent in the ovarythroughoutconsecutivereproductive 

cycles. As oogenesis advances,some of 

the oocytes will increasein diameterto 400–600 µm 

and appear as enlarged translucent spheres.Their 

cytoplasm is less basophilic and exhibits vesicular 

structure. However, crystalline yolk bodies are not 

detectable with light microscopy (Figure 2c). The 

distinct features of this stage are the appearance of 

PAS-positive envelope and differentiation of the 

granulosa cell layer (Figure 2c, inset). Deposition of 

crystalline yolk usually follows this stage, but can be 

delayedin somefish for one or two years. Low concentrations 

of vitellogenin (< 1 µg ml–1) are detected 

in plasma of white sturgeon at this stage (Linares- 

Casenave et al. 1994); morphological evidence of 

endocytosisat similar stage was reported in Siberian 

sturgeon (LeMenn & Pelissero 1991), suggesting 

the initiation of yolk precursor uptake by the oocyte. 

Vitellogenic growth of the oocyte starts at age 4–8 

years and a body weight of 15–30 kg, and continues 

for 16–18 months. Oocytes increase in diameter 

from 0.6 to 3.5 mm and change in color from light 

yellow to brown, grey, and finally to black, due to 

synthesis and deposition of melanin granules in the 

cortical cytoplasm. The crystalline yolk bodies first 

appear in the peripheral cytoplasm and, while increasing 

in size, exhibit centripetal progression 

(Figure 2d) similar to yolk deposition in the amphibian 

oocyte (Dumont 1972). Gradually, the yolk 

platelets and oil globules fill the entire cytoplasm 

except for the perinuclear area. When vitellogenic 

growth subsides (diameter> 3 mm), the oocyteundergoes 

major cytoarchitectural changes and becomes 

ovoid in shape with a slightly pointed animal 

pole. The germinal vesicle migrates to the animal 

pole and the large yolk bodies and oil globules aggregate 

in the vegetal hemisphere (Figure 2e, vege-

271 

Figure 4. Approximate length and seasonality of the testicular 

and ovarian cycles in domestic white sturgeon. based on observ a- 

tions of iteroparous broodfish raised in outdoor tanks. The biennial 

ovarian cycle is show n for odd and even y ears 

tal portion not shown). The egg envelope reaches 

maximum thickness and consists of three PAS-positive 

layers: zona radiata interna, zona radiata externa 

and gelatinous coat. The cortical alveoli form a 

distinct layer beneath the oolemma. 

During the vitellogenic phase of ovarian development, 

plasma concentrations of vitellogenin significantly 

increase. Hepatic synthesis of vitellogenin 

is stimulated by estrogen (Moberg et al. 1991a), 

which causes expression of the vitellogenin gene in 

the hepatocytcs (Bidwell et al. 1991, Bidwell & Carlson 

1995). Oocyte growth and changes in plasma vitellogenin 

level (measured as total plasma calcium) 

in females raised at the university facility are shown 

in Figure 3. Mean plasma vitellogenin concentration 

reaches 7 mg ml –1 (200 µg ml –1 calcium) during 

the late phase of vitellogenic growth and decreases 

significantly before spawning. Vitellogenesis in 

these females was first observed in November of 

1990, and ovulation was successfully induced in 

April 1992. Two putative vitellogenin proteins were 

detected in the plasma of vitellogenic females by 

SDS-PAGE, with estimated molecular masses of 

190 and 210 kDa (Figure 3, inset). 

Final ovarian maturation in white sturgeon (oocyte 

maturation and ovulation) appears to be similar 

to that described by Dettlaff et al. (1993) in A. 

gueldenstaedtii. Captive white sturgeon females can 

be induced to ovulate by administration of GnRHa 

or carp pituitary extracts when they reach a responsive 

stage (Lutes et al. 1987, Doroshov et al. 1994). 

At spawning, the number of ova removed by caesa- 

rean section ranged from 100 000–200 000, and the 

average fecundity measured in fish sacrificed for 

caviar production was 209 000 eggs at a mean body 

weight of 29 kg (n = 67). At ovulation, the ovary 

contains post-ovulatory follicles, previtellogenic 

oocytes, and atretic follicles with dark pigmentation 

(Figure 2f). The late phase of ovarian development 

is highly sensitive to environmental temperature 

and a prolonged exposure to water temperature of 

19º C induces ovarian atresia before completion of 

germinal vesicle migration and acquisition of the 

meiotic response by the oocytes (Webb et al. 1994). 

These observations and studies with Russian sturgeon, 

A. gueldenstaedtii and Siberian sturgeon, A. 

baerii, suggest that exposure to low temperature 

during the late phase of vitellogenesis is required 

for some sturgeon species to complete a normal 

ovarian cycle (Williot et al. 1991, Dettlaff et al. 

1993). 

Gonadal cycles 

Repeatedly spawned males of cultured sturgeon exhibit 

annual seasonal cycles of spermatogenesis, 

with meiosis occurring during the fall and winter, 

and spermiation during the spring (Figure 4). 

Sperm that was successfully used for insemination 

was obtained each spring from the same males during 

4 consecutive years. Additional evidence for an 

annual cycle in males was provided by observations 

on seasonal changes in the pituitary content of gonadotropins 

correlated with histological stages of 

gametogenesis (Moberg et al. 1995). 

The duration and seasonality of the ovarian cycles 

are currently being investigated. We collected 

data from 147 virgin females that were sampled on 

farms each fall for several years. The majority 

(67%) exhibited patterns ofa biennial cycle. similar 

to that in Figure 3, but some (29%) had a shorter 

duration of vitellogenesis (the stages as depicted in 

Figure 2c the first fall and in Figure 2e the following 

fall). Furthermore in small numbers of fish (4%) vitellogenesis 

continued for a period of 3–4 years. In 

approximately 23% of all females the onset of vitellogenic 

growth was arrested, and the advanced oocytes 

with differentiated envelopes and granulosa

272 

pituitary and plasma concentrations of two sturgeon 

gonadotropins (Moberg et al. 1995) also revealed 

that gonadal cycles in white sturgeon are 

controlled by seasonal factors. 

Age and body size at puberty 

Figure 5. The age and body size at puberty in cultured white sturgeon 

females. Data are pooled observations on the broodstock 

of five commercial farms (N = 184). 

layer (Figure 2c) persisted over a period of 1–3 years 

before the initiation of yolk deposition. The reabsorption 

of previtellogenic follicles and development 

of new oocytes could potentially occur within 

the annual sampling interval, but no atretic follicles 

were observed on the histological slides from any of 

these fish. 

Observations on the second ovarian cycle in repeatedly 

spawned females (n = 5) revealed a biennial 

cycle,with three of these fish spawning on odd 

years, 1991 and 1993, and two on even years, 1992 

and 1994 (Figure 4). All fish started the second vitellogenesis 

during the first fall after spring spawning, 

and their oocytes reached the late phase of vitellogenic 

growth in the fall of the following year. They 

were spawned a second time during a period from 

March to June, and the calendar date of the second 

ovulation in individual females was very similar to 

that of the first spawning. 

These preliminary observations reveal annual 

testicular and biennial ovarian cycles in cultured 

white sturgeon. Gonadal development in both sexes 

exhibits seasonal patterns, with testicular meiosis 

and ovarian vitellogenesis starting in the fall, and 

final gonadal maturation completed during the 

spring. The observations on seasonal changes in the 

Most (80–90%) cultured white sturgeon males 

reach puberty at age 3–4years and body weight of 

7–14kg. In commercial farms, sturgeon males are 

selected for spawning from the production stock at 

age 4 years and body weight 10–15kg. In the wild, 

white sturgeon males reach puberty at age 10–12 

years, and body weight of approximately 12 kg 

(PSMFC 1 ). Thus, the body size at first sexual maturity 

appears to be similar in wild and cultured males, 

but the latter reach puberty at a younger age. 

Cultured females reach puberty at an age from 6 

to 14 years, with fiftypercent maturing by age 8, at a 

mean body weight of 32 kg and a mean fork length 

of151cm (Figure 5). These data are based on alarge 

number of gravid females pooled from different age 

cohorts raised on farms, and the maturation rates 

may be affected by farm husbandry and the age 

groups life history. However, the proportions of 

mature females within each age group showed very 

similar trends (Doroshov et al. 1994, Logan et al. 

1995).The body weight of females that completed 

their first sexual maturation was highly variable, 32 

±10kg (× ± sd, range 12–61kg). Similar variability 

was found in wild-caught females used for farm 

spawning during the past four years (36 ± 13 kg, n = 

43), although the age and iteroparity of these fish 

could not be examined. The smallest mature wild 

female weighed 12 kg, and the largest ‘virgin’ female 

caught in San Francisco Bay (stage similar to 

Figure 2a) weighed 53 kg (S. Doroshov unpublished 

observations). A recent report indicates that the 

pubertal age of wild white sturgeon females ranges 

from 15 to 32 years (PSMFC 1 ). This suggests that a 

highly variable pubertal age and body size in cultured 

sturgeon may reflect the patterns existing in natural 

population. However, cultured females reach 

puberty at a considerably younger age compared to 

wild fish. Similar observations were reported for

273 

cultured Siberian sturgeon, A. baerii (Akimova et 

al, 1979, Williot et al. 1991). 

Neuroendocrine control 

Knowledge of the neuroendocrine regulation of reproduction 

in Acipenseriformes remains inadequate, 

but our recent observations on cultured 

white sturgeon appear to indicate general similarity 

of regulatory mechanisms with those of teleosts. 

Based on these preliminary observations, we propose 

a model for the neuroendocrine regulation 

of reproduction in white sturgeon (Figure 6). 

We believe the gonadotropin-releasing hormone 

(GnRH), and possibly the neurotransmitter dopamine 

(DA) interact on the pituitary gonadotropes 

to regulate the synthesis and release of two putative 

gonadotropins. The gonadotropins control gonadal 

development and gamete release, and stimulate the 

synthesis of gonadal steroids, androgen (A) and estrogen 

(E). The gonadal steroids, especially testosterone: 

appear to feedback on the pituitary, and 

possibly the hypothalamus, to influence the synthesis 

and secretion of gonadotropins. The function of 

the hypothalamic-pituitary-gonadal axis is further 

modulated by a number of exogenous and endogenous 

factors, including season, body size and age of 

fish, as previously discussed. The proposed model 

has been developed from the following data. 

The brains of white, A. transmontanus, and Russian 

sturgeon, A. gueldenstaedtii, contain the mammalian 

form of GnRH (mGnRH) and a small amount 

of chicken GnRH II (Sherwood et al. 1991, Lescheid 

et al. 1995). High concentrations of mGnRH in 

brains of mature Russian sturgeon caught during 

their spawning migrations, as well as its localization 

in the forebrain of Siberian sturgeon (Lepretre et 

al. 1993), suggest that this form of GnRH is responsible 

for pituitary gonadotropin release (Lescheid et 

al. 1995). High sensitivity of sturgeon pituitary gonadotropes 

to exogenous stimulation by mGnRH 

analog (D-Ala 6 , Pro 9 N-Et]GnRH, has been demonstrated 

by experiments on spawning induction in 

European sturgeon species (Goncharov et al. 1991) 

and studies on the effect of GnRHa injections on 

plasma concentrations of gonadotropins in stellate 

Figure 6. Hypothetical neuroendocrine reproductive axis of cultured 

white sturgeon based on current studies (see text for description). 

sturgeon, A. stellatus (Barannikova & Bukovskaya 

1990), and white sturgeon (Moberg et al. 1995). 

The presence of a dual gonadotropin control of 

gonadal development in sturgeon is being investigated. 

Gonadotropic hormone was first purified 

from pituitary glands of stellate sturgeon, and it was 

initially believed that Acipenseriformes possessed 

only a single form of GTH that regulated all aspects 

of reproductive development (Burzawa-Gerard et 

al. 1975a, 1975b). Recently, two potential gonadotropins 

have been isolated from Russian sturgeon 

pituitaries, designated sturgeon gonadotropin I, or 

stGTH I, and sturgeon gonadotropin II, or stGTH 

II (Moberg et al. 1995). Based on physiological evidence, 

these two gonadotropins appear to be functional 

analogs of the salmonid gonadotropins GTH 

I and GTH II (Kawauchi et al. 1989, Swanson et al. 

1989), possessing many of the same biological functions. 

Like GTH I in salmonids, stGTH I appears to 

induce and maintain follicular development and vitellogenesis, 

while stGTH II is instrumental in inducing 

ovarian maturation and ovulation (Moberg 

et al. 1995). 

Plasma levels of both stGTH I and stGTH II are 

low (< 1–2 ng ml –1 ) in reproductively immature sturgeon. 

With the onset of meiosis in males and vi-

274 

tellogenesis in females, the pituitary concentrations was found that stGTH II was more potent than 

of both gonadotropins increase, with the stGTH I stGTH I in inducing germinal vesicle breakdown, 

being the predominant gonadotropin in the pitui- GVBD (Moberg et al. 1991b). This effect. in contary. 

Plasma concentration of stGTH I also increas- junction with the increased pituitary and plasma 

es during vitellogenesis, similar to the increases of concentrations of stGTH II prior to final ovarian 

GTH I reported during the same state of develop - maturation, suggests that stGTH II gonadotropin 

ment in salmonids (Suzuki et al. 1988). These in- regulates the final reproductive events leading to 

creases in the pituitary and plasma concentrations spawning. 

of stGTH I suggest that this hormone regulates the In males, similar changes in the secretion of 

onset of vitellogenesis as has been observed in trout stGTHs occur during their annual reproductive cywhere 

GTH I stimulates the uptake of vitellogenin cle. In the winter during the meiotic state of sperby 

the developing oocytes (Tyler et al. 1991).While matogenesis, the mature white sturgeon male has 

it is not known whether stGTH I has a similar role, greater amounts of stGTH I than stGTH II in the 

we have observed that female sturgeon in the previ- pituitary. If GnRHa is administered during sperma - 

tellogenic state will not sequester circulating vitel- togenesis, stGTH I is also released in greater 

logenin, even in the presence ofelevated concentra - amounts than stGTH II consistent with stGTH I 

tions of plasma estrogen and vitellogenin (Moberg being responsible for regulating the meiotic phase 

et al. 1991a), when the concentrations of stGTH I of spermatogenesis. In the spring, during spermia - 

are low in both the pituitary and plasma. Further - tion. the pituitary concentration of stGTH II exmore, 

the administration of a gonadotropin releas- ceeds the levels of stGTH I and the GnRHa -ining 

hormone analog, GnRHa, will not stimulate the duced release of this gonadotropin is maximal, imsecretion 

of the gonadotropin in these females even plying that stGTH II may be responsible for conthough 

GnRHa administration will stimulate the trolling spermiation. In the summer, during 

secretion of stGTH I in mature male sturgeon reproductive quiescence, relative low amounts of 

(Moberg & Doroshov 1992) and induce ovulation both stGTHs are released following the administra - 

and spermiation in ripe fish (Doroshov & Lutes tion of GnRHa, indicating that the regulation of the 

1984, Fujii et al. 1991, Goncharov et al. 1991). These neuroendocrine axis is modulated by such environ - 

findings are consistent with the hypothesized role mental factors as season (Moberg et al. 1995). 

of stGTH I in initiating ovarian development and In some species of teleosts, the neurotransmitter 

the onset of vitellogenesis. 

dopamine acts as an endogenous inhibitor of 

Prior to the onset of final ovarian maturation and GnRH-induced pituitary secretion of GTH (Peter 

ovulation, pituitary concentration of stGTH II rises et al. 1991). A comparable effect has been found in 

sharply to a level greater than 100 µg mg -1 in the pre- sturgeon (Pavlick 1995). Administration of dopa - 

ovulatory white sturgeon female (Moberg et al. mine to mature white sturgeon males effectively in- 

1995). It is during this period of reproduction that hibited the GnRHa -induced elevation of both 

stGTH II becomes the predominant gonadotropin stGTHs in blood plasma as well as spermiation, 

in the pituitary. Comparable changes in gonadotro- while the administration of the dopamine antagpins 

have also been observed during the reproduc- onist pimozide potentiated stGTH I and stGTH II 

tive cycle of salmonids (Swanson et al. 1989). As was release when used in combination with GnRHa. 

observed for GTH II in salmonids (Suzuki et al. These results indicate a dopaminergic inhibition of 

1988), the plasma concentration of stGTH II in GnRH action in white sturgeon, similar to what has 

white sturgeon is not elevated until the time of final been observed in several teleost species. 

gonadal maturation and spawning, when it increas - Little is known about the feedback effects of the 

es to more than 20 ng ml –1 (Moberget al. 1995). We gonadal steroids on the regulation of the hypotha - 

have also observed a functional difference between lamic-pituitary -gonadal axis of sturgeon. From the 

the stGTHs in an in vitro oocyte maturation bioas- onset of the meiotic phase in gametogenesis, both 

say using ripe ovarian follicles of white sturgeon. It sexes in sturgeon exhibit high concentrations of

plasma androgens (Moberg et al. 1995, Cuisset et al. warm water. In the wild, most species of sturgeons 

1995). Recently, we demonstrated that the implants reach first sexual maturity at age 10 to 20 years, 

of exogenous testosterone in sexually undifferen- while in culture the age interval 3–10 years is most 

tiated white sturgeon will significantly elevate the frequently reported. Thus, Acipenseriformes appituitary 

concentrations of both stGTHs (Pavlick et pear to have a labile pubertal age that may be influal. 

1995). Likewise, pre-vitellogenic females im- enced by environmental factors and growth rates. 

planted with testosterone have higher levels of pi- One interesting aspect of oogenesis observed in cultuitary 

stGTHs than controls. suggesting that the tured white sturgeon was the ability of females to 

pituitaries of adult sturgeon are also sensitive to the maintain ovarian follicles in an arrested but adpositive 

feedback of testosterone. This positive vanced previtellogenic state for one or more years 

feedback effect of testosterone in sturgeon is com- before the onset of yolk deposition. This suggests 

parable to the reported effect of testosterone in that ovarian recrudescence may be affected by 

modern teleost species (Crim & Evans 1983). It still some endogenous and exogenous factors, resulting 

remains to be determined whether or not testoster- in highly asynchronous female puberty. High variaone 

can also have a negative feedback effect on the bility in ovarian development rates of captive fish 

secretion of the gonadotropins and what the poten- may be caused by culture stress and competition retial 

feedback effects of estrogen are. 

lated to high rearing densities, commonly utilized 

In vitro oocyte maturation is readily induced in on the commercial farms. 

white sturgeon by C-21 steroids, with 17α, 20β-Di- Sex-related differences in pubertal age and 

hydroxy-4-pregnen-3-one (17α, 20β-Dp) being length of the gonadal cycle were previously report - 

most potent (Lutes 1985). Our observations on ov- ed in wild and cultured Acipenseriformes (see Holulating 

domestic females showed consistent and cík 1989 for review). Males mature at a younger age 

significant increases in plasma concentrations of and usually have annual gonadal cycles whereas the 

17α,20β-DP correlated with an increase of stGTH females mature late and have ovarian cycles lasting 

II. Wild-caught pre-ovulatory white sturgeon fe- longer than one year. Estimates of breeding fremales 

also had significantly higher plasma concen- quency in wild sturgeon females range from one to 

trations of 17α, 20β-DP, compared to late vitellogen- ten years (Holcík 1989), but these assumptions are 

ic females that did not reach the responsive state of usually inferred from the age-body size population 

gonadal development (Lutes et al. 1987). Similar structure and the presence of spawning marks on 

data were obtained with migratory females of wild finray sections (Roussow 1957). Observations on 

Atlantic sturgeon, A. oxyrinchus (Van Eenennaam cultured sturgeon suggest a predominantly biennial 

et al. 1996). While the identity of the putative matu- ovarian cycle (Williot et al. 1991, Doroshov et al. 

ration-inducing substance (MIS) in white sturgeon 1994). Variations in the length of individual cycles 

has not been established, the potential similarity in maybe driven by exogenous (environmental) and 

the native MIS between sturgeon and salmonids endogenous (genetic) factors, but the current 

(Young et al. 1986) may lend further support to a knowledge of reproductive physiology in Acipensegenerally 

similar endocrine control of reproduction riformes is inadequate to answer these questions. It 

in the Acipenseriformes and modern teleosts. is possible that the length of the reproductive cycle 

in wild and cultured sturgeon is labile, as is their pubertal 

age. However, it is more likely that Acipenseriformes 

Conclusions 

have developed endogenous reproductive 

rhythms of specific duration, as indicated by their 

Our data support several previous studies with Siberian 

relatively advanced neuroendocrine control of re- 

sturgeon and the sturgeon hybrid (H. huso × production and the clearly apparent seasonality of 

A. ruthenus), which suggested that puberty and sexual 

the gonadal cycle. As in teleosts (Bromage et al. 

maturation of Acipenseriformes are accelerat- 

1993). annual photoperiod is likely to control game- 

ed by intensive culture utilizing artificial feed and togenesis in sturgeon, although no experimental 

^ 

^ 

275

276 

evidence is available, to our knowledge. The effect References cited 

of seasonal factors on reproduction of Acipenseristocks 

formes may play a role in differentiation of wild Akimova, N.V., V.S. Malyutin, I.I. Smolyanov & L.I. Sokolov. 

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1979. Growth and gametogenesis of the Siberian sturgeon 

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Contemporary status of the North American paddlefish, Polyodon spathula 

Kim Graham 

Missouri Department of Conservation, III0 South College Ave., Columbia MO 65201, U.S.A. 


Key words: Polyodontidae, commercial fishing, sport fishing, distribution, endangered status 

Synopsis 

North American paddlefish, Polyodon spathula were once abundant in most large rivers and tributaries of the 

Mississippi River basin, but numbers have declined dramatically in most areas during the past 100 years. 

Habitat destruction and river modification are the most obvious changes affecting their distribution and abundance. 

Although peripheral range has dwindled, paddlefish still occur over most of their historic range and are 

still found in 22 states. Populations are currently increasing in 3 states, stable in 14, declining in 2, unknown in 

3, and extirpated in 4. Sport harvests presently occur in 14 states, however two stales with traditionally important 

sport fisheries report decreased recruitment into the population and are planning more restrictive regulations. 

Commercial fisheries are reported in only six states. During the past 10 years, five states have removed 

paddlefish from their commercial list primarily because of declines in adult stocks due to overfishing or illegal 

fishing. Ten states are currently stocking paddlefish to supplement existing populations or to recover paddlefish 

populations in the periphery of its native range. 

Introduction 

spawning sites, interrupted natural spawning migrations, 

altered water flow regimes, dewatered 

The North American paddlefish, Polyodon spath- streams, and eliminated backwater areas that were 

ula is one of two living species of paddlefishes, the important as nursery and feeding areas. To a lesser 

other being the Chinese paddlefish, Psephurus gla- degree, industrial pollution, poaching adults for 

dius (for additional basic information on Pol yodon- caviar, and overfishing by commercial and sport 

tidae, see Russell 1986, Grande & Bemis 1991, Be- fishermen have adversely affected paddlefish popmis 

et al. 1997 this volume, and Wei et al. 1997 this ulations (Pflieger 1975, Carlson & Bonislawsky 

volume). Paddlefish once were abundant in most 1981, Pasch & Alexander 1986). 

large rivers and major tributaries of the Mississippi In 1989, the U.S. Fish and Wildlife Service was 

River basin (Carlson & Bonislawsky 1981), how- petitioned to include paddlefish on the list of 

ever since the turn of the century, these populations Threatened and Endangered Species under provihave 

declined dramatically in most areas (Gen sions of the Endangered Species Act of 1973. The 

gerke 1986). Habitat destruction and river modifi- U.S. Fish and Wildlife Service, after collecting supcation 

are the most obvious changes affecting the plemental infomation from all 22 states, agreed 

abundance and distribution of paddlefish. Con- that the listing of paddlefish as ‘threatened’ was not 

struction and operation of dams on mainstem warranted. Because of the uncertainty of the spestreams 

has had severe impacts (Sparrowe 1986. cies’ status in several portions of its range, the U.S. 

Unkenholz 1986). Dams eliminated traditional Fishand Wildlife Service recommended a reclassifi-

280 

Figure 1. Past and present distribution of North American paddlefish, Polyodon spathula and locations of sport fisheries (adapted from 

Carlson & Bonislawsky 1981). Map drawn by W. E. Bemis. 

1Neill, W.H.. B.R. Murphy, C.R. Vignali, P.W. Dorsett & V.M. 

Pitman. 1994 Salinity responses of paddlefish. Texas Parks and 

Wildlife Department Dingell-Johnson project F-31-R-20, Pro- 

ject 81. Final Report. 38 pp. 

cation from category 3C to a category 2 under authority 

of the Endangered Species Act of 1973, as 

amended. Category 3C is intended for taxa that 

have proven to be more abundant or widespread 

than previously believed and/or those that arc not 

subject to any identifiable threat. Category 2 indicates 

taxa for which information now in the possession 

of the U.S. Fish and Wildlife Service indicates 

that proposing to list as endangered or threatened is 

possibly appropriate, but for which conclusive data 

on biological vulnerability and threat are not currently 

available to support proposed rules. The U.S. 

Fish and Wildlife Service believes this classification 

will encourage further investigation and biological 

research of the species’ status throughout its range. 

Additionally, paddlfish were added to the list of 

Appendix II of the Convention on International 

Trade in Endangered Species of Wild Fauna and 

Flora (CITES) in 1992 primarily because of concern 

about illegal poaching for the international caviar 

trade. 

This paper reviews major changes in paddlefish 

status in the United States since Gengerke’s (1986) 

report, illustrates historical changes since the turn 

of the 20th century, discusses major reasons for declines, 

defines current range of paddlefish in the 

United States, describes current status of paddlefish 

in the United States, and predicts their future as 

a fisheries resource. 

Distribution 

Historically, paddlefish were abundant throughout 

the Mississippi River basin and adjacent Gulf drainages, 

with a few records from the Great Lakes 

(Gengerke 1986). Neill et al. 1 reported that several

281 

Figure 2. Status of North American paddlefish stocks in the United States. AL. Alabama; AR, Arkansas; IA. Iowa; IL. Illinois; IN. 

Indiana; KS. Kansas; KY. Kentucky; LA. Louisiana; MD. Maryland; MN. Minnesota; MO. Missouri; MS, Mississippi; MT. Montana; NC, 

North Carolina; ND. North Dakota; NE. Nebraska; NY.New York; OH. Ohio; OK. Oklahoma;PA. Pennsylvania; SD, South Dakota;TE, 

Tennesee; TX Texas; VA. Virginia; WI. Wisconsin; WV, West Virginia. Map drawn by W. E. Bemis. 

paddlefish stocked into large river systems of east 

Texas were reported captured in Galveston Bay. 

This ability to survive in brackish water probably 

explains the occurrence of several specimens captured 

by shrimp trawlers, and of two paddlefish 

originally tagged and released in Toledo Bend Reservoir 

in Louisiana that were recaptured in the 

Neches River in Texas. 

The former range of paddlefish in the United 

States encompassed 26 states (Figure 1). They have 

been extirpated in four states on the periphery of 

their range (Maryland, New York, North Carolina, 

and Pennsylvania). Even in states long considered 

strongholds for paddlefish (Iowa, Nebraska, Oklahoma, 

and Alabama), portions of their historical 

range has diminished. During the last 100 years, significant 

declines in major paddlefish populations 

have occurred in the Mississippi, Missouri, Ohio, 

and Red rivers. 

Status by state analysis 

In 1983, Gengerke (1986) contacted all states known 

or suspected to have paddlefish to gather information 

pertaining distribution, abudance and status 

of present day paddlefish populations. I contacted 

those same states to determine changes during the 

past 10 years. I will not repeat the 1983 information 

for individual states and will only discuss major 

changes since that time. 

Paddlefish populations are considered by resource 

agency personnel to be increasing in three 

states, stable in fourteen, declining in two, unknown 

in three, and extirpated in four (Figure 2). Since the 

last survey (1983), the number of states reporting 

paddlefish as stable or stable/increasing remains at 

fourteen. Fifteen of the twenty-two states recorded 

changes in the status of their paddlefish stocks. Of 

these, seven were positive changes, and eight indi-

282 

cated negative changes in status since 1983 (Table 

1). Significant positive changes were reported in Iowa, 

which changed status from declining to stable/ 

increasing: Kansas, which changed from declining 

to stable/increasing; South Dakota, which changed 

from declining to stable; Wisconsin, which changed 

from stable to increasing; and Texas and West Virginia, 

which changed from declining to increasing. 

All but two of these states (Iowa and Wisconsin) implemented 

stocking programs to supplement existing 

stocks or recover historic populations. 

North Dakota reported the most significant negativc 

change in status since 1983 by changing from 

stable/increasing to declining (Table 1). Additionally, 

Montana and Nebraska changed their status 

from stable to stable/declining. Most of the other 

declining shifts in status since 1983 are the result of 

states reporting that their stock inventories are unknown 

at this time. 

Several significant changes in the management 

and regulation of paddlefish during the last 10 years 

were prompted by recognition of continued degradation 

of paddlefish habitat, threats of industrial. 

Commercial, or agricultural contaminants in paddlefish, 

and an increase in the demand for paddlefish 

caviar. Since 1983, 86% of the states where paddlcfish 

still occur have changed their regulations of 

sport and/or commercial paddlefish fisheries (Tables 

l and 2). Alabama, Virginia, and West Virginia 

no longer allow a sport harvest, and Alabama, Io- 

Table 1. Classification and population status of paddlefish in all states containing paddlefish for 1994. as compared to 1983. 1 

State 

Classifications 

Status 

1983 2 1994 1983 2 1994 

Alabama Commercial Special Concern Decline Stable/DecIine 

Arkansas Commercial Sport/Commercial Increase Stable 

Illinois Commercial Sport/Commercial De cline Decline 

Indiana Sport Sport Stable Stable 

Iowa Commercial Sport Stable Stable 

Kansas Sport Sport Decline Stable/Increase 

Kentucky Commercial Commercial Stable Stable 

Louisiana Commercial Special concern Stable Stable 

Maryland Threatened Extirpated Extirpated Extirpated 

Minnesota Protected Threatened Stable Stable 

Mississippi Commercial 

Commercial Stable/Increase Stable 

Missouri Game Game Stable Stable 

Montana Sport Sport/Special concern Stable Stable/Decline 

Nebraska Sport Sport Stable Stable/Decline 

New York Extirpated Extirpated Extirpated Extirpated 3 

North Carolina Not Classified Endangered Extirpated Extirpated 4 

North Dakota Commercial Sport/Special concern Stable/Increase Decline 

Ohio Endangered Threatened Decline Unknown 

Oklahoma Commercial Non-game Unknown Stable 

Pennsylvania Extirpated Extirpated Extirpated Extirpated 

South Dakota Sport Sport Decline Stable 

Tennessee Commercial Sport/Commercial St ab le Unknown 

Texas Endangered Endangered Decline Increase 

Virginia Non-Game Threatened Stable Unknown 

West Virginia Sport Special concern Decline Increase 

Wisconsin Watch list Watch list Stable Increase 

1 

Paddlefish are considered to be extirpated from Maryland, New York, North Carolina and Pennsylvania. 

2 

From Gengerke (1986). 

3 

Sole report of a paddlefish in New York was one fish in 1800s. 

4 

There are two unconfirmed reports of paddlefish being taken during the last 19 years.

283 

wa, Louisiana, Oklahoma, and Virginia now prohibit 

commercial harvests (Table 2). Alabama, 

Louisiana, and West Virginia now consider paddlefish 

as a species of special concern and Virginia classifies 

them as threatened. Some states currently use 

quotas and length limits, while others utilize creel 

limits or protected zones to regulate their sport harvests. 

Some of the more important changes in classification 

and status of paddlefish stocks since 1983 

are as follows: 

Alabama (no sport or commercial fisheries, classified 

as special concern, status stable/declining) 

A no harvest regulation (sport and commercial) 

was implemented in 1989. Paddlefish in the Tennessee 

River are considered to be ‘very reduced in 

numbers’. Overharvest and habitat alterations are 

considered main threats. 

Arkansas (sport and commercial fisheries, classified 

as sport/commercial, status stable) 

All populations in major river systems of the state 

are regarded as self-sustaining. Arkansas currently 

utilizes seasonal restrictions on the upper White 

River and border waters to protect mature females 

from commercial harvest. Commercial fishermen 

are also restricted by a 76 cm eye-to-fork-of-tail 

length limit from fall until late spring as additional 

Table 2. Type of fishery allowed in all states containing paddlefish for 1994. compared to 1983, and current stocking programs. 1 

State Sport fishery Commercial fishery Stocking program 

1983 2 1994 1983 2 1994 1994 

Alabama Yes No Yes No No 

Arkansas Yes Yes Yes Yes Yes 

Illinois Yes Yes Yes Yes No 

Indiana Yes Yes 3 No No No 

Iowa Yes Yes Yes No No 

Kansas Yes Yes No No Yes 

Kentucky Yes Yes Yes Yes No 

Louisiana No No Yes No Yes 

Maryland No No No No No 

Minnesota No No No No No 

Mississippi Yes Yes Yes Yes No 

Missouri Yes Yes Yes Yes 4 Yes 

Montana Yes Yes No No No 

Nebraska Yes Yes 5 No No No 

New York No No No No No 

North Carolina No No No No No 

North Dakota Yes Yes No No No 

Ohio No No No No No 

Oklahoma Yes Yes Yes No Yes 

Pennsylvania No No No No Yes 

South Dakota Yes Yes 6 No No Yes 

Tennessee Yes Yes Yes Yes Yes 

Texas No No No No Yes 

Virginia Yes No Yes No No 

West Virginia Yes No No No Yes 

Wisconsin No No No No No 

1 Paddlefish are considered to be extirpated from Maryland, New York, North Carolina and Pennsylvania. 

2 From Gengerke (1986). 

3 

Paddlefish may be taken only by hook and line. Snagging is not a legal method of take. 

4 

Commercial fishing only allowed on Mississippi and lower St. Francis rivers. 

5 

Share tailwater fishery (1600-fish quota) below Gavins Point Dam with South Dakota. 

6 

Share tailwater fishery (1600-fish quota) below Gavins Point Dam with Nebraska.

284 

protection for females. The statewide commercial 

harvest during 1993 was estimated to be 136 000– 

181 000 kg. Most sport fisheries are located below 

dams on major tributaries to the Mississippi River. 

Arkansas is currently stocking juveniles into the 

White River (Beaver Reservoir) to establish anotherpaddlefish 

stock and hopefully a fishery.Habitat 

alteration, contaminants, and sand and gravel 

dredging are considered major threats. 

distribution by stocking juveniles into the Arkansas, 

Blue and upper Neosho rivers. Habitat alteration, 

contaminants, and illegal harvest are major 

management concerns. 

Kentucky (sport and commercial fisheries, classified 

as commercial, status stable) 

A commercial fishery is allowed on Kentucky and 

Barkley lakes and the Ohio River only. In 1993,the 

commercial harvest from Kentucky and Barkley 

lakes was 3906 kg. Kentucky’s major sport fishery is 

below Kentucky Dam, where fewer than 1000 paddlefish 

were harvested in 1993. Habitat destruction 

and contaminants in the entire Ohio River are considered 

major threats. 

Illinois (sportand commercialfisheries, classified as 

sport/commercial, status declining) 

Nearly 90 percent of the reported commercial harvest 

occurs in the Mississippi River. The recent decline 

in commercial harvest (21319 kg in 1993compared 

to 24 500 kg in 1983) may be related to poor 

reporting by commercial fishermen. Although Louisiana (no sport or commercialfisheries, classithere 

is a shortage of information, overfishing and fied as special concern, status stable) 

habitat loss are considered threats. 

In 1992, a three year moratorium on paddlefish harvest, 

including commercial and sport fishing, be- 

Indiana (sportfishing only, classified as sport, status came permanent. There is general concern regardstable) 

ing the impacts of overfishing of adult paddlefish 

An insignificant legal sport harvest is only by hook stocks throughout the state.Illegal caviar trade may 

and line, no snagging. Major concerns include ille- be a problem at times. Habitat alterations and congal 

harvest, habitat alteration and contaminants. taminants are considered threats. In cooperation 

with Texas, juvenile paddlefish are currently being 

Iowa (sport fishing only, classified as sport, status stocked into Toledo Bend Reservoir to establish a 

stable) 

population. 

Iowa closed its commercial fishery on the Missouri 

River in 1986 and the Mississippi River in 1987. Maryland (no sport or commercial fisheries, classi- 

Stocks in the pooled portion of the Mississippi Riv- fied as extirpated, status extirpated) 

er are thought to be declining slightly, whereas be- Paddlefish are currently considered extirpated 

low Lock and Dam 26, the stock is increasing. Io- from the state. 

wa’s sport harvest occurs below locks and dams on 

the pooled portion of the Mississippi River. Illegal Minnesota (no sport or commercial fisheries, classiharvest, 

habitat alteration, and contaminants are of fied as threatened, status stable) 

concern. 

Although paddlefish remain rare, the largest stock 

is found in the Mississippi River. Minnesota cur- 

Kansas (sportfishing only, classified as sport, status rently has a long-range management plan that instable/increasing) 

cludes a potential for stocking juvenile paddlefish 

Two sport fisheries below low dams on the Neosho into the Minnesota River below GraniteFalls. Haband 

Marais des Cygnes rivers flowing into Oklaho- itat alteration appears to be the most serious probma 

and Missouri, respectively, depend upon high lem. 

spring flows. In 1993, the Neosho River fishery 

yielded 87 paddlefish, while the Marais des Cygnes Mississippi (sport and commercial fisheries, classi- 

River fishery producedbetween 500–550 fish. Kan- fied as commercial, status stable) 

sas is currently attempting to restore the historic Paddlefish stocksin Pascagoula River aredeclining,

285 

presumably as a result of high commercial harvest 

for eggs in the mid-1980s. The remaining stocks in 

the state appear to be stable. The commercial season 

is closed state-wide in early spring and closed on 

the Pascagoula River system and border waters 

with Louisiana during late fall to early spring to protect 

mature females. Sport fisheries occur predominantly 

below dams on major tributaries to the Mississippi 

River. There is little information regarding 

the annual harvests of paddlefish by sport and commercial 

methods. Major management concerns are 

habitat destruction and possible overfishing. 

Missouri (sport and commercial fisheries, classified 

as game, status Stable) 

Sport fisheries occur in the upper portions of Lake 

of the Ozarks, Harry S. Truman Lake, and Table 

Rock Lake. The 1992 sport harvest above Harry S. 

Truman Lake was 4041 paddlefish. The most recent 

creel census at Lake of the Ozarks (1988) indicated 

that approximately 2000 paddlefish were harvested. 

and 350 paddlefish were estimated harvested 

during the last year of a creel census (1990) at Table 

Rock Lake. Lake of the Ozarks, Table Rock Lake, 

and Harry S. Truman Lake currently receive annual, 

supplemental stocking of early juveniles. No 

juveniles were stocked into Table Rock Lake from 

1991 to 1994 because of an apparent lack of interest 

in sport snagging due to chlordane advisories. In 

1994, the chlordane advisories were lifted and sport 

snagging interest increased to near previous levels. 

Major concerns are habitat alteration and poaching 

for eggs. Commercial fishing was closed on the Missouri 

River in 1990. The 1992 commercial harvest 

from the Mississippi River was estimated at 2188 kg. 

Montana (sport fishery only, classified as sport, but 

designated as a species of special concern, status stable/declining 

Sport fisheries are located on the Missouri River 

above Fort Peck Reservoir and in the Yellowstone 

River at Intake, Montana, and downstream to the 

confluence with the Missouri River. Recent information 

suggests the Yellowstone River stock (from 

Lake Sakakawea in North Dakota) is suffering 

from decreased natural recruitment. Declining reservoir 

productivity and poor survival of young are 

believed to be problems. In 1989, the Montana legislature 

passed an act which established a procedure 

for legally collecting and marketing paddlefish eggs 

taken during the Yellowstone River sport snagging 

season. An estimated 1360–4536 kg of paddlefish 

eggs have been collected each spring Cor caviar. A 

Montana/North Dakota paddlefish management 

plan suggests a reduced harvest quota lor the Garrison 

Dam paddlefish beginning in 1996. 

Nebraska sport fishery only, classified as sport, status 

stable/declining 

Nebraska currently shares a paddlefish fishery with 

South Dakota in the Gavins Point Dam tailwater. A 

1600-fish quota with a 88–1 14 cm eye-to-fork-of-tail 

slot length limit was established in 1989 and is routinely 

reached in less than one week. The most important 

concern is the need to restore part of the 

natural hydrography of the Missouri River, habitat 

alteration, waste management, and harvest manage 

m e n t . 

New York (no sport or commercial fisheries, classified 

as extirpated, status extirpated) 

The sole report of a paddlefish is from Chautauqua 

Lake during the late 1800s and was likely the result 

of unusual movement resulting froin flooding in the 

Ohio River Valley. 

North Carolina (no sport or commercial fisheries, 

classified as endangered status extirpated 

There are only two unsubstantiated records for the 

state; both are from Madison County. 

North Dakota (sportfishing only, classified as sport, 

but designated as a species of special concern, status 

declining) 

North Dakota’s major sport fishery is in the Missouri 

River above Lake Sakakawea and the Yellowstone 

River. Recent information suggests the paddlefish 

population in Lake Sakakawea is suffering 

from low natural recruitment. Declining reservoir 

productivity and predation of young by walleye and 

sauger may be a problem. In 1993, state administrative 

authorization allowed a procedure for legally 

collecting and marketing paddlefish eggs from this 

paddlefish population during the sport snagging

286 

season. During 1993–1994,2268–2726 kg of paddlef- Pennsylvania (no sport or commercial fisheries, 

ish eggs were collected for caviar. A Montana/ classified as extirpated, status extirpated) 

North Dakota paddlefish management plan sug- Pennsylvania initiated a recovery program in 1991 

gests a reduced harvest quota, beginning in 1996. to increase stocks in the upper Ohio and Allegheny 

rivers. Habitat alteration and water quality are be- 

Ohio (no sport or commercial fisheries, classified lieved to be most responsible for past declines; howthreatened, 

status unknown) 

ever, water quality in these streams has improved. 

Ohio prohibits snagging but allows pole and line 

harvest. Fewer than 10 fish were harvested state- South Dakota (sportfishery only, classified as sport, 

wide in 1993. Ohio is currently conducting radio te- status stable) 

lemetry studies in the lower Scioto and Ohio rivers. South Dakota shares responsibility with Nebraska 

Management concerns include dams and contami- for a 1600-fish quota and a 88–114 cm (eye-to-forknants. 

of-tail) slot length limit below Gavins Point Dam. 

They began a stocking program in mid-1970s in 

Oklahoma (sport fishery only, classified as non- Lake Francis Case to guarantee a broodstock 

game, status stable) 

source. Since 1990, South Dakota has been stocking 

Little information exists regarding paddlefish juveniles into Lake Francis Case where natural reabundance 

outside the Grand Lake system, how- production is suspected to no longer occur, and into 

ever a growing population is believed to exist in the Fort Randall Dam tailwaters where natural re- 

Keystone Reservoir. Oklahoma’s major sport fish- production is limited. 

ery occurs on the Grand River above Grand Lake 

of the Cherokees. Smaller fisheries are located be- Tennessee (sport and commercial fisheries, classified 

low several Arkansas River dams. Habitat alter- as sport/commercial, status unknown) 

ation and overfishing (legal and poaching for eggs) A modest sport harvest of about 2500 paddlefish 

are of concern. Early juveniles are being stocked in- annually is spread among several tailwaters, howto 

Kaw Reservoir. Commercial harvest was prohib- ever this harvest is considered insignificant comited 

in 1992. 

pared to the commercial harvest. All waters in the 

Table 3. Sport harvest of paddlefish in 1993 and commercial harvest of paddlefish in 1992.

287 

state are closed to commercial fishing except those 

designated as open. Commercial harvests are also 

controlled by various gear restrictions. Most of the 

commercially harvested paddlefish are taken from 

Tennessee and Cumberland river reservoirs. Commercial 

harvest is high (60 328 kg in 1992), but considerably 

less than 197 768 kg reported in 1975. 

Sport and commercial seasons are closed during a 

two-month period in the spring to protect adults 

during the spawning season. Concerns include 

overfishing, habitat destruction and contaminants. 

Several reservoirs receive maintenance stockings 

annually. 

Texas (no sport or commercial fisheries, classified as 

endangered, status increasing) 

Texas is currently utilizing an aggressive stocking 

program to recover paddlefish populations in six 

east-Texas streams. Early indications are that populations 

are increasing in most of these streams. 

Major concerns continue to be habitat destruction 

and water quality. 

Virginia (no sport or commercial fisheries, classified 

as threatened, status unknown) 

Paddlefish occur in Powell and Clinch rivers but in 

low numbers. Major reasons for decline include 

contaminants and siltation (soil and coal fines). 

West Virginia (no sport or commercial fisheries, classified 

as species of special concern, status increasing). 

West Virginia began stocking juveniles into the 

Ohio and Kanawha rivers in 1992. Prior to 1992, one 

or two paddlefish were reported annually. Navigational 

dams and habitat alterations are of major 

concern. 

Wisconsin (no sport or commercial fisheries, classified 

as watch-listed, status increasing) 

Wisconsin is presently conducting research on paddlefish 

populations in the Wisconsin and Mississippi 

rivers. A reintroduction plan (including stocking 

juveniles) is being considered above Prairie du Sac 

Dam on the lower Wisconsin River. Habitat degradation, 

water quality, and illegal harvest are major 

concerns. 

Sport harvests 

Sport harvest occurs throughout most of the existing 

range for paddlefish; however, many of these 

fisheries are small and dependent upon unpredictable 

river flows. Large sport fisheries, supported by 

self-sustaining or augmented stocks, exist only in 

the upper and central portions of the United States 

(Figure 1 and Table 3). Even these traditional sport 

fisheries are being challenged by increasing fishing 

pressure, continued habitat degradation and occasional 

mismanagement. Montana and North Dakota. 

once thought to have stable populations, are beginning 

to see effects of overfishing of adult stock 

presumably because of low natural recruitment. 

Slot length limits in South Dakota and Nebraska 

(on a shared tailwaters fishery) protect mature paddlefish, 

yet allow some harvest of large fish. Missouri 

is considering annual quotas and Oklahoma 

and Arkansas have reduced their daily bag limit. 

Since Gengerke’s (1986) report, Alabama, Louisiana, 

Virginia, and West Virginia no longer allow 

sport harvest of paddlefish. 

The most important sport fisheries are located on 

the Tennessee River at Kentucky Dam in Kentucky; 

the Yellowstone River at Intake, Montana; 

the Osage River at Warsaw, Missouri and the upper 

Osage River above Truman Lake, Missouri; Gavins 

Point Dam tailwaters on the Missouri River in Nebraska 

and South Dakota; the Missouri River at 

Williston, North Dakota (above Lake Sakakawea); 

and Highway Bridge 171 on the Missouri River in 

Montana (above Ft. Peck Reservoir). 

Commercial harvests 

It is apparent that commercial harvest of paddlefish 

is now less than reported by Gengerke (1986). It is 

not possible to obtain accurate information for 

commercial harvests from several states. Many 

states do not require commercial fishermen to report 

their catch and in some states where reporting 

is mandatory, results are suspect. Additionally, 

commercial fishermen routinely fish several drainages 

in several states and quantitative assessment is 

difficult.

288 

Since Gengerke’s (1986) report, five states (Alabama, 

Iowa, Louisiana, Oklahoma, and Virginia) 

have prohibited commercial harvest of paddlefish 

(Table 3). Most of these states were concerned 

about overfishing, illegal fishing or declines in adult 

stocks. 

Arkansas and Tennessee report the largest commercial 

fisheries (Table 3). Arkansas estimates 

136 000–181000 kg of paddlefishare takencommercially 

each year from its several river systems. These 

figures are reduced slightly since 1983because of a 

continued decline in some populations. Tennessee 

reports 60 328 kg harvested commercially in 1992, 

compared to 197 768 kg in 1975. All states bordering 

the pooled portion of the Mississippi River report 

declines in their commercial fisheries since 1983. 

All states bordering the Missouri River now prohibit 

commercial fishing for paddlefish because 

harvests were small and size of fish was decreasing. 

Commercial exploitation, particularly in southern 

reservoirs, continues to be a major factor affecting 

the viability of paddlefish populations throughout 

their range. The incentive for illegal harvest has increased 

tremendously in the past 10 years because 

paddlefish eggs for caviar routinely sell for $100 to 

$200per kg. The vulnerability of paddlefish to commercial 

(legal and illegal) harvest,behavioral characteristics, 

and low recruitment rate (slow maturation) 

is well documented by Pasch & Alexander 

(1986; also see Boreman 1997this volume).Because 

of these problems, several states have removed 

paddlefish from their commercial list or implemented 

regulations to protect paddlefish from 

overexploitation. 

Stocking programs 

Ten states currently stock paddlefish juveniles to 

supplement existing stocks where natural recruitment 

is lacking or insufficient to maintain populations, 

or are stocking to recover paddlefish stocks in 

the periphery of its native range (Table 3). Wisconsin 

and Minnesota have not yet stocked fish but 

have drafted plans to guide recovery efforts for paddlefish 

in the lower Wisconsin and Minnesota rivers, 

respectively. It is encouraging that Kansas, Ok- 

lahoma,Pennsylvania,Texas, and West Virginia are 

attempting to recover remnant stocks in selected 

watersheds. 

Conclusions 

(1) The primary difficulty in assessing the current 

status or trends of paddlefish populations in most 

states is a lack of information about population sizes, 

age structure, growth, or harvest rates. While 

several paddlefish populations appear to be stable 

or increasing, Polyodon spathula is in decline in 

much of its current range because of continued habitat 

modification and degradation, increased contamination, 

and overfishing. 

(2) Declines in paddlefish populations were identified 

by five of twenty-two states where paddlefish 

currently exist. Most of these states consider the 

loss or alteration of habitat as significant. Because 

of these serious resource impacts, states should continue 

seeking mitigation for habitat losses in select 

rivers to restore paddlefish habitat. Efforts should 

include restoration or maintenance of habitat diversity, 

including purchase or long-term easement 

on selected private lands so that old river channels 

and oxbows can be reconnected to main channels. 

Potential and known spawning areas should be protected 

from degradation. 

(3) Resource agencies must remain alert for illegal 

harvests of eggs for caviar, for paddlefish populations 

can be damaged quickly if illegal activities 

are not recognized and stopped. 

(4) Although the peripheral range of paddlefish 

has diminished slightly, they still occur in the majority 

of their original range, and in come cases are reinvading 

areas previously occupied. Aggressive 

stocking programs are currently in planning stages 

or actually underway to restore paddlefish to historic 

ranges. Water quality has improved in many 

previously polluted rivers and stocking should be 

successful. While states wait for stocked paddlefish 

populations to develop, they must quickly inventory 

available and potential spawning and nursery 

habitat and determine if paddlefish can prosper 

naturally. It has taken less than 100 years to destroy 

the future for many paddlefish populations. If state

289 

and federal resource agencies work together to correct 

mistakes made in the last century,North American 

paddlefish can have a guaranteed future. 


Two anonymous reviewers provided comments on 

the manuscript, and I also thank K. DeiSanti and T. 

Russell who provided a critical review of the manuscript, 

and the many state fisheries biologists, who 

compiled status, harvest, and present distribution 

information for the questionnaire. William E. Bemis 

drew the maps. 


Bemis, W., E. Findeis & L. Grande. 1997. An overview of Acipenseriformes. 


Boreman, J. 1997. Sensitivity of North American sturgeons and 

paddlefish to fishing mortality. Env. Biol. Fish. (this volume). 

Carlson, D.M. & P.S. Bonislawsky. 1981. The paddlefish, Polyodon 

spathula, fisheries of the midwestern United States. Fisheries 

6(2): 17–22,26–27. 

Gengerke, T.A. 1986. Distribution and abundance of paddlefish 

in the United States. pp. 22–35. In: J.G. Dillard, L.K. Graham 

& T.R. Russell (ed.) The Paddlefish: Status, Management and 

Propagation, N. Cent. Div.. Amer. Fish. Soc. Spec. Pub. No. 7. 





Pasch R.W. & C.M. Alexander. 1986. Effects of commercial fishing 

on paddlefishpopulations. pp. 46–53. In: J.G. Dillard, L.K. 

Graham & T.R. Russell (ed.) The Paddlefish: Status: Management 

and Propagation, N. Cent. Div., Amer. Fish. Soc. Spec. 

Pub. No. 7. 

Pflieger, W.L. 1975. The fishes of Missouri. Missouri Department 

of Conservation, Jefferson City. 343 pp. 

Russell, T.R. 1986. Biology and life history of paddlefish- areview. 

pp. 2–20. In: J.G. Dillard, L.K. Graham & T.R. Russell 

(ed.) The Paddlefish: Status, Management and Propagation, 

N. Cent. Div., Amer. Fish. Soc. Spec. Pub. No. 7. 

Sparrowe, R.D. 1986. Threats to paddlefish habitat. pp. 36–45. In: 

J.G. Dillard, L.K. Graham & T.R. Russell (ed.) The Paddlefish: 

Status, Management and Propagation, N. Cent. Div., 

Amer. Fish. Soc. Spec. Pub. No. 7. 

Unkenholz, D.G. 1986. Effects of dams and other habitat alter- 

ations on paddlefish sport fisheries. pp. 54–61. In: J.G. Dillard, 

L.K. Graham & T.R. Russell (ed.) The Paddlefish: Status, 

Management and Propagation, N. Cent. Div.. Amer. Fish. Soc. 

Spec. Pub. No. 7. 

Wei, Q., F, Ke, J, Zhang, p, Zhuang, J, Luo. R, Zhou & W. Yang. 


paddlefish in China. Env. Biol. Fish. (this volume).

Right side portrait of Scaphirhynchus platorynchus 98 cm TL from the Missouri River downstream of Great Falls, Fort Benton, Montana. 

Original by Paul Vecsei, 1996.



Life history and status of the shovelnose sturgeon, Scaphirhynchus 

platorynchus 

Kent D. Keenlyne 

U.S. Fish and Wildlife Service, 420 South Garfield Ave., Pierre, SD 57501–5408, U.S.A. 


Key words: range, commercial harvest, market value, Mississippi, Missouri River 

Synopsis 

The shovelnose sturgeon, Scaphirhynchus platorynchus, is a freshwater sturgeon of the Mississippi and Missouri 

rivers and their tributaries. It is one of the smaller North American sturgeons, seldom weighing more 

than 2.5 kg over most of its range except in the upper Missouri River, where individuals of over 7 kg have been 

found. Spawning occurs in spring at temperatures between 17 and 21 °C over rock or gravel substrate downstream 

from dams, near rock structures, or in tributaries. most males reach sexual maturity at 5 years, most 

females at 7 years. Adults do not spawn every year. Shovelnose sturgeon are found in large, turbid rivers and 

frequently concentrate in areas downstream from dams or at the mouths of tributaries. Population densities 

range up to 2500 fish per km. They are commonly found in areas of current over sandy bottoms or near rocky 

points or bars, where they feed primarily on aquatic invertebrates. The shovelnose sturgeon is classified as a 

sport species in 12 of 24 states where it occurs. Commercial harvest is allowed in seven states, where fresh 

shovelnose sturgeon sell for 55 to 88 cents per kg, smoked shovelnose for about $5.75 per kg, and roe from 33 

to 110 dollars per kg. About 25 tons of shovelnose sturgeon are harvested commercially each year. Shovelnose 

sturgeon are considered extirpated in three states, fully protected in four states, and rare, threatened, or of 

special concern in eight states. Populations are considered stable throughout most of the upper Mississippi, 

lower Missouri, Red, and Atchafalaya rivers. Three states,Wyoming, West Virginia, and New Mexico, have 

developed plans to reintroduce the species into rivers where it has been extirpated. 

Introduction 

The shovelnose sturgeon, Scaphirhynchus platorynchus, 

is indigenous to the Mississippi River 

drainage. The genus has occurred in this region for 

nearly 100 million years (Bailey & Cross 1954). Although 

one of the most abundant sturgeons in 

North America, its distribution has diminished in 

the last 100 years, and population numbers have 

been reduced throughout most of its range due to 

habitat alteration, overharvest, and water contamination. 

Although not as abundant as it once was, 

the shovelnose sturgeon is still one of the few sturgeons 

that can be harvested commercially in the 

United States (Helms 1974, Carlson et al. 1985). 

Considerable information has been published on 

the biology and life history of the shovelnose sturgeon, 

but no status review has been compiled for 

this species in 10 years, and no compilation of commercial 

harvest data exists on this species over its 

entire range. The purposes of this paper are to summarize 

the general biology and life history of the 

shovelnose sturgeon and to present information on 

its current status. Status information was obtained

292 

with a questionnaire sent to all 24 states within the 

range of this species; biology and life history information 

were obtained from a review of literature. 

Distribution,habitat,and abundance 

Species of the genus Scaphirhynchus represent a 

distinctive group of freshwater sturgeons confined 

to the larger rivers of the interior United States 

(Bailey & Cross1954). The pallid sturgeon,S. albus, 

is sympatric with the shovelnose sturgeon throughout 

the Missouri and Atchafalya rivers and the lower 

Mississippi River downstream of its confluence 

with the Missouri. The Alabama shovelnose sturgeon, 

S. suttkusi, is arare species recentlyproposed 

from the Mobile River basin of Alabama and Mississippi 

(Williams & Clemmer 1991). The shovelnose 

sturgeon is also known as sand sturgeon, hackleback, 

or switchtail and is the most common of the 

three species. The current distribution of the shovelnose 

sturgeon, as obtained from the questionnaires 

used in this study, is presented in Figure 1. 

Shovelnose sturgeon are primarily a bottom 

dwelling species (Barnickol & Starrett 1951, Moos 

1978,Curtis 1990).They live where there is a current 

of 20–40 cm sec –1 (Hurley et al. 1987, Curtis 1990). 

Shovelnose sturgeon are usually found in pools 

downstream from sandbars in unchannelized rivers 

(Schmulbach et al. 1975, Moos 1978, Durkee et al. 

1979);along the main channel border, downstream 

from dams. or in association with wing dams in rivers 

with navigational training structures (Hurley 

1983, Pennington et al. 1983, Carlson et al. 1985, 

Hurley et al. 1987, Curtis 1990); and in the riverine 

habitat upstream of reservoirs in impounded rivers 

(Held 1969,Curtis 1990). They are usually found in 

association with sand substrate. often near rock or 

gravel (Christenson 1975, Hurley 1983, Carlson et 

al. 1985), where a current exists (Coker 1930, 

Schmulbach et al. 1975, Carlson et al. 1985, Curtis 

1990). 

Abundance of shovelnose sturgeon seems to be 

related to the size of the rivers in which they live and 

to human activities. Coker (1930) stated that the 

fate of Mississippi River sturgeon was a tragedy of 

shortsightedness in the conduct of the fishery. Shovelnose 

sturgeon were once so common that they

were considered a nuisance to commercial fishermen 

and were destroyed when caught (Coker 1930). 

Barnickol & Starrett (1951) indicated that the decline 

of the shovelnose sturgeon in the Mississippi 

River also coincided with the development of the 

river as a navigation canal. The abundance of shovelnose 

sturgeon has been estimated for rivers of 

several sizes with a variety of habitats and varying 

degrees of modification: Schmulbach (1974) estimated 

2500 fish km –1 for the unchannelized Missouri 

River. Helms (1972) estimated 1030 fish km –1 for 

the navigation-altered Mississippi River. Christenson 

(1975) estimated 100 fish km –1 for the small Red 

Cedar River in Wisconsin, and Elser et al. (1977) 

estimated 403 to 537 fish km –1 for the Tongue River 

in Montana. 

Food, growth, and reproduction 

293 

their ages varied by as much as 19 years (Zweiacker 

1967). 

The shovelnose sturgeon is the smallest of the 

North American sturgeons. Carlander (1969) indicates 

a maximum weight for the shovelnose sturgeon 

of 4.5 kg with most specimens being less than 

2.5 kg. Shovelnose sturgeon in the upper Missouri 

River, however, are notably larger than specimens 

throughout most of its range. Peterinan & Haddix 

(1975) examined 427 shovelnose in Montana and 

found an average weight of 2.4 kg; 11% of the individuals 

weighed more than 3.6 kg, 5% more than 4.5 

kg. and specimens up to 7 kg were found. Keenlyne 

et al. (1994) found significant morphometric differences 

between upper Missouri River fish compared 

to downriver populations which suggests that a different 

strain of shovelnose sturgeon exists in the upper 

Missouri River. 

Spawning habitat of shovelnose sturgeon has not 

been described. Spawning is believed to occur over 

hard substrate in primary tributary streams to the 

Shovelnose sturgeon are opportunistic feeders that 

prey on aquatic invertebrates, primarily immature main rivers (Cross 1967, Peterman & Haddix 1975, 

insects (Hoopes 1960, Held 1969, Ranthum 1969, Christenson 1975, Elser et al. 1977) or along the bor- 

Elser et al. 1977, Modde & Schmulbach 1977, Dur- ders of the main river channels (Coker 1930, Moos 

kee et al. 1979, Carlson et al. 1985). Several studies 1978). Studies conducted before major modificaindicate 

that the abundance of food affects growth tions were made to river channels and tributary 

rates of shovelnose sturgeon. Altered stream flows flows concluded that shovelnose sturgeon swam up 

affect both the ability of shovelnose sturgeon lo find tributaries to spawn (Forbes & Richardson 1920, 

food (Modde & Schmulbach 1977) and the abun- Coker 1930). Moos (1978) stated that shovelnose 

dance of prey organisms (Elser et al. 1977). sturgeon only used tributaries infrequently and 

Carlander (1969) summarized shovelnose stur- chose to remain in the larger rivers. Cross (1967) 

geon growth data from fish collected from the Mis- suggested that shovelnose sturgeon may seek tribsouri 

River as the reservoirs were filling. and found utary streams for spawning when flows are high. 

them to be 213 mm total length (TL) at age 1, 274 Moos (1978) observed that shovelnose sturgeon 

mm at age 2,399 mm at age 5, and 503 mm at age 10. moved up to 540 km and stated that dams have 

In a study on the Mississippi River, Helms (1973) probably prevented movement to traditional 

found shovnose sturgeon to be 211 mm fork length spawning areas, contributing to a lack of recruit- 

(FL) at age 1, 328 mm at age 2. 495 mm at age 4.592 ment since damming of the upper Missouri River. 

mm at age 6, and 701 mm at age 10, Even though Although actual spawning has not been delengths 

of the Missouri River fish were in total scribed, the capture of fish in spawning condition 

length and the Mississippi River fish in fork length. indicates that shovelnose sturgeon spawn from late 

the Missouri River fish were much shorter at given April to June (Forbes & Richardson 1920, Coker 

ages. Zweiacker (1967) found that Missouri River 1930, Eddy & Surber 1947, Barnickol & Starrett 

shovelnose sturgeon nearly ceased growing and re- 1951,Christenson 1975,Elseretal. 1977,Moos 1978) 

producing alter the Missouri River dams were con- at water temperatures between 16.9 and 20.5 °C 

structed. Shovelnose sturgeon from 8 to 27 years of (Christenson 1975, Elseretal. 1977). Most males beage 

were all about the same length, even though come sexually mature at age 5, while most females

294 

do not mature until age 7 (Helms 1973). In areas of 

poor food supply. males and females become sexually 

mature at a smaller size (Moos 1978). Females 

do not spawn every year with the frequency of 

spawning influenced by food supply and ability to 

store adequate fat to produce mature gametes 

(Christenson 1975. Moos 1978). Gonads of mature 

males represent 2-6%of body weight and 10-22% 

of females (Zweiacker 1967, Helms 1973. Christenson 

1975, Moos 1978). 

Several authors have identified what are believed 

to be reproduction problems with this species. June 

(1977) reported finding shovehose sturgeon with 

mature eggs into July in Missouri River reservoirs 

with up to 52% of the females showing massive follicular 

atresia and concluded that this demonstrated 

unfavorable spawning conditions for the sturgeon 

as a result of river impoundment. He also reported 

high levels (2.1 % incidence rate) of hermaphroditism 

in shovelnose sturgeon; a phemonenon 

also noted on other Missouri River studies by Carlson 

et al. (1985), with a 3% incidence rate, and Moos 

(1978), with a 1.6% incidence rate. Carlson et al. 

(1985) also discovered hybridization with S. albus. 

Several authors have noted a lack of natural reproduction 

in areas of the Missouri River and have attributed 

it to man-made alterations to shovelnose 

sturgeon habitat (Bailey & Cross 1954, June 1977. 

Moos 1978). 

Current harvest 

The shovelnose sturgeon is presently classified as a 

sport fish in 12 states and a commercial species in 7 

(Table 1). It is considered extirpated in 3 states, is 

fully protected in 4, and is considered rare, threatened, 

or of special concern in 8 states. Some states 

have dual classifications and some classify it differently 

in various waters. 

Table 1. Classification, status. and type of fishery allowed in states within the range of the shovelnose sturgeon. 

State Classification Status Type of fishery 

Since 1940 Since 1990 Sport Commercial 

Alabama Extirpated Decline Extinct No No 

Arkansas Commercial Decline U nknown Yes Yes 

Illinois Sport/commerci al Unknown U n k n ow n Yes Yes 

lndiana None U nknown Unknown Yes Yes 

Iowa Sport/commercial Unknown Stable Yes Yes 

Kansas Sport Decline Unknown Yes No 

Kentucky Sport U nknown Unknown Yes Yes 

Louisiana Special concern Unknown Unknown No No 

Minnesota Sporticoncern Unknown Stable Yes No 

Mississippi Rare Unknown Unknown No No 

Missouri Sport/commercial Decline Unknown Yes Yes 

Montana Sport Unknown Stable Yes No 

Nebraska Sport Decline Stable Yes No 

New Mexico Extirpated Extinct Extinct No No 

North Dakota Protected Decline Stable No No 

Ohio Endangered Decline Unknown No No 

Oklahoma Special concern Decline Unknown N o N o 

Pennsylvania Extirpated Unknown Unknown No No 

South Dakota Protected Unknown Unknown No No 

Tennessee Extirpated Unknown Unknown No No 

Texas Endangered Decline Unknown No No 

West Virginia Extirpated Decline Extinct No No 

Wisconsin Sport/commercial Decline Unknown Yes Yes 

Wyoming Sport/concern Decline Stable Yes N o

295 

Sport and commercial harvests of shovelnose 

sturgeon are difficult to compare or analyze due to 

absence of similar data across its range. According 

to responses to a questionnaire used to obtain information 

for this project, sport harvest of shovelnose 

sturgeon generally is considered low with most 

of the harvest coinciding with the spring spawning 

season. Few anglers fish specifically for shovelnose 

sturgeon; much of the catch is incidental. Estimates 

of sport fishing exploitation rates are limited to the 

work of Christenson (1975) on the Red Cedar-Chippewa 

rivers in Wisconsin (2% annual exploitation 

rate) and Elser et al. (1977) on the Yellowstone and 

Tongue rivers in Montana (a 1% rate). No data are 

available on recent exploitation rates as a result of 

commercial harvest. 

Today, there is a significant commercial harvest 

from the Mississippi River upstream from the 

mouth of the Ohio River, from the lower Missouri 

River, and from the Wabash River. In states where 

commercial harvest data were available (Table 2), 

information was provided by commercial anglers as 

part of their licensing requirement. Helms (1972) 

considered such data to be conservative. Presently, 

about 25 tons of shovelnose sturgeon are harvested 

annually; 60% comes from the Mississippi River 

upstream of St. Louis, Missouri. Limited information 

on the values of shovelnose sturgeon products 

exists. 

Most harvest occurs in May and June and is believed 

to be associated with movement that coincides 

with spawning activity (Hurley 1983). Coker 

(1930) stated that shovelnose sturgeon tend to swim 

near the surface during the spawning run and Beck- 

er (1983) indicated that floating nets can be used by 

fishermen to catch sturgeon at that time. The fish 

are also vulnerable to propeller strikes by pleasure 

or commercial craft while swimming near the surface 

for several authors have noted finding fish with 

anterior ends of rostrums missing or severed caudal 

peduncles (Helms 1973, Christenson 1975, Moos 

1978). Helms (1972) reported that 42% of the shovelnose 

sturgeon are harvested during May and June. 

Most of the commercial harvest is taken with 

trammel nets, although some operators use traps. 

During spring, traps are often baited with sexually 

mature females, which are believed to attract more 

shovelnose sturgeon. Helms (1972) described the 

two major means of setting nets as dead or stationary 

sets in currents along the channel borders or 

drifting, where bottom conditions allow. Drifting of 

trammel nets can be very effective during periods 

when shovelnose sturgeon are relatively inactive 

and concentrated downstream from dams or near 

wing dams, or are located in deeper pools downstream 

from sand bars. When flows are reduced in 

winter and river waters drop in regulated rivers, 

shovelnose sturgeon concentrate and can become 

very vulnerable to netting. At this time, a technique 

that involves weighting one end of the trammel net 

and setting it near the edge of a scour hole and then 

sweeping the other end through the hole like a seine 

is effective. 

Some fish are sold locally or directly to the public 

by commercial anglers as hog dressed or eviscerated 

fish, while others are eviscerated fish with heads 

removed. In distant markets or where the market 

Table 2. Commercial harvest and prices (in dollars per kg) of shovelnose sturgeon by state in 1992. N.A. indicates data were not available.

296 

exceeds the supply, fish are often sold as smoked 

sturgeon. 

Shovelnose sturgeon are also harvested in late 

fall and early winter for both meat and the highly 

valued roe (Coker 1930). Moos (1978) reported that 

shovelnose sturgeon eggs are uniformly dark by the 

first of January and change little through the winter. 

Some of the best caviar is produced from fish taken 

at this time because the eggs are uniform in size and 

color, firm, relatively easy to process. and of high 

quality and taste before fat is incorporated into the 

eggs in spring during the final egg maturation process 

(Moos 1978). The general decline in prices of 

roe from north to south (Table 2) reflects proximity 

to market and quality of eggs. Southern states enjoy 

the advantage of having a longer ice-free period on 

the rivers, allowing commercial operators the opportunity 

to harvest sturgeon later in fall and earlier 

in spring, when the roe is best for producing quality 

caviar. 

Current status and outlook 

this species, is a continuing problem to the longterm 

health of the species, especially as damming 

and fragmentation may be affecting replacement, 

reproduction, and gene flow. 

In this survey, 12 states indicated that shovelnose 

sturgeon populations have declined in the last 50 

years, one state reported it to have become extinct, 

and 11 states did not have information necessary to 

make an assessment of population trends for that 

period. Six states considered shovelnose sturgeon 

populations to be stable since 1990, three states indicated 

that the species is now considered extirpated 

within their state, and 15 states did not have sufficient 

data to make trend analyses on this species. 

Three states, Wyoming, West Virginia, and New 

Mexico, are developing plans to restock shovelnose 

sturgeon into waters that they once inhabited. 

Hybridization of the shovelnose sturgeon with 

the pallid sturgeon is an emerging concern among 

sturgeon fishery managers. The possible introgression 

of genes from the more common shovelnose is 

viewed as a threat to the rare pallid sturgeon (Carlson 

et al. 1985, Keenlyne et al. 1994). Molecular 

technologies have been unable to differentiate 

among shovelnose species and their hybrids 

(Phelps & Allendorf 1983). Species like the shov- 

elnose sturgeon that likely evolved with polyploidy 

(Blacklidge & Bidwell 1993) are difficult to study 

through normal genetic testing procedures. Imposi- 

tion of recent introgressive hybridization may con- 

tribute to the present state of confusion about integrity 

of species and will continue to remain a problem 

for scientists and administrators who attempt 

to manage for shovelnose species in the future. 

The shovelnose sturgeon is the widest-ranging 

freshwater sturgeon in North America. There is little 

question that its range and many populations 

have been reduced as a result of human actions, 

either through overharvest early in the 20th century 

or through modification of riverine habitats by 

dams and river-training structures (Coker 1930, 

Barnickol & Starrett 1951, Carlander 1954, Modde 

& Schmulbach 1977). A comparison of the historic 

range (Lee et al. 1980) to the present range (Figure 

1) indicates that the species is now absent from the The welfare of the shovelnose sturgeon may have 

Rio Grande River and from upstream reaches of future implications to our large rivers in the central 

several large western rivers where movement has United States. Becker (1983) lists the shovelnose 

been blocked by dams and stream flow has been al- sturgeon as a host for glochidia of the commercially 

tered. 

valuable yellow sand-shell Lampsilis teres, pimple- 

In the questionnaire developed for this study, 19 back Quadrula pustulosa, and hickory-nut Obovastates 

responded that habitat alteration is a concern ria olivaria pearly mussels. Shovelnose sturgeon alin 

regard to the welfare of the shovelnose sturgeon, so are the only known host for the parasitic larvae of 

six mentioned pollution as a concern, one men- the hickory-nut mussel (Coker 1930). 

tioned overharvest, one mentioned hybridization, 

and three expressed no issues of concern. Flow alteration 

and habitat fragmentation, as a result of 

damming of many of the rivers within the range of

297 


I thank S. Whitmore, who developed the figure for 

this report, J. Zuboy and J. Schmulbach, who provided 

critical reviews of the manuscript, and the 

many state fishery biologists, who compiled status, 

harvest, and present range information for the 

questionnaire. 


Bailey, R.M, & F.B. Cross. 1954. River sturgeons of the American 


Pap. Mich. Acad. Sci., Arts, Let. 39: 169–208. 

Barnickol, P.G. & W. Starrett. 1951. Commercial and sport fishes 

of the Mississippi River between Caruthersville, Missouri and 

Dubuque, Iowa. Bull. III. Nat. Hist. Surv. 25: 267–350. 

Becker, G.C. 1983. Fishes of Wisconsin. University of Wisconsin 

Press, Madison. 1052 pp. 


by genome quantification in Acipenseriformes of 

North America. J. Hered. 84: 427–430. 

Carlander, H.B. 1954. History of fish and fishing in the upper 

Mississippi River. Upper Miss. River Cons. Comm., Rock Island. 

96 pp. 

Carlander, K.D. 1969. Handbook of freshwater fishery biology. 

Iowa State University Press, Ames. 752 pp. 

Carlson, D.M., W.L. Pflieger, L. Trial & P.S Haverland. 1985, 

Distribution, biology, and hybridization of Scaphirhynchus albus 

and S. platorynchus in the Missouri and Mississippi rivers. 

Env. Biol. Fish. 14: 51–59. 

Christenson, L.M. 1975. The shovelnose sturgeon Scaphirhynchus 

platorynchus (Rafinesque) in the Red Cedar - Chippewa 

rivers system Wisconsin. Wis. Dep. Nat. Resour., Res. Rep. 

No. 82. 23 pp. 

Coker, R.E. 1930. Studies of common fishes of the Mississippi 

River at Keokuk. U. S. Bur. Fish. Bull. 45: 141–225. 

Cross, F.B. 1967. Handbook of fishes of Kansas. Mus. Nat. Hist. 

Univ. Kans., Misc. Publ. 45: 1–357. 

Curtis, G.L. 1990. Habitat use by shovelnose sturgeon in Pool 13, 

upper Mississippi River, Iowa. M.S. Thesis, Iowa State University, 

Ames. 79 pp. 

Durkee, P., B. Paulson & R. Bellig. 1979. Shovelnose sturgeon 

(Scaphirhynchus platorychus) in the Minnesota River. Minn. 

Acad. Sci. 45: 18–20. 

Eddy, S. & T. Surber. 1947. Northern fishes. Univ. Minn. Press, 

Minneapolis. 267 pp. 

Elser, A.A., R.C. McFarland & D. Schwehr, 1977. The effect of 

altered streamflow on fish of the Yellowstone and Tongue rivers, 

Montana. Mont. Dept. Fish and Game Tech. Rept. 8: 1– 

180. 

Forbes, S.A. & R.E. Richardson. 1920. The fishes of Illinois. III. 

Nat. Hist. Surv. 3: 1–357. 

Held, J.W. 1969. Some early summer foods of the shovelnose 

sturgeon in the Missouri River. Trans. Amer. Fish. Soc. 98: 

514–517. 

Helms, D.R. 1972. Progress report on the first year study of shovelnose 

sturgeon in the Mississippi River. Iowa Conservation 

Commission, Des Moines. 22 pp. 

Helms, D.R. 1973. Progress report on the second year of study of 

shovelnose sturgeon in the Mississippi River. Iowa Conservation 

Commission; Des Moines. 33 pp. 

Helms, D.R. 1974. Age and growth of the shovelnose sturgeon, 

Scaphirhynchus platorynchus (Rafinesque), in the Mississippi 

River. Proc. Iowa Acad. Sci. 81: 73–75. 

Hoopes, D.T. 1960. Utilization of mayflies and caddisflies by 

some Mississippi River fish. Trans. Amer. Fish. SOC. 89: 32–34. 

Hurley, S.T. 1983. Habitat associations and movements of shovelnose 

sturgeon in Pool 13 of the upper Mississippi River. M.S. 

Thesis, Iowa State University, Ames. 82 pp. 

Hurley, S.T., W.A. Hubert & J.G. Nickum. 1987. Habitats and 

movements of shovelnose sturgeons in the upper Mississippi 

River. Trans. Amer. Fish. Soc. 116: 655–662. 

June, F.C. 1977. Reproductive patterns in seventeen species of 

warmwater fishes in a Missouri River reservoir. Env. Biol. 

Fish. 2: 285–296. 

Keenlyne, K.D., C.J. Henry, A. Tews & P. Clancey. 1994. Morphometric 

comparisons of Upper Missouri River sturgeons. Trans. 

Amer. Fish. Soc. 123: 779–785. 

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins,D.E. McAllister 

& J.R. Stauffer Jr. 1980. Atlas of North American freshwater 

fishes. North Carolina Biol. Surv., Pub. 1980–12, Raleigh. 

867 pp. 

Modde, T. & J.C. Schmulbach. 1977. Food and feeding behavior 

of the shovelnose sturgeon, Scaphirhynchus platorynchus; in 

the unchannelized Missouri River, South Dakota. Trans. Amer. 

Fish. Soc. 106: 602–608. 

Moos, R.E. 1978. Movement and reproduction of shovelnose 

sturgeon, Scaphirhynchus platorynchus, in the Missouri River. 

South Dakota. Ph.D. Dissertation. University of South Dakota, 

Vermillion. 216 pp. 

Pennington, C.H., J.A. Baker & M.E. Potter. 1983. Fish populations 

along natural and revetted banks on the lower Mississippi 

River. N. Amer. J. Fish. Manag. 3: 204–211. 

Peterman, L.G. & W.H. Haddix. 1975. Lower Yellowstone River 

fishery study. Montana Dept. Fish and Game, Prog. Report 1: 

1–56. 

Phelps, S.R. & E Allendorf. 1983. Genetic identity of pallid and 

shovelnose sturgeon (Scaphirhynchus albus and S. platorynchus). 

Copeia 1983: 696–700. 

Ranthum, R.G. 1969. Distribution and food habits of several species 

of fish in Pool 19, Mississippi River. M.S. Thesis, Iowa 

State University, Ames. 207 pp. 

Schmulbach, J.C. 1974. An ecological study of the Missouri River 

prior to channelization. University of South Dakota, Vermillion. 

34 pp. 

Schmulbach, J.C., G. Gould & C.L. Groen. 1975. Relative abundance 

and distribution of fishes in the Missouri River, Gavins 

Point Dam to Rulo, Nebraska. S. D. Acad. Sci. 54: 194–222.

298 

Williams, J.D. & G.H. Clemmer. 1991. Scaphirhynchus suttkusi, a Zweiacker, P. 1967. Aspects of the life history of the shovelnose 

new sturgeon (Pisces: Acipenseridae) from the Mobile Basin sturgeon. Scaphirhynchus platorynchus (Rafinesque), in the 

of Alabama and Mississippi. Bull. Alabama Mus. Nat. Hist. 10: Missouri River. M.A. Thesis, University of South Dakota, 

17–31. Vermillion. 46 pp.

Environmental Biology of Fishes 48: 299–309,1997, 


The status and distribution of lake sturgeon, Acipenser fulvescens, in the 

Canadian provinces of Manitoba, Ontario and Quebec: a genetic perspective 

Moira M. Ferguson 1 & George A. Duckworth 2 

1 

Department of Zoology and Institute of Ichthyology, University of Guelph, Guelph, Ontario NlG 2WI, Canada 

2 

Ontario Ministry of Natural Resources, Northwest Region, 140–4th Ave., Cochrane, Ontario POL 1 CO, Canada 


Key words: postglacial recolonization, anthropogenic influences, fish, Acipenseridae, conservation 

Synopsis 

Genetic analysis of mitochondrial DNA sequence variation indicates that most of a sample of 396 lake sturgeon, 

Acipenser fulvescens, from the northern part of their range belonged to either one of two haplotypes. 

The vast majority of fish from the Great Lakes/St. Lawrence and Mississippi drainages were of a single haplotype 

while those from the Hudson/James Bay were composed of both haplotypes. This haplotypic distribution 

suggests that fish from one refugium (possibly Missourian) recolonized the Hudson-James Bay drainage while 

those from a second (possibly Mississippian) recolonized the Laurentian Great Lakes and St. Lawrence River. 

Lake sturgeon still inhabit much of their native postglacial distribution in Manitoba, Ontario and Quebec. 

However, the stresses of commercial overexploitation and habitat alteration, usually through hydroelectric 

dam construction and operation, have either singly or in tandem brought about the reduction, if not extirpation, 

of some populations within the range. The largest zone of extirpation and population reduction has 

occurred in the Lake Winnipeg drainage area, which covers more than one-third of Manitoba. Other areas 

where populations have been reduced to remnant levels, if not extirpated, include the lower Laurentian Great 

Lakes of Lake Ontario and Lake Erie. In northern Ontario, lake sturgeon populations whose riverine habitats 

have been fragmented by two or more dams are substantially reduced from their former levels. In Quebec, 

more attention has been paid to limiting the exploitive stresses on lake sturgeon populations. Combination of 

the genetic and status data suggests that both northern and southern populations of lake sturgeon (possibly 

from two glacial refugia) have been impacted severely from anthropogenic influences. 

Introduction 

The lake sturgeon, Acipenser fulvescens, is one of 

the most widely distributed members of the North 

American fish fauna. Its native range includes three 

major watersheds: the Laurentian Great Lakes, 

Hudson-James Bay, and the Mississippi River 

(Houston 1987). The Canadian distribution of lake 

sturgeon includes the five provinces of Alberta, 

Saskatchewan, Manitoba, Ontario, and Quebec. It 

exists as far west as Edmonton on the North Saskatchewan 

River, as far east as St. Roch de Aulnaires 

on the St. Lawrence River, as far north as the 

Seal River, a tributary on the west coast of Hudson 

Bay, and as far south as the main Mississippi River 

and in most of its larger tributaries southward to 

southern Arkansas. 

The current distribution of lake sturgeon has 

been impacted by historical processes such as postglacial 

recolonization of the northern part of the

300 

range and anthropogenic influences including overfishing 

and habitat alteration. We discuss these factors 

and then evaluate the current status of this species 

in the Canadian provinces of Manitoba, Ontario, 

and Quebec from a genetic perspective. We also 

summarize and contrast the overall status in the 

United States. 

Influences on distribution 

Postglacial recolonization 

Wisconsinan glaciation was a major feature of the 

recent zoogeographic past of North America (Hocutt 

& Wiley 1986). At its maximum about 18 000 

years ago, the Wisconsinan ice sheet covered much 

of the extant Canadian range of lake sturgeon. 

Those populations that occurred in Canada prior to 

the Wisconsinan glacial period either perished or 

moved into refuges south of the ice sheet. Enormous 

amounts of meltwater formed rivers and large 

lakes, providing dispersal routes for reinvasion. Paleogeographic 

evidence suggests that lake sturgeon 

reinvaded the northern part of its range via the 

Warren, Brule, and Chicago dispersal routes from a 

Mississippian Refugium (Mandrak & Crossman 

1992). 

Distribution of mitochondrial DNA (mtDNA) 

genetic types (haplotypes) has been used to infer 

postglacial recolonization from refugia and test 

conclusions based on paleogeographic evidence 

(Billington & Hebert 1991). MtDNA is a closed circular 

molecule which is maternally inherited and 

not subject to recombination (Moritz et al. 1987). 

Nucleotide variation in mtDNA is usually detected 

indirectly by cutting the molecule with restriction 

endonucleases or by determining nucleotide sequences 

directly. MtDNA retains a history of past 

isolation for a longer period relative to nuclear 

DNA because of its transmission (Billington & 

Hebert 1991). Gene frequencies will diverge in both 

the nuclear and mitochondrial genomes once a single 

population becomes subdivided into two isolates 

because of the evolutionary processes of genetic 

drift and mutation. This divergence may be 

enhanced if the isolates become fixed for different 

mtDNA types because of stochastic lineage extinction 

(Avise et al. 1987). If the descendants of two 

populations originating from different refugia 

come into secondary contact after glacial recession, 

then gene frequencies at variable loci in the nuclear 

genome will homogenize until there is no evidence 

of past isolation. However, this process occurs more 

slowly in the mitochondrial genome because of its 

smaller genetic population size (114) relative to the 

nuclear genome, which means that four times as 

Table 1. Sampling locations and number of lake sturgeon analyzed 

for mtDNA haplotype variation. Fish were collected between 

1989-1993 unless otherwise indicated. 

Sampling location 

Hudson Bay-James Bay 

Moose River basin 129 

Waswanipi River 

12 a 

12 

Lower Nelson R. 

10 b 

Rainy River 16 

Total 179 

Great Lakes-St. Lawrence 

Lake St. Clair 12 

Lake Temiskaming 18 

Lake Winnebago 18 

Lake Ontario (1873) c 1 

Ottawa River (Rockland, Quyon, Gatineau) 17 a 

10 

Lake of Two Mountains 

11 a 

St. Lawrence River 

LacSaint-Louis 

11 a,d 

Montreal (1866) c 1 

Lac Saint-Pierre 

20 a 

22 

Gentilly 

11 a 

Quebec City 22 

Sturgeon River (Lake Superior) 21 

Total 195 

Mississippi 

Mississippi River (1870) c 1 

Flambeau River (Mississippi) 21 

Total 22 

a Data from Guenette et al. (1993), otherwise from Ferguson et 

al. (1993) and Ferguson (unpublished). 

b 

Sampled a single individual with a different haplotype at a sequence 

position other than 54. 

c 

Preserved specimen housed in the British Museum of Natural 

History, London. 

d Sampled a single individual with a different haplotype as determined 

by digestion with Bcl1. 

n

301 

Figure 1. Mitochondrial DNA haplotype frequencies in lake sturgeon from the nothern part of their range See Table 1 for sample sizes. 

Haplotype 1 = black. haplotype 2 = clear. 

much migration is required to erode mtDNA haplo- Hinc II) or nucleotide variation at position 54 in the 

type divergence than nuclear gene divergence. 275 base pairs sequenced (details in Ferguson et al. 

Thus, the basic premise is that fish originating from 1993). Both analyses provided equivalent haplotypdifferent 

refugia will differ genetically in mtDNA ic designations. Three populations from the Hudhaplotype 

frequencies (Billington & Hebert 1991). son-James Bay watershed in northern Manitoba. 

Ward et al. (1989) found that mtDNA haplotypes of Ontario, and Quebec shared the same two common 

walley, Stizostedion vitreum, cluster into three haplotypes. However, the vast majority of more 

main groups,each reflecting recolonization of Can- southerly fish from the Great Lakes/St. Lawrence 

adian waters from each of three glacial refugia. A and Mississippi watersheds were of a single haplosimilar 

approach has been used for lake whitefish, type.This included three specimens housed at the 

Coregonus clupeaformis (Bernatchez & Dodson British Museum of Natural History and collected in 

1990). lake charr Salvelinus namaycush arctic charr the late 1800’s.The only apparent disparity in this 

S. alpinus (Wilson 1995),and brook charr S. fontina- pattern was the collection of a very small number of 

lis (Danzmann & Ihssen 1995). 

haplotype 2 fish near the confluence of the Ottawa 

We analyzed mtDNA variation of lake sturgeon and St. Lawrence Rivers by Guenette et al. (1993). 

from the northern part of their range to assess fac- The distribution of mtDNA haplotypes (Figure 

tors which may influence the distribution of 1) can explained by two alternative scenarios 

mtDNA haplotype lineages (Ferguson et al. 1993, corresponding to a single refugium hypothesis ver- 

Guenette et al. 1993). Most of the 396 lake sturgeon sus a two relugium hypothesis. The resolution of 

analyzed were characterized by only two mtDNA the controversy depends on the ability of each scehaplotypes 

based on a restriction fragment length nario to explain the commonality of haplotype 2 

polymorphism (RFLP) analysis or direct sequene- fish in northern samples and rarity in southern saming 

of 275 nucleotides in the mtDNA control region ples. In the first scenario. the disjunct distribution of 

(Table 1. Figure 1). Fish could be categorized into haplotype 2 is because lake sturgeon used two distwo 

major haplotypes using either of two restriction tinct routes of colonization from two refugia (posenzymes 

which detected polymorphisms (Ava II, sibly Missourian and Mississippian) to reinvade the

302 

contemporary range of distribution. Fish from a 

Missourian refugium would have recolonized the 

headwaters of the James Bay and Hudson Bay areas 

of Ontario and Quebec through the connection between 

from throughout the Great Lakes and Mississippi 

regions would have had the same haplotype eliminated 

by chance, and it is difficult to imagine differential 

selection of mtDNA haplotypes. 

Lake Agassiz and Lake Ojibway-Barlow 

(about 9500 years ago) (Crossman & McAllister 

1986) resulting in a northerly distribution of de- Exploitation 

scendants. As mentioned previously, Mississippian 

fish would have used the Warren, Brule, and Chica Since the existence of aboriginal culture in North 

go dispersal routes to colonize the southern part of America, lake sturgeon have been a key food 

the range (Mandrak & Crossman 1992). The large source, especially during spring ceremonial festivnumber 

of haplotype 2 fish sampled from northern ities at lake sturgeon spawning sites. During the 

sites (Nelson River, Manitoba; Moose River basin, early 1800’s, lake sturgeon was also sought after as a 

Ontario; Waswanipi River, East Megiscane region, trade item since the isinglass (a form of gelatin ob- 

Quebec) coupled with the very high predominance tained from the inner lining of the swimbladder) 

of haplotype 1 fish in the south is consistent with the could be used as a clarifying agent in wine, beer and 

two refugium hypothesis. The observation that all jelly making. Records of its harvest were first kept 

21 fish sampled from the Flambeau River, a tribu- by the Hudson Bay Company which provided abotary 

of the Mississippi River were haplotype 1 lends riginal people access to markets (Holzshamm & 

further credence to the idea that populations de- McCarthy 1988). There is no evidence that the liarrived 

from a Mississippian refugium were haplo- vest levels of lake sturgeon prior to the 1860’s had 

type 1. According to the two refuge hypothesis, the any influence on population levels. 

three haplotype 2 fish collected by Guenette et al. Early settlers to North America did not value 

(1993) in the Ottawa River and Lake of Two Mountain lake sturgeon as a food source. This changed about 

tains could be the result of secondary contact 1855 when a market for caviar developed at Sandamong 

the two refugial groups; Lake Ojibway-Bar- usky, Ohio, on Lake Erie, followed by the sale of 

low was connected with the Ottawa River up until smoked flesh in 1860. Spurred by these market deabout 

8000 years ago (Crossman & McAllister mands, local markets and fisheries spread to lakes 

1986). According to the single refugium model, lake Huron. Ontario, Superior, Nipissing, and Nipigon 

sturgeon recolonized Canada from a single Missis- and Lake of the Woods. In every case, after an inisippian 

refugium (Guenette et al. 1993) a scenario tial high yield. the fisheries displayed a rapid and 

compatible with the paleogeographic evidence permanent decline to very low levels (Harkness & 

(Crossman & McAllister 1986, Mandrak & Cross- Diamond 1961). For example, the Lake Erie catch 

man 1992). Mississippian refugium fish would have fell from over 2500 tonnes per year to less than 500 

contained both haplotypes, one of which was large- tonnes between 1885–1895. 

ly eliminated in the southern part of the range via The development of commercial fisheries for 

stochastic lineage extinctions (Avise et al. 1987). lake sturgeon in Manitoba were delayed relative to 

The few haplotype 2 fish observed in the Lake of those in Ontario. The harvest from Lake Winnipeg 

Two Mountains and the Ottawa River would be the and its tributaries, the Red and Assiniboine rivers, 

remnants of a historically more common lineage. peaked at 445 tonnes in 1900 and crashed to 13 

We favor the two refuge hypothesis given the dis- tonnes by 1910 when the fishery was closed (Houstribution 

of haplotypes over the broader geograph- ton 1987). The fishery reopened after 6 years with 

ic scale illustrated in Figure 1. Stochastic lineage ex- fluctuating landings until 1928 when it was again 

tinction is expected to be random with respect to closed. Declining catches in Lake Winnipeg 

the extinction of haplotypes in specific populations. spurred interest in more northern locations such as 

It is difficult to envisage that all the southerly pop- the Nelson and Churchill rivers where commercial 

ulations sampled by us and Guenette et al. (1993) fishing began in 1907 and 1924, respectively. Succes-

303 

sive closures and openings characterized commercial 

fishing in these locations. In 1961, commercial 

fishing for sturgeon was closed in Manitoba but it 

resumed again in 1970, albeit at low levels. 

After fisheries in the larger lakes had declined, 

smaller northern inland waters became the subject 

of commercial interest. Impacts on these populations 

are masked by the aggregate reporting of statistics. 

For example, in Ontario, commercially harvested 

fish from all northern inland waters (rivers 

and lakes) were recorded in one category making it 

impossible to trace results from one particular waterbody. 

This is further exacerbated by incomplete 

reporting by commercial fisherman and the relatively 

low priority that managers place on ensuring 

compliance in this fishery. By the late 1980’s, the 

combined northern inland harvest in Ontario was 

twice that of the Great Lakes (Duckworth et al.1). 

Habitat alteration 

Habitat protection is considered to be the key factor 

in the conservation and rehabilitation of the remaining 

lake sturgeon stocks in Ontario (Duckworth 

et al. 1 ). Maintenance and enhancement of existing 

lake sturgeon habitat is considered the third 

highest priority in Manitoba after the maintenance 

of genetic integrity and the protection of existing 

stocks (Anonymous 2 ). Lake sturgeon require swift 

current and large rough substrate for spawning and 

embryo incubation. This dependence on riverine 

environments makes them vulnerable to development 

on rivers that alters habitat. 

Hydroelectric generation facilities affect both 

periodic and seasonal water level fluctuations, causing 

decreased production and loss of fish (Payne 

1987). Low water conditions after spawning can affect 

success of embryo survival as embryos experi- 

1 

Duckworth, G., T. Mosindy, E. Armstrong, G. Goodchild, G. 

Preston, M. Hart & C. Jessop. 1992. Adraft management strategy 

for lake sturgeon in Ontario. Edition 6, 31 July 1992. Ministry of 

Natural Resources Unpublished Manuscript. 

2 

Anonymous. 1992. A sturgeon management strategy for Manitoba: 

a discussion paper (draft). October 1992. Manitoba Natural 

Resources Department, Fisheries Branch Unpublished Manuscript. 

Figure 2. Mitochondrial DNA haplotype frequencies in lake 

sturgeon from the Moose River basin, Ontario. Hydroelectric 

generating stations are represented by slashes (data from Ferguson 

et al. 1993). Haplotype 1 = black, haplotype 2 = clear. 

ence variable water temperatures, low oxygen concentrations, 

and desiccation. Young fish can become 

trapped in shallow pools and subjected to 

heavy mortality through predation, temperature, 

and oxygen stress. Adults have become stranded in 

shallow pools and mortality occurs when pools become 

anoxic or freeze (Duckworth et al. 1 ). 

Dams also restrict movements of lake sturgeon, 

preventing fish from reaching critical habitat such 

as spawning sites, and by stranding fish between 

barriers. High water conditions associated with 

dams can also flood and eliminate rapids and chutes 

previously used by spawning fish (Duckworth et 

al. 1 ). A population genetics study of lake sturgeon 

within the Moose River Basin in northeastern Ontario 

suggested that there is significant gene flow 

among most sites in the watershed (Ferguson et al. 

1993, Figure 2). Dam construction or other artificial

304 

Figure 3. Status of lake sturgeon in the province. of Manitoba, Canada. 

barriers to migration could impact the genetic integrity 

of the species by fragmenting it into isolated 

stocks and causing the loss of genetic variability 

through evolutionary processes such as random genctic 

drift and inbreeding. Populations with low 

ered genetic variability may be less able to withstand 

future stresses. Genetic impacts of such anthropogenic 

influences are illustrated by the re- 

duced mtDNA haplotypic diversity in white sturgeon, 

Acipenser transtomontanus, from isolated sections 

of the Columbia River (Brown et al. 1992). 

The other impact on Canadian lake sturgeon 

comes from the effects of the forest products industry 

including construction of forest access roads, log 

driving, and pulp mill effluent. Roads often cross 

rivers at spawning sites due to the presence of rock

305 

Figure 4. Status of lake sturgeon in the province of Ontario, Canada. 

at the narrower cross sections. These can obstruct 

fish passage and reduce the amount of spawning 

habitat available. Erosion and siltation during and 

after road construction impairs water quality. Inpaired 

reproduction in such areas has also been suggested 

(Duckworth et al. 1992). Pulp and paper mill 

effluent deposits organic debris and decreases water 

quality by reducing dissolved oxygen and disrupting 

benthic communities. 

Current status of lake sturgeon 

We categorized regions of the postglacial distribution 

of lake sturgeon into areas where the species 

was cithcr common, rare, or absent (extirpated) 

(Figure 3-5). Data sets describing the distribution 

and abundance of lake sturgeon in the provinces of 

Ontario, Manitoba, and Quebec differ considerably, 

and interpretation was required to categorize 

geographical regions into the above categories. Data 

for Ontario are from the Ontario Ministry of Nat-

306 

Figure 5. Status of lake sturgeon in the province of Quebec, Canada. 

ural Resources files on individual locations where 

fish have been found during various lake and river 

surveys. These data were represented as individual 

dots on the map and could be translated into our 

absent, rare, and common designations by drawing 

lines on the map to enclose areas of similar dot density 

(Figure 3). Areas that contained no known populations 

(i.e., no dots on the map) were designated

as ‘absent’. Very few lake sturgeon were found in also lies between two dams and is considered to 

‘rare’ areas, whereas areas designated as ‘common’ have remnant populations with habitat impacts and 

contained many populations (i.e., dot density was exploitation having taken their toll. The Churchill 

high). Data for Manitoba (Rob Cann personal com- River populations are poor. The most inland 

munication) was of similar scope to the Ontario da- reaches of the river have remnant nonsustainable 

ta but differed in category designation (Figure 4). populations severely impacted by changes to the 

Our class of ‘absent’ was equivalent to their rem- hydraulic regime. Little is known about the status of 

nant/extirpated, our ‘rare’ was equivalent to their downstream populations in the Churchill system; 

poor/fair and ‘common’ was equivalent to good/un- the last section close to Hudson Bay supports only a 

impacted. Fortin et al. 3 compiled the data base for remnant population due to habitat changes associ- 

Quebec (Figure 5). Lake sturgeon distribution in ated with a major water diversion. Finally, the 

Quebec is limited to the southeast corner of the Hayes River stocks are less impacted, which might 

province and Fortin et al. reviewed the status of 14 be attributable to minimal habitat alteration. Depopulations 

within this distribution. These popula- spite being fished commercially, the populations 

tions were designated as having either ‘common’ or appear to be sustaining themselves. 

‘rare’ status with the intervening areas having ‘ab- In Ontario, robust, healthy populations are gensent’ 

categorization. Quebec populations qualify- erally limited to more remote northern rivers and 

ing for rare status were those where commercial lakes (Figure 4). The Mattagami-Groundhog, Frefisheries 

have been closed due to overexploitation derick House, Moose, Albany and Attawapiskat 

and, in one case, habitat alteration. The remaining rivers are prime examples (Duckworth et al. 1 ). Poppopulations 

continue to support commercial and ulations from Lake of the Woods (Mosindy & Rusubsistence 

native fisheries and were considered to sak 4 ) and possibly, the north channel of Lake Huron 

have common status. 

and southern Lake Huron appear to be increasing 

In Manitoba, lake sturgeon were plentiful and from recent depressed levels and appear capable of 

widely distributed as recently as one hundred years sustaining very modest fisheries (Duckworth et 

ago (Anonymous 2 ). There are now very few waters al. 1 ). Existing evidence suggests that populations in 

where lake sturgeon may still be commercially the Ottawa River, Lake Nipissing, Abitibi River, St. 

fished; the species has been identified as vulnerable Lawrence River, Lake Erie, Lake Ontario, and 

under the Manitoba Endangered Species Act. Ma- Lake Superior are severely depressed and cannot 

nitoba is considering the elimination of both sport sustain further harvest if they are to be rehabilitatand 

commercial harvests until stocks can be reha- ed. Although not formally adopted as policy, the 

bilitated or stabilized. Populations in the Nelson Ontario Ministry of Natural Resources is taking a 

River system vary from remnant to poor to good, conservative approach in allowing the commercial 

depending on the section of the river (Figure 3). and sport harvest of lake sturgeon stocks. Legal 

Stock status also varies within the Winnipeg River fishing has often been eliminated where stocks are 

system. Remnant populations occur near the Onta- low. The quotas on lake sturgeon were removed 

rio boundary. Populations in the next section west from commercial licenses in 1984 for Lake Erie, in 

are fair to good even though they occur between 1990 for Lake Superior and the Ottawa River, and 

two dams and aboriginal domestic harvest is consid- 1991 for Lake Nipissing and the Attawapiskat Rivered 

to be beyond sustainable yield levels. The final er. The current implementation of the Canadian 

section of the Winnipeg River near Lake Winnipeg federal habitat policy is protecting valuable lake 

sturgeon habitat. 

3 Fortin, R., S. Guenette & P. Dumont. 1992. Biologie, exploitation, 

modelisation et gestion des populations d’esturgeon jaune 

(Acipenser fulvescens) dans 14 reseaux de lacs et de rivieres du 

Quebec. Rapport de Recherche Commanditee, Presente au 

Gouvernement du Quebec, Ministere du Loisir, de la Chasse et 

de la Peche. Direction de la gestion des especes et des habitats. 

307 

4 

Mosindy, T. & J. Rusak. 1991. An assessment of lake sturgeon 

populations in Lake of the Woods and the Rainy River, 1987– 

1990. Lake of the Woods Fisheries Assessment Unit Report 

1991:01.

308 

Lake sturgeon are more restricted in their distri- the use of seine nets and set lines and limiting gill 

bution in Quebec than they are in either Manitoba net mesh from 190 to 203 mm. Commercial fisheries 

and Ontario, such that their range covers the south- in the Lake Temiskaming and northern areas are 

west corner of the province from La Grande River operated on an annual quota basis. Quotas on Lake 

on James Bay to the St. Lawrence River in the south Temiskaming are set at 0.08 kg ha –1 . This quota is 

(Figure 5). The eastern limit occurs on the St. Law- considered to be a sustainable harvest level and is 

rence at about the Saguenay River because of in- used as a model for the management of lake sturcreasing 

salinity. Even though no populations in geon fisheries in northern Quebec. Rccommenda- 

Quebec are known to have been extirpated, some tions have been made to cut 0.3 kg ha –1 quotas for 

have declined (Rejean Fortin personal communica- other northern locations in half. Furthermore. the 

tion). After reviewing the available information on quotas for such large systems should be determined 

the 14 populations referred to previously (Fortin et by available sturgeon habitat and not by the total 

al. 3 ), biologists recommended that four fisheries be waterbody area. Finally, pulse fishing, where the toclosed. 

These include the Ottawa River in the tal allowable harvest for several years is removed in 

south, the Hurricana and Gueguen rivers in the one year and then the fishery is closed in successive 

southcentral area of the distribution and the Baska- years, has been suggested in Quebec. 

tong Reservoir lying north of the Ottawa River. The In contrast to the Canadian situation where lake 

Ottawa and Hurricana River populations, are con- sturgeon are considered common in many parts of 

sidered overexploited. The Baskatong population the country, their distribution within the United 

is showing signs of stress through variable year-class States is fragmented. Lake sturgeon have been 

strength and may be restricted to suboptimal classed as a rare species overmuch of its range in the 

spawning habitat due to deposition of wood and de- United States by the U.S. Fish and Wildlife Service. 

bris. The Gueguen population does not appear to The species is considered threatened in Nebraska, 

be reproducing successfully as current harvesting Illinois, and Kentucky, rare in Minnesota, Missouri. 

yields very few small fish Lake sturgeon in the Me- Arkansas, and Alabama, endangered in South Dagiscane 

area, roughly centrally located in the distri- kota, Iowa, Indiana, Ohio, Vermont, Pennsylvania, 

bution, are considered vulnerable despite having a West Virginia, and Tennessee and depleted in Gehigh 

harvest level. Closure of the Megiscane pop- orgia by local state authorities (G. Priegel & T. 

ulations has not been recommended but restric- Thuemler personal communication). Wisconsin is 

tions on harvest have been suggested. 

the only state where lake sturgeon can be consid- 

The St. Lawrence River populations of Quebe ered common. 

are showing signs of overexploitation from the in- Combination of the mtDNA haplotype and statensive 

commerciall fishing that has occurred for tus data suggests that both northern and southern 

several generations (Figure 5). In recent years, the populations of lake sturgeon have been impacted 

commercial harvest from this system has been over by anthropogenic influences. For example, a pop- 

100 tonnes, probably the largest commercial lake ulation with multiple haplotypes and possibly repsturgeon 

fishery in North America (Dumont et al. resenting the descendants of a Missourian refugial 

1987). Lake sturgeon are abundant in the St. Law group (e.g., lower Nelson River) has been designatrence 

River near Montreal but populations are con- ed rare. Similarly, rare designation has been assidered 

poor in the upstream Lac St. Francois area signed to populations with single haplotypes (Lake 

and downstream from Lac St. Pierre (Trois Rivieres St. Clair, Ottawa River), possibly from a Mississiparea) 

towards the Saguenay River. Analysis of data pian refugium. Although our genetic analysis procollected 

in the 1980’s led to restrictions on the fish vides important information on the glacial history 

ery in the rives upstream from Trois-Rivieres. Elin- of lake sturgeon relevant to the conservation of this 

ination of certain permits and reducing the length of species it docs not have the resolution (genetic varithe 

season reduced the harvest while protection of ation) to identify management units. For instance, 

mature breeding fish was sought through restricting we cannot determine whether management units

309 

correspond to local populations or fish within particular 

drainages. This will require the utilization of 

more hypervariable marker systems such as simple 

sequence repeats (microsatellites). 


We thank Rob Cann and Rejean Fortin for providing 

us with status data, Jim Brown for the generous 

gift of Nelson River lake sturgeon mtDNA, and 

many individuals for providing lake sturgeon tissue. 

Louis Bernatchez, Michael Gatt, Blake Konkle, susan 

Lee, Michelle Malott, and Scot McKinley participated 

in the genetic analysis and Jim Finnigan 

produced the status maps. Neil Billington and an 

anonymous referee read the manuscript and provided 

many helpful comments. The genetic research 

was supported by funds from Ontario Hydro, 

Ontario Ministry of Natural Resources (Environmental 

Youth Corps), and the Natural Sciences 

and Engineering Research Council of Canada. We 

thank Vadim Birstein, John Waldman, and the Hudson 

River Foundation for giving us the opportunity 

to present this paper. 


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(ed.) The Zoogeography of North American Freshwater Fishes, 

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(Suppl.A):91–101. 

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in lake sturgeon (Acipenser fulvescens) from the St. Lawrence 

River and James Bay drainage basins in Quebec. Canada. Can. 

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Department of Lands and Forests. Fisheries and Wildlife 

Branch, Toronto. 121 pp. 

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American fishes. Wiley-Interscience, New York. 866 pp. 

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sturgeon (Acipenser fulvescens) as indicated by the returns of 

the Hudson’s Bay Company Lac la Pluie District. Can. J. Fish. 

Aquat. Sci. 45: 921–923. 

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in Canada. Can. Field-Naturalist 101: 171–185. 

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freshwater fishes into Ontario. Can. J. Zool. 70: 2247–2259. 

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mitochondrial DNA: relevance for population biology 

and systematics. Ann. Rev. Ecol. Syst. 18: 269–292. 

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(Acipenser fulvescens) from the Frederick House. Abitibi 

and Mattagami rivers, Ontario. pp. 10–19. In: C.H. Olver 

(ed.) Proceedings of a Workshop on the Lake Sturgeon (Acipenser 

fulvescens). Ont. Fish. Tech. Rep. Ser. No. 23. 

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Left side portrait tilted dorsally of Acipenser oxyrinchus 150 cm TL from St. Lawrence River at Kamouraska, Quebec, which now resides 

in the Montreal Biodome (hence the aquarium damage to the rostrum), the same specimen as on p. 184. The irregular rows of denticles 

above and below lateral scutes are all depressions (below). The 35 cm long head. above. of a large Huso huso from the Caspian Sea (1967) 

donated forthe Montreal Expo and then kept in the Toronto Metropolitan Zoo is now preserved in the royal Ontario Museum collection. 

Originals by Paul Vecsei, 1996.



Lake sturgeon management in the Menominee River, a Wisconsin-Michigan 

boundarywater 

Thomas F. Thuemler 

Wisconsin Department of Natural Resources, 1636 Industrial Parkway, Marinette, WI 54143, U.S.A. 


Key words: Acipenser fulvescens, regulations, exploitation, population estimates, standing stocks 

Synopsis 

The Menominee River, a boundary water between northeastern Wisconsin and the upper peninsula of Michigan, 

contains a sport fishery for lake sturgeon, Acipenser fulvescens, which is jointly managed by both states. 

Previous studies indicated that overfishing of this sturgeon population was occurring, and this investigation 

examined the impact of new angling regulations. The sturgeon population is fragmented into sections by 

hydroelectric dams. Stocks from the three main sections of the river were compared before and after implementation 

of the new angling regulations. Records of the legal harvest of lake sturgeon from each river section 

were obtained through a registration system, which has been in effect since 1983, and estimates of exploitation 

were derived from these data. Overfishing of lake sturgeon stocks in two of the three sections of the Menominee 

River is still occurring. Management recommendations are made which would allow for a continued 

fishery by providing further protection to the stocks. 

Introduction 

Lake sturgeon, Acipenser fulvescens, historically 

occurred in larger rivers and lakes in three major 

watersheds, the Great Lakes, the Mississippi River 

and the Hudson Bay, throughout the eastern portion 

of North America (Scott & Crossman 1973, Lee 

et al. 1980, Houston 1987). They are now considered 

to be threatened over most of their former range in 

the United States (Miller 1972). In Canada, this species 

is less abundant than formerly (see Ferguson & 

Duckworth 1997 this volume). Many populations 

are sufficient to provide modest managed fisheries 

(Houston 1987). In Wisconsin, several self-sustaining 

lake sturgeon populations support limited sport 

fisheries (Larson 1 , Thuemler 1985, Folz & Meyers 

1985). These fisheries are closely monitored to 

guard against overexploitation. There are no commercial 

fisheries for lake sturgeon in Wisconsin waters. 

The Menominee River forms the boundary between 

northeastern Wisconsin and the upper peninsula 

of Michigan, and flows into Green Bay. Being a 

border river, its fish populations are managed jointly 

by the states of Wisconsin and Michigan. Studies 

conducted in 1969 and 1970 and again in 1978 and 

1979 on the lake sturgeon fishery in the Menominee 

River (Priegel 2 , Thuemler 1985) suggested that exploitation 

was too high. Regulations were changed 

to protect the stock and prevent closure of the stur- 

1 

Larson, T.R. 1988. The lake sturgeon fishery of Lake Wisconsin, 

1978–1985. Fish Management Report #136, Wisc. Dept. Nat. 

Res., Madison. 34 pp. 

2 

Priegel, G.R. 1973. Lake sturgeon management on the Menominee 

River. Tech. Bull. 67, Wisc. Dept. Nat. Res., Madison. 24 

pp.

31 2 

Figure 1. Map of the Menomince River lake sturgeon study area 

showing hydroelectric dams that fragment the river into sections. 

Sturgeons in the three major sections – White Rapids sesction. 

Grand Rapids section, and Lower section – are managed as 

seperate stocks 

of 113 280 liters second –1 (Holmstrom et al. 3 ). It is a 

hardwater river having slightly alkaline. lightly 

stained brown water (Carlson et al. 4 ). The Menominee 

River Basin lies within the southern portion of 

the Canadian Precambrian shield It has an average 

gradient of 1.3 m km –1 and it flows over a mixed substrate 

of sand, rubble and bedrock. 

Ten hydroelectric dams on the river fragment its 

fish populations, as there are no fish passage facilitics 

at these sites. Lake sturgeon were historically 

found throughout the river up to the present site of 

the Sturgeon Falls Dam. This study concentrates on 

sturgeon populations in three distinct sections of 

river between the White Rapids Dam and the river 

mouth (Figure 1). The lowermost section of the river 

encompasses 3.9 km and is bounded by the Menominee 

Dam at its upper end and the waters of 

Green Bay at the low end (Lower section). Fish in 

the lower section of river can move freely into 

Green Bay, but the Menominee Dam blocks any 

upstream movement. About 2 km above the Menominee 

Dam is the Park Mill Dam. The entire section 

of river between these two dams is impounded water 

called the Lower Scott Flowage. The nest section 

of river is 34 km long and is bounded by the 

Grand Rapids Dam at its upper end and the Park 

Mill Dam at the lower end (Grand Rapids section). 

The uppermost section of river that contains lake 

sturgeon is 42 km long and is bounded by the Grand 

Rapids and White Rapids dams (White Rapids section). 

geon fishery. The current study examines the effectiveness 

of the new regulations. 

Geography of the Menominee River 

The Menominee River. formed by the confluence 

of the Brule and Michigammie rivers. flows Cor 154 

km in a southeasterly direction before it joins the 

waters of Green Bay near the cities of Marinette. 

Wisconsin and Menominee. Michigan (Figure 1). 

The Menommee River Basin encompasses just 

over 1544 square kilometers in the states of Wisconsin 

and Michigan and has a mean annual discharge 

Methods 

Sturgeon were sampled from the Menomince River 

using boomshocker electrofishing units (Thuemler 

1985). Surveys were conducted in 1970, 1978, and 

1990 on the White Rapids section, in 1979 and 1990 

in the Grand Rapids section and in 1991 in the Lower 

section of river. All surveys were conducted in 

3Holmstrom, B.K., C.A. Han & R.M. Erickson. 1983. Water resources 

data. Winsconsin water year 1982 U.S. Geological Survey 

Water Report WI-82-I. 326 pp. 

4 

Carlson, H.C.. L.M. Andrews & C.W. Threinen. 1975. Surface 

w ater resources of Marinette County. Wise. Dept. Nat. Res., Madison. 

110 pp.

Table1. Estimates ofthesize ofthe lake sturgeon population from different sections of the Menominee River. 

the 95% confidence intervals 

Shown in parentheses are 

313 

River section 

Year of population estimate 

1970 1978 1970 1990 199 I 

Low er section 893 

(457-1329) 

Grand Rapids section 2834 3201 

(1729-3939) (2526-3876) 

White Rapids section 2865 

2749 3156 

(2299-3430) (1997-3501) (2512-3800) 

July or August. All sturgeon captured in 1990 and 

1991 were measured in both total and fork length 

(TL and FL, respectively) to the nearest centimeter, 

but prior to 1990 only total length measurements 

were taken. A representative sample of sturgeon 

were weighed Capture-mark and recapture population 

estimates were made using the adjusted Peterson 

estimator (Ricker 1975). Separate population 

estimates were made for each of the three sections 

of river. Fish from both the initial and recapture 

runs were collected with the electrofishing 

gear. Recapture took place seven to ten days after 

the initial run. All sturgeon ≥ 25 cm TL were included 

and were tagged with either a Monel metal tag in 

the base of the dorsal fin or with a Floy dart tag in 

the caudal fin or with both. Because the number of 

fish recaptured in the various size groups was not 

large enough to make unbiased estimates, the number 

of fish actually sampled in each 2.5 cm size 

group was used to estimate the fraction of the total 

population in each size group. This method assumes 

that capture efficiencies are equal among the various 

size groups. Although this method does not al- 

Table 2. Estimated number of lake sturgeon in the White Rapids 

section of the Menominee River, by size group. 

TL (cm) 1970 survey 1978 survey 1990 survey 

< 107 2680 2543 2423 

> 107 185 206 733 

> 127 115 105 320 

> 140 57 45 121 

> 152 20 9 53 

> 165 2 0 9 

low one to calculate confidence intervals around 

the estimates, it is the best estimate possible given 

the data available. 

Legal harvest of lake sturgeon by sport anglers on 

the Menominee River only occurs during a two 

month fall season. Since 1983, licensed anglers have 

needed a special permit to fish for lake sturgeon in 

all Wisconsin waters. In 1974, a minimum size limit 

of 127 cm was imposed; prior to that time a 107 cm 

size limit had been in effect. In 1992, the bag limit 

for an angler was reduced from 2 fish season -1 to I 

fish season -1 . All legal fish taken in the sport fishery 

must be registered and tagged at a Department of 

Natural Resources approved station. All fish harvested 

are measured, weighed and checked for tags 

at that time. Harvest information from thc vai-ious 

sections of river was obtained through this registration 

tion system. 

Angler exploitation for the various sections of 

river was obtained by calculating the average annual 

harvest from registration data and dividing it 

by the estimated number of sturgeon over 127 cm 

Table 3. Estimated number of lake sturgeon in the Grand Rapids 

section of the Menominee River, by size group. 

TL (cm) 1979 survey 1990survey 

< 107 2584 2867 

> 107 250 334 

> 127 125 91 

> 140 37 24 

> 152 22 3 

> 165 0 0

~ 

314 

Table 4. Estimated number of lake sturgeon in the Lower section 

of the Menominee River, by size group. 

TL (cm) 

< 107 456 

> 107 

>127 

437 

108 

> 140 29 

> 152 0 

> 165 0 

1991 survey 

from the most recent population estimates (1990 

and 1991). 


Various studies report sturgeon lengths in either 

fork length or total length, but not in both measurements. 

This makes it difficult to compare age and 

growth information between studies. In this study 

the relationship between these two measurements 

was calculated. We measured both FL and TL for 

1839 lake sturgeon, between 25 and 175 cm TL. The 

relationship between these variables for lake sturgeon 

in the Menominee River is: 

TL = 3.52688 + 1.05682 FL; 

N = 1839; r = 0.998. 

All population estimates satisfied the requirements 

to insure unbiased estimates (MC - 4N) (Robson & 

Regier 1964). Lake sturgeon population estimates 

for sections of the Menominee River with 95 % confidence 

limits are given in Table 1. The estimated 

number of sturgeon over selected sizes in the three 

sections of river are shown in Tables 2, 3 and 4. 

Standing stock estimates for lake sturgeon from the 

different sections of river were calculated from the 

1990 and 1991 estimates. The Lower section had the 

highest standing stock of 67.8 kg hectare -1 , followed 

by the White Rapids section at 23.8 kg hectare -1 , 

and then the Grand Rapids section at 15.6 kg hectare 

-1 . 

Nearly 5000 lake sturgeon have been tagged in 

the different sections of the Menominee River since 

1969. In various surveys and through the registration 

process, 255 tagged sturgeon have been recaptured. 

Most of these fish were recaptured in the 

same section of river in which they were tagged. Of 

194 recaptured sturgeon originally tagged in the 

White Rapids section of the river, only four fish or 

2% were found to have moved, and they moved 

downstream into the Grand Rapids section. Sixty 

one sturgeon originally tagged in the Grand Rapids 

section of the river were recaptured and only 1 or 

1.6%, was recovered in the Lower section. 

Table 5 shows the annual harvest of lake sturgeon 

from the Menominee River since the inception of 

the registration system in 1983. Between 1500 and 

2000 anglers participate in the sturgeon fishery on 

the Menominee River each year. The number of anglers 

has increased steadily since the inception of 

the registration system. Roughly five percent of anglers 

successfully harvested a legal sturgeon. In the 

White Rapids section of the river the harvest has 

ranged from 8 to 33 fish annually, with an average of 

just under 19 fish year -1 . The average weight of an 

individual fish taken in this section was 16.1 kg, and 

the average weight of all sturgeon harvested was 

0.50 kg hectare -1 year -1 . In the Grand Rapids section 

of the river the average annual harvest has 

been 10.9 fish, with a range of 1 to 28 fish taken annually. 

These fish had an average weight of 15.8 kg 

and the average weight of all sturgeon harvested 

from the section was 0.35 kg hectare -1 year -1 . In the 

Table 5. Annual harvest of lake sturgeon from the three sections 

of the Menominee River. 

Year 

White Rapids Grand Rapids Lower section Total 

section section 

1983 9 9 1 19 

1984 8 4 1 13 

1985 12 1 2 15 

1986 13 10 12 35 

1987 20 15 23 58 

1988 21 14 22 57 

1989 32 28 20 80 

1990 18 13 22 53 

1991 19 9 33 61 

1992 23 3 46 72 

1993 33 14 40 87 

Total 208 120 222 550

Lower section of river the harvest has ranged be- able for this fishery. There are few published data 

tween 1 and 46 fish year –1 . Average annual harvest on exploitation rates on lake sturgeon fisheries. In 

in this section has been 20.2 fish at an average the Saint Laurent River in Quebec, exploitation 

weight of 16.6 kg and an average weight of all stur- rates ranged from 10 to 20% on different sections 

geon harvested of 3.37 kg hectare _ 1 

year _ 1 

. All har- (Dumont et al. 5 ). Exploitation rates of 15 to 20% in 

vest estimates were calculated based on the annual the Lac Saint-Pierre section of the Saint Laurent 

average harvest between 1983 and 1993. 

impacted the average length. weight and age of this 

Average annual exploitation rates on lake stur- stock (Fortin et al. 1993). The exploitation rate for 

geon from the three sections of river were: Lower the Lake Winnebago sturgeon population. between 

section 18.7%, Grand Rapids section, 12%, and 1976 and 1983, has averaged 2.5% and between 

White Rapids section, 8.5%. 

1953 and 1959 it averaged 4.3% (Folz & Meyers 

The lake sturgeon population in the Menominee 1985). The adult sturgeon stock in Lake Winnebago 

River is fragmented by numerous hydroelectric has more than doubled over the past thirty years un 

dams. Tagging studies showed that there is little der that type of exploitation. 

movement of juvenile or adult fish from one section Table 5 indicates an increasing annual harvest of 

of river to another. Dams create a barrier to all up- sturgeon in this section of river. This probably restream 

movement and very few marked fish sults from an increased number of anglers and the 

showed any inclination to move downstream. We greater number of legal size sturgeon available in 

have not tagged lake sturgeon less than 25 cm TL, so the White Rapids section. It appears that the curif 

downstream movement and dispersal occur, it rent harvest regulations are maintaining the sturmay 

take place at sizes > 25 cm TL. Lack of easy geon stock in this section of the Menominee River. 

movement by adults between the three sections of however if exploitation rates increase much over 

river necessitates that they be managed as distinct the present level, then further restrictions will have 

stocks. 

to be applied. Continual monitoring of this stock is 

recommended. 

White Rapids section 

The sturgeon stock in the White Rapids section responded 

positively to regulation changes over the 

past nineteen years. Although population size in 

this section has not increased markedly since the 

1970 estimate, its size structure has improved. The 

number of sturgeon over the minimum size of 127 

cm has more than doubled since 1970, while the 

number of undersized fish has shown a slight increase. 

There is no statistical difference (p < 0.05) in 

the mean length of sturgeon harvested when comparing 

data from the first six years of the registration 

system (1983–1988) with data from the last five 

years (I 989–1993). 

The exploitation rate of 8.5%, is the lowest of the 

three sections of river studied and it is lower than 

previously reported. Priegel 2 calculated exploitation 

rates of 13% in 1969 and 17% in 1970 for sturgeon 

in this section, and he suggested that exploitation 

rates no higher than 5% would be more desir- No. 23. 

Grand Rapids section 

315 

Standing stock of lake sturgeon in this section of river 

is lower than in either of the other two sections. 

Although the 1990 estimate of the population is 

similar to the 1979 estimate. the number of legal size 

sturgeon (> 127 cm) decreased by 27%. The average 

exploitation rate was 12% for the 1983 through I993 

period. There is no statistical difference (p < 0.05) in 

the mean length of sturgeon harvested when comparing 

the first six years of registration data (1983– 

1988) with the last five years (1989–1993). Table 5 

shows the annual harvest of sturgeon froin this section 

has been fairly stable over the period of the reg- 

5 

Dumont, P., R. Fortin G. Desjardins & M. Bernard. 1987. Biology 

and exploitation of lake sturgeon (Acipenser fulvescens) in 

the Quebee waters of the Saint-Laurent River pp. 37–76. In: 

C.H. Olver (ed.) Proceedings of a Workshop on the Lake Stur- 

geon (Acipenser fulvescens). Ontario Fisheries Tech. Rep. Ser.

316 

istration system. The drop in the number of legal 

size sturgeon in this section and the high exploitation 

rate are cause for concern, especially in a stock 

that has so few spawning size fish. Additional harvest 

restrictions are needed. 

Lower section 

The Lower section of the river currently supports 

the highest standing stock of lake sturgeon of any 

section of the Menominee River. This stock expanded 

as water quality improved over the last two 

decades. Sturgeon move freely between the river 

and the waters of Green Bay. The population estimate 

in 1990 was made during July, and it is not 

known how the standing stock changes seasonally. 

The number of sturgeon found in this section may 

be quite different during the fall fishing season. The 

exploitation rate for this section was 18.7%. 'This is 

higher than on either of the other sections of river. 

The size structure of the stock in July showed a lack 

offish over 152 cm in length. The harvest continued 

to increase. There is no statistical difference (p < 

0.05) in the mean length of sturgeon harvested 

when comparing the first six years of registration 

data (1983-1988) with the last five years (1989- 

1993). 

Further investigations are needed to determine 

the standing stock of sturgeon in this section of river. 

However the apparent high exploitation rate 

and the lack of any fish > 152 cm TL is a cause for 

concern. Current regulations should be modified to 

further restrict the harvest. 

Table 6. Portion of the season in which harvest of lake sturgeon 

has taken place on the Menominee River 1983-1993. 

Period of season 

1- 14 September 43 

15-30 September 29 

1-14 October 14 

15 October-1 November 14 

Percentage of the harvest 

Management recommendations 

Lake sturgeon stocks of the Menominee River, with 

the exception of those fish in the Lower section. 

spend their entire life in riverine habitat (Priegel 2 , 

Thuemler 1988). In many parts of their range lake 

sturgeon spawn in river systems but spend most of 

their life in lacustrine habitat (Lyons & Kempinger 

6 , Baker 7 , Houston 1987). Lake sturgeon are currently 

round and were historically abundant only in 

lakes or in large rivers with extensive shallow water 

areas (Harkness & Dymond 1961, Priegel & Wirth 

1977). In the Menominee Rivere lake sturgeon 

could historically move freely into and out of the 

waters of Green Bay. With the construction of dams 

on the river in the 1800s this population was fragmented 

into separate stocks. The long term goal of 

the Wisconsin and Michigan Departments of Natural 

Resources is to have free passage of lake sturgeon 

throughout their former range in the Menominee 

River (Thuemler & Schnicke 8 ). This goal will 

take many years to achieve and interim measures 

are needed to protect the current sturgeon stocks in 

the river. 

Two alternatives could be used to decrease exploitation. 

especially in the lower two sections of 

river. Imposition of a higher size limit is not being 

considered because it would tend to further bias the 

harvest towards larger female fish. Shortening the 

current two month fishing season would be possible, 

however the season would have to be shortened 

to about two weeks to effect a 50% reduction in exploitation 

(Table 6). The second alternative would 

be complete closure of the season every other year. 

This should halve the exploitation rates and yet still 

allow some harvest, and might be acceptable if a 

catch and release only season operated in the year 

when harvest was prohibited. This would permit an- 

6 

Lyons, & J.J. Kempinger. 1992. Movements of adult lake sturgeon 

in the Lake Winnebago system. Wisc. Dept. Nat. Res., Res. 

Report 156. Madison. 

7 Baker, J.P. 1980. The distribution, ecology, and management of 

the lake sturgeon (Acipenser fulvescens Rafinesque) in Michigan. 

Mich. Dep. Nat. Res., Fish. Res. Report No. 1883. Ann Arbor. 

95 pp. 

8 

Thuemler, T.E. & G. Schnicke. 1993. Menominee River fisheries 

plan. File Report. Wisc. Dept. Nat. Res., Madison. 51 pp.

tem, Wisconsin. pp. 135–146. In:F.P. Binkowski & S.I. Doroshov 


Potential, Dr W.J. Junk Publishers. Dordrecht. 

Fortin, R. J.R. Mongeau, G. Desjardins & P.Dumont. 1993. 

Movements and biological statistics of lake sturgeon (Acipenser 

fulvescens) populations from the St. Lawrence and Ottawa 

River system, Quebec. Can. J. Zool. 71: 638–650. 

Harkness, W.J.K. & J.R. Dymond. 1961. The lake sturgeon. Ontario 

Department of Lands and Forests. Fish and Wildlife 

Branch. Maple. 97 pp. 

Houston, J.J. 1987. status of the lake sturgeon, Acipenser fulvescens, 

in Canada. Can. Field Nat. 101: 171–185. 

Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister 

& J.R. Stauffer. Jr. 1980 Atlas of North American freshwater 

fishes. North Carolina Biol. Surv., Publication #1980–12. 

867 pp. 

Miller, R.R. 1972 . Threatened freshwater fishes of the United 

States. Trans. Amer Fish. Soc. 101: 239–252. 

Priegel, G.R. & T.L. Wirth. 1977. The lake sturgeon: its life history, 

ecology and management. Wisc. Dept. Nat. Res. Publica- 

tion 4–3600(77). Madison. 20 pp. 

Ricker,W.E. 1975. Computation and interpretation of biological 

statistics of fish populations. Bull. Fish. Res. Board Can 191. 

382 pp. 

Robson, D.S. & H.A. Regier. 1964. Sample size in Peterson 

mark-recapture estimates. Trans. Amer. Fish. Soc. 93: 215– 

226. 

Scott, W.B. & E.J. Crossman. 1973. Freshwater fishes of Canada 

Bull. Fish. Res. Board Can. 184 966 pp. 

Thuemler, T.F. 1985 The lake sturgeon, Acipenser fulvescens, in 

the Menominee River, Wisconsin-Michigan. Env. Biol. Fish. 

14: 73–78. 

Thuemler, T.F. 1988. Movements of young lake sturgeons 

stocked in the Menominee River, Wisconsin. Amer. Fish. Soc. 

glers continued opportunity to fish for lake sturgeon 

and yet provide the additional needed protec 

tion for the lake sturgeon stocks. 


I wish to thank the Wisconsin Public Service Corporation. 

who donated the funds necessary to conduct 

the investigations on lake sturgeon in 1990 and 1991. 

I would also like to thank Gary Schnicke, Michigan 

Department of Natural Resources, Greg Kornely 

and Brian Belonger, Wisconsin Department of Natural 

Resources, for their aid in collecting survey data 

and their valuable advice on data analysis and review 

of this manuscript Various personnel at the 

privately owned registration stations also played an 

important role by collecting accurate harvest data. 

The helpful suggestions of two anonymous reviewers 

was appreciated. William E. Bemis was corresponding 

editor for the manuscript. 


Ferguson, M.M. & G.A. Duckworth. 1997. The status and distribution 

of lake sturgeon, Acipenser fulvescens in the Canadian 

province of Manitoba, Ontario and Quebec: a genetic perespective 


Folz, D.J. & L.S. Meyers. 1985. Management of the lake sturgeon. Symp. 5: 104–109. 

Acipesnserfulvescens, population in the Lake Winnebage sys- 

317

Landsat image of the lower-reach of the Connecticut River in western Massachusetts and Connecticut. The location of the Holyoke Dam 

at South Hadley Falls is indicated with the white arrow. Holyoke Dam creates an impoundment (barely discernible in this Landsat image) 

that is known as the Holyoke Pool. Despite the presence of a fish lifting facility at Holyoke Dam, the Connecticut River population of 

shortnose sturgeon, Acipenser brevirostrum has been effectively divided since construction of the first dam at this site in the 1840s. The 

spawning site for the downstream stock of sturgeon is located immediately below Holyoke Dam. Sturgeons restricted to the Holyoke 

Pool spawn several kilometers above the dam at what is probably the historic spawning site for the entire Connecticut River population 

(see Kynard 1997 this volume). Image courtesy of Curtice Griffin and the New England Gap Analysis Program (scale bar= 30 km). 

Comments by W.E. Bemis: also see Bemis & Kynard (1997 this volume).



Life history, latitudinal patterns, and status of the shortnose sturgeon, 

Acipenser brevirostrum 

Boyd Kynard 

National Biological Service, Conte Anadromous Fish Research Center PO Box 796, Turners Falls MA 01376, 

U.S.A. and Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts,Amherst, 

MA 01003, U.S.A. 


Key words: adaptation, spawning migration, dam impacts, behavior, anadromy, Acipenseridae 

Synopsis 

Historically, shortnose sturgeon inhabited most major rivers on the Atlantic coast of North America south of 

the Saint John River, Canada. Today, only 16 populations may remain. Major anthropogenic impacts on shortnose 

sturgeon are blockage of spawning runs by dams, harvest of adults (bycatch and poaching), dredging of 

fresh/saltwater riverine reaches, regulation of river flows, and pollution. The pattern of anadromy (adult use 

of salt water) varies with latitude. The pattern may reflect bioenergetic adaptations to latitudinal differences 

between fresh and salt water habitats for thermal and foraging suitability. The greater adult abundance in 

northern and north-central populations likely reflects a historical difference with southern populations that is 

currently accentuated by increased anthropogenic impacts on southern populations. Adult abundance is less 

than the minimum estimated viable population abundance of 1000 adults for 5 of 11 surveyed populations. and 

all natural southern populations. Across the latitudinal range, spawning adults typically travel to about river 

km 200 or farther upstream. Dams built downstream of spawning reaches block spawning runs, and can divide 

amphidromous populations into up- and downstream segments. Conservation efforts should correct environmental 

and harvest impacts. not stock cultured fish into wild populations. 

Introduction 

the Endangered Specics Act of 1973 indicated populations 

are likely present in 16 rivers (Table 1). Ad- 

Shortnose sturgeon, Acipenser brevirostrum, is a ditional surveys may yet find a few undiscovered 

small sturgeon that attains a maximum length of populations. 

about 120 cm weight of 24 kg, and lives a maximum Since Dadswell et al. (1984) compiled biological 

of 50–60 years (Dadswell et al. 1984, Figure 1). information on shortnose sturgeon, additional 

Adults resemble similar-sized juvenile Atlantic studies on location and characteristics of foraging 

sturgeon, A. oxyrinchus oxrinchus that historically and spawning habitats, adult abundance, and mico-occurred 

in the lower mainstenis of major Atlan- gration patterns have been conducted throughout 

tic coast rivers from the Saint John River, New the species’ range. This is the best information on 

Brunswick, Canada, to the St. Johns River, Florida, latitudinal variation of these life history traits for 

United States. Fisheries data and surveys during the any sturgeon species. A comparison among intra- 

22 years since listing of shortnose sturgeon under specific populations for life history characteristics

320 

Figure 1. Lateral view of adult male shortnose sturgeon Acipenser brevirostrum (94 cm IL) from the Connecticut River, Massachusetts, 

U .S.A. 

often reveals patterns that are not obvious, and can 

lead to identification of adaptations and evolutionary 

processes (Frank & Leggett 1994). This report 

summarizes much of the information on shortnose 

sturgeon life history, examines latitudinal variation 

in anadromy and spawning migrations, investigates 

impacts of dams on spawning migration and abundance, 

and reviews threats to the species. Explanations 

that are proposed for behavioral patterns will 

hopefully stimulate discussion and testing of hypot 

h eses . 

Range and colonization 

estuary. The lack of marine movements by most 

adults suggests that the recolonization rate of shortnose 

sturgeon to rivers where they have been extirpated 

would be slow. The lack of evidence for successful 

recolonization of any river where shortnose 

sturgeon was extirpated by Atlantic sturgeon fisheries 

and dams 100 years ago in the mid-Atlantic 

(Ryder 1890, Smith 1985), supports the hypothesis 

of a slow recolonization rate. 

Rare individuals that are occasionally captured 

at sea near the coast (review by Dadswell et al. 1984) 

could represent emigrants that colonize new rivers 

and maintain gene flow among populations. The 

phenomenon of marine migrants is not understood. 

but available information on marine captures in 

northern and southern parts of the range presented 

by Dadswell et al. (1984), and corrected for misiden- 

The present range of shortnose sturgeon is disjunct, 

with northern populations separated from southern 

populations by a distance of about 400 km near the tified North Carolina captures by Ross et al. (1988), 

geographic center. No known populations occur indicates a greater incidence of marine emigrants in 

from the Delaware River, New Jersey, to the Cape the north compared to the south. Because northern 

Fear River, North Carolina (Table 1). Historically, populations are also larger than southern populapopulations 

were likely present in all large rivers in tions, there may be a relationship between populathis 

area,which includes Chesapeake Ray (Dad- tion size and number of marine emigrants. If this is 

swell et al. 1984). Because the separation distance is so, only a large population like the Hudson River 

great between northern and southern populations, population may be providing emigrants. 

there may be no interchange of adults. 

Density dependent regulation of population 

Unlike adult Atlantic sturgeon that range widely abundance that depends on emigration of fish in realong 

the coast (Murawski & Pacheco 1 ), most short- lation to food abundance is found in stream dwellnose 

sturgeon adults remain in their natal river or ing salmonids. and may be present in other fishes 

that have limited movements and a restricted range 

1 

(Frank & Leggett 1994). Populations of shortnose 

Murawski, S.A. & A.L. Pacheco 1977. Biological and fisheries 

data on Atlantic sturgeon, Acipenser oxyrhynchus (Mitchill). sturgeon have limited movements and a restricted 

Nat. Mar. Fish Serv., Sandy Hook Lab., Sandy Hook. Tech. home range within their river and estuary. Further 

Report No. 10. 78 pp. 

young sturgeon have a size dependent dominance

321 

hierarchy that determines use of foraging habitat 

(C. Cauthron & B. Kynard unpublished data). Thus, 

a behavioral mechanism may be present in adults 

that could regulate density and emigration in each 

river relative to resource abundance. 

Abundance of adults 

Commercial harvest data are not a useful indicator 

of the historical abundance of shortnose sturgeon 

because catches of Atlantic and shortnose sturgeons 

were combined (Smith 1985). Consequently, 

recent trends in abundance arc only available for 

two rivers- the Hudson and Connecticut. The Hud- 

son River population has increased since the 1970s 

concurrent with the decline of Atlantic sturgeon 

from about 30 000 to 38 000 (Bain 1997 this volume). 

and the Connecticut River population seems unchanged 

since the 1970s (Taubcrt 1980a, Buckley & 

Kynard', Savoy & Shake', M. Kieffer & B. Kynard 

2 

Buckley, J. & B. Kynard. 1983. Studies on shortnose sturgeon. 

Massachusetts Cooperative e Fisheries Research Unit. University 

of Massachusetts. Amberst. Report to National Marine 

Fisheries Service. Gloucester and Northeast Utilities Service 

Co . I hartford. 40 pp. 

3 Savoy, T. & D. Shake. 1992. Sturgeon status in Connecticut waters. 

Proj. AFC-20-1, Conn. Dept. Env. Prot., Report to U.S. Fish 

& Wildl. Scrv.. Newton Corner. 51 pp. 

Table 1. Twenty Atlantic coast rivers showing the north to south distribution of shortnose sturgeon. Each river is characterized for studies 

done since 1984 and best estimate of adult abundance. 

River Province/State Studies a Abundance Source 

Saint John R. New Brunswick none 18 000 Dadswell (1979) 

Penohscot R. Maine P 0 Squiers (pers. comm.) 

Kennebec R. Maine none 7000 Squiers et al. 6 

Androscoggin R. Maine M, A. S 3.000 Squiers 7 , Squiers et 

al. 14 , spawner extrapolation 

Merrimack R. Massachusetts P, A. M, H. S < 100 c Kieffer & Kynard (1 996) 

Taunton R. Massachusetts P 0 Buerkett & Kynard (1 1993) b 

Connecticut R. Massachusetts A, M. H. S. D. 1200 Savoy & Shake 3 , 

& Connecticut C, CU. B. PA 

Kieffer & Kynard unpublished data 

Hudson R. New York A, M. H. D, F 38 000 Bain (1997) 

Delaware R. New Jersey A, M, H. S 13 000 O’Herron et al. (1993) 

Cape Fear R. North Carolina P. M. S, B, PA < 100 c Moser & Ross (1994) 

Pee Dee R. South Carolina none 1000 c Marchette & Smiley 8 

Santee-Cooper R. South Carolina P, M. PA no data Cooke unpublished data 

Edisto R. South Carolina none no data Dadswell et al. (1984) 

Ashepoo R. South Carolina none 

no data 

Dadswell et al. (1 984) 

Savannah R. South Carolina A. M. H. C, CU, 1676 d Smith et al. (1994), Collins 

ST, & et al. (1991) 

Ogeechee R. Georgia P. A, M H. S. B 216 Rogers & Weber (1994) c 

Altamaha R. Georgia A. M. H. S. B 650 Rogers & Weber 9 , unpublished data 

Satilla R. Georgia P 0 Rogers unpublished data 

St. Marys R. Georgia P 0 Rogers & Weber 4 

St. Johns R. Florida none no data Dadswell et al. (1984) 

a 

Studies key: P- presence, A- abundance /size frequencies, M -movements, H-summering/wintering habitat, S - spawning migrations/ 

habitat, D - sex determination, C - contamination, CU - culture, ST - stocking, B - bycatch, PA - passage, P - pollution. 

b 

Buerkett, C. & B. Kynard. 1993. Survey for sturgeons in the Taunton River, Massachusetts, Report to Massachusetts Div. Mar. Fish., 

Boston. 23 pp. 

c 

Estimate based on best judgement of experts. 

d Estimate includes adults produced from wild and cultured fish introduced 1984-1992 (Smith et al. 1995). 

e 

Rogers, G.S. & W. Weber. 1994. Occurrence of shortnose sturgeon (Acipenser brevirostrum) in the Ogeechee - Canoochee River 

system, Georgia during the summer of 1993. Report of Georgia Dept. Nat. Res. 13 pp.

322 

Figure 2. Comparison of seven northern and north-central populations 

with five southern populations for adult abundance. Estimates 

for populations in the Cape Fear anti Santee-Cooper rivers 

are expert opinions. 

unpublished data). Additional study may find the 

Hudson River population even larger than 38 000. 

Abundance of adults has been estimated for a total 

of seven populations in northern or north-central 

rivers and for five southern populations. Abundance 

varies From tens of thousands (Saint John, 

Hudson, and Delaware rivers) to lens in the Merrimack 

and Cape Fear rivers (Table 1). The great 

abundance of adults in the Delaware River suggests 

that large populations were likely present in other 

large rivers, like the Potomac and Susquehanna rivers, 

located at the center of the range. For the past 

100 years, a dissolved oxygen block at Philadelphia 

has prevented most spring and summer up- or 

downstream migration of fishes (Chittenden 1974). 

This pollution block may also have prevented 

shortnose sturgeon from using the estuary and emgrating 

to nearby rivers in Chesapeake Bay. Adult 

shortnose sturgeon in the Delaware River are presently 

restricted to only 75 km (Brundage & Meadows1982, 

Hastings et al. 1987, O’Herron et al. 1993). 

Recent improvement in water quality may result in 

renewed access of shortnose sturgeon to the lower 

Delaware River and tidal interface (an additional 

100 km), and could result in a dramatic increase in 

abundance. It may also provide emigrants to recolonize 

those Chesapeake Bay rivers that have suitable 

habitat. 

Adult abundance is significantly higher in northern 

populations than in southern populations 

(Mann Whitney Test, one tail, p < 0.02, Figure 2). 

This difference may reflect a historical pattern of 

smaller southern populations due to intrinsic differences 

in river characteristics. But Rogers & Weber 4 

believe that a relatively pristine large southern river 

like the Altamaha River, Georgia, should support 

more than 650 adults. All natural southern populations 

are below or near the minimum viable population 

level of 1000 adults suggested for vertebrates 

(Thompson 1991). 

Anthropogenic factors are likely responsible for 

the present low abundance of shortnose sturgeon in 

southern rivers. All surveyed southern populations 

are exposed to three or more of the following impacts: 

harvest (bycatch and poaching), dams, river 

flow regulation, pollution (particularly, paper mill 

effluent), and dredging of fresh/saltwater interface 

reaches. Most southern rivers have never been surveyed 

well for shortnose sturgeon, or not in many 

years. Recent surveys of two Georgia rivers found 

degraded water quality and other impacts; shortnose 

sturgeon were absent in both (Table 1). The 

status of shortnose sturgeon in the St. Johns River, 

Florida. is unknown, but a remnant population may 

be present. The southernmost limit of shortnose 

sturgeon distribution that has been recently documented 

is the Altamaha River, Georgia. 

The Savannah River was stocked with more than 

4 

Rogers, S.G. & W. Weber. 1995. Status and restoration of Atlantic 

and shortnose sturgeons in Georgia. Report of Georgia Dept. 

Nat. Resources. 28 pp. 

5 Even the most well-designed and carefully managed fish culturing 

methods inherently (and often unintentionally) select certain 

types of individuals that may or may not be adapted for conditions 

in the wild.

323 

97 000 cultured 5 shortnose sturgeon less than 9 

weeks old from 1984 to 1992 (Smith et al. 1995). 

Only 19% were tagged, so identification of wild and 

cultured individuals is impossible. These fish malure 

at age 4–5, so stocking has already contributed 

to the estimated total number of 1676 adults (T. 

Smith personal communication). Stocking cultured 

fish into the wild population may directly threaten 

the long-term existence of the Savannah River population 

by disrupting the population's genetic adaptations 

to local environmental conditions (Waples 

1991, Fleming 1994). Stocking cultured fish is not a 

permanent solution to environmental or harvest 

problems that cause low population abundance; 

these problems still remain in the Savannah River. 

Some of the stocked young have recruited to the 

adult cohort, so abundance of adults has temporarily 

increased. Because the estimate of adults includes 

wild and stocked fish, the Savannah River 

population was not included in analyses of abundance 

trends of the species. 

Latitudinal pattern of anadromy 

Capture-tagging-recapture and telemetry studies of 

adult shortnose sturgeon indicate a latitudinal pattern 

in the amount of time spent in salt water. 

Adults at the extreme northern part of the range 

(northern rivers – Saint John, Androscoggin, and 

Kennebec rivers. Maine; Table 1) use saline water 

for all or most of the year (Dadswell 1979, Squiers el 

al. 6 , Squiers 7 ). Adults leave the estuary and forage 

in Saint John River fresh water for only a few 

months in spring and summer (e.g. June-August) 

when river temperature is warmest. Some adults 

overwinter in 30% seawater. Adults in less northerly 

rivers to the center of the range (north-central 

rivers – Merrimack River, Massachusetts, to the 

6 Squiers, T.S., L.S Flagg. M. Smith. K. Sherman & D. Ricker. 

1981. American shad enhancement and status of sturgeon stocks 

in selected Maine waters. Maine Dept. Mar. Resour., Report to 

Nat. Mar. Fish. Serv., Gloucester. pp. 20–64. 

7 

Squiers, T.S. 1982 Evaluation of the 1980–82 spawning run of 

shortnose sturgeon (Acipenser brevirostrum) in the Androscoggin 

River, Maine. Maine Dept. Mar. Resour., Final Report to 

Central Maine Power Co., Augusta. 15 pp. 

Delaware River) use saline water the least. Adults 

forage and spawn in fresh water for years, then enter 

the fresh/saltwater reach, usually only briefly 

(Buckley & Kynard 1985a, Dovel et al. 1992, O’Herron 

et al. 1993, Kieffer & Kynard 1993). This pattern 

of fresh and saltwater use is termed freshwater amphidromy 

(Kieffer & Kynard 1993). Because feeding 

occurs when temperature exceeds about 7° C 

(Dadswell 1979), north-central rivers provide suitable 

thermal foraging conditions in fresh water for 

about 7 months (April - October). This is likely the 

longest continuous period of a suitable thermal regime 

for foraging in fresh water. Adults in some 

southern rivers (Cape Fear, Pee Dee, Savannah, 

and Altamaha rivers) forage in or just upstream of 

the fresh/saltwater interface moving to high salinity 

water either briefly. or for a long period, during fall 

and winter (Marchette & Smiley 8 , Hall et al. 1991, 

Moser & Ross 1994, Rogers & Weber 9 ). Some 

adults in the Altamaha River remain in freshwater 

reaches after spawning, but extent of this freshwater 

use is not known. River temperatures that exceed 

28–30° C during the summer create unsuitable 

thermal conditions in most freshwater reaches. 

During summer most adults and juveniles 1-year 

old and older remain at the fresh/saltwater interface 

in a few deep, cool water refuges (Hall et al. 

1991, Flournoy et al. 10 , Rogers & Weber 4.9 ). These 

southern populations seem to use fresh water envronment 

Iess than any populations known. 

An exception to the previous pattern salt water 

use by southern adults is found in the dammed Santee-Cooper 

River system. South Carolina, where 

adults remain upstream of dams all year in fresh water 

(e.g. one adult captured in 1984 at river km 190, 

D. Cooke personal communication; 19 adults cap- 

8 

Marchette, D.E. & R. Smiley. 1982. Biology and life history of 

incidentally captured shortnose sturgeon. Acipenser brevirostrum, 

in South Carolina. Report of South Carolina Wildl. Mar. 

Res., Brunswick. 57 pp. 

9 

Rogers, S.G. & W. Weber. 1995. Movements of shortnose stugeon 

in the Altamaha River system. Georgia. Georgia Dept. 

Nat. Resour., Contrib. 57. 78 pp. 

10 Flournoy, P.H., S.G. Rogers & P.S. Crawford. 1992. Restoration 

of shortnose sturgeon in the Altamaha River. Georgia. Georgia 

Dept. Nat. Resour., Final Report to U.S. Fish & Wildl. Serv., Atlanta. 

Proj. AFS-2. 54 pp.

324 

southern and northern shortnose sturgeon, but suf- 

ficient data are not available for conclusions. Short- 

nose sturgeon located upstream of Holyoke Dam at 

river km 140 of the Connecticut River have the 

slowest growth rate of any surveyed (Taubert 

1980a). This suggests growth advantages are associ- 

ated with foraging in the lower river or fresh/water 

water interface. 

Length at maturity (45-55 cm FL) is similar 

throughout the latitudinal range of shortnose stur- 

geon, but southern fish mature at younger ages than 

do northern fish (Dadswell et al. 1984). Males ma- 

ture at 2-3 years in Georgia, 3-5 years in South Car- 

olina, and 10-11 years in the Saint John River; fe- 

males mature at 4-5 years in Georgia, 7-10 years in 

the Hudson River, and 12-18 years in the Saint John 

River. Northern adults live 30-67 years; southern 

adults live 10-25 years. These data are based on 

studies that used pectoral rays to age fish, a proce- 

dure that is not verified with fish of known age. 

tured in 1991 by poachers in the Congaree River, 

headwaters of the Santee River, M. Collins personal 

communication). Also, the presence of migrating 

ripe adults in the tidal reaches of both rivers (D. 

Cooke personal communication) and adults in 

headwaters above dams is strong evidence that 

adults in these populations are amphidromous, like 

those in north-central rivers. It seems likely that before 

the rivers were dammed, adults moved from 

fresh/saltwater foraging areas to discrete headwater 

reaches unknown to biologists. This could be 

done by spawned fish, which would be far upriver 

after spawning. This situation may also occur undetected 

in other southern rivers. The extent of 

fresh water use in all southern rivers needs further 

examination. 

The latitudinal pattern of saltwater use may reflect 

bioenergetic adaptations for obtaining the optimal 

environment for foraging and growth. Important 

components of shortnose sturgeon bioenergetics 

are likely the spatio-temporal pattern of forage 

abundance in river and estuarine areas and the 

length of time a suitable thermal regime is available 

for foraging in fresh water. An acceptable thermal 

regime in fresh water is shortest in northern rivers. 

longest in north-central rivers where fish spend the 

most time in fresh water, and may be intermediate 

in southern rivers. Southern rivers have a suitable 

thermal regime in fresh water during the fall, winter, 

and spring, but available data indicate most fish 

do not enter fresh water to forage; instead; they use 

the fresh/saltwater interface. If so, perhaps forage 

abundance in southern rivers is higher in the fresh/ 

saltwater interface than in fresh water. 

Lifehistory 

Growth 

Dadswell et al. (1984) reviewed growth throughout 

the latitudinal range. Growth of juvenile fish in all 

populations is rapid, with growth of 14-30 cm during 

the first year. Southern fish grow the fastest, but do 

not reach the larger size of northern fish. which continue 

to grow throughout life. This phenomenon 

may be related to different bioenergetic styles of 

Spawning 

Spawning periodicity of males and females is poorly 

understood. Males spawn more frequently than females 

in all northern populations, but perhaps not 

in all southern populations. Dadswell (1979) estimated 

that the Saint John River males spawned at 

2-year intervals and females at 3 to 5-year intervals. 

Annual spawning by some males is documented in 

the Merrimack, Connecticut, and Hudson rivers 

(Dovel et al. 1992, Kieffer & Kynard 1996, M. Kieffer 

& B. Kynard unpublished data). Collins & Smith 

(1996) indicate that some Savannah River fish of 

both sexes spawn during successive years. Abundance 

of spawning females can vary annually by an 

order of magnitude in both northern and southern 

rivers (Buckley & Kynard 2 . Smith et al 11 ). Moreover, 

fecundity is highly variable among populations. 

Fecundity of females from the Saint John River 

ranged from 27 000 to 208 000 eggs (average, 

11 

Smith,T.1.J., E. Kennedy & M.R. Collins. 1992. ldentification 

of critical habitat requirements of shortnose sturgeon in South 

Carolina. South Carolina Wildl. & Mar. Resour. Dept., Report 

to US. Fish & Wildl. Serv. Proj. AFS-17 105 pp.

325 

11568 eggs per kg body weight; Dadswell et al. 

1984). Females in the Saint John River have the 

highest mean potential lifetime fecundity, 197 000 

eggs, compared to 111 000 eggs for Pee Dee River 

females (Boreman et al. 12 ). Males dominate the sex 

ratio of spawners (not the total population) in all 

rivers. Sex ratios of male:female spawners in 2 

northern and 1 southern river are for Hudson River 

– 2.5:1 (Pekovitch 13 ); Connecticut River – 3.5:1 

(Taubert 1980b) and 3 to 7:1 (Buckley & Kynard 

1985b, M. Kieffer & B. Kynard unpublished data); 

and Savannah River – 3.5:1 (Collins & Smith 1996). 

Shortnose sturgeon vary in prespawning migration 

pattern and the type present may reflect energetic 

adaptations to migration distance, river discharge 

and temperature, and physiological condition 

of fish (Kieffer & Kynard 1993). The three patterns 

of migrations are (1) a short 1-step migration 

done in spring only a few weeks before spawning, 

(2) a long 1-step migration done many weeks in late 

winter and spring before spawning, and (3) a short 

2-step migration composed of a long fall migration, 

which places fish near the spawning site for overwintering, 

then a short migration like the short 1- 

step in spring to spawn. Amphidromous adults in 

the Merrimack, Connecticut, and Delaware rivers 

that overwinter only a short distance (< 25 km) 

downstream of the spawning area use a short 1-step 

migration (Buckley & Kynard 1985a, Kieffer & Kynard 

1993, O’Herron et al. 1993,M. Kieffer & B. Kynard 

unpublished data). Of the Connecticut River 

prespawning adults that in the fall prior to spawning 

need to move a total of 80 km or more to spawn, 

70% use a 2-step migration and 30% use a long 1- 

step spring migration (Buckley & Kynard 1985a). 

No long 1-step spring migration was found in Connecticut 

River prespawners that, as of their fall location, 

had to move 140 km or farther to spawn. 

Although total migration distance is unclear, 

12 

Boreman, J., W.J. Overholtz, & M.P. Sissenwine. 1984. A preliminary 

analysis of the effects of fishing on shortnose sturgeon. 

Nat. Mar. Fish. Serv., Woods Hole, Mass., Ref. Doc. No. 84-17.19 

pp. 

13 

Pekovitch, A. W. 1979. Distribution and some life history aspects 

of the shortnose sturgeon (Acipenser brevirostrum) in the 

upper Hudson River estuary. Report of Hazleton Environ. Sci. 

Corp., III. 23 pp. 

prespawning Saint John River adults have a 2-step 

migration and fish must likely move about 45-65 km 

in spring (Dadswell 1979). The 2-step migration pattern 

used by most Connecticut River adults that 

need to move 80 km may be an energetic adaptation 

to take advantage of warmer river temperature, reduced 

river discharge, and superior physiological 

condition of fish in the fall compared to spring. Only 

adults in southern rivers (Savannah, Altamaha, and 

Pee Dee rivers) have a long 1-step migration that 

exceeds 80 km. Most southern fish migrate to about 

river km 200 or farther in late winter (Marchette & 

Smiley 8 , Hall et al. 1991, Rogers & Weber 4,9 ). Although 

details are lacking, both fall and spring migrations 

were found in the Altamaha River (Rogers 

& Weber 1995 4 ). This indicates a greater diversity of 

migration patterns than found previously in south - 

ern rivers. The presence of long 1-stepwinter migrations 

that exceed 200 km in southern rivers may be 

related to warmer river temperatures or the ability 

of southern adults to continue feeding in winter, or 

both. These conditions provide energy resources 

for a long migration that are not available for north - 

ern adults. Northern adults cease foraging in November, 

about 5 months before most fish initiate a 

short 1-step spawning migration. Although some 

adult shortnose sturgeon in a population migrate 

upstream in fall and some migrate in spring, all 

spawn together. The pre-spawning migrations of 

winter and spring ‘races’ of European sturgeon species 

(Berg 1959) likely also reflect different migration 

styles of adults that eventually spawn together. 

Shortnose sturgeon spawn in late winter (southern 

rivers) to mid-spring (northern rivers) when river 

temperature increases to about 9°C. Spawning 

usually ceases at 12-15° C (Dadswell et al. 1984, 

Buckley & Kynard 1985b, Hall et al. 1991, O’Herron 

et al. 1993, Squiers et al. l4 , Kieffer & Kynard 1996). 

When high Connecticut River discharge delayed 

spawning in 1994, a few females spawned successfully 

at 18° C (M. Kieffer & B. Kynard unpublished 

14 

Squiers, T.S., M. Robillard & N. Gray. 1993. Assessment of potential 

shortnose sturgeon spawning sites in the upper tidal reach 

of the Androscoggin River. Report of Maine Dept. Mar. Resour., 

Augusta, Maine. 43 pp.

326 

data). Savannah River fish held for culture also 

spawned at 17-18° C (Smith et al. 1985). 

Spawning occurs at moderate river discharge levels 

and high discharge can deleteriously affect 

spawning. In the Connecticut and Merrimack rivers, 

spawning occurs after peak spring flows, when 

only rain events or regulated flows create high discharge 

(Taubert 1980b, Buckley & Kynard I985b, 

Kieffer & Kynard 1996). For adults that spawn directly 

below a hydropower dam in tailrace flows, 

the facility’s operation controls the suitability of 

water velocities for spawning and rearing of eggs 

and embryos. High river discharge in May of 1983. 

1991,1992, and 1996 during the normal spawning period 

of Connecticut River adults likely inhibited females 

from spawning by creating unacceptably fast 

water velocities at or near the bottom (Buckley & 

Kynard I985b. M. Kieffer & B. Kynard unpublished 

data). All information supports Buckley & Kynard 

(1985b) that acceptable river conditions (flows) 

must be available before endogenous factors trigger 

ovulation and spawning. 

Although channels are used for spawning in 

many rivers, Connecticut River females used a wide 

range of water depths, so depth may be less important 

that water velocity. Channel with gravel substrate 

was likely used for spawning in the Saint John 

River (Dadswell 1979), channel with gravel, rubble, 

and ledge bottom in the Androscoggin River 

(Squiers et al. 14 ), channel with rubble in the Merrimack 

River (Kieffer & Kynard 1996), shallow rilfle 

channels in the Delaware River (O’Herron et al. 

1993), channel curves with rocks, gravel/sand/logs 

in the Savannah River (Hall et al. 1991, Collins & 

Smith 1995), and channel with gravel, cobble, and 

large rocks adjacent to bluff formations in the Altamaha 

River (Rogers & Weber 9 ). Connecticut River 

females tracked for 3 years during spawning used 

water depths of 1.2-10.4 m and bottom velocities of 

0.4–1.8 m sec –1 (mean, 0.7 m sec –1 ; Kieffer & Kynard 

1996, P. Vinogradov, M. Kieffer &B. Kynard unpublished 

data). 

Telemetry of spawning fish throughout the species’ 

range indicates that spawning occurs during a 

few days to 2-3 weeks (Androscoggin River - 

Squiers et al. 14 , Merrimack River - Kieffer & Kynard 

1996, Connecticut River -Buckley & Kynard 

1985b, M. Kieffer & B. Kynard unpublished data, 

Delaware River - O’Herron et al. 1993; and Savannah 

River -Hall et al. 1991). The end of spawning is 

easily determined because fish leave the spawning 

area and move downstream, some at the rapid rate 

of 32 km d –1 

(Buckley & Kynard 1985b, Hall et al. 

1991, Kieffer &Kynard 1996). When shortnose sturgeon 

move up- or downstream, they follow the 

channel (M. Kieffer & B. Kynard unpublished data). 

Eggs, embryos, and larvae 

Early life history is complex in this lithophilous species 

(Balon 1975, 1985). Females deposit brown to 

black demersal eggs (approximately 3.5 mm diameter) 

that quickly adhere to bottom material and 

increase to approximiately 4 mm diameter. Embryos 

hatch in 111 hours at 18-20° C or about 200 

hours at 12° C (Buckley &Kynard 1981, Smith et al. 

1995). Free embryos (eleutheroembryos) 1-8 days 

old are 7-11 mm long, black in color, pliotonegative, 

and seek cover during final development (Richmond 

& Kynard 1995). Embryos have large yolksacs, 

poorly developed sensory systems and can 

only swim using swim-up and drift behavior. The 

photonegative behavior of embryos suggests that 

they would hide under any available cover in 

spawning areas. Eleutheroembryos develop into 

feeding larvae (about 15 mm TL) in 8-12 days at 15- 

17° C, and, as Bemis & Grande (1992) pointed out, 

this is a period of rapid change in the acquisition of 

sensory, feeding, and locomotor systems. Larvae 

have well-developed eyes, open electrosensory 

(ampullary) organs, a mouth with teeth, and fins 

that enable them to swim normally. In laboratory 

tests, larvae were photopositive, nocturnally active. 

and preferred white substrate and the deepest water 

available (Richmond & Kynard 1995). The selection 

of deep water by larvae was also indicated 

by their capture in river channels (Taubert & Dadswell 

1980, Bath et al. 1981). 

Recent laboratory studies of Connecticut River 

larvae found most ceased downstream migration 

after 2 days, although some emigration continued 

for 14 days (C. Cauthron & B. Kynard unpublished

327 

data). This is sufficient time to move many kilometers 

downstream, but not sufficient time to move to 

the estuary from any known unobstructed spawning 

location. 

Tolerance of early life stages to increasing salinity 

and low dissolved oxygen increases with age. Twenty-two 

day old larvae from the Savannah River tolcrated 

a maximum of 9 ppt salinity and required 

more than 3 mg l –1 oxygen, while fish about 300 days 

old tolerated 25 ppt salinity for 18 hours and most 

survived short periods of 3 mg 1 –1 oxygen (Jenkins et 

al. 1993). 

Young-of-the-year 

Behavior and movements of young-of-the-year 

(YOY) are not fully understood in any river, but data 

from rivers throughout the range suggest that fish 

remain upriver in fresh water for about 1 year. In the 

Saint John River, YOY and older juveniles remain 

in fresh water, growing slowly for several years 

(Dadswell 1979). Some Hudson River YOY occur 

within 18 km of Troy Dam, the upstream limit of 

spawning. They apparently remain in fresh water 

for about 1 year before moving downstream to the 

fresh/saltwater interface (Carlson & Simpson 1987, 

Dovel et al. 1992). 

Sparse information is available on feeding and 

habitat use of YOY. Carlson & Simpson (1987) 

found YOY foraged in channel habitat on amphipods 

and dipteran larvae on mud not sand substrate. 

Saint John River YOY used deep water and 

intermediate depth areas (Pottle & Dadswell). 15 

One-year old juveiles and adults 

With the exception of the Saint John River, where 

all juveniles remain in fresh water for several years 

(Dadswell et al. 1984), l-year old and older juveniles 

in other populations join adults and show similar 

spatio-temporal patterns of habitat use. During all 

15 

Pottle, R. & M. J. Dadswell. 1979. Studies on larval and juvenile 

shortnose sturgeon (Acipenser brevirostrum ). Report to North 

east Utilities Service Co., Hartford. 79 pp. 

year in the Connecticut, Hudson, Savannah, and 

Altamaha rivers, and in the Saint John River during 

summer juveniles use the same fresh water or fresh/ 

saltwater interface as adults (Dadswell 1979, Hall et 

al. 1991, Savoy & Shake 3 , Dovel el al. 1992, Flournoy 

et al. 10 , Rogers & Weber 9 ). Juveniles 2-3 year old 

and adults occur together in freshwater concentration 

areas in the Connecticut River (Taubert 1980a, 

M. Kieffer & B. Kynard unpublished data). Juveniles 

1-year and older and adults in the Connecticut 

River had similar summer home ranges (respective 

means, 6.3 and 4.9 km) and winter home ranges (respective 

means, 2.7 and 2.6 km; B. Kynard, D. Seibel, 

M. Kieffer & M. Horgan unpublished data). 

The similarity of home ranges further indicates that 

juveniles use space similar to adults. 

Concentration areas used by juveniles and adults 

in fresh water are often located upstream of natural 

constrictions or in headwaters of dammed reaches. 

locations where river velocity slows and creates 

large sandy shoals (Buckley & Kynard 1985a, Kieffer 

& Kynard 1993). Perhaps. these geomorphological 

features create hydraulic conditions that favor 

substrate for freshwater mussels, a major food item 

of adults (Dadswell et al. 1984). Adults also feed on 

introduced bivalves, including the introduced zebra 

mussel, Dressena polymorpha (M. Bain personal 

communication). 

Habitat use of juveniles and adults has been studied 

in several rivers. Juveniles in the Saint John, 

Hudson, and Savannah rivers use sand and mud 

substrate in deep channels (Pottle & Dadswell 15 , 

Hall et al. 1991, Dovel el al. 1992). Some Saint John 

River adults foraged during summer in backwaters 

of fresh to low salinity lakes with aquatic vegetation 

or on mud substrate along river banks (Dadswell 

1979). During summer and winter in freshwater 

reaches of the Connecticut River, juveniles and 

adults selected similar geomorphological reaches of 

curves and runs with island, but not straight runs 

(Seibel 1993). Juveniles and adults forage in channel 

and shoal areas (Dadswell 1979, O’Herron el al. 

1993), but Connecticut River juveniles used shoals 

more at night than adults (Seibel 1993). Although 

use of channel and shoal areas was highly variable 

among individuals during summer and fall, all Connecticut 

River juveniles and adults overwintered in

328 

have a broad niche breadth; thus, the species should 

be capable of occupying a wide geographic range, 

many habitats, and producing large populations 

(Brown 1984). The great individual variability for 

foraging has likely contributed to the extraordinary 

persistence of shortnose sturgeon during the many 

habitat changes they have experienced during their 

long existence. 

location of first dam (km) 

Figure 3. Relationship in 10 populations between the maximum 

Spawning migration and impact of dams 

upstream spawning location of shortnose sturgeon and location 

of the first (lowermost) dam A 1:1 relationship of spawning loca- Spawning site locations in three unobstructed rivers 

tion to dam location is indicated by the 45° line. 

and two rivers with the first dam located more than 

240 km upstream provide information on the natdeep 

water channel habitat within or directly down- ural pattern of shortnose sturgeon migratory disstream 

of the summer range. No telemetered juve- tance. The maximum upstream spawning site locanile 

or adult tracked in the Connecticut River ever tion of fish in unobstructed rivers is river km 220- 

used the Holyoke Dam reservoir area except when 225 in the Delaware River. river km 275-278 in the 

moving up- or downstream to areas of use. 

Savannah River. and river km 210-220 in the Alta- 

In estuarine environments, most juveniles and maha River. This indicates a common pattern of miadults 

forage together in the fresh/saltwater inter- grating upstream to about river km 200 or farther 

face where salinity is variable, substrate is usually (Hall et al. 1991. O’Herron et al. 1993, Rogers & 

mud and sand, and vegetation is often present. Weber 9 , Collins & Smith 1996). Some Savannah 

Adults in the Saint John estuary foraged over sand/ River fish stopped at river km 179-190, but even 

mud or mud substrate with emergent macrophyte these fish migrated almost to river km 200. Also, 

vegetation in 5-10 m depths in summer and over- some Altamaha River migrants stopped at river km 

wintered in the lower estuary in deep water with 50-125, the lowermost potential spawning location 

mud substrate. Kennebec and Androscoggin river found in any unobstructed river. If these fish 

adults foraged on tidal mud flats with patchy macro- spawned, then there is more variation for spawning 

phyte vegetation and18-25 ppt salinity (McCleave location in the Altamaha River than elsewhere in 

et al. 1977). or in shallow or deep tidal channels with the species’ range. Because this pattern is not supsalinity 

of 0-21 ppt that often had vegetation ported by observations from other rivers, and 

(Squiers et a]. 6 ). Adults overwintered in deep water spawning was not verified, the Altamaha River miin 

the lower estuary (Squires et al. 7 ). Pee Dee River grants need further study. In addition, adults in the 

adults foraged in the fresh/saltwater interface (0.5-1 Hudson River spawn near Troy Dam (river km 246, 

ppt salinity) during spring and summer. then over- Dovel et al. 1992). Pee Dee River adults likely 

wintered downstream in the lower estuary in 15 ppt spawn in the reach downstream of Blewett Falls 

salinity (Dadswell et al. 1984). A similar pattern was Dam at river km 298 (Ross et al. l988), although 

found in the Savannah River (Hall et al. 1991). but some spawned at river km 192 (Marchette & Sminot 

in the Altamaha River. where fish occur less in ley 8 ) similar to the pattern observed in the Savanhigh 

salinity water (Flournoy et al. 10 , Rogers & nah River. Thus, all adults in four rivers (two north- 

Weber 9 ). 

central and two southern) migrate to about river km 

All telemetry studies of foraging behavior of ju- 200 or farther to spawn. No data were collected 

veniles and adults cited previously and diet studies from the far northern rivers because all have dams 

cited in Dadswell et al. (1984) found much individu- in the lower river that block upstream migration. 

al variability. This suggests that shortnose sturgeon Saint John River adults may spawn in the reach be-

329 

low Mactaquac Darn (river km 137-120, Dadswell 

1979). 

Adults likely have a behavioral drive to reach a 

historical spawning area that is located at about river 

km 200 km or farther. When a dam blocks the 

spawning migration, females apparently move as 

far upstream as they can, then may or may not 

spawn in the reach below the dam. Comparison of 

maximum upstream spawning locations in rivers 

throughout the range shows an almost 1:1 relationship 

of known or suspected spawning locations and 

location of the first dam (Figure 3). Exceptions are 

rivers with dams located 300 km or farther upstream, 

i.e., the Savannah River (dam at river km 

300). the Delaware River (dam at river 331 ), and the 

Altamaha River (dam at river km 441). Only runs in 

these rivers likely escaped blockage, either partially 

or totally, by dams. Although Connecticut River 

fish appear to be an exception (Figure 3), they also 

spawn near river km 200 downstream of a dam (the 

second dam located at river km 198, not the first 

dam at river km 140). Merrimack River fish do not 

attempt to move Farther upstream than river km 32, 

and do not spawn directly downstream of Essex 

Dam at river kin 46 (Kieffer & Kynard 1996). This 

different migratory behavior is not likely related to 

the small number of fish present because rare Cape 

Fear River shortnose sturgeon continue to migrate 

as Tar upstream as possible (e.g. to Lock & Dam No. 

l at river km 96, Moser & Ross 1994). All evidence 

from other north-central rivers indicates the present 

spawning pattern of the Merrimack River fish 

is not likely the historical pattern. Closer examination 

of Kennebec River adults, where ripe males 

were captured at river km 58 (Squiers et al. 7 ), may 

show that prespawning adults gather at river km 58, 

but spawn as far upstream as they can go (e.g., below 

the dam at river km 69). 

A dam built downstream of a spawning reach will 

block the migration of anadromous spawners, but it 

may divide amphidromous populations into an upriver 

segment, with access to the spawning site, and 

a lower river segment whose upstream spawning 

and foraging migrations are blocked by the dam. 

This is likely the situation in the Connecticut River 

with Holyoke Dam at river km 140. It also may be 

the situation in the Santee (Wilson Dam at river km 

140) and Cooper rivers (Pinopilis Dam at river km 

80) which currently share the upriver reach of the 

Santee River. In the Santee-Cooper river system. 

the occurrence of ripe lower river adults and headwater 

adults indicates that the dams divided the 

original population, which was likely amphidronious, 

not anadromous. Although only two divided 

populations are known, other rivers may contain or 

have contained in the past, an undetected upriver 

population segment Persistence of an upriver population 

segment is likely determined by many factors. 

particularly fishing mortality and availability 

of spawning conditions. In particular, the Holyoke 

Dam was built on the site of a large rapids near 

South Hadley Falls, Massachusetts. This was not a 

high waterfall, and historical records document 

spearfishing for sturgeon in the rapids, evidence 

that they were able to pass this potential obstruction. 

After Holyoke Dam was built in 1849, however, 

the upriver segment of the Connecticut River 

population persisted unknown to biologists for almost 

100 years. 

In a divided population, upriver fish can move 

downstream past the dam and join lower river fish, 

but the reverse is difficult if not impossible Downstream 

movement of juveniles and adults has been 

documented in the Connecticut River, where it appears 

to be a natural movement pattern timed to 

occur with increased river discharge (Seibel 1993, 

M. Kieffer & B. Kynard unpublished data). Although 

some fish from the upriver segment move 

downstream pass the dam, the pattern is variable 

(as with other movement patterns of the species), 

and will take years of study to decipher. Lower river 

migrants can enter fishlifts at Holyoke Dam, but 

passage is infrequent with 81 fish lifted from 1975 to 

I995 (Holyoke Fishlift data). Three adult/year 

(range, 0-13) are lifted during April-October with 

most fish lifted singly on one day in the spillway lift 

(B. Kynard unpublished data). Although this level 

of passage insures gene flow, the small number of 

fish lifted annually contributes little to total reproduction. 

All evidence indicates spawning by the Connecticut 

River upriver segment is the main source of 

recruitment for the entire population. A spawning 

run of lower river fish annually migrates upstream

330 

lumbia River (Anders 16 ). The phenomena of migratory 

sturgeons establishing freshwater residency 

upstream of dams is not understood, but it occurs 

under similar circumstances with other sturgeons - 

white sturgeon. A. transmontanus, in the mid-Columbia 

River (North et al. 1993)and lake sturgeon, 

A. fulvescens, in rivers of the Great Lakes (Thuemler 

1985).The Connecticut and Santee/Cooper river 

populations have been referred to as partially landlocked 

(Dadswell et al. 1984), but no evidence of a 

natural historical division exists. To clarify terminology, 

perhaps naturally landlocked populations 

should be designated landlocked, and segments of 

migratory populations upstream of dams designat- 

ed damlocked. 

Figure 4. Relationship in nine populations between the abundance 

of adult shortnose sturgeon and maximum upriver spawning 

location. The regression line represents the equation: population 

size = 14435 ln (river km) - 50987, r 2 = 0.99, p < 0.001. 

to HolyokeDam;these fish are ripe and artificially 

cultured eggs develop normally (Buckley & Kynard 

1981,1985b, Richmond & Kynard 1995). However, 

intense netting for eggs and embryos showed that 

no females spawned in 1993-1994, and probably 

only1 of 50 estimatedfemales spawnedin 1995 (P. 

Vinogradov unpublished data). These results just 

below Holyoke Dam were concurrent in all years 

with successful spawning and production of many 

eggs and embryos by tagged females 54 km upstream 

near Turners Falls Dam (river km 198). 

Thus, the successful breeding portion of the Connecticut 

River population is mainly the estimated 

300 or so upriver adults, of which about 25% spawn 

annually (M. Kieffer & B. Kynard unpublisheddata). 

The estimated 850 lower river adults (Buckley 

& Kynard 2 , Savoy & Shake 3 ) likely contributelittle 

to reproduction. Because only about one-third of 

the total Connecticut River adults are able to spawn 

successfully, low population abundance should be 

expected. Similar results of variable spawning success 

among divided population segments of white 

sturgeon, A. transmontanus, was found in the Columbia 

River (Parsley& Beckman1994). 

Thereis only one naturally landlocked sturgeon 

population (e.g., resident population above a natural 

barrier) in the coastal rivers of North America 

_ the federally endangered Kootenai River white 

sturgeon, which occurs in the headwaters of the Co- 

Biological significance of spawning location 

Upstream spawning location may be an important 

component of reproductive success for shortnose 

sturgeon. A comparison of nine populations across 

the species’ range for the relationship between 

maximum upstream spawning location and adult 

abundance used the following equation: 

population size = 14435 ln(river km) - 50987. 

The regression line fits the data well (r 2 = 0.99) and 

was significant (< 0.001, Figure 4). Spawning location 

has a positive relationship to population size 

and this relationship is best represented when 

scaled with natural logs. Spawning location was 

positively related to abundance in northern and 

north-central populations, with only the abundance 

of adults in the Connecticut and Delaware rivers located 

far below the regression line. Reasons for the 

low adult abundance in both these rivers were discussed 

previously. Recent results from the Hudson 

River received after the analysis indicates the population 

has increased to 38 000 (Bain 1997 this volume). 

This would cause the regression line to be located 

above the present position on Figure 4, but 

16 

Anders, P, 1993, Kootenai River white sturgeon studies. 

Report to U.S. Army Corps of Engineers. Bonneville Power 

Admin., Portland. 16 pp.

331 

would not change the basic relationships. Abundance 

of the Saint John River population, whose 

migration is likely blocked, would be located well 

below the new regression line. In general, the two 

southern rivers (Altamaha and Pee Dee) do not fit 

the pattern of the northern and north-central rivers, 

and neither would the Savannah River, even with 

enhanced abundance due to stocking. Perhaps, 

abundance of southern populations is not related to 

spawning location, but their spawning locations are 

far upriver, like northern populations. The low 

abundance of southern adults may be affected more 

by anthropogenic impacts than by spawning location. 

More research is needed to understand factors 

that affect abundance of southern populations. 

Why do females have a strong behavioral drive to 

move to river km 200-300 km to spawn? Perhaps, 

the behavior is related to finding suitable substrate 

and bottom velocity for spawning. However, in the 

Connecticut River these habitat conditions are 

available at downstream reaches, particularly Enfield 

Rapids, Connecticut, at river km 110. But prespawning 

fish continue upstream until blocked by 

Holyoke Dam. Migration patterns previously discussed 

suggest that three behavioral patterns of 

shortnose sturgeon insure that early life stages rear 

far upstream: (1) spawning females migrate far upstream, 

(2) larvae migrate a short distance, and (3) 

YOY are non-migratory for about 1 year. The behavior 

of females, larvae, and YOY may be adaptations 

that insure young fish do not contact salt water 

until salinity tolerance develops. Larvae may also 

gain a survival advantage from predators by delaying 

downstream migration until they are larger. 

Superior survival of fish reared upstream of saltwater 

is supported by two kinds of information. 

Least squares linear regression comparisons of 10 

rivers for relationships between adult abundance 

and two independent variables, (1) distance from 

spawning location to head of tide, and (2) distance 

from spawning location to salt water (maximum intrusion 

of salinity) found significant relationships 

with both factors (respectively, r 2 = 0.88, p < 0.0005, 

r 2 = 0.75, p < 0.025). The relationship with head of 

tide was particularly strong. Both analyses support 

the hypothesis of increased survival associated with 

spawning distance upstream, but both independent 

variables are closely correlated and provide no conclusions 

regarding salinity. However, results of 

stocking 2-9 week old fish in the Savannah River 

also indicated rearing distance upstream may affect 

survival. Fish released and presumably reared between 

river km 103-273, upstream of head-of-tide 

(river km 83), had an adult return rate of 1.3%, 

while fish stocked at river km 65-58, downstream of 

head-of-tide, had a 0.4% return rate (Smith et al. 

1995). In the Savannah River, salinity penetrates in 

summer to river km 36, but contact of stocked YOY 

with salinity was not monitored. Smith et al. (1995) 

speculated that different acclimation and imprinting 

times produced the different returns. There is 

insufficient information for firm conclusions, but 

evidence in the present report indicates that rearing 

location upstream is important for survival of early 

life stages and population abundance. 

Survival and recruitment 

There is only limited information on survival of 

early life stages. Richmond & Kynard (1995) found 

that substrate with abundant crevices is likely critical 

for survival of eggs and embryos. Mortality of 

eggs due to the fungus Saprolegnia, although high in 

cultured eggs, was only 8% (mean of five daily samples 

of mid-developed eggs) at a Connecticut River 

spawning site (M. Horgan & B. Kynard unpublished 

data). Fish predation on eggs at the same spawning 

site also was insignificant. No data are available on 

mortality of embryos or larvae, but losses due to 

predation and unsuccessful initiation of feeding are 

probably high in these motile life periods. Yearclass 

strength is likely established early in life, probably 

within 1-2 months. 

Dredging in freshsaltwater reaches of rivers containing 

shortnose sturgeon may destroy or alter juvenile 

and adult habitat. Fish may also be impinged. 

No adults were impinged during evaluations done 

in the Delaware River (Hastings 17 ), but nothing is 

17 

Hastings, R.W. 1983. A study of the shortnose sturgeon (Acipenser 

brevirostrum population in the upper tidal Delaware River: 

assessment of impacts of maintenance dredging. Final Report 

to U.S. Army Corps of Engineers, Philadelphia. 29 pp.

332 

known about small juveniles that may be less able to Conservation 

avoid impingement. Smith et al. 11 believe the low 

abundance of Savannah River juveniles was caused The primary need of shortnose sturgeon conservaby 

dredging in the fresh/saltwater interface. A sim- tion is completion of a recovery plan for the species. 

lar situation may exist in other rivers. 

This plan will guide the direction of future conser- 

Shortnose sturgeon are protected from directed vation efforts. Generally, conservation should infisheries, 

but they are captured across their range as sure that existing populations survive and increase 

bycatch, mainly in gill net fisheries for American to carrying capacity. All aspects of the species’ life 

shad, AIosa sapidissima. Dadswell (1979) estimated history indicate that shortnose sturgeon should be 

incidental fishing mortality of adults in the Saint abundant in most rivers. Thus, the expected abun- 

John River gill net fishery was less than 10% of total dance of adults in northern and north-central popmortality. 

In the Connecticut River, Savoy & ulations should be thousands to tens of thousands of 

Shake 3 estimated 2-25 adults were taken annually adults (Figure 4). Expected abundance in southern 

by the American shad fishery, and some fish are also rivers is uncertain, but large rivers should likely 

caught by sport fishers angling for catfish, Ictalurus have thousands of adults. In small southern rivers, 

spp. Marchette & Smiley 8 also reported catch of periodic removal of even small numbers of adults 

shortnose sturgeon by sport fishers in South Car- by poachers will probably make all other conservaolina. 

Recent evaluation of sturgeon bycatch in tion measures unsuccessful. Impacts of fishing by- 

American shad gill net fisheries and shrimp trawl catch should be identified and reduced. In rivers 

fisheries in South Carolina and Georgia found that where spawning migrations are blocked by dams. 

gill net fisheries captured about 2% of the adults. Of long-term solutions should be found for passing mithose 

captured. 11% died and 15% were injured grants (if spawning habitat remains upriver). Be- 

(Collins & Smith 1996). Even if spawning migrants cause spawning habitat requirements are known, 

are released after capture by commercial fishers. the usefulness of creating artificial spawning areas 

handling greatly disrupts their migration (Moser & should be investigated for spawning runs blocked 

Ross1994). 

by dams. Migratory movement patterns and river 

Poaching of adults in southern rivers using gill reaches used for foraging and spawning of all popnets 

and traps seems widespread. Although no esti- ulations should be identified and protected. Spawnmate 

of poaching exists. poachers captured 8 of 10 ing location and habitat should continue to be idenradio-tagged 

migrants below Pinopolis Dam on the tified, particularly in southern rivers. Acceptable 

Cooper River (D. Cooke personal communication) spawning conditions for fish blocked by dams 

and 11 adults were trapped in the upper Santee Riv- should be maintained. The effect of contaminants 

er (M. Collins personal communication). Adults on shortnose sturgeon reproduction and survival 

are extremely vulnerable to poaching because they are unknown and should be investigated in these 

group together in concentration areas and a com- long-lived fish. Finally, long-term monitoring of 

monly available inexpensive gear (gill nets) cap- population dynamics, abundance, and recruitment 

tures them. 

is needed in all populations to establish trends. 

Gill net fisheries bycatch and poaching are likely Using cultured fish for supplementing populahaving 

a signifant impact on southern, but not on tion abundance or restoring extirpated populations 

northern populations. The last attempt to estimate should be done carefully. Restoration should be atthe 

effects of harvest on shortnose sturgeon was tempted only after suitable habitat conditions for 

done more than 10 years ago using data from pop- all life intervals exist and a suitable donor stock is 

ulations in the Saint John, Hudson, and Pee Dee riv- available. The Delaware River stock should probers 

(Boreman et aI.12). Given the new information ably be used to restore Chesapeake Bay rivers. This 

on losses of fish to bycatch and poaching in south- restoration may be important to avoid long term geern 

rivers, the effect of fishing mortality on south- netic isolation between northern and southern segern 

populations should be reevaluated. 

ments of the range. Supplementary stocking of cul-

tured Fish into existing populations should only be 

used when wild populations are near extirpation 

and anthropogenic impacts cannot be corrected be 

fore the population is extirpated. Enhancement 

stocking may temporarily increase adult abundance, 

but it may alter the genetic basis of local adaptations 

of the wild population, possibly resulting 

in long-term reduction of individual fitness and de- 

cline of the population (Waples 1991, Flemming 1994). 


Thanks to Vadim J. Birstein John Waldman and 

Robert Boyle for the invitation to attend the International 

Conference on Sturgeon Biodiversity and 

conservation. I thank members of the shortnose 

Sturgeon Recovery Team (Mary Moser, Gordon 

Rogers and Tom Squiers) and Mark Collins and 

Doug Cooke of South Carolina for providing additional 

information, reviewing the manuscript, or 

both. John Waldman, Matt Droud, Vadim J. Birstein 

and William E. Bemis contributed editorial reviews 

and suggestions. Martin Horgan performed 

statistical analyses. 


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Status and management of Atlantic sturgeon, Acipenser oxyrinchus, in 

North America 

Theodore I. J. Smith 1 & James P. Clugston 2 

1 

South Carolina Department of Natural Resources, P.O. Box 12559, Charleston, SC 29422, U.S.A. 

2 National Biological Service, 7920 NW 71st St., Gainesville, FL 32653, U.S.A. 


Key words: Acipenseridae, gulf sturgeon, fisheries, life history, culture, regulations, value 

Synopsis 

The Atlantic sturgeon, Acipenser oxyrinchus, consists of two subspecies distributed along the Atlantic coast of 

North America from Labrador to the east coast of Florida (Atlantic sturgeon subspecies -A. o. oxyrinchus) 

and along the Gulf of Mexico from Florida Bay, Florida to the mouth of the Mississippi River (Gulf sturgeon 

subspecies-A. o. desotoi). The species has been exploited throughout its range with landings peaking around 

the turn of the 20th century followed by drastic declines shortly thereafter. During recent years, landings in 

Canadian waters have increased substantially (approximately 129 metric tons in 1993) while in the United 

States landings are more controlled or prohibited (approximately 22–24 metric tons in 1993). Recently, the 

Atlantic States Marine Fisheries Commission developed a Fishery management plan for Atlantic sturgeon, 

and the United States Fish & Wildlife Service and Gulf States Marine Fisheries Commission drafted a Gulf 

Sturgeon Recovery/Management Plan. Fishery managers in Canada are in the process of establishing more 

stringent fishery regulations for sturgeon.Thus, the impact on populations due to harvesting should be substantially 

reduced. Current research focus includes: life history and population status studies, stock delineation, 

and development of culture and stock enhancement techniques. Implementation of the findings of such 

studies may be helpful in the restoration of depleted stocks. 

Introduction 

As one of North America’s prized fish species, the 

Atlantic sturgeon, Acipenser oxyrinchus, served 

not only as food but also as an item of commerce for 

early European settlers. However, due to a combination 

of unregulated harvesting, damming of 

spawning rivers, and water pollution, the abundance 

of this species has dramatically declined, and 

harvest is now prohibited throughout much of its 

range. In the few areas where it is harvested, landings 

are relatively low, totaling about 200 metric 

tons (mt). This large anadromous species matures 

at an advanced age and utilizes rivers, bays, estuaries,coastal 

and continentalshelf waters during its 

life cycle. Thus, it is highly susceptible to fishing and 

to human-induced habitat perturbations. During 

recent years, there has been increased interest to 

protect this species and restore populations. This 

concern is exemplified through development of 

fishery recovery and management plans. 

Acipenser oxyrinchus has a broad distribution in 

major coastal river systems and estuarine and marine 

waters of eastern North America. Recently, it 

was reported that the species name ‘oxyrhynchus’ 

has been misspelled for over 100 years and that the

336 

1 

Murawski, S. A. & A. L. Pacheco. 1977. Biological and fisheries 

data on Atlantic sturgeon, Acipenser oxyrhynchus (Mitchill). 

Nat. Mar. Fish. Ser., Tech. Ser. Rep. 10: 1–69. 

original correct spelling is ‘oxyrinchus’ (Gilbert 

1992). Thus, the original spelling is used in this paper. 

The species is represented by two subspecies 

(Vladykov 1955, Wooley 1985, Birstein 1993). 

Along the Canadian coast, the northern subspecies, 

A. o. oxyrinchus, (referred to as Atlantic sturgeon 

throughout the remainder of the paper), occurs in 

Hamilton Inlet on the Atlantic coast of Labrador 

(Bachus 1951), and is common in the Gulf of St. 

Lawrence, the St. Lawrence River, the Saint John 

River, New Brunswick, and in the Bay of Fundy 

(Murawski & Pacheco 1 ). In United States waters, 

this subspecies occurs along the entire Atlantic 

coast to the St. Johns River in eastern Florida (Vladykov 

& Greeley 1963). In eight of fifteen coastal 

states, harvesting Atlantic sturgeon is prohibited. 

The southern subspecies, A. o. desotoi. (referred 

to as ‘Gulf sturgeon’ throughout this paper) has a 

more restricted range and occurs in most river systems 

of the northern Gulf of Mexico from the 

mouth of the Mississippi River to the Suwannee 

River and in coastal waters as far south as Florida 

Bay, Florida (Wooley & Crateau 1985). The Gulf 

sturgeon differs from the Atlantic sturgeon in relative 

head length and pectoral fin length, shape of 

dorsal scutes, and length of spleen (Vladykov 1955, 

Vladykov & Greeley 1963). Wooley (1985) reexatio 

of spleen length to fork length was the only sta- 

mined these differences and determined that the ratistically 

reliable characteristic to distinguish between 

subspecies. The Gulf sturgeon was listed as 

‘threatened’ under the Endangered Species Act in 

1991 and is no longer harvested. 

Genetic tools are now being used to examine the 

population structure of Atlantic and Gu1f sturgeons. 

Bowen & Avise (1990) used restrictive fragment 

length polymorphism (RFLP) analysis of the 

entire mitochondrial genome and reported that 

sturgeon exhibited low genotypic diversity, small 

sequence differences between mtDNA genotypes, 

and limited sharing of genotypes between the two 

coasts. More recently, Ong et al. (1996) utilized direct 

sequence analysis of the mtDNA control region 

and provided genetic evidence supportive of 

the subspecies designations for Atlantic and Gulf 

sturgeon. 

Life history and ecology 

There is substantial information on the life history 

and ecology of Atlantic sturgeon and detailed reviews 

have been provided by Murawski & Pacheco 1 , 

Hoff 2 , Rulifson & Huish (1982), Van Den Avyle 3 , 

Smith & Dingley (1984), Smith (1985), Gilbert 4 , and 

Taub 5 . The Atlantic sturgeon is the second largest 

acipenserid fish in North America with a maximum 

total length of 4.3 m (Scott & Crossman 1973, by 

comparison, white sturgeon, A. transmontanus, 

achieve maximum 6.1 m TL). Atlantic sturgeon undertake 

upriver spawning migrations beginning in 

February/March in the southern rivers, April/May 

in the mid-Atlantic region, and May-July in Canadian 

waters (Smith 1985). Female Atlantic sturgeon 

mature at about 7–19 years in SC (Smith et al. 6 ) and 

27–28 years in the St. Lawrence River (Scott & 

Crossman 1973). Female Gulf sturgeon mature at 

about 8–12 years in Florida (Huff 7 ); females do not 

spawn every year so recruitment is very low. In 

2 Hoff, J. G. 1980. Review of the present status of the stocks of 

Atlantic sturgeon. Acipenser oxyrhynchus (Mitchill). Southeast. 

Mass. Univ., Report to Nat. Mar. Fish. Ser., North Dartmouth. 

136 pp. 

3 

Van den Avyle, M. J. 1983. Species profiles: life histories and 

environmental requirements (South Atlantic) - Atlantic sturgeon. 

U.S. Fish Wildl. Ser., Div. Biol. Ser. FWS/OBS–82/11. U.S. 

Army Corps Eng., TREL–82–4. 38 pp. 

4 

Gilbert, C. R. 1989. Species profiles: life histories and environmental 

requirements of coastal fishes and invertebrates (Mid- 

Atlantic Bight) – Atlantic and shortnose sturgeons. U.S. Fish 

Wildl. Ser. Biol. Rep. 82(11.122), U.S. Army Corps of Engineers 

TR EL–82–4.28 pp. 

5 Taub, S. H. 1990. Fishery management plan for Atlantic sturgeon 

(Acipenser oxyrhynchus). Fisheries Management Rep. No. 

17 of Atlantic States Marine Fisheries Commission. 73 pp. 

6 Smith, T. I. J., D. E. Marchette & R. A. Smiley. 1982. Life history 

ecology, culture and management of Atlantic sturgeon, Acipenser 

oxrhynchus oxyrhynchus Mitchill, in South Carolina. 

S.C. Wildl. Mar. Resour. Res. Dep., Final Rep. to U.S. Fish Wildl. 

Ser. Proj. AFS–9. 75 pp. 

7 Huff, J. A. 1975. Life history of Gulf of Mexico sturgeon, Acipenser 

oxyrhynchus desotoi, in Suwannee River, Florida. Florida 

Dep. Nat. Resour., Mar. Resour. Publ. 16, St. Petersburg. 32 pp.

some areas, a small fall spawning migration consist- spring and also a substantial portion of the fish haring 

of ripe Atlantic sturgeon adults has also been vested in the autumn fishery. In addition, it is bereported 

(Smith et al. 1984). Although actual lieved that the Hudson River provides a substantial 

spawning locations are not well known they are be- number of the juveniles that aggregate in the Delalieved 

to include flowing water over hard substrates ware Bay. In 1990, studies suggested that there may 

(rocks, rubble, shale, and sand). 

be genetic structuring among Atlantic sturgeon in 

Information on the early life history for both sub- various Atlantic coast drainages (Bowen & Avise 

species is scarce and based primarily on culture 1990). This hypothesis was supported when Atlanstudies. 

For Atlantic sturgeon, the highly adhesive tic sturgeon from the Saint Lawrence and Saint 

eggs require incubation times of 94 h (20°C) to John rivers, Canada, the Hudson River, and rivers 

about 140 h (18° C) (Smith et al. 1980). The yolksac is in Georgia were identified as genetically distinct 

absorbed in about 10 days, and the small fish begin a populations (Waldman et al. 1996a, b). 

demersal existence. Hatching time for artificially Much information exists on the biology of Gulf 

reared Gulf sturgeon eggs ranges from 54 h at 22.7– sturgeon in the Apalachicola and Suwannee rivers 

23.3°C to 85 hat 18.4°C (Parauka et al. 1991). Little of Florida (Huff (1975, footnote 7), Wooley & Crais 

known of the behavior and habitat requirements teau 1985, Odenkirk 1989, Foster 1993, Mason & 

of these small fish and it is assumed that they slowly Clugston 1993, Clugston et al. 1995). Gulf sturgeon 

move downriver from the spawning sites. Once At- usually begin to migrate into coastal rivers from the 

lantic sturgeon subadults attain a size of ≥ 30 cm, Gulf of Mexico during mid to late February as the 

they are regularly captured in tidally influenced rivers warm to 16–19° C. Migration continues 

lower river and estuarine areas (Dovel & Berggren through May and peaks during late March or early 

1983, Lazzari et al. 1986, Collins et al. 1996). Some April in the Suwannee River, when the river temmovement 

of juveniles between river systems oc- perature reaches about 20° C (Foster 1993, Clugston 

curs (Dovel & Berggren 1983). Most juvenile Atlan- et al. 1995). Fish of all sizes (1.0–75.0 kg) move uptic 

sturgeon remain in slightly brackish water near river and settle in various reaches of the river from 

the river mouth/estuarine zone for a number of river km 24 to km 215. Downstream movement usumonths 

or years (Kieffer & Kynard 1993) and then ally begins in mid-November as the water cools to 

move into coastal and continental shelf waters 20° C. All sturgeon in the Suwannee River, except 

where they grow and mature. 

young of the year, return to the Gulf of Mexico by 

Information on the characteristics of Atlantic early December. Small sturgeon (0.2–2.5 kg) resturgeon 

populations is being developed. Based on main in and near the river mouth during winter and 

tagging studies, Atlantic sturgeon are known to un- spring. Larger fish move to unidentified areas in the 

dertake extensive coastal migrations (Holland & Gulf of Mexico. 

Yelverton 8 , Murawski & Pacheco 1 , Hoff 2 , Rulifson Gulf sturgeon over one year of age do not eat 

& Huish 1982, Smith et al. 6 , Dovel & Berggren during the summer and fall despite an abundant 

1983). However, tagging studies provide little infor- supply of benthic organisms in the Suwannee River 

mation on the source of recruits to various stocks (Mason & Clugston 1993). In spring, stomachs of 

and such information is basic to effective manage- subadults and adults that migrate from the Gulf of 

ment. Recently, using mitochondrial DNA analysis, Mexico into the Suwannee River and small stur- 

Waldman et al. (1996a) found that the Hudson Riv- geon that remain near the river mouth are full of 

er contributes most of the Atlantic sturgeon cap- benthic invertebrates. Based on capture, mark and 

tured in the New Jersey intercept fishery in the recapture studies, juvenile and adult Gulf sturgeon 

decrease in weight during the summer while in 

freshwater (Wooley & Crateau 1985, Clugston et al. 

8 Holland, B. F., Jr. & G. E Yelverton. 1973. Distribution and biological 

studies of anadromous fishes offshore North Carolina. 

1995). Net growth of Gulf sturgeon results from a 

N.C. Dep. Nat. Econ. Res. Spec. Sci. Rep. 24. Morehead City. 132 Series of weight gains while they are in the Gulf of 

pp. 

Mexico during winter and spring, and weight losses 

337

338 

was in flood, 8.1 m and 5.5 m deep, respectively, 

where eggs were collected. Temperature at both locations 

was 18.3° C. Additional eggs were collected 

during late March and April 1994 at river km 201 to 

221 when water temperatures ranged from 18.8 to 

20.1°C. 

Studies are underway to genetically characterize 

the Gulf sturgeon. Results to date show definitive 

inter-regional differentiation of mtDNA genotypes 

indicating that fish from rivers in the eastern, central 

and western Gulf are genetically distinct (Isaac 

Wirgin personal communication). Further, it is suggested 

that the homing fidelity of Gulf sturgeon 

may be quite high and that mtDNA differentiation 

among fish from geographically proximal rivers 

may be possible. 

Reasons for decline 

Figure1. Reported landings of Atlantic and Gulf sturgeon. Data 

lor Canada prior to 1940 show only landings from the Saint John 

River. New Brunswick (a. M. Dadswell personal communication); 

after 1940. the figure shows combined landings for the 

Saint John and St. Lamrence (Quebec) rivers (a + b, G. Trencia 

personal communication). U.S.-Atlantic Coast landings are 

based on NMFS data and may include shortnose sturgeon prior 

to 1972. Gulf of Mexico landings arc based on J. M. Barkuloo 10 . 

during summer and fall when they are in coastal rivers. 

High water termperature was suggested as the 

main cause of feeding inactivity in the Suwannee 

River (Mason & Clugston 1993). Although this river 

remained cooler than near-shore Gulf of Mexico 

waters during summer, river temperatures were still 

believed to exceed optimum temperature for feeding 

and growth. Foster (1993), located juvenile and 

adult Gulf sturgeon in 29°C water in the Suwannee 

River using radio transmitters. 

Gulf sturgeon spawn in the upper reaches of the 

Suwannee River (Clugston et al. 1995). The smallest 

sturgeon (76 g and 85 g) ever reported from this 

river were captured at river km 215 and 237 during 

the winter of 1991. Verification of spawning in this 

area was accomplished with the collection of sturgeon 

eggs on artificial substrates near river km 215 

in April 1993 (Marchant & Shutters 1996). The river 

Exploitation 

Early utilization of Atlantic sturgeon can be traced 

to 2190 B.C. in New England (Ritchie 1969), however, 

major fisheries for Atlantic sturgeon began 

during the last quarter of the 19th century. These 

fisheries focused on the spring migrations when the 

sturgeon moved into coastal rivers to spawn. Although 

most historical sturgeon landings data are 

probably inaccurate and do not include fishing effort, 

they do reflect major trends in harvest. Some 

Atlantic sturgeon landings may have included the 

smaller (maximum size 1.4 m TL) shortnose sturgeon, 

A. brevirostrum up until 1973 when this species 

was listed as endangered. However, most landings 

are probably based on the much larger Atlantic 

sturgeon. U.S. landings, recorded initially in 1880 by 

the US Fish Commission, peaked about 1890 when 

approximately 3350 mt were landed (Figure I). Because 

the fish were so vigorously pursued. all major 

fisheries collapsed within about 10 years with landings 

in 1901 less than 10% (295 mt) of the former 

peak. Today, fisheries are still depressed and more 

closely regulated. During 1990–1992, mean total 

U.S. landings were 82.4 mt or 2% of that reported in 

1890. 

The major U.S. historical fisheries for the Atlan-

339 

tic sturgeon occurred during the period 1870-1920. 

They were initially centered on the Delaware River 

and the Chesapeake Bay system with most landings 

reported by New Jerscy (NJ) and Delaware (DE) 

and, to a lesser degree, by Virginia (VA) (Murawski 

& Pacheco 1 ). During the early period of peak exploitation, 

substantial landings were also reported 

by North Carolina (NC), South Carolina (SC), and 

Georgia (GA). By the late 1970s and early 1980s, 

SC, GA, and NC accounted for approximately 80% 

of the U.S. landings (Table 1). In recent years, landings 

have again shifted and are now centered in the 

Hudson River, and coastal New York (NY) and NJ. 

During 1990-1992, NY and NJ reported approximately 

93% of U.S. landings. 

Some sturgeon harvested in directed fisheries 

were taken using pound nets, weirs, stake row nets, 

trammel nets, trawls, harpoons, and snares. However, 

large floating and anchored gill nets with 

stretch mesh sizes of 33-41 cm and depths of 4-8 m 

were the most commonly used fishing gear (Cobb 9 , 

Galligan 1960. Huff 7 , Smith et al. 1984). In a recent 

9 

Cobb, J. N. 1900. The sturgeon fishery of Delaware River and 

Bay. Rep. U.S. Comm.Fish and Fisheries for 1899, Part 25: 369- 

380. 

review of U.S. Atlantic sturgeon fisheries, Taub 5 

determined that incidental captures of Atlantic 

sturgeon contributed more to total landings than 

did directed sturgeon fisheries. For example, in 1987 

nearly 77% of the total reported landings were incidental 

to other commercial fisheries. Such fisheries 

used a variety of gear (e.g., trawls, haul seines, 

pound nets, gill nets) to catch various groundfishes. 

shad. shrimp, and lobster bait. Sturgeon landed in 

these fisheries were usually subadults. Recent studies 

in SC and GA confirm that sturgeon bycatch still 

occurs and reported the incidental capture of sturgeons 

in the shad gill net and penacid shrimp trawl 

Gsheries (Collins et al. 1996). This trend of harvesting 

both subadults and adults continues in the remaining 

major U.S. fisheries. Harvests in NY are 

primarily mature adult Atlantic sturgeon from the 

Hudson River and juveniles and young adults from 

the coastal fisheries. The NJ fishery lands mostly 

immature fish in its directed and incidental fisheries. 

The Atlantic sturgeon also has a long history of 

exploitation in Canadian waters. During the period 

of peak exploitation, the only long term harvest record 

is from the Saint John River fishery Harvest 

pattern for this fishery was similar to that in the U.S., 

Table I. Reported landings (metric tons, mt) of Atlantic sturgeon in the United Slates by stale in 1982, 1987, and 1992 (based on NMFS 

data) . 

State 1982 1987 1992 

Landings Rank’ Landings Rank Landings Rank 

Maine 1 .2 0.4 0.0 

New Hampshire 0.0 0.4 0.0 

Massachusetts 1 .0 3.1 4 < 0.1 

Rhode Island 0.5 1 .9 1.2 

Connecticut 0.0 0.0 0.0 

New York 9.9 4 17.1 1 17.8 2 

New Jersey 3.3 5 9.1 2 38. 1 1 

Delaware 0.6 < 0.1 0.0 

Maryland 0.5 0.5 0.6 

Virginia 1.7 0.0 0.0 

North Carolina 10.6 3 6.2 3 0.0 

South Carolina 45.4 1 0.0 0.0 

Georgia 12.8 2 2.9 5 1.0 

Florida (E. coast)

340 

with landings substantially reduced from those reported 

before the turn of the century (Figure 1). 

From about 1951–1982, U.S. landings generally exceeded 

those reported from Canada. However, 

there has been a consistent trend of increased catches 

from Canada with 1990–1992 landings (mean 130 

mt) near peak levels. 

There are two major Canadian fisheries: one centered 

in the St. Lawrence River between St. Joachim 

and Cacouna, Quebec (Guy Trencia personal 

communication); and, another in the Saint John 

River, New Brunswick (Michael Dadswell personal 

communication). Both are directed fisheries. The 

increase in Canadian landings during the past 12 

years is primarily from the St. Lawrence River fishery, 

which supports about 35 fishermen. Fish taken 

from the St. Lawrence River are rarely mature. In 

recent years, only 1–2 fisherman fish for, Atlantic 

sturgeon in the Saint John River fishery with annual 

landings on the order of 5–10 mt. 

The Gulf sturgeon fishery also experienced a major 

decline since about the turn of the century (Figure 

1) based on commercial landing statistics compiled 

by Barkuloo 10 . Directed fisheries occurred 

only along the Florida (FL) and Alabama (AL) 

coasts. There are periods of increased harvest but, 

as with the Atlantic sturgeon, no effort information 

is available to calculate catch per unit effort. 

Over-harvesting is believed to be the single major 

cause of the precipitous declines in abundance of 

Atlantic sturgeon (Ryder 1890, Vladykov & Greeley 

1963, Hoff 2 , Taub 5 ). Vulnerability to overfishing 

is clear as mature fish were relatively easily captured 

during spring spawning migrations and juveniles 

were harvested from estuarine nursery habitats. 

Damming of spawning rivers 

Construction of dams in some northeastern and 

southeastern rivers excluded Atlantic sturgeon 

from historical spawning sites. In the northeast, 

10 Barkuloo, J. M. 1988. Report on the conservation status of the 

Gulf of Mexico sturgeon, Acipenser oxyrhynchus desotoi. U.S. 

Fish and Wildlife Service, Panama City. 33 pp. 

such dams include those at the head of the Androscoggin 

River (1807) and Kennebec River (1837) in 

Maine, the dam at Lawrence (1847) on the Merrimack 

River in New Hampshire, and the Enfield 

Rapids Dam on the Connecticut River (Hoover 11 , 

Galligan 1960, Murawski & Pacheco 1 ). In South 

Carolina, Atlantic sturgeon have been excluded 

from historic spawning sites since about 1870 when 

mill dams and water supply dams were constructed 

on the Peedee, Wateree, Congaree and Savannah 

rivers (Leland 1968). Similarly, dams have limited 

Gulf sturgeon access to migration routes and historic 

spawning areas throughout the Gulf of Mexico 

(Murawski & Pacheco 1 , Wooley & Crateau 1985, 

USFWS & Gulf States Marine Fisheries Commission 

12 ). A dam constructed in 1962 across North Bay 

of the St. Andrew Bay system in FL prevents passage 

of all anadromous species as does the Ross 

Barnett dam on the Pearl River. The Jim Woodruff 

Lock and Dam constructed in 1957 on the Apalachicola 

River also appears to provide complete restriction 

as no tagged sturgeon have been taken upriver 

of this structure and no evidence exists which 

indicates that the Gulf sturgeon can pass through 

the lock system (USFWS & Gulf States Marine 

Fisheries Commission 12 ). 

Pollution and industrialization 

Much of the Atlantic sturgeon’s historic riverine 

habitat has been degraded by water pollution and 

extensive dredging (Taub 5 ). Along the middle Atlantic 

coast and the Gulf of Mexico, water degradation 

from industrial and domestic discharges impacted 

spawning and nursery habitats (Hoover 11 , 

Galligan 1960, Leland 1968, Murawski & Pacheco 1 , 

Barkuloo 10 ). The 1970 National Estuary Study indicated 

that dredging and filling activities were particularly 

destructive to fish habitat and reported 

that 73% of the U.S. estuaries have been moderate- 

11 Hoover, E. E. 1938. Biological survey of the Merrimack watershed. 

Fish Game Comm., Concord. 238 pp. 

12 U.S. Fish and Wildlife Service & Gulf States Marine Fisheries 

Commission. Gulf Sturgeon Recovery/Management Plan. Atlanta, 

Georgia. 170 pp.

341 

ly to severely degraded. Dredging and filling disturbs 

benthic fauna, eliminates deep holes and alters 

rock substrates, all important to sturgeon. Anecdotal 

evidence indicates that old river bottom not 

subjected to maintenance dredging is preferred by 

Atlantic sturgeon (Taub5). Contaminants have not 

been intensively examined in the Atlantic sturgeon 

but an early study indicated that concentrations of 

polychlorinated biphenyls (PCBs) in St. Lawrence 

and Hudson River Atlantic sturgeon generally exceeded 

Food and Drug Administration guidelines 

(2 mg 1 -1 ) for human consumption (Murawski & Pacheco 

1 ). In 1986, New York Department of Environmental 

Conservation analyzed Atlantic sturgeon 

from the Hudson River and found low levels (0.15 

to 1.70 mg 1 -1 ) in all tissues except the brain which 

contained an average concentration of 7.92 mg 1 -1 

PCBs (Sloan 1987). Gulf sturgeon collected from a 

number of rivers from 1985 to 1991 were analyzed 

for pesticides and heavy metals (Bateman & 

Brim13). Concentrations of arsenic, mercury, DDT 

metabolites, toxaphene, polycyclic aromatic hydrocarbons, 

and aliphatic hydrocarbons were sufficiently 

high to warrant concern. Such products are 

known to cause reproductive failure, reduced survival, 

and various physiological alterations in fish. 

13 

Bateman, D. H. & M. S. Brim. 1994. Environmental contaminants 

in Gulf sturgeon of northwest Florida 1985-1991. USFWS, 

Pub. No. PCFO-EC 94-09, Panama City. 23 pp. 

Table2. Ex-vessel price ($ per kgwhole weight) for Atlantic sturgeon 

landed in New York, New Jersey and Georgia during 1988- 

1992*. 

Year 

Price ($ per kg) 

New York New Jersey Georgia 

1988 2.46 2.70 8.13 

1989 3.03 3.02 7.86 

1990 3.98 3.99 10.00 

1991 4.02 2.36 12.50 

1992 4.44 3.53 13.37 

Mean 3.59 3.12 10.37 

* Based on NMFS data and G. Rogers personal communication. 

Figure 2. Ex-vessel value and landings for the Atlantic sturgeon 

fishery from 1980-1992. 

Value and employment 

The former sturgeon fisheries were economically 

important and provided substantial direct (fishermen) 

and indirect employment such as net manufacturing, 

boat building, food processing, and shipping 

(Murawski & Pacheco 1 ). Today, however, sturgeon 

fisheries have an insignificant impact on coastal 

economies and provide no full time employment. 

Sturgeon fishermen now number approximately 

100 (35 in Canada; 65 in U.S.) and all use the fishery 

as a source of supplemental income. 

The reported ex-vessel value of U.S. landings of 

Atlantic sturgeon has fluctuated from $59 000 to 

$365 000 (mean $155 000) during the period 1980 to 

1992. During this time, landings have ranged from 

about 40 to 100 mt while ex-vessel price and value 

have increased (Figure 2). Average price during 

1980-1982 was $1.27 per kg whole weight and $3.58 

per kg during 1990-1992. When the ex-vessel prices 

and values of the fishery are adjusted for inflation 

during this period (deflated using Consumer Price 

Index for fishery products), there has been a 53% 

increase in real ex-vessel price and a 41% increase 

in real value of the Atlantic sturgeon fishery since 

1980-1982. States reporting landings based partially 

on incidental captures and landings of juveniles 

have a lower mean ex-vessel price than those with 

directed fisheries where adults are harvested. For 

example, ex-vessel prices during 1988-1992 for 

landings from NY and NJ (where much of the harvest 

is subadults) averaged $3.59 per kg and $3.12

342 

per kg, respectively (Table 2). In GA, where there is 

a directed gill net fishery focused on capture of roe 

females, the ex-vessel average price was $10.37 per 

kg during the same period. 

A detailed analysis of the South Carolina fishery 

was performed for 1977 to 1982 and the total value 

of the caviar exceeded the total value of the flesh 

(Smith et al. 1984). In SC, the ex-vessel price of processed 

caviar was $66 per kg versus $2.42 per kg for 

the dressed carcass in 1982. The current prices for 

caviar in GA are about $121 per kg ex-vessel, $278 

per kg wholesale, and $350 per kg retail (Bertha 

Boone, Walters Caviar Co. personal communication). 

In New York, prices as high as $220 per kg 

ex-vessel have been reported (Holloway 1994). 

During 1993, ex-vessel dressed carcass (headless, 

finless and gutted) price was about $5-7per kg in 

GA but after further processing and smoking in NY, 

the product retailed for $33-40 per kg (Bertha 

Boone, Walter’s Caviar Co., personal communication). 

Management 

Until recently, management of Atlantic sturgeon 

was the responsibility of the individual states and 

other regional jurisdictional entities. This resulted 

in a wide diversity of regulations involving licensing, 

harvest size, fishing gear, seasons, and reporting 

requirements (Smith 1985, Taub 5 ). In U.S. waters, 

lack of uniform regulations is no longer a problem 

but in Canadian waters, sturgeon fishery regulations 

are different for the St. Lawrence and Saint 

John Rivers (Table 3). 

In 1990, the Atlantic States Marine Fisheries 

Table 3. Management regulations for taking Atlantic sturgeon, Acipenser o. oxyrinchus, in 1994. Harvesting of Gulf sturgeon, Acipenser 

oxyrinchus desotoi, is prohibited. 

Area Type of fishery Laws and regulations 

Canada 

St. Lawrence R. 

St. John R. 

directed 

directed 

United States 

Maine closed landings prohibited 

New Hampshire closed landings prohibited 

Massachusetts closed landings prohibited 

Rhode Island 

Connecticut 

New York 

incidental 

incidental 

directed and 

incidental 

amount of gill net limited by fishing zone; minimum gill net stretch mesh 17.5 cm; net owner 

identification 

minimum fish length 122 cm TL; minimum gill net stretch mesh 33 cm; open season except 

June 

minimum fish size 213 cm TL, license required in freshwater 

minimum fish size 213 cm TL; trawl license required; maximum of 3 fish per day per vessel 

minimum fish size 152 cm TL; special sturgeon license required; open seasons: 15 May-15 

Jun in Hudson R. and marine district; 1 Oct-30 Nov in marine district; landed fish must be 

tagged, reported, and biological data collected 

New Jersey directed and 

incidental minimum fish size 152 cm TL; special sturgeon license required; individual quotas; logbook 

Pennsylvania closed 

records; allow access to fish for collection of biological data 

landings prohibited 

Maryland 

Delaware 

Virginia 

incidental 

directed 

closed 

minimum fish size 213 cm TL; commercial finfish license required; maximum gill net stretch 

mesh size 8.9 cm 

minimum fish size 213 cm TL; commercial gill net license required 

landings prohibited 

North Carolina closed landings prohibited 

South Carolina closed landings prohibited 

Georgia 

directed minimum fish size 213 cm TL; minimum gill net stretch mesh 30 cm; gill nets only; open 

season 15 Feb-15 Apr, commercial saltwater fishing license required 

Florida closed landings prohibited

Commission (ASMFC) completed development of coastal waters but harvest in freshwater has been 

a Fishery Management Plan (FMP) for Atlantic prohibited since 1972. Louisiana (LA) permitted 

sturgeon (Taub 5 ). The goal of the FMP is ‘to provide commercial harvest until 1990 while the Mississippi 

the framework to allow restoration of the Atlantic fishery has been closed since 1974. Florida classified 

sturgeon resource to fishable abundance through- both subspecies as ‘species of special concern’ and 

out its range’. Fishable abundance was defined as prohibited harvest on both coasts beginning in 1984. 

an annual harvest of about 317 mt or about 10% of Under the Endangered Species Act, it is illegal 

the historic landings in 1890. The FMP has several for anyone to take, kill, possess or sell the Gulf sturmanagement 

objectives which include: protection geon. Classification as ‘threatened’ prompted the 

from further stock depletion: expansion of knowl- establishment of a Gulf Sturgeon Recovery/Manedge 

concerning the stock(s); enhancement and agement Task Team which recently completed a 

restoration; and coordination of research and man- Gulf Sturgeon Recovery/Management Plan 

agement activities throughout the species’range. To (USFWS & Gulf States Marine Fisheries Commisachieve 

these objectives, 13 specific management sion 12 ). A major short-term objective of the Gulf 

recommendations were identified. The recommen- sturgeon plan is to prevent further reduction of exdation 

of greatest immediate importance was that isting wild populations of this subspecies. The longeach 

state limit harvest by establishing a fishing mo- term objective is to establish population levels that 

ratorium; or, by establishing a minimum harvest would allow delisting the Gulf sturgeon by discrete 

size of 213 cm TL (191 FL) coupled with a monitor- management units. 

ing program; or, by developing a ‘conservation 

equivalency’ plan which is acceptable to ASMFC. 

Other recommendations include identification and Culture and stock enhancement research 

protection of critical habitats, documentation of 

movements, evaluation of status and genetic characteristics 

of populations, development of propagation 

techniques, and evaluation of hatchery fish for 

stock restoration purposes. 

Development of the FMP focused attention on 

the Atlantic sturgeon and has resulted in efforts to 

protect and conserve the remaining populations in 

US. waters. In 1994, NJ submitted an acceptable 

plan to ASMFC, thereby bringing all Atlantic states 

into compliance with the primary recommendation 

to control harvest (Table 3). 

In Canada, there are plans to improve management 

and prevent over-harvest of Atlantic sturgeon 

in the St. Lawrence River. In addition to regulation 

of total amount of netting and minimum mesh size 

(17.8 cm stretch), all nets must be identified with the 

owner’s name beginning in 1994. In subsequent 

years, there are plans to regulate fishing season and 

fish harvest size to prevent overfishing (Guy Trencia 

personal communication). 

Early fishery workers were aware of the catastrophic 

decline in sturgeon landings. After detailed study 

of the fisheries, they concluded that ‘the only means 

of maintaining and increasing the industry was 

through artificial propagation which should be successfully 

accomplished at a comparatively insignificant 

outlay’ (Ryder 1890). At the time, sturgeon 

were considered second in economic importance to 

the lobster (Stone 1900). The first artificial spawning 

was achieved by the New York State Fish Commission 

using fish from the Hudson River in 1875 

(Harkness & Dymond 1961). Based on this limited 

success, the US. Fish Commission initiated artificial 

propagation studies on the Delaware River in 

1888. This work and that of other culturists was 

thwarted by difficulties associated with collecting 

ripe males and females simultaneously and fungal 

infection of the incubating eggs. No substantial successes 

were achieved, and by 1912 most work on 

sturgeon culture had been abandoned in the U.S. 

Prior to its classification as a ‘threatened species’ 

in 1991, Gulf sturgeon harvest regulations varied 

among the coastal states along the Gulf of Mexico. 

Alabama (AL) permitted commercial harvest in 

343

344 

and Canada (Dean 1894, Leach 14 . Harkness & Dymond 

1961, Hoff 2 , Smith & Dingley 1984). 

considerations: stocking numbers, sizes and locations: 

and, planning and evaluation (St. Pierre 15 ). 

In recent years, there has been renewed interest 

in culturing North American sturgeons (Smith 

1990). A cooperative USFWS effort was establish- Prospects 

ed in SC focused on propagation of Atlantic sturgeon 

(Smith et al. 6 ). In 1979 and 1951, Atlantic stur- In the U.S., the Gulf sturgeon is fully protected from 

geon were successfully stripped using injection of harvest while fishing for Atlantic sturgeon has been 

acetone-dried pituitary glands (Smith et al. 1980, severely curtailed or halted in all states. In addition, 

1981). In 1993 and 1994, success was obtained in there is national focus on all eight North American 

stripping Hudson River Atlantic sturgeon using sturgeons and the paddlefish as evidenced by the 

LHRHa (Richard A. St. Pierre personal communi- recent development of a document titled ‘Framecation). 

Studies arc underway to develop culture work for the Management and Conservation of 

techniques at USFWS and National Biological Ser- Paddlefish and Sturgeon Species in the United 

vice (NBS) facilities in PA. Such studies include diet States’. This document. prepared by the National 

research on all life stages, pathology, and sperm Paddlefish and Sturgeon Steering Committee 16 , 

cryopreservation. After 20 months, cultured Atlan- identifies problems and provides guidance Tor 

tic sturgeon grew to 66 cm TL and 1.2 kg. In fall 1994, needed research. 

5000 cultured juveniles (approximately 10 cm TL) The recent adoption of ASMFC recommendawere 

tagged with coded wire tags and stocked in the tions to control minimum harvest size (213 cm TL) 

Hudson River. To date, several of these fish have or to establish a ‘conservation equivalency’ meabeen 

reported captured. 

sure is a major first step for preservation of Atlantic 

The first artificial spawning of Gulf sturgeon was sturgeon in U.S. waters. Not only will landings be 

achieved with fish from the Suwannee River on 22 greatly reduced but juveniles will also be protected. 

March 1989 (Parauka et al. 1991) and efforts to de- Based on current quotas and fishery regulations, tovelop 

culture techniques are continuing. To exam tal 1994 harvest in the U.S. is expected to be about 20 

ine the potential for stock enhancement, about 1200 mt with a minimum fish harvest size of 152 cmTL. In 

of the 20–30 cm TL sturgeon were tagged using pas- Canada, there is substantial concern about the resive 

integrated transponders (PIT tags). These fish cent increase in landings in the St. Lawrence River 

were released by NBS and University of Florida fishery. Consequently, fishery managers are analyzpersonnel 

at 10 sites in the Suwannee River during ing landings data and planning implementation of 

December 1992. By February 1995. 6.2% of the strict harvest regulations during the next several 

stocked fish have been captured by NBS as part of years to protect the sturgeon from overfishing. 

this continuing effort. 

In addition to regulatory issues, emphasis has 

Due to the interest in stocking for restoration and been placed on answering the basic, life history 

management purposes, the ASMFC recently re- questions needed for effective management of the 

quested the Atlantic Sturgeon Aquaculture and species. Culture and marking techniques are being 

Stocking Committee to recoininend stocking guide- developed for possible use in stock enhancement 

lines. A series of recommendations were developed efforts for both subspecies and guidelines have 

which addressed a variety of issues including: origin 

and numbers of broodstock; genetic and ecological 

14 Leach, G. C. 1920. Artificial propaption of sturgeon. review of 

sturgeon culture in the United States. Rep. U.S. Fish Comm. 

1919: 3–5. 

15 

St. Pierre, R. A. 1995. Breeding and stocking protocol for cultured 

Atlantic sturgeon. Rep. Atlantic Sturgeon Aquaculture 

and Stocking Committee. Atlantic States Marine Fisheries Commission. 

17 pp. 

16 

National Paddlefish & Sturgeon Steering Committee. 1993. 

Framework for the management and conservation of paddlefish 

and sturgeon species in the United Slates. USFWS, Division of 

Fish Hatcheries, Washington. DC. 41 pp.

een prepared by the Atlantic Sturgeon Aquacul- Acknowledgements 

ture and Stocking Committee (Smith 17 , St. Pierre 15 ). 

Preliminary stock enhancement work with Atlantic This paper is a joint contribution of the South Carand 

Gulf sturgeons. and shortnose sturgeon (Smith olina Marine Resources Center (contribution numet 

al. 1995) is encouraging, but substantial addition- ber 343) and the Southeastern Biological Science 

al work will be required to fully test the concept. Center, National Biological Services. We greatly 

Atlantic sturgeon movement and recruitment data appreciate the information and comments provided 

are being collected through USFWS and ASMFC by Guy Trencia, Direction Regionale de Quebec, 

cooperation. Tagging and reporting of recaptured and Michael Dadswell, Acadia University. We 

fish is encouraged by the establishment of a central thank the many reviewers, especially Gordon Rogdata 

repository in MD. Tags are provided free and ers, Wally Jenkins, Mark Collins, Lorna Patrick, 

anyone encountering sturgeon during various re- Frank Parauka, and Ken Sulak. 

search and monitoring activities is requested to tag 

and release sturgeon as well as collect basic biological 

data. In states with ‘conservation equivalency’ References cited 

status, detailed biological information is collected 

from all fish landed, Further, incidental capture and Bachus, R. H. 1951. New and rare records of fishes from Lahrador. 

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to establish culture and stocking parameters, 

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605.



Atlantic and shortnose sturgeons of the Hudson River: common and 

divergent life history attributes 

Mark B. Bain 

New York Cooperative Fish and Wildlife Research Unit, Department of Natural Resources, Fernow Hall, Cornell 

University, Ithaca, NY 14853, U.S.A. 

Received10.1.1995 Accepted 1.5.1996 

Key words: Acipenseridae, Acipenser oxyrinchus, Acipenser brevirostrum, distribution, habitat use, movements, 

size, maturity, age, growth 

Synopsis 

The Hudson River estuary supports substantial number of Atlantic sturgeon, Acipenser oxyrinchus, and 

shortnose sturgeon, Acipenser brevirostrum. Both species have complex life cycles that have been studied 

sporadically in the past 50 years. The life cycle of the shortnose sturgeon may be divided into four life intervals: 

lion-spawning adults, spawning adults, eggs and larvae, and juveniles. The life cycle of the Atlantic sturgeon is 

reviewed in six intervals: non-spawning adults, female spawners, male spawners. eggs and larvae. early juveniles. 

and late juveniles. Both species are long-lived, mature at advanced age, have rapid and similar growth 

during the first few years of life, feed on generally similar taxa, use deep channel habitats for all life intervals, 

and have complex migratory patterns with distinct. seasonal, concentration areas. Atlantic and shortnose 

sturgeons differ, however, in ages and sizes at maturity, maximum size. timing and location of spawning, 

migratory behaviors, and management. Use of marine habitats and long-distance coastal migrations are restricted 

to Atlantic sturgeon, but some evidence indicates that large Atlantic sturgeon juveniles reside in 

riverine habitats along the Atlantic coast during warm months. Movements and habitat use by both sturgeons 

in the Hudson River estuary contrasts with the spatial segregation of the species reported in other river systems. 

Juvenile shortnose sturgeon and early juvenile Atlantic sturgeon have almost the same distributions in 

the Hudson River estuary during all seasons. During this period ofco-occurence both species are very similar 

in size, grow at about the same rate, feed on similar foods. and share deep, channel habitats. Adult shortnose 

sturgeon distribution overlaps with the distribution of juvenile Atlantic sturgeon, and the latter coninence 

river emigration at a size comparable to co-occurring adult shortnose sturgeon. Life history information 

on the Hudson River sturgeons substantiates the need to carefully conserve these species because of 

vulnerability to exploitation and habitat disruption. 

Introduction 

The Hudson River supports substantial populations 

of Atlantic sturgeon. Acipenser oxyrinchus 

and shortnose sturgeon, Acipenser brevirostrum. 

The Atlantic sturgeon is one of North America’s 

largest fishes, and an important commercial species 

in the Hudson River and Atlantic coast waters (species 

reviewed in Smith & Clugston 1997, this volume). 

In contrast, the shortnose sturgeon is the 

smallest species of Acipenser in North America. 

and a charter member (included in the original US

348 

Endangered Species Act, 1973) of the U. S. endan- species was assigned to the National Marine Fishergered 

species list (species reviewed in Kynard 1997 ies Service 4 . Dadswell (1979) provided the first 

this volume). 

thorough study of the life history of shortnose stur- 

Observations of sturgeon in the Hudson River geon, and a comparably detailed analysis of the 

date back to the earliest historical accounts of hu- biology of any Atlantic sturgeon population has not 

man settlement in the region. Both species were ve- been reported. Despite numerous and varied rery 

abundant, often captured for food, and easily ob- ports on the biology of both Hudson River sturserved 

by people during some part of the year. The geons, life history reviews within the last 10 years 

first scientific accounts of the Hudson River stur- have concluded that important life cycle attributes 

geons emerged from the New York State Biological remain poorly known or unknown (Gilbert 1989, 

Survey conducted in the mid-1930s (Curran & T.I.J. Smith 1985). In only one case (Saint John Riv- 

Ries 1 , Greeley 1937 2 , Towns 3 . These studies docu- er and estuary, New Brunswick, Canada) has abunmented 

some basic life history attributes such as dant populations of both species been studied 

distribution in the river. sizes and ages of mature (Dadswell 1979), and they were found to segregate 

fish. and diet. Almost no additional information on the basis of habitat, presumably to minimize 

was collected on the Hudson River sturgeons for 40 competition. 

years, but then in the 1970s major concerns emerged In this paper, I review the knowledge of Atlantic 

about the effect of electric generating stations on and shortnose sturgeon in the Hudson River estufish 

resources of the Hudson River (Barnthouse et ary by summarizing information from biologists goal. 

1984). William Dovel led extensive studies ing back to 1937. This summary is organized around 

(Dovel & Berggren 1983, Dovel et al. 1992) which distinct life intervals of each sturgeon in an effort to 

provide most of our current knowledge on the Hud- present a complete picture for both species. Finally, 

son River sturgeons. Electric utilities that operate the potential interactions between the two species 

power plants along the Hudson River initiated will be considered because the Hudson River has 

comprehensive environmental monitoring pro- sizable populations of both species, and some evigrams 

that continue today. Some biologists (Carl- dence (Dadswell 1979, Dadswell et al. 5 , Dovel et al. 

son & Simpson 1987, Geoghegan et al. 1992, Hoff et 1992) suggests that competition between them may 

al. 1988, Young et al. 1988) working with monitoring influence habitat use. 

program samples and data provided relatively re- Sturgeon are limited to the lower 246 km of the 

cent reports of sturgeon distributions and life histo- Hudson River (Figure 1) where habitats range from 

ry attributes. 

a typical freshwater river channel to a brackish wa- 

Understanding the complex life cycles of the stur- ter fjord (for physicochemical and morphological 

geons has challenged biologists for more than 50 reviews see Coch & Bokuniewiez 1986 and others in 

years. Until recently; the shortnose sturgeon was the same volume, Limburg et al. 1989, Smith 1992). 

believed to be an anadromous fish, and therefore This estuary system is nearly straight and oriented 

the responsibility for recovering this endangered in a north-south direction from the New York City 

harbor (southern tip of Manhattan Island; km 0 [km 

for river location in kilometers above mouth]) to 

the Troy Dam (Federal Green Island Dam; km 246 ) 

near Albany, New York. The normal tidal ampli- 

1 Curran, H.W. & D.T. Ries. 1937. Fisheries investigations in the 

lower Hudson River. pp. 124–145. In: A Biological Survey of the 

Lower Hudson Watershed, Supplement to the 26th Annual Report 

of the New York State Conservation Department, Albany. 

2 Greeley, J.R. 1937. Fishes of the area with annotated list. pp. 

45–103. In: A Biological Survey of the Lower Hudson Watershed. 

Supplement to the 24th Annual Report of the New York 

State Conservation Department, Albany 

3 

Townes. H.K., Jr. 1937. pp 217–230. In: A Biological Survey of 

the Lower Hudson Watershed. Supplement to the 26th Annual 

Report of the New York State Conservation Department Albany. 

4 

U.S. Federal Register- Vol. 39, No. 230, Pages 41367–41377; 27 

November 1974. 

5 Dadswell, M.J., B.D. Taubert. T.S. Squires, D. Marcette & J. 

Buckley 1984. Synopsis of biological data on the shortnose sturgeon. 

Acipenser brevirostrum LeSueur, 1818 NOA A Technical 

Report NMFS 14, National Marine Fisheries Service, Washington, 

D.C.

349 

Figure 1. Life intervals and seasonal distribution of shortnose sturgeon in the Hudson River estuary relative to river features, river 

distances upstream of upper New York City bay, and salinity. Fall and somtimes spring distibutions arc not shown because these seasons 

are transitional periods. Width of the distribution lines and symbols indicates relative density of individuals. 

tude ranges from 0.82 to 1.43 m causing a tidal volume 

(mean 5 670 - 8 500 m 3 s –1 depending on location) 

from 10 to 100 times river discharge (mean 623 

m 3 s –1 ; Limburg et al. 1989). The Hudson River 

channel is large (mean width 1280 m) and generally 

deep (mean depth 10 m), but lacking any significant 

gradient. However, channel morphology varies 

with sections averaging as much as 5.5 km wide and 

34 m deep (maximum depth = 53 m). Much of the 

river channel is shaped by rock with fine grain (e.g., 

sand and clay) sediments composing the substrate. 

The lower 100 kin of the Hudson River estuary is 

saline (> 0.1 ppt salt) during seasons of low freshwater 

discharge with salinity generally below 10 ppt. 

Shortnose sturgeon 

Shortnose sturgeon is best described as an amphidromous 

(defined in McDowall 1987, see also Bemis 

& Kynard 1997 this volume) species since use of 

marine waters is limited to the estuaries of their natal 

rivers (see Kynard 1997 this volume). On one occasion, 

shortnose sturgeon were reported in waters 

of coastal New Jersey adjacent to the mouth of the 

Hudson River (Dovel et al. 1992). Within the Hudson 

River Estuary. shortnose sturgeon display complex 

migratory behavior that has been inconsistently 

described in past investigations. The life history 

for Hudson River shortnose sturgeon will be reviewed 

in four intervals that vary in characteristics

350 

Figure 2. Shortnose sturgeon sizes and ages reported for the 

Hudson River from Dadswell et al. 5 using their compilation of 

unpublished data in modified form, and the total Iength of shortnose 

sturgeon aged by Dovel et al. (1992; open circles). The 

dashed line separates juvenile and adult life intervals at 55 cm 

total length or about 50 cm fork length. 

(Figure 1; also see the species review by Kynard 

1997 this volume). 

Non-spawning adult interval 

In many or all populations of shortnose sturgeon, 

adult fish do not spawn every year. Dadswell (1979) 

reported that females spawn every third to fifth 

year, and males every second year in the Saint John 

River, New Brunswick. This pattern may differ in 

the Hudson River because Dovel et al. (1992) reported 

the occurrence of tagged shortnose sturgeon 

at the spawning grounds in successive years. Nonspawning 

adults appear to use different habitats 

and display different migratory behavior than 

adults within a year of spawming. 

The maximum sizes reported (Dadswell et al. 5 ) 

for Hudson River shortnose sturgeon were a female 

weighing 7.2 kg (94.5 cm fork length [FL], 105 cm 

total length [TL]) and a male weighing 5.3 kg (89 cm 

FL, 99 cm TL). However, Dovel et al. (1992) documented 

an even larger but unsexed shortnose sturgeon 

from the Hudson River: 107 cm TL and 10.7 

kg. The age record for shortnose sturgeon is 67 

years with the oldest Hudson River specimen aged 

at 37 years (Dadswell et al. 5 ). Most shortnose sturgeon 

captured in the Hudson River estuary in research 

and monitoring programs (1983-1988) were 

adults ranging in size from about 4.5 to 80 cm TL 

(Geoghegan et al. 1992) or about 8 to 20 years of age 

(Figure 2). Pooled across the sexes, maturity criteria 

that can be used for the Hudson population of 

shortnose sturgcon would be 50 cm FL (Table 1) and 

about 6 years of age (sexes pooled, Figure 2). The 50 

cm FL criteria (55 cm TL) is useful for field handled 

Table 1. Ages and sizes of the life intervals of shortnose and Atlantic sturgeons in the Hudson River. Data reported are generalized 

because of minor variations in specific values reported in other studies (see text for discussion of specific data). 

Life interval Age range (yr) Fork length a (cm) Total length a (cm) 

Shortnose sturgeon 

Larva < 0.08 ≥ 2 

Male juveniles 0.08–≥ 3 ~ 2-50 2-55 

Female juveniles 0.08–≥ 6 ~ 2-50 2-55 

Male adults ≥ 3 > 50 > 55 

Female adults ≥ 6 > 50 > 55 

Atlantic sturgeon 

Larva < 0.08 ≤ 3 

Early juveniles 0.08-2 ~ 2-44 ~ 3-49 

Intermediate juveniles 3-6 45-63 50-70 

Late juveniles 6-11 > 63-134 > 70-149 

Non-spawning adults ≥ 12 ≥ 135 ≥150 

Female spawners ≥15 ≥180 ≥ 200 

Male spawners 12-20 ≥135-190 ≥ 150–210 

a 

Fork length and total length sizes were made to fit the conversion formulae reported by Dadswell et al. 5 for shortnose sturgeon: FL = 0.9 

× TL; TI = 1.1 × FL.

351 

Figure 3. Life intervals and seasonal distribution of Atlantic sturgeon in the Hudson River estuary relative to river features, river distances 

upstream of upper New York City bay, and salinity. Fall distributions are not shown because this season is transitional. Width of the 

distribution lines and symbols indicates relative density of individuals. Sea distributions includes long-distance migrations to waters 

outside the Hudson River estuary. 

fish because sex cannot be determined except at the 

time of spawning by observation of sperm or eggs. 

From late spring through early fall, adult shortnose 

sturgeon are distributed in deep, channel habitats 

of the freshwater and brackish reaches of the 

Hudson River estuary. River monitoring (1969- 

1980) of fish distributions by the Hudson River electric 

utilities (Hoff et al. 1988) recorded adult shortnose 

sturgeon from a large portion of the estuary 

(Figure 1): most captures occurred between km 38 

through 122, and no captures upstream of km 166. 

Later river monitoring (Geoghegan et al. 1992) 

showed a similar pattern. During this apparent 

growth and feeding period, the diet of shortnose 

sturgeon in the Hudson River likely includes insects 

and crustaceans with molluscs being a major component 

(25 to 50% of the diet; Curran & Ries 1 , 

Townes 3 ). 

As water temperature declines in the late fall, 

adult shortnose sturgeon typically concentrate in a 

few overwintering areas. Dovel et al. (1992) concluded 

that most or all adults form an overwinter 

concentration near Kingston (approximately km 

140). However, river monitoring in late fall indicates 

another concentration near Haverstraw (km 

54–61). Life history studies for some shortnose stur-

352 

behavior so I treat them as one life history interval 

(Figure 1). 

Growth rates for shortnose sturgeon vary by region 

and sex but all fish mature at approximately 

the same size throughout their range: 45–55 cm FL 

(50–60 cm TL) for males and females (Dadswell et 

al. 5 ). For the Hudson River population, Greeley 2 reported 

that males first spawn at 3 to 4 years of age 

(average 44.5 cm FL), and females first spawn at 6 

to 8 years of age (average 51.5 cm FL, Table 1). However, 

Dadswell (1979) concluded from fin ray inte - 

rannular increments that first spawning may follow 

maturation by 1 to 2 years in males and as much as 5 

years in females. Therefore, Greeley 2 may have 

overestimated the age at maturity. 

From late spring through early fall, all adult 

shortnose sturgeon have a dispersed distribution as 

described above for non-spawning adults. Adult 

shortnose sturgeon that will spawn the following 

spring congregate in an overwintering site near the 

Figure 4. Individual Atlantic sturgeon sizes and ages reported for spawning grounds. In the Hudson, a single large 

the Hudson River by Dovel & Berggren (1983; solid dots) and overwintering concentration of pre-spawning 

Van Eenennaam et al. (1996; open dots for females, + symbols for 

adults is well documented to form annually in deep, 

males). The circled points indicate individuals determined to be 

in spawning condition by Van Eenennaam et al. (1996). The archannel 

habitats a few kilometers downstream of 

row for late juveniles indicates a gap in the age and size series Sturgeon Point (km 139). Many fish were readily 

corresponding with an absence of fish from the Hudson River. captured at this site by Dovel et al. (1992), and it was 

known as a productive fishing area prior to protec - 

geon populations (Dadswell et al. 5 ) and observa - 

tions in the Hudson River (Geoghegan et al. 1992) 

indicate that non-spawning adults behave different - 

tion of the species. From information on other populations 

(Dadswell 1979), females at the overwin - 

tering site may not feed prior to spawning, but 

ly from adults entering reproductive condition. males do feed during this period. Food items are 

Adults that will not be in reproductive condition the 

following spring concentrate in brackish waters. In 

the Hudson, this overwintering area appears to be 

located between km 54 and 61 (Figure l). In the 

spring, these fish migrate upstream and disperse 

through the tidal portion of the river. 

probably similar to those reported above for nonspawning 

adults. In mid-April, adult fish move upstream 

to the spawning grounds extending from below 

the Federal Dam at Troy to about Coxsackie 

(km 239–190; Dovel et al. 1992, Hoff et al. 1988). 

Spawning occurs from late -April to early May. Afterward, 

the adults disperse downriver into the 

summer range. 

Spawning adult interval 

Shortnose sturgeon spawn once in spring, usually at 

a single location as far upriver as the population 

ranges. Pre-spawning adults overwinter in one large 

concentration widely separated from those adults 

that will not spawn the following spring. Females 

and males have the same migratory and habitat use 

Egg, embryo and larva interval 

Eggs of shortnose sturgeon adhere to solid objects 

on the river bottom, and newly hatched embryos remain 

on the bottom (Buckley & Kynard 1981,Taubert 

1980). Hatching size ranges from 7 to 11 mm TL

353 

(Buckley & Kynard 1981, Taubert 1980), with Hudson 

River embryos ranging in size from 15 to 18 mm 

TL at 10 to 15 days of age (Pekovitch 6 ). After hatching. 

embryos gradually disperse downstream over 

much of the Hudson River estuary (Hoff el al. 

1988). Shortnose sturgeon larvae captured in the 

Hudson River were associated with deep waters 

and strong currents (Pekovitch 6 , Hoff et al. 1988). 

At 20 mm TL. shortnose sturgeon in the Hudson 

River had fully developed external characteristics 

indicating a transition to the juvenile interval (Pekovitch 

6 ; Table 1). No further information is available 

on this interval of the shortnose sturgeon life 

cycle. 

Juvenile in terva l 

Juvenile shortnose sturgeon (2–55 cm TL; Table 1), 

use a large portion of the tidal reach of the Hudson 

River. Dovel et al. (1992) indicated that yearling juvenile 

sturgeon grow rapidly (to 30 cm TL in first 

year, Figure 2) and disperse downriver to about km 

55 by fall. Juveniles have been captured in the same 

deep channel habitats used by adults. During midsummer 

the juvenile distribution centers on the 

mid-river region (Geoghegan et al. 1992). By late 

fall and early winter, most juveniles occupy the 

broad region of the Hudson River near Haverstraw 

(kin 55–63: Dovel et al. 1992, Geoghegan et al. 

1992). However, there is no evidence that juveniles 

move out of the lower river into coastal marine waters. 

Juvenile shortnose sturgeon feed on smaller and 

somewhat different organisms than do adults (Carlson 

& Simpson 1987). Common prey items are aquatic 

insects (chironomids), isopods, and amphipods. 

Unlike adults, molluscs do not appear to be an 

important part of their diet (Dadswell 1979). 

6 Pekovitch, A.W. 1979. Distribution and some life history aspects 

of the shortnose sturgeon (Acipenser brevirostrum). Hazleton 

Environmental Sciences Corp., Northbrook. 23 pp. 

Atlantic sturgeon 

Atlantic sturgeon are anadromous. Spawning occurs 

in freshwater, but male and female fish reside 

for many years in marine waters. Atlantic sturgeon 

undertake long-distance migrations along the Atlantic 

coast. Atlantic sturgeon marked in the Hudson 

River by Dovel & Berggren (1983) were recaptured 

in marine waters and river mouths from just 

south of Cape Hatteras, North Carolina to just 

north of Cape Cod, Massachusetts. In addition to 

these marine movements. Atlantic sturgeon display 

complex migratory behavior within the Hudson 

River. Here, I review the life cycle for Atlantic sturgeon 

in the Hudson River in six intervals that vary 

by habitat, migratory behavior, and size (Figure 3). 

Also see Smith & Clugston (1997 this volume) for a 

general review of Atlantic sturgeon life history and 

fishery. 

Nun-spawning adult interval 

The inter-spawning period for Atlantic sturgeon is 

thought to range from 3 to 5 years depending on sex 

(discussed below). During non-spawning years. 

adults use marine waters either all year or seasonally. 

Little is known about their behavior in marine 

waters except that adult-size fish ( ≥ 150 cm TL, Table 

l) marked in the Hudson River have been recaptured 

in coastal waters and river mouths from North 

Carolina to Massachusetts. The largest commercial 

harvest of adult Atlantic sturgeon from the Hudson 

River population occurs in marine waters throughout 

the New York Bight (Waldman et al. 1996). Female 

Atlantic sturgeon apparently grow in marine 

waters, whereas males appear to grow little after 

maturity (Figure 4). In marine habitats, Atlantic 

sturgeon eat amphipods, isopods, shrimps, molluses, 

and fish (Scott & Crossman 1973). 

The maximum age for the species is 30 years 

(Scott & Crossman 1973) with a similar estimate for 

the Hudson River (T.I.J. Smith 1985). The largest 

known Atlantic sturgeon was a female 427 cm TL, 

and 368 kg (Saint John River, New Brunswick; Van

354 

Den Avyle 7 ). Large Atlantic sturgeon are likely to 

be females because of marked sexual dimorphism 

(Figure4). 

stream ofa spawning site to accommodate dispersal 

of embryos and larvae. 

Male spawning interval 

Female spawning interval 

Mature, male Atlantic sturgeon enter the Hudson 

Adult female Atlantic sturgeon differ sharply from River starting in April and at least some remain in 

adult males in size, growth, migratory behavior, and the Hudson River as late as November (Dovel & 

age structure (Figure 3). Spawning female sturgeon Berggren 1983). Spawning males are 12 or more 

are age 15 or older, weigh more than 34 kg, and are years old and from 150 to 210 cm TL (Van Eenengreater 

than 200 cm TL (Van Eenennaam et al. naam et al. 1996. Table 1). Van Den Avyle 7 reported 

1996, Table 1). Dovel & Berggren (1953) reported a that the maximum size lor males is 213 cm TL which 

slightly older age at first spawning (18 years) but the is similar to the sizes recorded in the Hudson River 

same minimum size. Age and growth data (Van Ee- spawning stock (Figure 4). No spawning males over 

nennaam et al. 1996) clearly indicate steady growth 20 years old have been recorded in the Hudson Rivin 

females (Figure 4) and data from Dovel & Berg- er. Male Atlantic sturgeon may not spawn annually, 

gren (1983) are consistent with this pattern. 

and the period between spawnings has been esti- 

Adult females enter the Hudson River Estuary mated to range from 1 to 5 years (T.T.J. Smith 1985). 

for spawning beginning in mid-May. They migrate From limited sturgeon telemetry by Dovel & 

directly to the spawning grounds which are deep, Berggren (1983), males appear to move upstream 

channel or off-channel habitats (Dovel & Berggren on incoming tides and then remain stationary for 

1983). The female sturgeon return to marine waters several hours. During their upstream migration, 

quickly after spawning (C.L. Smith 1985). The male sturgeon meander back and forth across the 

spawning period ranges from May through July or channel, but stay in water greater than 7.6 m deep. 

possibly August in the Hudson River estuary Van Eenennaam et al. (1996) observed that adult 

(Dovel & Berggren 1983, Van Eenennaam et al. male sturgeon appear at spawning sites in associ- 

1996). Female sturgeondo not appearto feed on the ation with females, indicating that they search for 

spawning run in freshwater (T. I. J. Smith 1985). females while moving about in the river. 

Dovel & Berggren (1983) report that spawning 

occurs near the salt wedge (km 55) early in the season 

(late May), moving upstream to km 136 during Egg, embryo and larva interval 

June and early July. However, Van Eenennaam et 

al. (1996) collected spawning Atlantic sturgeon only 

at two historically important fishing sites known to 

be spawning areas (Figure 3): near Hyde Park (km 

130) and Catskill (km 182). Van Eenennaam et al. 

(1996) argue that spawning is unlikely to occur near 

brackish water because sturgeon eggs, embryos and 

larvae are intolerant of saline conditions, and some 

significant length of river habitat is needed down- 

7 

Van Den Avyle, M.J. 1984. Species profiles: life histories and 

environmental requirements of coastal fishes and invertebrates 

(South Atlantic) – Atlantic sturgeon. U.S. Fish and Wildlife Service 

FWS/OBS-82/11.25. Washington. D.C. 17 pp. 

Eggs of Atlantic sturgeon are adhesive and the embryos 

remain on the bottom in deep channel habitats. 

Atlantic sturgeon embryos have been recorded 

in the Hudson River from km 60 through 148 

(Dovel & Berggren 1983); a range including some 

brackish waters. Sturgeon embryos and larvae have 

limited salt tolerance, so their habitat must be well 

upstream of the salt front (Van Eenennaam et al. 

1996: as illustrated in Figure 3). No furtherinformation 

is available on this interval of the Atlantic sturgeon 

life cycle. 

Atlantic sturgeon embryos are about 7 mm TL at 

hatching, and in hatcheries, they reached 19.9 mm 

TL in 20 days (Smith et al. 1980). The transition

355 

from larva to juveniles appears to occur at about 30 

mm TL (Table 1)based onHudson River specimens 

(Bath et al. 1981). 

Juvenile riverine interval 

The juvenile period ofthe Atlantic sturgeon life cycle 

is marked by major ecological changes, and it 

can be divided into two life history intervals: early 

and latejuvenile (Figure 3). The precise division between 

these intervals is unclear because changes 

are gradual, although growth is very rapid (Figure 

4). Consequently, I added a third intermediate interval 

for age and growth statistics shown in Table 1. 

The first juvenile interval is limited to riverine habitats. 

Relatively good information is available for 

this interval due to research in the Hudson River 

estuary. 

Juvenile Atlantic sturgeon are well distributed 

over much of the Hudson River from July through 

September, and they use deep channel habitats as in 

other life intervals (Figure 3). The largest numbers 

ofjuveniles appear to be located from km 63 to 140 

(Dovel & Berggren 1983). As water temperature 

drops below 20° C in the fall, juveniles form an 

overwintering distribution in brackish water between 

km 19 to 74 (Dovel & Berggren 1983). From 

October through June, this region of the Hudson 

River contains many juveniles and they appear to 

move little during the period. Upstream dispersion 

ofjuveniles begins in late spring. Some juvenile Atlantic 

sturgeon have been recorded in the overwintering 

area used by pre-spawning, adult shortnose 

sturgeon (Esopus Meadows, km 134) as early as 

mid-April which indicates some variation in the 

general migration pattern. 

Juvenile Atlantic sturgeon grow quickly in the 

first three years oflife (70 cm TL at age 3, Figure 3) 

but growth slows considerably if they remain in the 

Hudson River estuary (Dovel & Berggren 1983). 

Riverine juveniles feed on aquatic insects, amphipods, 

isopods, and small molluscs (Scott & Crossman1973). 

Juvenile marine interval 

After 2 to 6 years of residence in the Hudson River, 

juvenile Atlantic sturgeon migrate to marine waters. 

Dovel & Berggren (1983) reported that some 

males leave the river in year 2, while females may 

stay in the river until year 5 or 6. This migration to 

marine waters marks a major change in ecology, behavior, 

and growth for Atlantic sturgeon. Table l 

shows approximate ages and sizes for early (riverine) 

juveniles, late (sea migrant) juveniles, and intermediate 

juveniles because the later includes the 

group that gradually emigrates from the river during 

a period ofrapid growth. After about 10 years at 

sea, juvenile sturgeon reach adult size (about 150 

cm TL, Table 1 for sexes pooled). 

Little is known aboutAtlantic sturgeon in marine 

waters except that large juveniles are often captured 

in Long Island Sound and off the Long Island 

and New Jersey coasts in commercial fishing gear. 

Reviews of Atlantic sturgeon life history (e.g., Van 

Den Avyle 7 ) and information specific to the Hudson 

River estuary (Dovel & Berggren 1983, C.L. 

Smith 1985) describe post-emmigrationjuveniles as 

inhabitants ofmarine waters. However, large juveniles 

(50–150 cm TL) may reside in riverine habitats 

along the Atlantic coast during warm months. Atlantic 

sturgeon sampling in the Hudson River has 

documented the occurrence of large juveniles 

(sometimes called pre-adults; Dovel & Berggren 

1983, Van Eenennaam et al. 1996). DataofDovel & 

Berggren (1983) on tag recaptures show that most 

fish were reported from river mouths and the lower 

sections of coastal rivers from Cape Cod to Chesapeake 

Bay. Murawski & Pacheco 8 described a similar 

pattern for tagging and recaptures in the St. 

Lawrence River, Quebec. Late juvenile Atlantic 

sturgeon often enter and reside in rivers that lack 

active spawning sites (e.g. Merrimack River, Massachusetts: 

Kieffer & Kynard 1993). Most Atlantic 

sturgeon in rivers of the central US Atlantic coast 

are probably from the Hudson River population 

8 

Murawski, SA. & A.L. Pacheco. 1977. Biological and fisheries 

data on Atlantic sturgeon, Acipenser oxyrhynchus (Mitchell). 

National Marine Fisheries Service Technical Series 10, Highlands. 

69 pp.

356 

(Waldman et al. 1996). Consequently, late juvenile 

Atlantic sturgeon from the Hudson River may annually 

use other riverine habitats during warm 

months before returning to the Hudson for spawning. 

Discussion 

first few years of life. In general, sturgeon are characterized 

as indiscriminate bottom-reeding carnivores, 

and specific information on diet indicates 

they feed on generally the same food items in the 

Hudson River. Both sturgeon have complex migratory 

patterns in the Hudson River with distinct, seasonal. 

and predictable concentration areas. Finally, 

both sturgeons primarily use deep channel habitats 

for all life intervals. 

Despite many similarities in life history. Atlantic 

and shortnose sturgeons differ in some obvious 

ways. Adult sizes are greatly different, and the sizes 

Sturgeon (family Acipenseridae) are the modern 

descendants of the original ray-finned fish that 

achieved greatest abundance and diversity 280 to 

345 million years ago. Atlantic, shortnose, and all and ages at maturity diverge. The timing and locaother 

sturgeon retain many ancestral body charac- tion of spawning is so diffrent that it appears imteristics 

and ways of living that distinguish them as possible that the two species behaviorally interact 

relict fishes (see Bemis et al. 1997 this volume). during this key life interval. Use of marine habitats 

Among North American fishes, sturgeons exhibit a and long-distance coastal migrations are restricted 

unique combination of life history attributes: ad- to Atlantic sturgeon. With respect to management, 

vanced age and large size at maturity, eggs that are one species is heavily exploited while the other is 

numerous and small in relation to body size, and fully protected under the US Endangered Species 

spawning that is episodic and seasonal (Winemiller Act. 

& Rose 1992). Beyond being unique, these charac- Widespread occurrence of Atlantic and shortteristics 

make sturgeon especially vulnerable to nose sturgeons in many Atlantic Coast rivers of 

population collapse due to overfishing (Boreman North America raises questions as to how two spe- 

1997 this volume). Life history information on the cies can co-exist with so many shared life history at- 

Hudson River sturgeons fits these generalizations tributes. The prevailing view (e.g., Dadswell et al. 5 , 

and it substantiates the need to carefully conserve Dovel et al. 1992, Kieffer & Kynard 1993) has been 

thesespecies. In addition,life history details such as that the two species are spatially segregated in rivseasonal 

areas of concentration, migration times ers in association with salinity; with shortnose sturand 

routes, and specific spawning locations high- geon oriented to freshwater, and Atlantic sturgeon 

light the vulnerability of both shortnose and Atlan- concentrated in brackish water except at spawning 

tic sturgeon to easy exploitation and habitat disrup- and very early life. However, a review of the movetion. 

Fortunately, in the case of the Hudson River ments and habitat use ofboth species in the Hudson 

estuary, key habitats for spawning, rearing, and River estuary conflicts with these interpretations. 

overwintering are intact and suitable for the spe- Juvenile shortnose sturgeon and early juvenile 

cies. Also, both species of sturgeon are managed Atlantic sturgeon have virtually identical distributhrough 

either endangered species protection tions in the Hudson River estuary during all sea- 

(shortnose sturgeon; US Endangered Species Act) sons. During this period ofco-occurrence, both speor 

fishery restrictions (Smith & Clugston 1997 this cies are very similar in size, grow at about the same 

volume), even though the latter may not be ade- rate, feed on similar foods: and share deep channel 

quate to sustain the current population (Young et habitats. Furthermore, the distribution of adult 

al. 1988, Boreman 1997 this volume). 

shortnose sturgeon overlaps with that of juvenile 

The two sturgeons in the Hudson River share Atlantic sturgeon. Interestingly, the period of river 

many common life history attributes. Both are long- emigration of juvenile Atlantic sturgeon closely 

lived and mature at advanced age compared to al corresponds with the age (intermediatejuveniles in 

most all other fishes in the Hudson River. Both spe- Table 1) when they reach a size (ca. 55 cm TL) equal 

cies have rapid and similar growth rates during the to the minimum adult size of shortnose sturgeon.

357 

The protracted period of Atlantic sturgeon emigration 

(4 years) indicates that the two species overlap 

considerably in space, rood, and habitat. Also, the 

pattern of emigration in conjunction with comparability 

in size and habits between the species suggests 

that co-exploitation of space and food resources 

may be important in the migratory behavior of juvenile 

Atlantic sturgeon. 

The apparently extensive co-occurrence of the 

two sturgeons in the Hudson River estuary has not 

been clearly identified in previous investigations on 

the Hudson River. Although sturgeon biologists 

working on the Hudson River undoubtedly captured 

both species simultaneously in their work, 

analyses and reports have always been oriented to a 

single-species. This review is the First to simultanegeons 

in the Hudson River. The conclusion that the 

ously report details of the life history of both sturtwo 

specics are not spatially segregated for large 

parts of their life histories indicates that the Hudson 

River estuary may be unique within the joint ranges 

of the two species. 


I thank William E. Bemisfor his strong encouragement 

and confidence that motivated the writing of 

this paper. I also thank Vadim J. Birstein, Robert H. 

Boyle, and John Waldman for organizing the International 


Conservation, where a first version of this paper 

was presented. William E . Bemis, VadimJ. Birstein, 

and John Waldman deserve much credit for working 

with the authors and papers included in this volume. 

This work is a contribution from research 

sponsored by the Hudson River Foundation with 

supplemental support provided by the U. S. Army 

Corps of Engineers. Jeremy Knight, John Waldman, 

Andy Kahnle, Steve Nack, and Nancy Haley 

reviewed an early version of the manuscript, and 

provided constructive comments and suggestions 

for improvement. 


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W. Van Winkle & D.S. Vaughan. 1984. Population biology in 

the courtroom: the Hudson River controversy. BioScience 34: 

14–19. 

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Developtment and idenfication of larval Atlantic sturgeon 

(Acipenser oxyrhynchus) and shortnose sturgeon (A. brevirostrum) 

from the Hudson River estuary. Copeia 1981: 711– 

717. 

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Buckley, J. & B. Kynard 1981. spawning and rearing of shortnose 

sturgeon from the Connecticut River. Prog. Fish-Cult. 43: 74– 

76. 

Carlson, D.M. & K.W. Simpson. 1987. Gut contents of juvenile 

shortnose sturgeon in the upper Hudson estuary Copeia 1987: 

706–802. 

Coch, N.K. & H.J. Bokuniewiez 1986. Ocenographic and geologie 

framework of the Hudson system. Northeastern Geol. 

8: 96–108. 


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(Osteichthyes: Acipenseridae), in the Saint John River estuary 

New Brunswick, Canada. Can. J. Zool. 57: 2186–2210. 

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Estuary. New York. New York Fish and Game J. 30: 140– 

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the shortnose sturgeon (Acipenser brevirostrum Lesecur, 1818) 

in the Hudson River estuary. New York pp. 187-216. In: C. L. 

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of the shortnose sturgeon in the Hudson River estuary, 1984- 

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the 1980s, State Univ. New York Press, Albany. 

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biology of shortnose sturgeon in the Hudson River estuary. pp. 

171–189.In:C.L.Smith (ed.)FisheriesResearchintheHudson 

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and Atlantic sturgeons in the Merrimack River, Massachuselts, 

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the shortnose sturgeon, Acipenser brevirostrum Env. Biol. 


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Symposium, Can. Spec. Publ. Fish. Aquat. Sci. 106. 

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spawning and culture ofthe Atlantic sturgeon, Acipenser oxyrhynchus(Mitchell).Prog.Fish-Cult. 

42:147–151. 

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brevirostrum) in Holyoke Pool, Connecticut River, Massachusetts. 

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recommendations for a Hudson River Atlantic sturgeon fishery 

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Environmental Biology of fishes 48: 359–370. 1997. 


Biological characteristics of European Atlantic sturgeon, Acipenser sturio, 

as the basis for a restoration program in France 

Patrick Williot, Eric Rochard, Gérard Castelnaud, Thierry Rouault, Rémy Brun, Mario Lepage & Pierre Elie 

Cemagref, Division Aquaculture et Pêche, BP 3, 33612 Cestas, France 


Key words: population structure, artificial reproduction, wild juvenile farming, endangered species 

Synopsis 

The European Atlantic Sturgeon, Acipenser sturio, has received increased attention in France because of 

population declines due to overfishing and deterioration of spawning grounds. Conservation of this species 

requires many actions, including publicizing the necessity to protect this fish and its habitats, investigations on 

catches and probable spawning grounds, and on artificial reproduction, which is still in an experimental stage. 

During its sea life, European Atlantic sturgeon occur from the Bay of Biscay to the Bristol Channel and North 

Sea. Presently, the number ofyoung fish in the Gironde Estuary during summertime is low and the population 

has a unimodal age structure. At the time this paper was written, the last recorded reproduction of sturgeon in 

the Gironde system occurred in 1988 (new evidence of reproduction was discovered in 1995). Growth of young 

fish from the 1988 cohort was faster thanthat previously determined for others cohorts. Overourstudy period 

(1980-1994), the availability of wild broodfish declined. Successful artificial reproduction of wild-caught females 

requires an optimal physiological state; any delay decreases their reproductive potential. Acclimatiza 

tion of wild-caught juveniles to fresh water was most successful when fish were transported and held upon 

arrival in low salinity water. For such wild-caught juveniles, the first food intake usually occurs several months 

after capture, but remains irregular. These findings will be used to improve ongoing efforts to restore A . sturio. 

Introduction 

France (Magnin 1962), Portugal and Spain (Classen 

1944, Gutierrez Rodriguez 1962), in the Adriatic 

The European Atlantic sturgeon, Acipenser sturio 

∨ 

Sea (Holcík et al. 1989) and in the Black Sea (Antiis 

a species distinct from the North American At- pa 1934, Ninua 1976). Populations have since delantic 

sturgeon, A. oxyrinchus, although many bi- clined along the Iberian Peninsula (Almaea 1988, 

ological features are similar (see Birstein & Bemis Elviraet al. 1991, Elvira& Almodovar1993),France 

1997 this volume). Since the middle ofthe 19th cen- (Castelnaud et al. 1991), and the Romanian course 

tury, populations of A . sturio have been declining, of the Danube River (Bacalbaca-Dobrovici 1991, 

the decline occurring faster in the northern part of 1997 this volume). At present, we know of only two 

their overall distribution area (Roule 1922, Berg relict populations: one inhabits the Gironde and its 

∨ 

1948, Magnin l959b, Kinzelbach 1987,Holcík et al. tributaries, the Garonne and Dordogne rivers in 

1989, Maitland & Lyle 1990, Debus 1995). In the France; the other occurs in the Rioni River basin 

middle of the twentieth century, European Atlantic (Black Sea) in Georgia (former USSR). 

sturgeon existed along the southwest coast of In France, A . sturio is considered endangered

360 

Figure 1. Life history of A. sturio in the Gironde Estuary system. Major points in the life history are numbered. Modified from Anonymous(1995). 

(Lepage & Rochard 1995). In the past, it was fished 

for its flesh (Benecke 1986), mainly in the southwest 

region of the country (Laporte 1853, Roule 1922). 

Sturgeon were exploited in the Garonne and Dordogne 

rivers, in the Gironde Estuary, and adjacent 

continental shelf waters (Letaconnoux 1961). Caviar 

fishing occurred from 1920 to 1970 (Castelnaud et al. 

1991). Demand for caviar increased fishing pressure 

on adults while thejuveniles continued to be exploited 

for flesh. Increased fishing effort, combined with 

the impact of dams and gravel extraction which limit 

the reproduction by decreasing the availability of 

spawning grounds (Trouvery et al. 1984, Rochard et 

al. 1990), resulted in decline of the species.

361 

By the early 1970s, A. sturio was no longer an economically 

important resource and it became clear 

that its survival would require a long term program 

encompassing protection ofboth the species and its 

habitats, improvement of biological and ecological 

knowledge, and probably, restocking. It was shown 

in the former USSR (Barannikova 1987, Khodorevskaya 

et al. 1997 this volume) that restocking not 

only improved sturgeon catches in the Caspian and 

Azov seas, but also saved the beluga, Huso huso, 

population in the Caspian Sea from extinction. 

Most individuals of H. huso in the Caspian Sea are 

now of hatchery origin. 

We started our investigations on the wild A. sturio 

in the Gironde system during the late 1970s. Basic 

life history information on this population is 

summarized in Figure 1. In the early 1980s, we performed 

studies of artificial reproduction on Siberian 

sturgeon, A. baerii, using it as a biological model 

to avoid additional impact on indigenous populations 

of A. sturio. The availability during the 1980s 

of Siberian sturgeon also allowed us to initiate studies 

on nutrition and on methods of early sex determination. 

This paper presents information on A. sturio including 

the status of wild populations, characteristics 

of available broodfish, results of experiments 

on artificial breeding and rearing of larvae, and adaptation 

of juveniles to farm conditions. We also 

present the main directions of our proposed restoration 

program. 


Capture-mark-recapture 

Our tagging program focusing on large juveniles, 

which enter the lower Gironde Estuary for summer 

feeding (Magnin 1962), started in 1981. Fishing operations 

are conducted with the collaboration of local 

fishermen using drifting trammel nets. Fishermen 

are compensated on the basis of the mean expected 

loss of income. The fish are measured, 

weighed, and tagged (Petersen disc) to delineate 

the distribution and migration pattern of this population 

(Trouvery et al. 1984). In 1985, we modified 

tagging experiments in order to assess (using the 

Jolly-Seber method) the size of the stock which enters 

the Gironde Estuary in summer (Rochard 

1992). We used a specially designed tie-on tagmade 

of a stainless steel wire with a vinyl tube marker 

(Hallprint Pty. Ltd.) placed through the muscle anterior 

to the dorsal fin (Castelnaud 1988). Trawling 

has been performed since 1986 to enhance oursampling 

effort (Castelnaud et al. 1991). 

Age determination 

We modified (Rochard & Jatteau 1991) the aging 

method for sturgeon (Classen 1944, Cuerrier 1951, 

Magnin 1959a) to avoid additional mortality on this 

endangered species as already reported by Kohlhorst 

(1979). Only a small piece of the first ray of a 

pectoral fin was used (Cochnauer et al. 1985). We 

used the Walford graph and the Von Bertalanffy 

growth function (Rochard & Jatteau 1991) to establish 

seasonal age-growth relationship (Rochard 

1992). 

Location of spawning grounds 

We established an inventory of potential spawning 

grounds in the lower part of the Garonne and Dordogne 

rivers (Trouvery 1980) using echo sounding 

equipment and information obtained from experienced 

fishermen. 

Artificial reproduction 

Eachyear before the expected spawning migration, 

we asked fishermen (via the local newspaper) to 

contact Cemagref in case of accidental catches of A. 

sturio during the lamprey and shad fishing season. 

The only way we can obtain wild broodfish is to pay 

a high price for them (despite the fact that sturgeon 

fishing is illegal). Fish were transported carefully to 

the hatchery for measurement (total length, TL and 

body weight, W) and immediate determination of 

sex, as most do not exhibit external characteristics 

of gender. Abdominal massage may lead to sperm

362 

Figure 2. Map of the distribution of captures of A . sturio in the eastern Atlantic and North Sea. 

emission from males. In the other cases, we checked 

the gonads by making a small abdominal cut. We 

determined the reproductive potential of females 

by examining three characteristics of the eggs: their 

mean largest size (n = 15); their polarization index 

(PI), defined as the ratio of the distance separating 

the germinal vesicle from the animal pole to the 

largest dimension ofthe egg (Kazanskii et al. 1978); 

and the in vitro maturation competence ofeggs (observation 

of germinalvesicle break down: GVBD; n 

= 30), according to the method described for A. baerii 

(Williot et al. 1991) and also used on white sturgeonA 

. transmontanus (Lutes et al. 1987). We characterized 

males as immature (do not yield any 

sperm, even by stripping), running (sperm is running 

naturally), and non-motile sperm (running but 

spermatozoa do not move in water). 

To induce spawning, we injected fish with carp 

hypophysis powder at a rate of 5 mg kg –1 and 2 mg 

kg –1 of body weight for the females and males, respectively. 

Sperm was removed from the males by 

massage and ova were collected by laparotomy (approximately 

5 cm long) near and above the genital 

opening. The abdominal cut was sewn up with four 

cross stitches. Processes usedforinsemination, neutralization 

of the sticky egg envelope, and incubation 

methods, were the same as those used for A. 

baerii (Williot et al. 1991). During all of the above

363 

Figure 3. Accidental captures of A. sturio between 1987 and 1993, 

showing numbers of tagged versus non-taggsd individuals reported. 

Communication with the public 

We printed and distributed booklets and posters 

about A. sturio to fishermen of the Atlantic coast of 

France. We mailed more specific materials to all 

French fisheries administrators, organizations of 

fishermen, and to French and western European 

fish research laboratories. We organized local 

meetings to explain our goals and previous results, 

and established an information network. To in- 

crease public awareness, we collaborated with the 

media (local, regional, and national newspapers; radio 

and television). To roster scientific cooperation, 

we organized the first international symposium on 

stated operations. the water temperature was sturgeon, held in Bordeaux in 1989 (Williot 1991). 

~ 17°C. 

Rearing of larvae 

Larvae were fed mainly with live nauplii of Artemia 

salina and other zooplankton or frozen natural Cood 

(chironomid larvae or Tubifex sp.) alone or mixed 

with chicken egg yolk, beef spleen, and an experimental 

artificial diet made of beef liver and yeast 

(Kaushik et al. 1986). Water temperature for rearing 

was approximately 17°C. 


Current status of the population 

Adoptation of wild immature fish to farm conditions 

We first tested direct adaptation of large juveniles 

fish from brackish (15 to 20‰) to fresh water. The 

analysis of published data (Magnin 1962) and use of 

the updated growth information (Rochard & Jatteau 

1991) imply a possible successful adaptation of 

sturgeon ≥ 105 cm TL to freshwater. Our experiments 

used riverine or well water at a constant tenperature 

of 18° C. Methods for long term acclimatization 

of wild immature European Atlantic sturgeon 

to farm conditions were based on previous 

success with other sturgeon species, A. naccarii 

(Arlati et al. 1988), A. transmontanus (Struffenegger 

1992), and H. huso (Goncharov personal coinmunication). 

Figure 1 summarizes background information 

necessary to understand the Gironde population of 

Acipenser sturio, which has currently the only 

known spawning stock of this species in western Europe. 

During its sea life, A. sturio occurs over a wide 

range (Figure 2), from the Bay of Biscay to the Briss 

e 

+ 

E 

Figure 4. Changes in the age structure of juvenile A. sturio in the 

Gironde Estuary between 1985 and 1992. Juvenile European Atlantic 

sturgeon move from the sea into the estuary (April-September).

364 

tol Channel and North Sea (Castelnaud et al. 1991). 

It inhabits shallow littoral areas, with 83% of catches 

occurring between 10 and 70 m depth. From 1988 

to present, the number of accidental catches on the 

continental shelf area has decreased progressively 

(Figure 3). 

Declarations of accidental captures of A. sturio 

increased after our public awareness campaign, so 

public awareness is essential for the success of our 

restoration program. More tagged fish than untagged 

fish were reported among accidental captures 

at sea (Figure 3). Perhaps fishermen informed 

us and released the fish more often when a fish was 

tagged. Curiously, tags used for scientific purposes, 

which sometimes increase mortality due to tag injuries 

or other effects: may in this case actually prevent 

some mortality. 

The population (1984–1988) in the Gironde Estuary 

had a low number (500–2000 individuals) of 

young fish (3–8years) during the summer (Castelnaud 

et al. 1991, Rochard 1992). During our study 

period (1987–1994), the last recordednatural reproduction 

(as evidenced by winter catches of small 

fish approximately 25.0 cm TL) likely occurred in 

summer 1988. 1 

The structure ofthe stock that enters the Gironde 

during the summer has changed over time (Figure 

4). Before 1990. we observed a typically polymodal 

structure (Castelnaud et al. 1991) as a result of yearly 

reproduction. After 1990, the structure of the 

stock presented only one mode, corresponding to 

the 1988 cohort. No sign of pathology has been detected. 

The age 0–5 year growth of the 1988 cohort 

was significantly faster (Rochard & Jatteau 1991, 

Rochard 1992) than that determined previously by 

Magnin (1962) when the stock was far larger. The 

difference is not attributable only to methodological 

differences between studies (Rochard 1992) but 

may be a density dependent effect (Therrien et al. 

1988). 

Thanks to the sex determination methods of 

Cuisset (1993, developed originallyforA . baerii)we 

shall be able to obtain data on the sex ration of A. 

1 In the spring of 1995, Gemagref reported the first evidence of 

natural reproduction in 1994 of European Atlantic sturgeon in 

the Gironde since 1988 (editors note, March 1996). 

sturio by measuring plasma concentrations of 11-ketotestosterone 

or vitellogenin. 

Habitats 

No new physical obstacles to spawning migration 

have been erected since the construction of the 

darns of Bergerac on the Dordogne River in 1851 

and of Golfech near Agen on the Garonne River in 

1971 (Figure 1). In 1981, gravelextractionstoppedin 

the Dordogne River: only one site is still exploited 

in the lower part of the Garonne River (Rochard et 

al. 1990). Cadmium (mainly dissolved) in the Gironde 

Estuary is at concentrations 10 to 20 times 

higher than those measured in other French Atlantic 

estuaries (Maurice 1994). This heavy metal 

comes from old mines in the upper part of the Garonne 

River basin, which stopped working in the 

early 1970s. 

Exploitation 

Acipenser sturio has been protected in France since 

1982: fishing, transport, and commerce are strictly 

forbidden. Nevertheless, some sturgeon are caught 

in the near continental shelf and in the mouth of 

some estuaries as by-catch of sole and other bottom 

fishes. At present, this is the main direct anthropogenic 

impact on this stock. 

Status of wild spawners 

Of 40 catches of wild sturgeon, 75% were males and 

25% females. Most of them (90%) were caught before 

1989, and the last female was caught in 1987. 

This sex ratio is exactly the opposite (74%F – 

24%M) of that reported by Magnin (1962) for a 5 

year sampling period in the Gironde (n = 96) and by 

Elvira et al. (1991) for captures in the Guadalquivir 

River (Southwestern Spain) from 1932–1943. The 

latter study indicated that the skewed sex ratio was 

an artefact of selectivity of the nets, which could althe 

Gironde basin from mid-April to the end 

so be true in our study. Ripe broodfish occurred in 

of

365 

Table 1. Results of attempts to spawn wild caught females of Acipenser sturio (1981–1994). 

I981 

1983 

1984 

I985 

I986 

1987 

1988 

The only female ovulated, but due to over-maturation, the quality of eggs was poor. Nearly 700 embryos hatched, but only ten 

survived the first month of rearing after which rearing was discontinued. 

The two females did not ovulate, probably because of under-maturation 

The PI of eggs of the only captured females did not decrease by 6 days after stocking; the eggs became softer and more delicate 

as probable expression of damage. Became male A. sturio were not available simultaneously we attempted hybridization of A. 

sturio with Siberian sturgeon A. baerii, but ovulation and spermiation were poor, and only a few abnormal embryos hatched 

and died quickly. 

The two females ovulated perfectly, and the fertilization rate was close to 80% in both cases; incubation lasted 4.6 days and 

mean hatching success was 80%, but all free embryos died. 

The first female was weak and lacked the ability to reproduce (GVBD = 0). It died 2 days later and autopsy showed fatty 

gonads. a sign of under-maturation. A second female, caught very late, had already spawned. 

The reproductive potential ofthe only female was low (GVBD = 9%) without any change in one week. Hormonal stimulation 

at a rate of 0.6 mg kg–1( 12% of the normal dose used for reproduction) increased the sensitivity of eggs (GVBD = 63%), but at 

too a low level to expect successful reproduction (Williot et al. 1991). Sentivity (GVBD) decreased two days after to only 

23%. New hormonal treatment did not improve the physiological condition of this female. 

The only female caught was not mature. 

the Gironde Estuary does not seem to have 

changed since Magnin (1962). He reported that 

78% of the spawning fish were caught in May and 

first half of June; we caught 68% during that period. 

Our age estimates are very close to those ofthe pre- 

viously studied stock in the Guadalquivir River 

(Spain, see Classen 1944), with some fish being ol- 

der than those of the Rioni River (Georgia, see Ni- 

nua1976). 

June; the only fish caught later was a female that 

had already spawned. Most catches (68%) took 

place from early May to 15 June. Half of the fish 

were caught in the Garonne River, one third in the 

Dordogne River (more concentrated in the lower 

part), andthe rest in the Gironde Estuary. One male 

was caught three times (1981, 1984, and 1987), always 

in the Dordogne River. Of the fish caught in 

the Gironde Estuary, none was suitable for reproduction, 

because the inales and one female were immature 

and the second female had already 

spawned. 

Females weighed almost twice as much as males 

(41.6 kg and 23.7 kg, respectively) and females averaged 

30 cm longer than males (193 cm and 163 cm 

respectively). Assuming that the age-size relationship 

established by Rochard & Jatteau (1991) is valid 

for these fish, we estimated the minimum mean 

age (using mean TL) to be 10 and 15 years for males 

and females, respectively. 

The upstream migration period of broodfish in 

Artificial reproduction 

From 1981 until 1994, we collected 10 females for 

artificial collection ofeggs (Table 1). Only20% (n = 

2) of the females showed an optimal physiological 

state, the others being under-mature or over-mature. 

We rarely had both sexes simultaneously. Also, 

we collected only five mature males (Table 2). 

We induced successful ovulation only when feinales 

were caught in an optimal physiological state. 

Table 2. Results of attempts to spawn wild caught males of Acipenser sturio (I981–1987). 

1981 

1985 

1987 

Both males yielded sperm after 9 and 6 days of stocking, respectively (even one that was not running upon arrival). 

Two males yielded sperm 3 and 4 weeks after stocking, but only with two hormonal injections at 12 hour intervals and at rates 

of 20% and 100% of the normal dose, respectively. 

One male yielded sperm after 4 weeks of stocking (one injection) and, another one, in poor condition upon arrival, did not 

yield any sperm 6 days after stocking. Between 1981–1994 it seems that the quality of spermatozoa became poorer, as measured 

by its motility in water

366 

as occurred in 1985. In the case of immature fish, it mate age of 3 weeks. Some had started to feed, but 

was difficult or impossible to bring them into repro- live food (cladocerans) obstructed the digestive 

ductive condition. This also has been reported for tract. causing death. 

A. stellatus, a species for which Dettlaff & Davydo- In the future it will be necessary to select digestva 

(1979) show that good reproduction can be ible prey species available in late spring in large 

achieved when fish are held for fewer than four quantities (or easy to produce) with an appropriate 

clays. In contrast, Doroshov & Lutes (1984) size (worms, insect larvae. small crustaceans). In 

achieved good results with wild females of A . trans- mass rearing, this procedure is time-consuming, 

montanus held up to 4 months. It is important to costly, and can introduce pathogens. Specific weanascertainwhetherthese 

differences are species-spe- ing practice with inert food is also needed, even 

cific or due to our procedures. 

though that is far more difficult than for other stur- 

The physiological condition of males appears to geon species (Monaco et al. 1981, Dabrowski et al. 

be deteriorating as spermatozoa are increasingly 1985, Giovannini et al. 1991). The imposed experinon-motile. 

The possible influence of cadmium on mental water temperature (17° C) was slightly lower 

spermatogenesis should be explored as some pollu- than in the rivers at the time of capture. Also, it has 

tants disturb the reproductive cycle (Billard & Gil- been shown for teleost species such as Dicentrarlet 

1984). Second samples of sperm may be obtain- chus labrax, Saprus aurata (Barnabe 1989) and Coable 

from males three to four weeks after capture. regonus lavaretus (Champigneulle 1988) that better 

That has been achieved with a two hormonal injec- rearing occurs at water temperatures higher than 

tion procedure (instead of one), consisting respec- that of spawning. For both these reasons, the value 

tively of 20% and 100% of the normal dose (2 mg of higher rearing temperatures (22–24°C) should 

kg –1 ) of carp hypophysis powder at a 12 hour inter- be tested on A. sturio. 

val, the fish being held at the same water temperature. 

Because females and males arc seldom 

caught simultaneously, it would be useful to confirm 

whether such a process could be improved by appropriate 

Adaption of wild immature sturgeon to farm conditionzanskii 

management of water temperature (Ka- 

1981). Also, it is necessary to evaluate long 

term preservation of A. sturio sperm, as has been 

done with several other sturgeon species (Cherepanov 

et al. 1993, Drokin et al. 1993). Using sperm 

from several males would also increase genetic heterogeneity 

of the offsprings. Although we found 

that hybridization between A. sturio and A. baerii is 

possible, further investigation is needed to conclude 

if the non-viable embryos obtained were due 

to the poor quality of the sexual products, or to genetic 

incompatibility. 

Rearing of larvae 

We recovered nearly 700 embryos in 1981, and 

230 000 and 70 000 from the two females stripped in 

1985. In 1981, about ten larvae were still alive after 

one month of rearing, after which rearing was discontinued. 

In 1985, all free embryos died at approxi- 

We caught 20 large juveniles fish in early July 1991, 

of which only one met the size criterion (TL < 105 

cm) for successful acclimatization to fresh water. 

We used 2 m diameter tanks. Upon arrival, most 

fish had lost their righting response as a result of the 

stress of both catching and transport. Heavy mortality 

occurred in the first 24 hours for fish < 105 cm 

TL (mean TL = 79 cm) after direct transfer to fresh 

water. Survivors were divided into two groups, one 

remaining in fresh water and the other in brackish 

water (salinity = 5–10‰); however, all of these fish 

eventually died, the last one three weeks after 

stocking and without having Ted over that time. The 

first fish transferred to brackish water died later 

than the others (< 0.05, Mann-Whitney U test). The 

largest fish (TL = 130 cm, W = 10.8 kg) was still alive 

in fresh water by the end of August, but never fed 

naturally. We force-fed it pellets from one to three 

times a day. After having lost about 25% of its

367 

weight, this individual regained weight, but never 

recovered its natural feeding behavior. 

These observations show that we must minimize 

stresses to successfully adapt fish to farm conditions. 

In 1993, we used larger tanks (3 and 4 in diameter) 

supplied with low salinity (5‰)thermoregulated 

(18°C) water in darkness to keep fish calm. 

Soon after the arrival of fish, salinity was slowly 

lowered to 0‰. Each tank ran as a closed system in 

which nitrogen compounds, pH, and temperature 

were controlled. The bottom of one tank was covered 

with 10 cm depth of 8–10 mm gravel. Two Fish 

caught in mid-August were stocked into one tank 

and two others into the second tank in late September. 

Their sizes (TL = 105.8 + 1.2 c m W = 5.4 ± 0.2 

kg) were close to the goal of < 105 cm TL. The fish 

were fed shrimps, mostly frozen Palaemonetes varians, 

Crangon crangon, and Palaemon longirostris, 

and when available, live Palaemon longirositis. 

All four fish caught in 1993 were still alive in 1994: 

three began to eat shrimp after 160 days, and after 

200 days, the last individual fed. During the period 

of starvation they lost about 20% of their body 

weight. They were progressively weaned onto pellets, 

but shrimp remained the preferred food. 

Whatever the food, their consumption is irregular, 

and we did not find any relationship between feeding 

and the two types of tank bottom. 

We suggest that quick adaptation lo fresh water 

of fish ≥ 105 cm is possible but that normal food intake 

is needed within 5.5 to 6.5 months. In the future, 

better results may be obtained by reducing all 

possible causes of stress. We intend to improve 

catch, transport, and stocking conditions, particularly 

using brackish water (15‰) until fish begin to 

feed and only thereafter begin the transfer to fresh 

water. 2 

Restoration program for A. sturio 

Biological features of A . sturio in western Europe 

2 

Several of these problems mere solved during the I995 season, 

when Cemagref successfully capt ured and artificially stripped 

adults and subsequently stocked juveniles into the Gironde system 

(editors note, March, 1996 

(unimodal population structure, decline in occasional 

marine catches, increased growth rates, and 

non-motile sperm) are symptoms of the dramatic 

decline of this species. We met with many difficulties 

(inability for the females to achieve reproductive 

maturation in captivity, feeding of larvae, and 

adaptation to farm condition). 2 

Four main problems must be solved for successful 

restoration. The first is obtaining broodstock and 

producingA. sturio for restocking. This involves determining 

the best methods of capture and transportation 

of wild fish to our research station, assessment 

of good conditions for short and long term acclimatization 

to farm conditions, maturation of 

broodstock emphasizing water temperature, improving 

reproduction methods for females and 

males, production of juveniles, preparation of juveniles 

before release (counting, tagging, transport), 

release of fish, and finally, in case mature wild 

spawning fish are caught, experiments spanning artificial 

stripping to release of juveniles. The second 

problem is increasing natural reproduction of A. 

sturio .We plan to study spawning grounds in order 

to be able to improve those which are degraded and 

to create artificial ones, as has already been done 

elsewhere (Vlasenko 1974, Gendron 1988). The 

third problem is increasing our basic knowledge of 

the biology and status of the present population, 

with special emphasis on its distribution. migration, 

and structures. Fourth, biologists involved in the 

restoration program must attract the attention of. 

and educate, the public about the current condition 

of the species. 

It is often difficult to obtain financial support because 

the effectiveness of restoration programs can 

be estimated only on a long term basis. But, from a 

long term financial point of view it has already been 

demonstrated that ‘the management of endangered 

species is intrinsically a policy of loss minimization’ 

(Point 1991). Such awareness must be promoted. 

Because all sturgeon species are more or less endangered, 

and because they cross many international 

boundaries, their management needs international 

cooperation and investment.

368 

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Sturgeons and the Aral Sea ecological catastrophe 

Iliya Zholdasova 

Institute of Bioecology, Karakalpak Branch of the Academy of Sciences of Uzbekistan, Nukus, Republic Karakalpakstan 


Key words: Amu-Dar River, Syr-Dar River, Pseudoscaphirhynchus kaufmanni, P. fedtschenkoi, P. hermanni, 

Acipenser nudiventris, pollution, acclimatization, Nitzschia 

Synopsis 

A short description of the catastrophic changes in the ecology of the Aral Sea basin during the three last 

decades is presented. These changes have influenced the status of two acipenserid endemics to the area, the 

large Amu-Dar shovelnose, Pseudoscaphirhynchus kaufmanni, and the ship sturgeon, Acipenser nudiventris. 

The main biological characteristics of both species in the new environmental conditions are given. Previous 

unsuccessful attempts to introduce other acipenserid species into the area are also described. International 

cooperation is neededfor saving the last surviving species representing the genus Pseudoscaphirhynchus. The 

only two other species of the same genus, P. fedtschenkoi and P. hermanni, have already become victims of the 

Aral Sea catastrophe and are apparently extinct. 

Introduction 

1993). Two sturgeon species, the Syr-Dar and small 

Amu-Dar shovelnose sturgeons, were among the 

Historically the endemic fauna of the Aral Sea ba- first victims of this disaster and seem to be extinct. 

sin included four acipenserid species: the large The Syr-Dar shovelnose sturgeon was aregional en- 

Amu-Darshovelnose sturgeon, Pseudoscaphirhyn- demic and occurred in the Syr Darya River basin 

chus kaufmanni (Bogdanov, 1874), small Amu-Dar only (Berg 1948). The last report on this sturgeon in 

shovelnose sturgeon, P. hermanni (Kessler, 1877), Kazakhstan refers to 1952–1953 (Dairbaev 1959, 

Syr-Dar shovelnose sturgeon, P. fedtschenkoi Mitrofanov et al. 1986). The small Amu-Dar shov- 

(Kessler, 1872), and ship sturgeon, Acipenser nudi- elnose sturgeon was a regional endemic ofthe Amu 

ventris (Lovetsky, 1828) (Nikolskii 1938,1940, Berg Darya River, and initially it was described as a rare 

1948, Tleuov & Sagitov 1973, Tleuov & Tleuberg- species (Nikolskii 1938, Berg 1948). It has not been 

nov 1974). All shovelnose sturgeons are freshwater found since 1982. It is believed that this species has 

species, while the ship sturgeon is an anadromous disappeared completely (Pavlov et al. 1985) 1 .Defish. 

scription of the contemporary status of the two re- 

During the last 30 years, the environmental con- maining endemic species, Pseudoscaphirhynchus 

ditions in this region changed drastically because of kaufmanni and Acipenser nudiventris, in the conthe 

drying of the Aral Sea and extreme pollution 

(Aladin & Potts 1992); the whole change is known 

now as the Aral Sea environmental disaster or catastrophe 

(Feshbach & Friendly 1992, Peterson 

1 

In April 1996 three P. hermanni were cought near the town of 

Kerki (Salnikov et al. 1996).

374 

Figure 1. Map of the Aral Sea area. Two shorelines are shown: 1960 and 1989. Locations of catches of the large Amu-Dar shovelnose 

sturgeon between 1989 and 1993 are marked with arrows. 

text of environmental changes in the area, is the 

main goal of this paper. 

The Aral Sea disaster: catastrophic changes in the 

ecosystem of the Amu Darya River and Aral Sea 

Changes in the Amu Darya River 

The Amu Darya River is the longest river of Central 

Asia, being 2325 km long. It starts in the mountain 

regions of Pamir and Hindu Kush and has no 

tributaries downstream for the last 1257 km of its 

length. In the past, it entered the Aral Sea near the 

town of Muynak which was located in the Amu Darya 

River delta; at present, the river ends at a distance 

of 100 km from the shrunken sea. A map of 

the region is given in Figure 1. 

The Aral Sea ecological catastrophe was initially 

caused by intensive and irrevocable removal of water 

from the Amu Darya and Syr Darya rivers for 

irrigation. This resulted in a considerable reduction 

in the discharge ofwater from the rivers into the Aral 

Sea, which, in turn, caused the drying outofthe sea, a 

gradual shrinking ofits size, and a gradual increase in 

its salinity. The most significant impact was in the 

lower reaches of the Amu Darya River. Supplying 

irrigation channels, lakes, and artificial reservoirs 

with water became impossible without special dams, 

which were constructed in the lower reaches of the 

river beginning in 1967. These dams are still needed 

for distribution of water from the river, even after 

construction of the Takhiatash Dam (220 km from 

the mouth) and Tuyamuyun Hydrocomplex with its 

system of reservoirs (450 km from the river mouth). 

Dams constructed on the Amu Darya River in 

the 1960s cut offmany anadromous fishes, including 

the ship sturgeon, from the sea. This caused a sharp 

decline in abundance of the ship sturgeon by the 

middle 1970s. Moreover, use of mineral fertilizers 

and pesticides for cotton agriculture resulted in an 

incredibly high level of pollution. Water of the riv-

375 

ers and lakes was extremely contaminated by chemicals 

due to disposal of drainage waste from the area 

of irrigated land cultivation (Chembarisov 1989). 

The increasedmineralization (from 1000 to 1420 mg 

1 –1 ) and contamination of the drainage waters with 

pesticides, mineral fertilizers, and salts changed the 

hydrochemical regime of the rivers and lakes. In the 

1950s, the mean content of ions in the Amu-Darya 

waterwas 540 mg1 –1 (Rogov 1957), while during the 

last decade it varied between 600 and 1500 mg1 –1 

The highest level of pollution is in the lower 

reaches ofthe Amu Darya River. In 1989 2 , the mean 

annual mineralization of water was 1525.5 mg1 –1 

near the towm of Nukus (215 km from the mouth), 

and in 1990, 936.8 mg1 –1. 

Changes in the hydrochemical regime of the 

Amu Darya River were augmented by decreases in 

the annual discharge. The mineral content of water 

in the Amu Darya River depends to a great extent 

on fluctuations in the volume of water discharge. 

Until the time when river flow became regulated 

(the 1960s), the fluctuations were caused mostly by 

variations in the melting of glacier-snow in the upper 

reaches. A spring-summer peak of water and a 

dry fall were quite distinct. Even now these seasonal 

fluctuations in the water level are expressed in 

the upper and middle reaches of the river. In the 

2 

Yearbook on Surface Water Quality and Efficiency of Water 

protection Measures in Uzbekistan in 1989.1991. Goskomgidromet 

USSR. Tashkent, Pt. I. Vol. 4. Book 1–5 (in Russian). 

lower reaches these seasonal variations are less pronounced 

because so much water is removed by irrigation 

channels and reservoirs. In this area the salinity 

of water is very high because of a low water 

flow. Thus, in 1989 and 1990 mineralization during 

the full-water period in the lower reaches was 437– 

679 and 336–598 mg1 –1 respectively. It increased 

significantly in the dry season to 922–3999 mg1 –1 in 

1989 and to 973–1868 mg1 –1 in 1990. 

Increases in mineralization were accompanied by 

the general contamination ofwater in the river. Pollutants 

included almost all dangerous chemical substances: 

oil products, phenols, heavy metals, organicsubstances, 

etc. (Table 1). In 1989–1990, a tendency 

towards a decrease in pesticide content in the 

Amu-Darya water was noticed. In 1990 and 1991, 

the concentration of DDT and its metabolites in the 

Tuyamuyun Reservoir was 0.1–20.0 mg1 –1 , and the 

concentration of other organochlorine pesticides, 

0.015–0.616 mg1 –1 . Pollution caused death of silver 

carp, Hypophthalmichthys molitrix, on a massive 

scale in this reservoir. 

Changes in the Aral Sea 

The Aral Seaecosystem has undergone considerable 

change during the last 30 years. It was the fourth biggest 

lake on the planet. It changed from a brackishwater 

lake with an average water salinity 10.3 in 1961 

to a salt-water one with a salinity of 37–38. Water lev- 

Table 1. Water pollution in two areas of the Amu Darya River, near towns of Termez (middle reaches) and Nukus (lower reaches). 

Chemicals Termez Nukus 

1989 1990 I989 1990 

Concentration MAC Concentration MAC Concentration MAC Concentration MAC 

factor* factor * factor* factor* 

Phenols 0.004 mg I 1 43 0.008 mg1 –1 83 0.004 mg1 –1 43 0.0I0 mg1 –1 103 

Oil products 0.18 mg1 –1 3.63 0.04 mg 1 1 0.83 0.15 mg1 1 33 – – 

Copper 8.8µg1 –1 8.83 10.0 µg I 1 103 10 .0µg 1 -1 103 10.7µg I 1 10.63 

Nitrate nitrogen 0.037 mg1 –1 1.93 0.027 mg1 –1 1.43 0.042 mg1 –1 0.23 1.42 2.13 

α - benzene hexachloride 0.028 mg1 –1 2.83 0.019 mg1 –1 1.93 ND – ND – 

γ-benzenehexachloride 0.013 mg1 –1 1.33 0.015 mg1 –1 1.53 ND – ND – 

* Number of times of MAC (Maximum Allowable Concentrations. PDK in Russian), are given according to the Soviet standards (see 

Feshbach & Friendly 1992); ND = not determined.

376 

el had decreased by 16.4 in by the end of 1993. Water 

volume decreased more than three times. and now it 

is less than 300 km 3 . The size of the sea was reduced 

from 65.4 to 30.0 thousand km 2 , and the shoreline 

receded in some places by 100 km or more. The 

southern brackish-water Adjibaiskii, Muynakskii, 

Sarbas, Abbas, and Zhaltyrbas bays, which different 

fishes used as spawning areas, are at present dry. 

By 1987 the Aral Sea was divided by a sand bar 

into two basins, the Bolshoe (Large) and Maloe 

(Small) seas (Figure 1). The Bolshoe Sea receives 

water from the Amu Darya River: the drainage 

waste water from the irrigated area to the south 

from the Aral Sea also goes into this basin. The bed 

in the mouth part of the Syr Darya River has been 

changed and it now enters into the Maloe Sea. 

At present, both rivers are disconnected from the 

Aral Sea: the Syr Darya River has not reached the 

sea since 1975, and the Amu Darya,since 1982. Connection 

of the Ainu Darya River with the sea was 

first interrupted in the middle 1970s, when the volume 

of the river water upstream from the Takhiatash 

Dam decreased to such an extent that water 

was fully withdrawn for irrigation and no downstream 

flow took place. After this, the delta of the 

river considerably changed. Regulated flows of 

clear water (historically water in the Ainu Darya 

River was extremely muddy) from the Tuyamuyun 

Reservoir caused deepening of the river bed by 4–5 

in or more below the dam. Water goes to the sea 

through a system of small lakes located in the natural 

bed of the river and in the former sea bays. The 

artificially regulated discharge volume of water is 

extremely small. The sea level continues to decrease 

and its water salinity increases. 

As a consequence of all these events, fishing in 

the Aral Sea stopped in 1984. At present, practically 

all endemic fish species have perished. They were 

replaced by the species introduced in the 1960s. 

such as Hypophthalmichthys molitrix, Aristichthys 

nobilis, Parabramis perkinensis, Ctenopharyngodon 

idella, and others (Zholdasova et al. 1991). 

Due to the contemporary level ofwater in the Aral 

Sea, as well as in the Amu and Syr Darya rivers, there 

is no hope that populations of anadromous fishes, including 

the ship sturgeon, could be restored. 

Acipenserid endemics of the Aral Sea basin under 

conditions of the environmental disaster: biology 

and status 

The large shovelnose sturgeon 

The large Amu-Darya shovelnose sturgeon, Pseudoscaphirhynchus 

Kaufmanni is an endemic of the 

Amu Darya River. It is an endangered species on 

the verge of extinction. Itwas included in the Uzbek 

SSR Red Data Book 3 and in the USSR Red Data 

Book 4 . Until the 1960s, it inhabited the Ainu Darya 

River from its source to its mouth (Nikolskii 1938, 

Tleuov & Sagitov 1973). 

The major part of the large shovelnose sturgeon 

population was located in the foothill and valley arcas 

of the river. Sturgeon were largely concentrated 

near the villages of Kerki-Chardzhou-Ildzhik in the 

upper and middle reaches of the river and were 

caught there commercially in the 1930s. Pseudoseaphirhynchus 

Kaufmanni was also numerous in the 

lower reaches of the Amu Darya River. In the late 

1970s, large shovelnose sturgeonjuveniles constituted 

up to 26% of all young fish in the lower reaches 

of the Amur Darya River (Tleuov 1981). Pseudoscaphirhynchus 

kaufmanni inhabited small irrigation 

channels connected with the river as well. Although 

it is a freshwater species, the shovelnose sturgeon 

can tolerate some salinity: it was found in the nearmouth 

area of the Aral Sea in salinity 8.5‰ (Gosteeva1953). 

At present, this species is preserved only in the 

middle reaches of the Amu Darya River. Studies 

carried out in 1989 after a 15-year break (Zholdasova 

et al. 1990) and in 1991 (together with Sergei Gamalei, 

Moscow Aquarium, Russia) showed that 

large shovelnose sturgeon are still concentrated in 

their usual habitats in the middle reaches of the river, 

within a region between the two towns of Kerki 

and Chardzhou. This species was not reported 

downstream from Chardzhou in 1989 and in 1990- 

1991 (Zholdasova et al. 1991). Sturgeon were also 

3 

Uzbek SSR Red Data Book. 1983. Vol. 1. Vertebrates. FAN, 

Tashkent. 128 pp. (in Russian), 

4 

USSR Red Data Book. 1984. Vol. 1. Lesnaya Promyshlennost, 

Moscow. 390 pp. (in Russian).

377 

not found in the lower reaches of the river during prise 30.5% of the food. Fishes are represented by 

the 1980s. 

C. kuschakewitschi and species of the genus Rhino- 

The large Amu-Dar shovelnose sturgeon lives in gobius. 

turbid, muddy waters. It inhabits shallow-water Under the current conditions, the large shovelparts 

of the river with sandy or stony-pebble bot- nose sturgeon continues to reproduce in the Amu 

toms (Nikolskii 1938, Tleuov & Sagitov 1973). In Darya River. In April–May 1989 we did not find 

1989–1991, I also found sturgeon in the main chan- ripe females ready for spawning or already 

nel of the river with sandy bottom at a depth of 1.0- spawned. Females were mostly at stage II or II–III 

1.5 m, as well as at the edges of pools with turbid of maturity [according to the scale of Nedoshivin 

water, and near sand bars. 

(1928)]. However, there were males at stage IV or 

In the past, the maximum size reported of the IV- V. According to the results obtained by Boris 

large shovelnose sturgeon was 75 cm, and the maxi- Goncharov (personal communication), in the remum 

weight, 2 kg (Berg 1948). In 1965–1966, the av- gion near the town of Chardzhou in 21–30 Septemerage 

body length was 37 cm and the average ber 1991, individuals at stage IV predominated 

weight, 241 g (Tleuov & Sagitov 1973). The size of among males, while females were mostly at stage II. 

fish studied by us in 1989 and 1991 varied from 9.3 to The rate of reproduction of the population is very 

38.0 cm, being 23.6 cm on average, and the weight, low. In 1991, only a single late embryo and two onefrom 

3.2 to 270 g (100.2 g on average). The age of year old juveniles were collected in the low reaches 

individuals caught was from 1 to 6 years. The whole of the river (Pavlovskaya & Zholdasova 1991). 

length ofthe largest fish, including the tail filament Early development and larvae of P kaufmanni 

was 69.4 cm (33.5 cm without the filament). and the were described recently (Schmalhausen et al. 1991, 

weight was 250 g. Dettlaff et al. 1993). 

The age of individuals in the population has In 1993, I caught three large shovelnose sturgeon 

changed compared to that in the 1960s. In the 1960s, during my expedition to the Ordybai Channel of the 

the age of fish varied from 1+ to 14+ with a predom- Amu Darya River delta. They were young individuinance 

of 3 to 6 year old fish (Tleuov & Sagitov als of about 20 cm in length (without the tail fil- 

1973). In the late 1980s, the population consisted ament) and about 50 g in weight. A shovelnose sturmostly 

of young (from l to 6 years old) fish, with a geon of a similar size, caught near the town of Nupredominance 

of 3-year (36.8%) and 4-year old in- kus in the Kattyagar irrigation channel was also redividuals 

(41.6%) (Zholdasovaet al. 1990). The rate ported in summer 1993. The appearance of sturgeon 

of linear growth has also slowed down compared in their former habitats in the lower reaches of the 

with the 1960s. Apparently, this decrease in growth Amu Darya River is evidently related to a signifrate 

was caused by a change in sturgeon diet: an icant volume and stable downstream flow in 1993. It 

analysis of the content of stomachs showed a de- is noteworthy that during the last three years the 

crease in a proportion of fishes consumed by stur- mean discharge in the Amu Darya River has been 

geon compared to the 1960s. 

3.7 times higher than during the previous decade. 

Adult shovelnose sturgeon are benthophagous Also, the river flow is turbid and goes apparently 

with predatory inclinations (Nikolskii 1938, Berg directly through the Tuyamuyun Reservoir. Unfor- 

1948, Tleuov & Sagitov 1973). In the 1960s. in the tunately, I have no information on the level of 

middle reaches of the Amu Darya River, five fish chemical pollution of the water in 1992–1993. But a 

species constituted up to 64.5% of the diet of large general decrease in usage of pesticides and mineral 

shovelnose sturgeon:juvenile Barbus brachycepha- fertilizers has recently been observed, mostly due to 

lus,Aspius aspius, Acipenser nudiventris, Capoeto- economic problems. 

brama kuschakewitschi, andNoemacheilusoxianus. The large shovelnose sturgeon occurs exclusively 

At present, the diet is more diverse; in addition to in the fast running turbid waters of the Amu Darya 

fishes (36.6% of the food biomass), the larvae of 15 River. Since these fish were never found in the 

species of midges of the family Chironomidae com- lakes, Nikolskii (1938) believed that in stagnant wa-

378 

ter sturgeon die rapidly. I assume that in the lowwater 

period from the middle 1970s until the late 

1980s, the decrease in the flow velocity, clearing of 

water and the decrease in the size of river beds prevented 

migration of shovelnose sturgeon from the 

middle to the lower reaches of the Amu Darya River. 

In 1989 and 1991, sturgeon were concentrated in 

the regions of the river where the drainage waste 

enters into it. Possibly, this was caused by the existence 

of organisms inhabiting these waste waters because 

of their enriched salt and organic materials 

content. This influence of drainage waters possibly 

resulted in a much greater biodiversity of the benthic 

fauna: the number ofspecies increased from 55 

(10 higher taxa) in 1974 to 83 species (17 taxa) in 

1989. Species diversity ofchironomids, ephemeropterans, 

and molluscs increased: new immigrant mysids 

and shrimps appeared. Fifteen species and 

forms of chironomids were found in diet of sturgeons 

in May and October 1989. Studies on the distribution 

of benthic fauna in the river bed and areas 

of its concentration may facilitate a search for sturgeons. 

Unfortunately, the attempts to breed P. kaufmanni 

in captivity in 1983–1985 were unsuccessful: in all 

experiments the embryos died at 10–12 days after 

hatching (Goncharov et al. 1991). 

Ship sturgeon (Tleuov 1981). 

The ship sturgeon, Acipenser nudiventris, is a large 

anadromous fish occurring in the Black, Caspian, 

and Aral Sea basins (Berg 1948, Sokolov & Vasilev 

1989). In the Aral Sea the ship sturgeon was the only 

representative of the genus Acipenser (Nikolskii 

1940). Ship sturgeon reached a length of 160 cm and 

a weight of 45 kg (Tleuov & Sagitov 1973). In 1933- 

1934, ship sturgeon were introduced from the Aral 

Sea into Lake Balkhash (Kazakhstan), where they 

grew faster than in the Aral Sea (Dombrovskii et al. 

1972). 

Before the flow in the Amu Darya and Syr Darya 

rivers was regulated, the ship sturgeon thrived everywhere 

in the Aral Sea. For spawning they migrated 

mainly into the Syr Darya River in which 

they moved 1800 km or more upstream (Mitrofanov 

et al. 1986). In the Amu Darya River, the spawning 

areas of this species were located in a large region 

from the Kyzylzhar Cape (103 km upstream from 

the river mouth) up to Faizabadkal Cape (more 

than 1500 km from the river mouth). 

There were two forms of the ship sturgeon, the 

winter and summer ones. The Aral Sea population 

of sturgeon was comprised predominantly of the 

winter form. Its migration into the Amu Darya River 

usually started at the beginning of spring flood, in 

the second half of April. Mass migration continued 

from the beginning of May until September. sometimes 

until the end of October. Sturgeon stayed the 

whole winter in the river and spawned next year in 

spring. The age of fish migrating for spawning into 

the rivers was from 7 to 30 years with a predominance 

(82.1%) of 20–21 year old individuals (Tleuov 

1981). 

The main spawning grounds of the ship sturgeon 

were located in the middle reaches of the Amu Darya 

River. between the towns of Chardzhou and 

Turtkulem: here about 50–60% of the progeny appeared 

(Tleuov & Sagitov 1973). Spawning also 

took place near the town of Nukus The spawning 

period of ship sturgeon began in March at a water 

temperature above 10°C and continued until the 

end of May at a temperature of 21–23°C. The absolute 

fecundity of the Aral ship sturgeon varied from 

52 259 to 554 700 eggs, being 389 731 on average 

After spawning, ship sturgeon returned to the sea 

where they fed until the next maturation. They fed 

mostly on molluscs: among them, Hipanis minima, 

Dreissena polimorpha, and D. caspiana predominated 

(88%) (Tleuov 1981). Fish young were rarely 

found in sturgeon stomachs. After introduction of 

certain fishes in the Aral Sea, when gobies and sand 

smelts appeared in great amounts in the sea, a transition 

of the ship sturgeon to piscivory was noticed. 

Piseivory started at the age of two years and at the 

age ofthree years sturgeon consumed mainly fishes 

(up to 61 % of their food). This transition to more 

piscivorous feeding occurred in the second half of 

the 1960s (Tleuov 1931). 

From the late 1920s to the 1970s. there were numerous 

attempts to introduce other sturgeon spe-

379 

cies (including stellate sturgeon, Acipenser stellatus, 

and Russian sturgeon, A . gueldenstaedtii) into the 

Aral Sea, but none of them was successful (Bykov 

1961,1970, Karpevich 1975, Balymbetov1981). The 

first stocking of stellate sturgeon from the Caspian 

intothe Aral Seain the 1920–1930s greatly impacted 

the endemic Aral Sea population of the ship sturgeon. 

A gill trematode, Nitzschia sturionis, was in, 

troduced together with the stellate sturgeon. It 

caused an epizooty and the death of ship sturgeon 

on a massive scale in 1936–1937 (Osmanov 1971). 

Before this, ship sturgeon was a commercially important 

species: its catch was 3000–4000 metric tons 

annually in 1928–1935 (Nikolskii 1940). After the 

Nitzschia epizootyin1936–1937, commercial fishing 

wasbanned on 1 June 1940 (Tleuov & Sagitov 1973, 

Mitrofanov et al. 1986). In the 1960–1970s, an experimental 

catch of 700–9300 kg annually was allowed. 

Later virtually the whole population of ship 

sturgeon in the Aral Sea was destroyed by illegal 

fishing during spawning. 

From the end of the 1970s, no findings of the ship 

sturgeon in the lower reaches of the Amu Darya 

River were reported. Ship sturgeon were not found 

among young fishes migrating downstream in 1989 

(Pavlovskaya & Zholdasova 1991). Ship sturgeon 

have not been found in the Amu Darya River during 

the last 7-8 years, except two reports of local 

fishermen: in December1990, near the town ofIldzhik 

(4kg), and in March 1991, 35 km upstream from 

the town of Chardzhou (2 kg). Therefore, the Aral 

Sea form of A. nudiventris is practically extinct. Possibly, 

a small population of this form still exists in 

Lake Balkhash, where these fish were introduced 

fromthe Aral Seain the 1930s (Pechnikova 1964). If 

so, this population might be used to reintroduce of 

the ship sturgeon into the Aral Sea. 


I am very thankful to Vadim Birstein, John Waldman 

and Robert Boyle for inviting me to the International 


Conservation. I am also grateful to Vadim Birstein 

and anonymous reviewers for their editorial notes 

on the manuscript and to William E. Bemis for 

drawing the map. 


Aladin, N.V. & W.T. Potts. 1992. Changes in the Aral Seaecosystem 

during the period 1960–1990. Hydrobiologia 237: 67–79. 

Balymbetov, S.K. 1981. On the salinity resistance of some fish 

recommended for introduction into the Aral Sea. pp. 26–27. 

In:Biological Foundations ofFishery in the Central Asian and 

Kazakhstan Water Bodies, Ilim, Frunze (in Russian). 


countries, Vol. 1, Part 1. Akademia Nauk USSR, Moscow & 

Leningrad (in Russian; English translation published by Israel 


Bogdanov, M. 1874. A report on a newly discovered acipenserid 

fish at the meeting of Zoological Section. Trudy Sankt-Peterburgskogo 

obshchestva ispytatelei prirody 5: 48 (in Russian). 

Bykov, N E . 1961. Materials on acclimatization of fishes and 

other vertebrates in the Aral Sea. pp. 45–50. In: Biological 

Foundations of Fishery in Central Asian Republics and Kazakhstan, 

Frunze (in Russian). 

Bykov, N.E. 1970. On acclimatization of stellate sturgeon (Acipenserstellatus) 

in the Aral Sea. Trudy VNIRO 76: 192–195 (in 

Russian). 

Chembarisov, E.I. 1989. Runoff and water mineralization in 

large collectors in Central Asia. Vodnye Resursy 1: 49–53 (in 

Russian). 

Dairbaev, M.M. 1959. Formation, composition and distribution 

of ichthyofauna in water bodies of the Syr Darya River irrigation 

system. pp. 286–299. In:Collected Papers on Ichthyology 

and Hydrobiology 2, Izdatelstvo Akademii Nauk KazakhSSR, 

Alma-Ata (in Russian). 

Dettlaff, T.A., AS. Ginsburg & O.1. Schmalhausen. 1993. Sturgeon 

fishes. Developmental biology and aquaculture. Springer 

Verlag, Berlin. 300 pp. 

Dombrovskii, G.V., N.P. Serov & V.N. Dikanskii. 1972. Biology 

and fishing of the ship sturgeon, Acipenser nudiventris Lov., in 

the Balkhash-Ili basin. Trudy TSNIORKh 4: 146–148 (in Russian). 

Feshbach, M. & A. Friendly, Jr. 1992. Ecocide in the USSR. 

Health and Nature Under Siege. Basic Books, New York. 376 

PP. 

Goncharov,B.F.,O. 1Shubravy&V.K. Uteshev. 1991. Reproduction 

and early development of Pseudoscaphirhynchus kaufmanni 

Bogdanow under artificial environmental conditions. 

Ontogenez 22: 485–492 (in Russian, English translation Soviet 

J. Dev. Biol. 22: 296-301). 

Gosteeva, M.N. 1953. Finding ofthe shovelnose sturgeon, Pseudoscaphirhynchus 

kaufmanni (Bogd.), in brackish water. Voprosy 

Ikhtiologii 1: 115–116 (in Russian). 

Karpevich, A.F. 1975. Theory and practice of acclimatization of 

aquatic organisms. Pishchevaya Promyshlennost, Moscow. 

432 pp. (in Russian).

380 

Kessler, K.F. 1872. On a remarkable fish of the family of stur- Pechnikova, N.V. 1964. Results ofacclimatization ofthe Aral Sea 

geons discovered by A. P. Fedtchenko in the Syr Darya River. ship sturgeon (Acipenser nudiventris Lov.) in Lake Balkhash. 

Izvestiya Obshchestva lyubitelei estestvoznaniya, antropolo- Voprosy Ikhtiologii 4: 142–152 (in Russian). 

gii i etnografii 10: 70–76 (in Russian). 

Rogov, M.M. 1957. Hydrology of the delta of the Amu Darya 

Kessler, K.F. 1877. Fishes of the Aralo-Caspian-Pontine region. River. Gidrometeoizdat, Leningrad. 254 pp. (in Russian). 

Trudy Aralo-Kaspiiskoi ekspeditsii 4: 190-196(in Russian). Salnikov, V.B., V.J. Birstein & R.L. Mayden. 1996. The contem- 

Lovetsky, A. 1828. On the fishes belonging to the sturgeon genus porary status of the two Amu Darya River shovelnose sturand 

inhabiting waters of the Russian Empire. Novyi Magazin geons. Pseudoscaphirhynchus kaufmanni and P. hermanni. 

Estestvennoi Istorii, Fiziki, Khimii i Svedenii Ekologiches- Sturgeon Quart. 4(3): 8–10. 

kikh, Izdannyi I. Dvigubskim, Chast 6, Moscow (in Russian. Schmalhausen, O.I.1991. Prelarval development of Pseudosca- 

French translation Bull. Sci. Nat. 23: 131–134 (1831)). 

phirhynchus kaufmanni. Ontogenez 22: 493–513 (in Russian, 

Mitrofanov, V.P., G.M. Dukravets, H.E. Peseridi & A.N. Polto- English translation Soviet J. Dev. Biol. 22: 302–315). 

rykhina. 1986. Fishes of Kazakhstan, Vol. 1. Izdatelstvo GY- Sokolov, L.I. & V.P. Vasilev. 1989a. Acipenser nudiventris Love- 

LYM, Alma-Ata. 271pp. (inRussian). 

∨ 

tsky, 1828. pp. 206–226. In: J. Holcík (ed.) The Freshwater 

Nedoshivin,A.Ya.1928. Materials on the Don Riverfishery. Tru- Fishes ofEurope,Vol. 1,Pt. II, GeneralIntroductiontoFishes, 

dyAzovo-Chernomorskoi Nauchno-Promyslovoi Ekspeditsii Acipenseriformes, AULA-Verlag, Wiesbaden. 

4: 1–175 (in Russian). Tleuov, R.T. 1981. New regime of the Aral Sea and its influence 

Nikolskii, G.V. 1938. Fishes of Tadjikistan. Izdatelstvo Akademii on ichthyofauna. Izdatelstvo FAN, Tashkent. 190 pp. (In Rus- 

NaukUSSR, Moscow-Leningrad. 228 pp. (in Russian). 

sian). 

Nikolskii, G.V. 1940. Fishes of the Aral Sea. Moscovskoe Obsh- Tleuov, R.T. & N.I. Sagitov. 1973. Acipenserid fishes of the Aral 

chestvo Ispytatelei Prirody, Moscow. 216 pp. (in Russian). 

Sea. FAN Press, Tashkent. 155 pp. (in Russian). 

Osmanov, S.O. 1971. Parasites of fishes of Uzbekistan. FAN. Tleuov, R.T. & Sh. Tleubergenov. 1974. Fishes of Karakalpakiya. 

Tashkent. 532 pp. (in Russian). 

Nukus. 95 pp. (in Russian). 

Pavlov, D.S., YuS. Reshetnikov, M.I. Shatunovsky & N.I. Shilin Zholdasova,I.M.,L.P. Pavlovskaya,L.N. Guseva&V.T. Utebae- 

1985. Rare and endangered fish species of the USSR and prin- va. 1990. Status of populations of rare and threatened species 

ciples for listing them in the Red Data Book. Voprosy Ikhtio- of the Amu Darya River and measures purposed to protect 

logii 25: 16–25 (in Russian, English translation: J. Ichthyol. 25: them. Information No. 483. FAN, Tashkent. 12 pp. (in Rus- 

88–99). sian). 

Pavlovskaya, L.P. & I.M. Zholdasova. 1991. Anthropogenic Zholdasova, I.M., L.P. Pavlovskaya& S.K. Lyubimova. 1991. On 

changes in the fish fauna of the Amu Darya River (based on the death of fishes in the Tuyamuyun Reservoir (Amu Darya 

data from sampling drift of eggs and larvae). Voprosy Ikhtio- River). Bulletin Karakalpakskogo Otdeleniya Akademii 

logii 31: 585–595 (in Russian, English translation: J. Ichthyol. Nauk Uzbekskoi SSR 1: 18–24 (in Russian). 

31:106–117).



Threatened fishes of the world: Pseudoscaphirhynchus spp. (Acipenseridae) 

Vadim J. Birstein 


Pseudoscaphirhynchus kaufmanni (Bogdanov, 

1874) 

Common names: Large Amu-Dar shovelnose sturgeon (E), 

Grand nez-pelle de lAmou daria (F), Bolshoi Amudarinskii 

Lzhelopatonos (R), Sumrai or Beltkumys (Karakalpakian), 

Elan Luiryk or Tuchkan Kuiryk (Uzbek and Turkmen). 

Conservation status: Endangered (Uzbek SSR Red Data Book 

1983, USSR Red Data Book 1984, Turkmen SSR Red Data Book 

1985,1996 IUCN Red List). 

Identification: D 25–37, A 15–24 rays, 10–15 dorsal scutes, 28–40 

lateral scutes, and 5–11 ventral scutes. Very unusal appearance. 

Body is fusiform, the fore part rather thick. Head ends in abroad 

spade-like snout. There are 2–4 backward pointing spines on the 

tip of the rostrum. Two similar spines are located on the upper 

side of the head in front of very small eyes. The snout is flattened 

on its upper surface and completely flat on the lower surface, 

where there are two pairs of barbels. Head shields are visible. 

The upper lip of the transverse mouth is divided in the middle, 

the lower lip is broader than the upper and is also slightly divided. 

Regularly distributed granulations lying between the scute 

rows. Below the dorsal fin base and above the anal fin base there 

are small flat scutes. All paired fins and the anal fin are rounded. 

Pectoral fins have a very strong and sharp first ray. The caudal is 

prolonged on its upper heterocercal lobe in a long filament. Historically, 

the maximal size of the fish was 75 cm and the 2 kg in weight. In the 1960s, the average size was 37 cm, and 241 g weight. Two forms 

were described in the 1960s: common and dwarf. Dwarf adults were smaller than the common ones and their dorsal, anal, and ventral fins 

were located closer to the tail than incommon form. In the early 1990s, the dwarf form predominated in thepopulation. Dorsumfrom grey 

to almost black, ventrum white. William E. Bemis modified the figures from originals published by Nikolskii (1938). 

Distribution: Endemic to the Amu Darya River and its tributaries (Central Asia). Historically, P. kaufmanni was distributed along the 

river from the upper reaches (Pyandzh River) to the delta. Presently, there are two populations: in the Vakhsh River, and the middle 

reaches of the Amu Darya River. In the early 1990s, only a few individuals were recorded in the lower reaches of the Amu Darya River. 

Abundance: No exact estimations. Habitat and ecology: P. kaufmanni live at a depth of 1.0–1.5 m in highly turbulent muddy water. Fish 

inhabit shallow-water parts of the river with fast current, sandy or stony-pebble grounds. Adults feed mainly on small fish, with insect 

larvae forming the rest of the diet. Reproduction: Takes place in late March-early May at a water temperature of 14–16 C. Males become 

mature at 5–7 years, and females, at 6–8 years. Intervals between spawning periods possibly last 4–5 years. Fecundity is 3127–36558 

(common form) or 996–1910 (dwarfs). Hybridization: Historically, easily hybridized with the other species of Pseudoscaphirhynchus, P. 

hermami.Threats: Changes in the environment caused by the drying out ofthe Aral Sea. Presently, the Amu Darya River does not reach 

the Aral Sea. Dams andchannels constructed in the 1970s–1980s affected the water regime ofthe river. Also, the level of water pollution in 

the river is very high. Conservationaction: An international recovery project is planned by scientists of Karakalpakstan (a part of 

Uzbekistan), Turkmenistan, the United States, and, possibly, Russia.

382 

Pseudoscaphirhynchus hermanni (Kessler, 1877) 

Common names: Small Amu-Dar shovelnose sturgeon (E), Petit 

nez-pelle de lAmou daria (F), Malyi Amudarinskii Lzhelopatonos 

(R). 

Conservation status: Critically endangered (1996 IUCN Red 

List),Endangered (UzbekSSR Red Data Book 1983, USSR Red 

Data Book 1984, Turkmen SSR Red Data Book 1985). 

Identification: D 27–35, A 15–21 rays, 10–13 dorsal scutes, 30–38 

lateral scutes, and 6–10 ventral scutes. Morphologically it is similartoP. 

kaufmanni,but smaller (20.7–27.0 cm). Its snout islonger 

than that of P. kaufmanni. This species does not have a long caudal 

filament. The snout is shovel-shaped andthe rostrum is more 

rounded than in P. kaufmanni. There are no spines on the snout. 

The snout grows longer with age. Pectoral fins have a fold which 

curls dorsally. Scutes are not armored with spines or the spines 

are very short. Each dorsal and lateral scute covers almost half of 

the following one. There are granules between the rows of 

scutes. As in P. kaufmanni, there are 3–4 flat scutes between anal 

and ventral fins. Eyes are extremely small. Two outerbarbels are 

2–3 times longer than the inner ones. Dorsum deep brown, ventrumwhite. 

Distribution: Endemic to the Amu Darya River (middle and 

lower reaches). Abundance: Historically rare; in April 1996 

three specimens were caught forthe first time in the last 15 years. 

Habitat and ecology: Practically unknown. Adults are benthophagous 

feeding mostly on midge larvae. Reproduction: Unknown. 

Hybridization: Historically. easily hybridized with P. kaufmanni. Threats: Changes in environment caused by the drying out of the 

Aral Sea, construction of dams and channels which affected the water regime in the Amu Darya River, and a very high level of water 

pollution in the river. Conservation action: None. During the carrying out the recovery plan for P. kaufmanni, it will be possible to make 

the estimation of the status of P. hermanni. 

Pseudoscaphirhynchus fedtschenkoi (Kessler, 1872) 

Common names: Syr-Dar shovelnose sturgeon (E), Nez-pelle du Syr daria (F), Syrdarinskii Lzhelopatonos (R). 

Conservation status: Critically endangered (1996 IUCN Red List), Endangered (KazakhSSR Red Data Book 1978, USSR Red Data 

Book1983). 

Identification: D 30–34. A 19–20 ray, 15–22 dorsal scutes, 38–46 lateral scutes, and 6–11 ventral scutes. It is small: with the caudal filament, 

up to 36 cm: without the filament. 20.7–27.0 cm. It has more dorsal scutes and a longer snout than the two Amu Darya species, P. 

kaufmanni and P. hermanni. The pectoral fins have a fold similar to that in P. hermanni. There are no spines on the head. The size and 

shape of the snout varies considerably. Historically, there were three morphs: (1) a common morph with a long rostrum without a long 

caudal filament: (2) morpha brevirostris Berg with a short snout and a long caudal filament; (3) morpha intermedia Berg with a middlesized 

snout and a filament. 

Distribution: Endemic of the Syr Darya River, middle and lower reaches (Central Asia). Abundance: No reports since the 1960s; practically 

extinct. Habitat and ecology: Unknown, Adults were benthophagous feeding mostly on midge larvae. Reproduction: Spawning 

during late April. Threats: Changes in the environment caused by the drying out of the Aral Sea. The Syr Darya River. as the Amu Darya 

River, does not reach the Aral Sea now. Conservation action: None. 

Berg, L. S. 1905. Fishes of Turkestan. Scientific results of the Aral expedition, No. 6, St. Petersburg. 261 pp. (in Russian). 

Berg, L. S. 1948. The freshwater fishes of the USSR and adjacent countries, Vol. 1. Part 1. Akademia Nauk USSR, Moscow & Leningrad 

(in Russian, English translation published by Israel Program for Scientific Translations, Jerusalem. 505 pp. 

Bogdanov, M. 1874. A report on a newly discovered acipenserid fish at the meeting of Zoological Section. Trudy Sankt-Peterburgskogo 

obshchestva ispytatelei prirody 5: 48 (in Russian).

Kessler, K. E 1872. On a remarkable fish of the family of sturgeons discovered by A. P. Fedtchenko in the Syr Darya River. Izvestiya 

Obshchestva lyubitelei estestvoznaniya. antropologii i etnografii 10: 70–76 (in Russian). 

Kessler, K. F. 1873. On a remarkable fish of the family of sturgeons discovered by M. A. P. Fedchenko in the River Suir-dar. Ann. & Mag. 

Nat. Hist. Ser. 4. No. 70: 269–276. 

Kessler, K. E 1877. Fishes of the Aralo-Caspian-Pontine region. Trudy Aralo-Kaspiiskoi ekspeditsii 4: 190-196 (in Russian). 

Mitrofanov,V. P., G. M. Dukravets, H. E. Peseridi & A. N. Poltorykhina. 1986. Fishes of Kazakhstan. Vol. 1, GYLYM Press, Alma-Ata. 271 

pp. (inRussian). 

Nikolskii, G. V. 1938. Fishes of Tadjikistan. Izdatelstvo Academii Nauk SSSR, Moscow-Leningrad. 228 pp. (in Russian). 

Salnikov, V.B., V.J. Birstein & R.L. Mayden. 1996. The contemporary status of the two Amu Darya River shovelnose sturgeons, Pseudoscaphirhynchus 

kaufmanni and P hermanni. Sturgeon Quart. 4(3): 8–10, 

Tleuov, R. T. & N. I. Sagitov. 1973. Acipenserid fishes of the Aral Sea. FAN Press, Tashkent. 155 pp. (in Russian). 

Zholdasova, I. 1997. Sturgeons and the Aral Sea ecological catastrophe. Env. Biol. Fish. (this volume). 

383

Head from ventral and right side of Acipenser oxyrinchus 200 cm T L juvenile, from St. Lawrence River at Kamouraska, Quebec, which 

now resides at the Montreal Biodome (see the typical damage to the tip of the rostrum). Originals by Paul Vecsci. 1996.

Environment Biology of fishes 48: 335-398, 1997. 


Molecular analysis in the conservation of sturgeons and paddlefish 

Isaac I. Wirgin 1 , Joseph E. Stabile 1 & John R. Waldman 2 

1 

Nelson Institute of Environnment Medicine, New York University Medical Center, Long Meadow Road, 

Tuxedo NY, 10987, U.S.A. 

2 

Hudson River Foundation, 40 West 20th Street, Ninth Floor, New York, NY 10011, U.S.A. 


Key words: mitochondrial DNA, nuclear DNA, Acipenser, Scaphirhynchus, Polyodon, stock identification, 

hybridization 

Synopsis 

Sturgeon and paddlefish populations worldwide have declined because of anthropogenic influences. The 

structure and magnitude of genetic diversity of natural populations serves to buffer these fishes against environmental 

variation and should be maintained. Modern molecular biological techniques provide the ability to 

sensitively characterize and quantify the extent of genetic variation in natural populations. We provide a 

summary of those problems in sturgeon population biology that are amenable to investigation with DNA 

approaches, and their applications to date. These have included genetic identification and discrimination of 

taxa. identification of hybrids, stock identification, mixed-stock analysis, and estimation of gene flow and 

homing fidelity. To date, almost all studies have been restricted to North American fauna. Improvements to 

these technologies, including nondestructive sampling, should permit more widespread application of molecular 

approaches to problems of acipenseriform conservation. We suggest that the use ofmore sensitive molecular 

tools such as analyses of hypervariable repetitive and non-coding single copy nuclear DNA may assist 

management even in those taxa which exhibit overall low levels of genetic diversity. 

Introduction 

The worldwide diversity of sturgeons and paddlefishes 

is currently threatened, and in fact, the extirpation 

of some forms in Europe and Asia has been 

reported (Rochard et al. 1990, Birstein 1993, Waldman 

1995). At the same time, population abundanees 

of most species arc at historically low levels, including 

many North American taxa (e.g., Kynard 

1997 this volume, Smith & Clugston 1997 this volume). 

Although molecular analysis has rapidly become 

a primary tool in the management and comervation 

offishes (Hallerman & Beckmann 1988, Wirgin 

& Waldman 1994, Bernatchez 1995), its use for 

problems involving acipenseriforms has lagged, 

perhaps due to the scarcity of many of these species 

and the consequential difficulty of obtaining adequate 

numbers of tissue samples. However, improvements 

to DNA analysis technologies, including 

nonlethal sampling, slackening of tissue preservation 

requirements. and the ability of PCR to allow 

analysis of minute amounts of tissue have 

relaxed many of the constraints that challenged 

sample collection. Thus, we anticipate an expanding 

role for molecular analysis in the conservation 

of these highly threatened fishes. 

Wirgin & Waldman (1994) listed 12 areas of investigation 

in fisheries biology amenable to DNA 

analyses. Here, we review studies in these areas in 

which molecular techniques have been applied to 

problems in the conservation of sturgeons and paddlefishes. 

We also suggest other areas to which

386 

Moreover, variation in the size of mtDNA within 

individuals (heteroplasmy) was seen in A . trans- 

montanus, but not A . oxyrinchus (Stabile et al. 

1996). A thorough review of the acipenseriform ge- 

nome appears in Birstein et al. (1997 this volume). 

these techniques may be applied. Additionally, we 

present a genetic comparison between two ambiguously 

differentiated, putative sturgeon species, 

Acipenser oxyrinchus (American Atlantic sturgeon) 

and A . sturio (European Atlantic sturgeon). 

Characteristics of the acipenseriform genome Molecular studies of acipenseriformsdirected 

toward management and conservation 

All acipenseriforms are polyploids and their chromosomes 

can be arranged as a series 4n–8n–16n ldenitification and discrimination of taxa 

(Birstein et al. 1993, Blacklidge & Bidwell 1993, Birstein 

et al. 1997 this volume). Chromosome num- In the U.S., the taxonomic status of threatened or 

bers are very high: 120, 240, and possibly, 500. Two endangered populations of vertebrates is important 

forms of chromosomes are found: normal-sized in determining the degree of protection they may 

‘macrochromosomes’ and very small ‘microchro- receive under the Endangered Species Act 

mosomes’. A number ofstudies have indicated slow (O’Brien & Mayr 1991). For Acipenser oxyrinchus 

rates of DNA and protein evolution of sturgeons the Altantic ( A . o. oxyrinchus) and Gulfforms ( A. 

andpaddlefishes (Birstein 1993): we believe thatex- o. desotoi) were designated subspecies based on diftended 

generation times in comparison with most ferentiation of morphological features, although 

other fishes may decelerate their molecular evolu- only two Gulf specimens were examined (Vladykov 

tion. Acipenseriforms hybridize readily in the lab- 1955). Wooley (1985) reanalyzed these morphologoratory 

and in nature, at even the intergeneric level ical features of a larger sample of Gulf sturgeon and 

(Birstein et al. 1997 this volume). 

concluded that only one. relative spleen length, was 

In most respects, the structure and evolutionary diagnostic. However, values for relative spleen 

change of the acipenseriform mitochondrial DNA length of the two forms were not discrete and it may 

(mtDNA) genome is typical of vertebrates. Esti- be that differences in these values are ecophenotypmates 

of the size of mtDNA in Acipenser transmon- ic innature. Ong et al. (1996) used direct sequencing 

tanus (white sturgeon, 16.1–16.7 kilobases, Brown et of a hypervariable area (203 base pairs) of the conal. 

1992) and Acipenser fulvescens (lake sturgeon, trol region of mtDNA to quantify the extent of ge- 

16.6-16.9kb, Guenette et al. 1993) are within the netic differentiation between the two putative subrange 

of most other vertebrate taxa (16.5 ± 0.5 kb, species. Representatives of each subspecies from 

Meyer 1993). Gene composition and gene order of populations across their distributions were suracipenseriform 

mtDNA have not been directly in- veyed and three fixed differences were found 

vestigated; however, the mtDNA control region of among 15 polymorphic sites. An additional two nu- 

A . transmontanus is organized similarly to other cleotides were nearly fixed. Although polymorvertebrates 

(Buroker et al. 1993). 

plisms also were detected within populations 

Differences in the size of the mtDNA molecule across the distribution of each subspecies, no fixed 

have been observed among acipenserids. In A. differences among populations were found. Ong et 

transmontanus (Buroker et al. 1990) and A. fulves- al. (1996) concluded that these data strongly supcens 

(Ferguson et al. 1993), the overall size of the ported the designation of subspecies of A . oxyrinmtDNA 

molecule differs among individual speci- chus. 

mens (both within and among populations) because The relationship between A. oxyrinchus and A. 

of variable numbers of tandem repeat units within sturio has long been debated. These fish are found 

the control region. In contrast, no evidence of on opposite sides of the North Atlantic and are phemtDNA 

length variation was observed among spec- notypically very similar. Aciperiser oxyrinchus ocimens 

of A. oxyrinchus (Waldman et al. 1996b). curs widely along the Atlantic coast of North Amer-

387 

Figure I. Comparison of mtDNA control region sequence from Acipenser sturio and the Atlantic and Gulf of Mexico subspecies of 

Acipenser oxyrinchus. Alignment begins nine nucleotides upstream of the terminal association sequence (TAS 1) of tRNA proline. The 

position of the polymorphic sites observed among all 159 specimens of A. oxyrinchus are highlighted in bold. The position of the three 

fixed sites between the subspecies of A . oxyrinchus are noted by asterisks. 

ica. Acipenser sturio, which once had a similarly 

broad range in Europe and Asia, now occurs only in 

very low abundances in both the Gironde River, 

France, and the Black Sea (Rochard et al. 1990). 

Some workers have considered the Atlantic sturgeon 

to be synonymous with or a subspecies of A. 

sturio (Scott & Scott 1988, Birstein I993), but Vladykov 

& Greeley (1963) and Magnin (1964) recommended 

they be given separate specific status. 

pending additional research. We obtained a tissue 

sample from one A. sturio specimen captured during 

1994 in the Gironde River. We then compared a 

portion (203 bp) of the control region of mtDNA 

between A. sturio and A . oxyrinchus 

We found a minimum of 31, and a maximum of 33 

nucleotide substitutions between the individual of 

A. sturio and 159 individuals of both subspecies of 

A. oxyrinchus (Figure 1). Three sites also exhibited 

nucleotide additions or deletions. In comparison, 

the number of nucleotide substitutions between 

any pair of specimens of the two subspecies of A. 

oxyrinchus ranged between five and eight, with no 

additions or deletions. Excluding additions or deletions. 

nucleotide divergence between A. oxyrinchus 

and A . sturio was approximately 15%, much higher 

than the maximum of 3.5% between two subspecies 

of A. oxyrinchus (Ong et al. 1996). There are no unambiguous 

criteria for the interpretation of molecular 

data in determining taxonomic status (e.g., 

O’Brien & Mayr 1991, Wayne 1992). However, we 

believe that the level of differentiation observed argues 

strongly for full species status of each of the 

western and eastern Atlantic sturgeons. 

Scaphirhynchussuttkusi (Alabama sturgeon) has 

recently been described (Williams & Clemmer 

1991); this exceedingly rare species is restricted to 

the Mobile River basin of Alabama and Mississippi. 

Scaphirhynchus suttkusi are morphologically similar 

to S. platorynchus (shovelnose sturgeon). but 

differ significantly in six meristic and at least eleven 

mensural variables. The extent of genetic similarity 

between S. suttkusi (one specimen) and S. platoryn-

388 

Scaphirhynchus albus and S. platorynchus have 

been recognized as similar, but distinct species of 

river sturgeon within the Mississippi River drainage 

(Forbes & Richardson 1905). Significant differenc- 

es in meristic, morphometric, and life history characteristies 

support this taxonomic division. In re- 

cent years, a small but increasing number of fish col- 

lected from the Missouri and Mississippi rivers ex- 

hibited intermediacy in the expression of these 

discriminatory characters, suggesting the existence 

of inerspecific hybrids (Carlson et al. 1985). Pop- 

ulations of both species, but particularly of S. albus, 

currently are severely depleted, probably due to 

habitat alterations, and S. albus is listed as endangered 

by the U.S. Fish and Wildlife Service (Dryer 

& Sandoval 3 ). Hybridization betwcen two sturgeon 

species under these circumstances would not be un- 

expected; Hubbs (1955) concluded that anthropo- 

genic impacts and sharp imbalances in the abun- 

dances of potentially hybridizing species signifi- 

cantly increase the frequency of hybridization 

events in fishes. 

Genetic studies were conducted to quantify the 

relatedness of S . albus and S. platorynchus and to 

cluded that the mtDNA data support the morph- identify markers which could be used to identify F 1 

ological and biogeographic arguments for recogniz- and later generation hybrids. Protein electrophoreing 

S. suttkusi as an endangered ‘species’ of ‘distinct sis studies revealed only low levels of polymorpopulation 

segment’ as defined by the U.S. Endan- phism within and between these taxa and those loci 

gered Species Act. Analysis of additional speci- (3 of 37) which were polymorphic did not display 

mens of S. albus and S. platorynchus from the lower significant interspecific allelic differences (Phelps 

Mississippi River (nearer the range of S. suttkusi is & Allendorf 1983). Thus, protein electrophoresis 

proved insensitive in distinguishing these species, 

perhaps due to its focus on gene products that are 

1 Genetic Analyses, lnc. 1994. Genetic studies of Scaphirhynchus 

essential for survival and that tend to be conserva- 

shus and S. albus (pallid sturgeon) was compared 

using PCR products (amiplicons) (Genetic Analyses 

1 ). Acipenser fulvescens and the two subspecies of 

A. oxyrinchus were analyzed to provide additional 

points of reference. PCR primers were designed 

based on conserved sequences (among mammals) 

for eight nDNA genes and these were shown to amplify 

sturgeon DNA and to produce amplicons. 

These aniplicons were then digested with a battery 

of different restriction enzymes and DNA band 

sharing was compared between two putative taxa. 

The level of genetic differentiation between S. suttkusi 

and the other two species of Scaphirhynchus 

was greater than that between subspecies of A. oxyrinchus 

but less than that between the two species 

of Acipenser. The authors also concluded that distinct 

species designation for S. albus and S. platorynchus 

may not be valid, but instead. that the two 

forms may represent morphological variants of a 

singlespecies. 

A later, expanded mtDNA study (Campton et 

al 2 ) also found very low levels of divergence between 

S. suttkusi (N = 3) and the other two Scaphirhynchus 

species. A unique haplotype distinguished 

the three specimens of S. suttkusi from all individuals 

of the other two species of Scaphirhynchus collected 

from the upper Missouri River, but this haplotype 

differed from the most common haplotype 

found among S. albus and S. platorynchus by only a 

single nucleotide substitution. Campton et al. 2 con- 

needed to confirm the genetic discreteness of S. 

suttkusi from its congeners. 

Analyses of hybridization and introgression 

spp. Report to the U.S. Army Corps of Engineers, Omaha District: 

U.S. Fish and Wildlife Service, Bismarck, North Dakota; five across taxa. 

U.S. Army Corps of Engineers, Mobile District. 41 pp. Recently, direct analyses of nuclear DNA 

2 Campton, D.E., A.I. Garcia. B.W. Bowen & F.A. Chapman. (nDNA) and mtDNA were used to further discrimi- 

1995. Genetic evaluation of pallid, shovelnose, and Alabama 

sturgeon (Scaphirhynchus albus, S. platorynchus and S. suttkusi) 

based on control region (D-loop) sequences of mitochondrial 

DNA. Final Report to the U.S. Fish and Wildlife Service, Bismarck 

North Dakota. 35 pp. 

3 Dryer, V.P. & A.J. Sandoval. 1993. Recovery plan for the pallid 

sturgeon (Scaphirhynchus albus). U.S. Fish and Wildlife Service, 

Denver. 55 pp.

nate between S. albus and S. platorynchus with the ferences exist among two or more spawning popexpectation 

that higher levels of diversity would be ulations, they may be considered separate stocks 

detected with these more sensitive approaches. Nu- and managed as distinct units (Waldman & Wirgin 

clear DNA sequences were PCR amplified with 1994). Acipenseriforms investigated for stock difconserved 

primers and these PCR products were ferences include two freshwater species, Polyodon 

then digested with a battery of different restriction spathula (American paddlefish) and A . fulvescens; 

enzymes and DNA band sharing was compared be- and three anadromous sturgeons. S. stellatus (steltweenthe 

two putative taxa. Variability among indi- late sturgeon), A . transmontanus, and A . oxyrinviduals 

in the digestion patterns of amplicons was chus. 

seen only at a prealbumin-related locus (Genetic Genetic studies on populations of P. spathula 

Analyses, Inc. 1 ). A comparison of allelic frequen- have been conducted on both the protein and DNA 

cies between S. albus and S. platorynchus at the levels. Carlson et al. (1982) observed extremely low 

prealbumin-related locus showed no significant dif- levels of protein variation in P. spathula and did not 

ferences. 

detect evidence of differentiation among popula- 

Campton et al .2 sequenced more than 400 bp of tions. In contrast, using both protein analysis and 

mtDNA from the control regions of S. albus (N = restriction fragment length polymorphism (RFLP) 

18) and S. platorynchus(N = 20) and found 8 haplo- analysis of mtDNA, Epifanio et al. 4 found greater 

types from an area of sympatry in the upper Mis- levels of genetic polymorphisms among P. spathula 

souriRiver. However, these haplotypes overlapped collected from21 populations, including the Missisbetween 

the two species to the extent that maxi- sippi, Pearl, Alabama, andNeches drainages. Howmum 

parsimony analysis did not reveal two distinct ever, the majority of protein variation was observed 

species-congruent branches, but χ 2 analysis did within populations and was of little use in elucidatshow 

significant haplotypic frequency differences ing population structure. Mitochondrial DNA ge- 

(p < 0.001) between the species. Control region of notypes showed greater geographic partitioning 

other acipenserids were similarly sequenced to with both northern (mid-Missouri River) and 

serve as references: mean nucleotide diversity southern haplotypes evident, suggesting the existamong 

specimens of the three scaphirhynchids was ence of some population structure within their 

0.58%, compared to 1.20% for A . transmontanus. overall distribution. 

Also, the mean nucleotide diversity was 0.62% be- Acipenser fulvescens also is widely distributed in 

tween S. albus and S. platorynchus, compared with North America. Porter et al. 5 used protein electro- 

14.1% between A . transmontanus and A . mediros- phoresis to compare the genetic status ofA . fulvestris 

(green sturgeon). Campton et al. 2 were unable cens from Lake Erie with other populations from 

to dismiss hybridization as a factor in the differen- the Laurentian Great Lakes. Only the lactate detiation 

of S. albus and S. platorynchus, but they fa- hydrogenase enzyme system (LDH) revealed usevored 

the hypothesis that the two species maintain ful population-level variation. Although the Lake 

some degree of reproductive isolation. 

Erie population was the least variable of those surveyed, 

one of its three LDH phenotypes was not 

found among other populations. Guenette & Fortin 

Identification of stocks and assessment of 

genetic variability 

(1993) found low levels of mtDNA variation in A . 

fulvescens from the St. Lawrence River and James 

389 

Several studies have assessed genetic differentiation 

among hypothesized stocks of sturgeons and 

paddlefishes. Identification of genetic stocks requires 

that individuals fromhypothesized stocks be 

o 

surveyed for genetic variability, usually at rapidly 

evolving sites. If statistically significant genetic dif- 

4 

Epifanio, J., M. Nedbal& D.P. Phillipp. 1989. A population genetic 

analysis of paddlefish (Polyodon spathula). Report to Missouri 

Department of Conservation. 63 pp. 

5 

Porter, P B., T. Cavender, P. Fuerst & T.Nickell. 1995 The genetic 

status of lake sturgeon in Lake Erie and other populations from 

the Laurentian Great Lakes. Report to Ohio Department of Natural 

Resources. 47 pp.

390 

Bay drainages. No differences in mtDNA haplo- tween populations of A. transmontanus from the 

types were detected in sturgeon from different loca- Fraser and Columbia rivers (Brown et al. 1992, 

tions in the St. Lawrence River; however, haplotyp- 1993). In the most recent glacial advance, the lower 

ic frequencies differed from those in the Waswanipi Columbia River was believed to remain an ice-free 

River in the James Bay basin. The lower mtDNA refugium, whereas the Fraser River was completely 

heterogeneity in fish from the St. Lawrence River glaciated. Sequence variation of the control region 

was interpreted to reflect greater anthropogenic in- was consistent with the hypothesis that the Columfluences 

on population abundance. 

bia River was the founder source for the Fraser Riv- 

Ferguson et al. (1993, 1997 this volume) used population (Brown et al. 1993). However, levels 

RFLP analysis of mtDNA and direct sequencing of of overall mtDNA diversity were significantly highthe 

control region of mtDNA to investigate stock er among fish from the Fraser River than the Costructure 

of A . fulevscens from Canadian systems, lumbia River, despite the greater recency of the 

with an emphasis on the Moose River basin in On- Fraser River population (Brown et al. 1992). It was 

tario. Little differentiation of mtDNA haplotypes hypothesized that lower genetic diversity in the Cowas 

found among major tributaries of the Moose lumbia River population resulted from reduced ac- 

River basin, suggesting an absence of discrete cess to historic spawning areas due to the construcstocks. 

However, sturgeon from the Moose River tion of dams. Brown et al. (1992) also found signifbasin 

exhibited significantly higher levels of icant differences in mtDNA haplotype frequencies 

mtDNA diversity and were genetically differentiat- between samples from the Fraser River and Columed 

from fish from the Great Lakes-St. Lawrence bia River, indicating that these two rivers support 

drainage and other Hudson Bay-James Bay popula- genetically distinct populations of sturgeon. Betions. 

These workers hypothesized that mtDNA cause haplotype differences were not fixed between 

differentiation in sturgeon from Canadian waters the two populations, the authors suggested that low 

resulted from post-Pleistocene colonization from levels of gene flow between systems may be occurseparate 

refugia in the Mississippi and St. Lawrence ring. Alternatively, we suggest that given the brief 

River drainages. Further investigation of mtDNA time since divergence of these populations, the acdiversity 

in extant stocks of A . fulvescens in eastern cumulation of significant differences in genotype 

and western U.S. drainages should resolve this frequencies indicates effective reproductive isolaquestion. 

tion of these systems. 

Acipenser stellatus is an abundant sturgeon spe- Populations of A.oxyrinchus occur in drainages 

cies in the Caspian Sea. Stock structure of this spe- of the Gulf of Mexico and along the Atlantic coast 

cies in the southern portion of the Caspian Sea was of North America. Acipenser oxyrinchus desotoi 

investigated by restriction enzyme digestion of the (Gulf sturgeon) are considered threatened by the 

PCR amplified ND5/ND6 region of mtDNA. Al- U.S. Fish and Wildlife Service. Historically, A. o. 

though polymorphic haplotypes were identified, no desotoi were found in major river systems extendsignificant 

differences in haplotype frequencies ing from central Florida to the Mississippi River; 

were detected among fish from four regions. which many of these drainages still host depleted populaled 

to the conclusion thatA. stellatus in the southern tions (USFWS and GSMFC 6 ). Efforts are being 

Caspian Sea probably represent a single stock (M. considered to restore depressed populations 

Pourkazemi personal communication). through hatchery supplementation. However, 

Acipenser transmontanus occurs from California knowledge of the stock composition ofA. o. desotoi 

to Alaska with viable fisheries currently centered in was federally mandated prior to the initiation of rethe 

Columbia River, Washington and the Fraser storative efforts, so that native gem pools are pre- 

River, British Columbia. Both sequencing of the 

rapidly evolving control region of mtDNA and 

6 

U.S. Fish and Wildlife Service and Gulf States Marine Fisheries 

RFLP analyses of the entire mtDNA molecule were Commission. 1995. Gulf sturgeon recovery plan. Atlanta, Georgia. 

used to examine the extent of differentiation be- 

170 pp.

391 

Figure 2. Gulf of Mexico rivers from which specimens of Acipenser oxyrinchus were obtained. 

served. The Suwannee River population has been low rivers, (4) Choctawhatchee River, and (5) Apaextensively 

studied over the past decade and prob- lachicola, Ochlockonee. and Suwannee rivers. These 

ably contains the largest population of sturgeon results suggest strong reproductive isolation of A. o. 

along the Gulf of Mexico. Miracle & Campton desotoi stocks on at least a regional basis, and point 

(1995) examined the extent of genetic variation in to the inadvisibility of mixing of hatchery-reared 

sturgeon from the Suwannee River to determine if progeny of broodstock froin different Gulf rivers. 

its population constituted a single homogeneous Also, we used RFLP analysis of mtDNA with five 

unit. Sequence analysis of 268 base pairs of a highly diagnostic restriction enzymes to characterize the 

variable area of the mtDNA control region did not stock structure of populations of A . o. oxyrinchus 

reveal significant genetic heterogeneity among along the Atlantic coast, including the St. Lawrence 

sturgeon from different sampling locations. 

River, Quebec; St. John River. New Brunswick; 

We used RFLP and sequencing analysis of Hudson River, New York; Edisto River. South CarmtDNA 

to assess the stock structuring of A. o. des- olina; and Four rivers in Georgia; the Altamaha, 

otoi populations among eight drainages (Figure 2) Ogeechee, Savannah, and Satilla (Waldman et al. 

extending from the Mississippi River to the Suwan- 1996a, b). Chi-square analysis showed the eight 

nee River (Stabile et al. 1996). RFLP analysis using populationscould be grouped as three highlydifferfour 

diagnostic restriction enzymes yielded eight entiated (p

392 

a 

b 

Figure 3. UPGMA phenograms of the interpopulation diversity indices for the (a) RFLP data, and (b) control region sequence data for 

Acipenser oxyrinchus from the Gulf of Mexico. 

northern populations that recolonized glaciated 

drainages from more genotypically diverse populations 

in southern, nonglaciated regions. 

Mixed-stock analysis 

For somewide ranging species, fisheries have developed 

distant from spawning and nursery areas, and 

these fisheries may harvest individuals from more 

than one stock. For management purposes, it is important 

to quantitatively estimate the relative contributions 

of individual stocks to mixed fisheries to 

allow managers to protect threatened stocks at sites 

distant from their natal rivers. Successful application 

of genetic approaches to mixed-stock analysis 

is dependent on the existence of significant differentiation 

of genetic characters among spawning 

stocks which contribute to the mixed fishery (Utter 

& Ryman 1993, Xu et al. 1994). To conduct mixed

393 

stock analysis, frequencies of genotypes must be 

characterized in reference spawning stocks and in 

the mixed fishery. 

A targeted coastal fishery for A . o. oxyrinchus 

has developed in recent years along the mid-Atlantic 

coast of New Jersey and New York (New York 

Bight) and bycatch fisheries have been reported off 

the southeastern coast of the U.S. (Collins et al. 

1996). Waldman et al. (1966a) performed RFLP 

analysis of specimens of A. o. oxyrinchus from eight 

populations from Canada to Georgia and concluded, 

based on haplotype frequency differences, that 

three statistically discrete (p < 0.0001) stocks exist: 

(1) Canadian, (2) Hudson River, and (3) southeastern. 

Haplotypic frequency data ofthese stocks were 

then used in a mixture model (constrained least 

squares;Xu et al., 1994) to estimate the relative contributions 

of each of these stocks to a sample of Atlantic 

sturgeon (N = 112) from the fishery in the 

New York Bight off New Jersey. This analysis 

showed a 97% to 99% contribution from the Hudson 

River stock. with the remainder from the southeastern 

stock. The overwhelming contribution of 

the Hudson River stock was attributed both to (1) a 

hypothesized tendency for marine migrating Atlantic 

sturgeon to remain within the geographic provinces 

of their natal rivers (the Hudson River is within 

the Virginian province), and (2) to the absence of 

other robust American Atlantic sturgeon populations 

within the Virginian province. 

Gene flow and homing ,fidelity 

Most populations of sturgeons are anadromous or 

potamadromous and thus, migrate from marine or 

lake waters to rivers to spawn (Bemis & Kynard 

1997 this volume). However, almost nothing is 

known of the degree of homing fidelity shown by 

acipenseriforms. Although homing fidelity offishes 

may be studied directly by means of capture-markrecapture 

(e.g., Melvin et al. 1986), the relativescarcity 

and high value of sturgeons precludes such an 

approach. An alternative is to assess homing fidelity 

indirectly through genetic analysis (Tallman & 

Healey1994). 

Homing fidelity of sturgeons through genetic 

analyses would best be assessed among populations 

in rivers that drain to a common water body and 

that historically have a stable geographic history to 

avoid confoundment by founder effects as a consequence 

of recolonizations. Stabile et al. (1996) used 

both RFLP and sequencing analysis of mtDNA to 

estimate gene flow among five stocks of A. o. desotoi 

that occur in eight drainages that feed the Gulf 

of Mexico between Mississippi and Florida. The 

five stocks were defined based on χ 2 analyses (p < 

0.05) of haplotype frequencies; some stocks were 

equivalent to single populations, whereas others 

were regional stocks macle up to two or more populations. 

Pairwise gene flow estimates (N m ) between 

stocks were derived from F st values (Wright, 

1943) obtained via AMOVA analysis (Excoffier et 

al.1992). 

Pairwise estimates of gene flow (Table 1) among 

the Gulf stocks based on sequencing analysis ranged 

from 0.15 between the western (Lake Ponchartrain 

and Pearl River) stock and the Escambia River-Yellow 

River stock, to 1.2 between the Escambia 

River-Yellow River stock and the eastern stock 

Table 1. Estmates of gene flow among populations of Acipenser oxyrinchus desotoi. Values above diagonal are based on data from 

restriction fragment length polymorphism analysis of mitochondrial DNA (mtDNA): values below diagonal are based on data from 

sequence analysis of 203 base pairs of mtDNA control region. 

Western Pascago ula Escambia- Choctawhatchee Eastern 

Yellow 

Western – – 0.26 0.1 I 0.23 

Pascagoula 249.75 – – – – 

Escambia-Yellow 0.15 0.23 – 0.45 0.66 

Choctawhatchee 0.22 0.35 0.79 – 0.09 

Eastern 0.11 0.27 1.20 0.97 –

394 

(Apalachicola, Ochlockonee, and Suwannnee riv- Conclusions and recommendations 

ers). Gene flow estimates derived From RFLP analysis 

were even lower on average, and ranged from The comparatively few molecular analyses directed 

0.09 between the western and Choctawhatchee Riv- to conservation of acipenseriforms have yielded 

er stocks to 0.66 between the western and Escambia unique and important information. Some of these 

River-Yellow River stock. 

studies have refined notions concerning species and 

These gene flow values are very low in compari- subspecies status; our analysis of mtDNA control 

son with estimates for other anadromous fishes. Es- region differences between the American and Eutimated 

annual straying rates among populations of ropean Atlantic sturgeons shows that should relict 

Pacific salmons have ranged between about 1% and populations of the latter become extinct, restocking 

27% (reviewed in Adkindson 1996). Laughlin & with A. oxyrinchus would constitute introduction of 

Turner (1996) used two statistical methods to esti- a foreign species. Likewise, the study by Ong et al. 

mate N m of Morone saxatilis (striped bass) among (1996) supporting subspecies designations for Atthree 

Virginia tributaries of Chesapeake Bay: the lantic and Gulf forms of A. oxyrinchus reinforces 

private allele approach of Barton & Slatkin (1986) the current status of the latter as a threatened subyielded 

an estimate of N m = 14.2, whereas the F st ap- species under the U.S. Endangered Species Act. 

proach yielded an estimate of N m = 2.7. In a capture- Unfortunately, to date, conservation directed 

mark-recapture study, Melvin et al. (1986) estimat- molecular studies of acipenseriforms at the species 

ed an annual straying rate of 3% among Canadian level and below have almost exclusively been repopulations 

of Alosa sapidissima (American shad). stricted to North American species. Highly sensi- 

Moreover, the low gene flow estimates for A. o. tive determination of the genetic relationships 

desotoi were obtained across populations that occur among extant species. stocks, and between extinct 

in eight rivers, the mouths of which are arrayed and closely related extant taxa are possible. Much 

across little more than 500 km of coastline. Sturgeon of the latter analyses will use archived museum 

from these rivers have the opportunity to mix in the samples as sources of DNA. Birstein (1993) provid- 

Gulf of Mexico during winter. These mtDNA data ed many examples of Eurasian sturgeons that are 

show that despite the geographic proximity of these phenotypically differentiated (i.e., large and small 

rivers, stocks ofA . o. oxyrinchus generally exchange ‘forms’) below the species level but that have not 

less than one female per generation, a level sufficient received genetic analysis. Even if financial reto 

permit differentiation at the stock level (Adkin- sources are currently not available: samples can be 

son 1996). Gene flow estimates also were generally collected and archived for Future analyses. 

higher among proximal stocks. suggesting that what Population surveys also have been limited largely 

straying occurs does so in ‘stepping stone’ fashion to North America. Genetic analyses of P. spathula 

(Kimura & Weiss 1964) in which migrants among and A. fulvescens - paddlefish and sturgeon species 

semi-isolated populations are exchanged chiefly with similar and broad North American distribuwith 

neighboring populations. If this is true for A. o. tions – have revealed relatively little genetic variadesotoi, 

then such spatially restricted straying should tion and only minor substructing among populahave 

contributed to the geographic structuring ob- tions. In comparison, coastal species such as A. oxserved 

among these populations (Adkinson 1996). .yrinchus and A. transmontanous exhibit higher levels 

Stabile et al. (1996) hypothesized that the homing of polymorphism and greater geographic populaimperative 

of A. o. desotoi for spawning purposes is tion structuring. The reasons for this disparity are 

strong, but that it may be reinforced by metabolic not apparent, and are contrary to comparisons 

constraints. Acipenser oxyrinchus desotoi returns to among other freshwater and anadromous fishes 

rivers from the Gulf of Mexico to summer near cold (Waldman & Wirgin 1994). We cannot be sure if 

water springs; tagging has shown that individuals arc present levels of genetic diversity among these four 

recaptured at the same cool water refuges in which species reflects prebottleneck levels, given the 

they were first tagged (Clugston et al. 1995). widespread anthtopogenically-imposed bottle-

necks on their populations. However, it is likely that used (Krueger et al. 1981). The single study of gene 

the paucity of genetic diversity and shallow genetic flow in an acipenserid suggests that hatchery-based 

differentiation among populations ofthe two fresh- restocking may be necessary to reestablish sturgeon 

water species is at least partly due to a combination populations in a reasonable length of time in drainof 

Pleistocene bottlenecks and recent recoloniza- ages where they are extinct. That is, ifgene flow estion 

of northern waters, prolonged generation timates among populations of A . o. desotoi are intimes 

leading to low mutation rates, and continued dicative of general levels of straying for acipensergene 

flow among populations that remain largely rids, then straying rates less than 1.0 per generation. 

linked through their inhabitation of few discrete combined with the long generation times of sturdrainages. 

Although the anadromous sturgeons of geons, means that natural restocking may require 

North America were not exempt from glacial influ- decades before it even is initiated, notwithstanding 

ences, post-Pleistocene genetic diversity was main- additional decades necessary for population growth 

tained, except in far northern drainages recolonized (Boreman 1997 this volume). Circumstantial evibyA 

. oxyrinchus. 

dence for extremely slow rates ofnatural restocking 

Genetic analyses to date of the freshwater sca- through straying is provided by the example of the 

phirhynchids show very limited genetic variation, Maryland tributaries of Chesapeake Bay, where 

consistent with P. spathula and A . fulvescens – spe- there has been no indication of recolonization by A. 

cies that are largely sympatric with S. albus and S. oxyrinchus over many decades in rivers that once 

platorynchus. Low genetic variation within Scaphir- supported large populations (David Secor personal 

hynchus is in accordance with pre-existing biogeo- communication). 

graphic theories suggesting recent speciation with However, a generic problem with the hatchery 

Wisconsinian glacial events (70 000 to 10 000 years production of sturgeons is the need to acquire suffibefore 

present). However, the taxonomic bounda- cient broodstock to prevent inbreeding (Nelson & 

ries among the three putative scaphirhynchid spe- Soul6 1987). Commonlyacceptedguidelines forfish 

cies remain unclear. but of great importance to their production arc for an effective population size of 

conservation status under the U.S. Endangered 100 or more individuals (Kincaid 1983, Kapuscinski 

Species Act (ESA). Future molecular analyses of & Lannan 1986, Allendorf & Ryman 1987). But, giv- 

Scaphirhynchus spp. and other North American en the generally large size and scarcity of sturgeons. 

acipenserifoms will not only attempt to assess ti-a- annual hatchery reproduction at these effective 

ditional taxonomic divisions such as species and population levels are unrealistic for most restorasubspecies, 

but also their Evolutionarily Significant tion efforts aimed toward single stocks. If lower 

Units as mandated under the Endangered Species than recommended numbers of broodstock must be 

Act (Waples 1995). 

used, one way to reduce inbreeding would be to use 

Molecular analyses to date also are relevant to genetic screening of inviduals With the data from 

consvervation efforts involving hatchery-based these analyses, hatchery crosses can be optimized to 

stocking (St. Pierre 7 ). Anadromous sturgeons show maximize diversity and yet still maintain stock-spestock 

structure, implying that interpopulation cific gene frequencies. We envision that a priori 

transfers will have genetic repercussions; to maxi- knowledge of the genetic composition of broodmize 

the likelihood that stocked fish will have high stock can help ease the burden ofrigorous demands 

fitness for a particular environment, broodstock for large numbers of broodstock. 

from the same environment as wild fish should be Rapid technical advances in the development of 

molecular biological approaches will allow for their 

routine application in the future to problems of the 

7 St. Pierre, R.A. 1996. Breeding and stocking protocol for cultured 

Atlantic sturgeon. Final Report from the Atlantic Sturgeon 

conservation of sturgeons and paddlefishes. It is 

aquaculture andStocking Committeetothe Atlantic States Marine 

Fisheries Commission Atlantic Sturgeon Management from non-destructively obtained tissues such as 

now possible to obtain DNA sequence information 

Board. 17 pp. 

barbels, fin clips, or blood, from early life intervals 

395

396 

We thank Patrick Williot for the tissue sample of 

European Atlantic sturgeon. Work was funded by 

the National Oceanic and Atmospheric Adminis- 

tration award # NA46RG0090 to the Research 

Foundation of the State University ofNew York for- 

the New York Sea Grant Institute. The U.S. Government 

is authorized to produce and distribute re- 

prints for governmental purposes notwithstanding 

any copyright notation that may appear hereon. 

Views expressed herein are those of the authors and 

do not necessarily reflect the views of NOAA or any 

1993, Bemis & Findeis 1994). A study is now under- of its subagencies. This work also was supported by 

way (DeSalle & Birstein 1996) to develop forensic the U.S. Fish and Wildlife Service and the Hudson 

molecular markers to help identify illegally pro- River Foundation and NIEHS center grant 

cured and mislabeled acipenserid products. Also, ES00260. 

most acipenseriforms are difficult to sex except at 

spawning. Nonlethal molecular gender determination, 

as has been developed for oncorhynchus tshawytscha 

(chinook salmon, Devlin et al. 1994), would 


be useful for many management purposes. 

Additionally, contaminant exposure has been 

proposed as a major factor in the decline of certain 

sturgeon populations (Birstein 1993). However, 

quantitative data on comparative exposure histories 

or possible biological effects are largely lacking. 

We suggest that a molecular biomarker approach, 

in which structural alterations at anonymous genet- 

such as single eggs, embryo or larva, and even from 

archived museum specimens. Additionally, a variety 

of DNA level approaches have been developed 

which allow for investigations which focus on characters 

whose rate of change varies from extremely 

slow to exceedingly rapid (Wirgin & Waldman 

1994). This permits quantiification of genetic relationships 

extending from the interspecific to interindividual 

levels. We strongly encourage the use of 

nDNA-based approaches to resolve management 

questions concerning taxa such as Scaphirhynchus 

in which low levels of genetic diversity have been 

reported. Because of the polyploid character of the 

acipenserid genome, it is highly likely that many duplicated 

gene loci have been relieved of functional 

constraints and were free to rapidly evolve. Thus, 

the nuclear genome of sturgeon species should offer 

a wealth ofrapidly evolving single copy or repetitive 

DNA sequences for analysis. 

Several other avenues for future molecular research 

of sturgeons and paddlefishes are apparent. 

Poaching of these fishes across North America and 

Eurasia is a major threat to their existence: much of 

this illegal harvest is sold in world markets (Birstein 

tion. This approach has been used successfully to 

quantify the exposure histories of species such as 

Parophrys vetulus (English sole. Stein et al. 1992) 

and Microgadus tomcod (Atlantic tomcod, Wirgin 

et al. 1994) from North American estuaries. Furthermore, 

increased levels of gene expression in fish 

from contaminated environments have been correlated 

with higher level biological effects at the population 

level (Wirgin & Garte 1994). 


icloci or expression levels of xenobiotically responsive 

genes are quantified, can help fill this void. The 

extent of DNA sequence variation at these loci or 

levels of expression of inducible genes such as cytochrome 

P4501A or metallothionein can allow for a 

comparison of the exposure histories of sturgeons 

from environments with differing degrees of pollu- 

Adkinson, M.D. 1996. Population differentiation in Pacific salmon: 

local adaptation. genetic drift. or the environment? Can. J. 

Fish. Aquat. Sci. 52: 2762 2777. 

Allendorf, F.W. & N, Ryman 1987. Genetic management of 

hatchery stocks. pp. 141–159. In: N. Ryman & F. Utter (ed.) 

Population Genetics and Fishery Management, University of 

Washington, Seattle. 

Barton, N.H. & M. Slatkin 1986 A quasi-equilibrium theory of 

the distributions of rare alleles in a subdivided population. 

Heredity 56: 409-415. 

Bemis, W.E. & E.K. Findeis. 1994Thesturgeon’s plight. Nature 

370:602. 

Bemis, W.E. & B. Kynard. 1997 Sturgeon rivers: an introduction 



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Sensitivity of North American sturgeons and paddlefish to fishing mortality 

John Boreman 

UMass/NOAA Cooperative Marine Education and Research Program, The Environmental Institute, Blaisdell 

House, University of Massachusetts, P O. Box 30820, Amherst MA 01003–0820, U.S.A. 


Key words: reproductive potential, exploitation, endangered species, chondrosteans, eggs per recruit 

Synopsis 

Sturgeonsand paddlefish exhibitunusual combinationsof morphology, habits, andlife historycharacteristics, 

which make them highly vulnerable to impacts from human activities, particularly fisheries. Five North American 

sturgeons (shortnose, Gulf pallid, Alabama, and green sturgeon) are listed as endangered or threatened 

by management authorities. Managers have instituted fishery closures for the three other species of North 

American sturgeons (Atlantic, white. and shovelnose) and paddlefish because of low stock abundance at 

some point in this century. Reproductive potential in four species 1 examined (Atlantic, white, and shortnose 

sturgeon, and paddlefish) is more sensitive to fishing mortality than it is for three other intensively-fished 

coastal species in North America: striped bass. winter flounder, and bluefish. The sturgeons and paddlefish 

are generally longer-lived than the three other coastal species, and also have an older age at full maturity, 

lower maximum fecundity values, and older ages at which 50% of the lifetime egg production is realized with 

no fishing mortality. 

Introduction 

sturgeon, and shovelnose sturgeon); (2) adults 

move into brackish water (white sturgeon and 

Of the 25 chondrostean species still living in the shortnose sturgeon); or (3) adults move into the 

Northern Hemisphere. the paddlefish, Polyodon ocean (white sturgeon, green sturgeon. and Atlanspathula 

and eight species of sturgeon are found in tic sturgeon). All of the species reproduce in fresh 

North American waters (Birstein 1993): Atlantic water. 

sturgeon, Acipenser oxyrinchus, shortnose stur- Sturgeons and paddlefish exhibit unusual combigeon, 

Acipenser brevirostrum,white sturgeon, Aci- nations of morphology, habits, and life history charpenser 

transmontanus lake sturgeon, Acipenser ful- acteristics, which make them highly vulnerable to 

vescens, green sturgeon, Acipenser medirostris pal- impacts from human activities, particularly fisherlid 

sturgeon Scaphirhynchus albusshovelnose stur- ies. In North America, human activities known to 

geon Scaphirhynchus platorynchus and Alabama impact sturgeons and paddlefish are industrial and 

sturgeon, Scaphirhynchus suttkusi They inhabit municipal pollution, blockage of access to habitats 

fresh, brackish, and sea water systems in North by dikes and dams, channelization and elimination 

America. and exhibit three types of life history pat- of backwater areas, dewatering ofstreams, physical 

terns (after Rochard et al. 1990): (1) their entire life destruction of spawning grounds, inundation of 

history is spent in fresh water (paddlefish, lake stur- habitat by reservoirs, and overfishing (Baker 1980, 

geon, white sturgeon, pallid sturgeon, Alabama Carlson & Bonislawsky 1981, Trautman 1981, Beck-

400 

er 1983. Kallemeyn 1983. Cochnaueret al. 1985, Rochard 

et al. 1990, Moyle et al. 1 ). 

Five of the North American sturgeons are listed 

as endangered or threatened by management authorities: 

shortnosesturgeon (Dadswell et al. 1984), 

green sturgeon (Moyle et al. 1 ), pallid sturgeon 

(Keenlyne & Jenkins 1993). Alabama sturgeon 

(Williams el al. 1989). and Gulfsturgeon, Acipenser 

oxyrinchus desotoi (Mason & Clugston 1993), which 

is a subspecies of Atlantic sturgeon. Although not 

officially listed as endangered or threatened, three 

other species of North American sturgeons and 

paddlefish have been reduced to such low densities 

at some point in this century that fishery closures 

were instituted. Harvesting of lake sturgeon in the 

Lake Winnebago system, Wisconsin, was prohibited 

from 191.5 to 1931 due to a concern over the drop 

in abundance (Folz & Meyers 1985). Harvest of 

white sturgeon in the Snake River was terminated 

after 1983 due to a decline in abundance, and a total 

fishery closure was recommended for sections of 

the river (Cochnauer et al. 198.5). In Wisconsin and 

Iowa, non-fishing zones below navigation dams 

were adopted to protect shovelnose sturgeon from 

overfishing (Becker 1983). A three-year moratorium 

on commercial harvest of paddlefish was initiated 

in Louisiana in 1986 and the recreational creel 

limit was reduced to one fish per day because of declines 

in stock levels (Reed et al. 1992). 

Although draconian fishing restrictions have 

been instituted for many of the North American 

chondrosteans, demand for the species has not diminished. 

Since the middle 1800s, North American 

sturgeons have been the target of intensive fisheries, 

primarily for caviar and also for their meat 

(fresh, smoked, or tinned); angling for sport is also 

growing more popular, especially for white and lake 

sturgeons (Rochard et al. 1990). When sturgeons 

became unavailable for the lucrative caviar market, 

some fisheries switched to paddlefish (Carlson & 

Boinislawsky 1981, Reedetal. 1992). 

1 

Moyle, P.B.. R.M. Yoshiyama, J.E. Williams & E.D. Wikramanayake. 

1996 Fish species of special concern in California (second 

edition). Prepared for the State of California, The Resources 

Agency, Dept. Fish and Game Int Fish. Div., Rancho 

Cordova, California (in press). 

In this paper, I examine the sensitivity of North 

American sturgeons and paddlefish to fishing and 

early life mortality. Specifically, I present the impact 

of fishing mortality on reproductive potential for 

several representative sturgeon and paddlefish 

populations, and examine whether adjustments to 

fishing mortality could be used to offset reductions 

in reproductive potential caused by other sources of 

mortality due to human activities. I also compare 

the chondrosteans to other fish species currently 

supporting intensive fisheries in North America 

(striped bass in the Hudson River, New York, winter 

flounder in Cape Cod Bay, Massachusetts, and 

bluefish along the Atlantic coast of North America) 

to demonstrate how life history characteristics 

make the chondrosteans more sensitive to fishing 

mortality. 

Methods 

Effects of fishing mortality on reproductive potential 

For purposes of this paper, I define reproductive 

potential as the potential lifetime egg production of 

an age 1 female (eggs-per-recruit, EPR). This measure 

is the sum of the number of eggs she is likely to 

produce at each age times the probability that she 

will survive to that age (Boreman et al. 1993): 

where ρ i is the proportion of females mature at age 

i, is the average fecundity of an age-i female, F j is 

the instantaneous rate of fishing mortality during 

periodj, M j is the instantaneous rate ofnatural mortality 

during period j , and n is the oldest spawning 

age. The maximum value for potential lifetime egg 

production (EPR max ) is achieved when no fishing 

mortality occurs (Fj = 0 for all j). As F is increased, 

EPR will decline due to the lessened probability 

that an age1 female will survive to the next age, given 

the increased risk of fishing mortality along with 

the risk of natural mortality she also must endure. 

Relative sensitivity of reproductive potential to a 

Specific rate of fishing mortality is the ratio of the 

EPR-value calculated for that rate to EPR max 

. 

(1)

Restricting fishing mortality to offset losses from the Hudson River has a minimum size limit of 152 

other sources 

cm (Kahnle et al 3 ). I did not attempt to divide fishing 

mortality into sport or commercial. For short- 

Fishery managers have the option of regulating nose sturgeon and paddlefish, I assumed that all agfishing 

mortality to offset impacts of mortality from es 1 and older would be equally vulnerable to any 

unknown or largely uncontrollable sources, such as increase in mortality beyond that already incorpochanges 

in river flows and contaminant toxicity, rated into the natural mortality rates. 

which usually occur in fish stocks during the first Values for life history parameters of female 

year of life. To maintain stationary population striped bass in the Hudson River are from 

abundance, i.e., population abundance that is nei- Goodyear (1988). The values are for the population 

ther increasing nor declining over generations, the prior to closure ofthe fishery in the river in 1976 due 

survival rate of a female egg to age 1 (S 0 ) must be to chemical contamination, and represent a period 

equal to two times the reciprocal of the EPR-value when coastal landings of striped bass from the Hud- 

(assuming the sex ratio of deposited eggs is 50:50), son River and elsewhere along the Atlantic coast of 

sothat: 

North America were at their peak (Boreman & 

EPR . S 0 = 2. 

Austin 1985). Boreman et al. (1993) list parameter 

(2) values for female winter flounder in Cape Cod Bay, 

and parameter values for female bluefish along the 

Ifsurvival rateduring age 0 declines, the population Atlantic coast are given in MAFMC 4 . 

abundance can be maintained if EPR is increased to 

a level that keeps the product of age 0 survival and 

EPR equal to two, assuming that the population has Results and discussion 

sufficient compensatory capabilities to maintain 

stationarity under all mortality conditions. 

Effects of fishing mortality on reproductive potential 

To prevent harvesting of spawners below the re- 

Data sources placement level of their progeny, Goodyear (1993) 

recommends maintaining levels of spawning stock 

Sufficient information exists in available publica- biomass per recruit that are at least 20% of the maxtions 

to estimate EPR values for three sturgeon imum (when F = 0), unless evidence exists for expopulations 

and one paddlefish population in ceptionally strong density-dependence in the pop- 

North America: white sturgeon in the Columbia ulation. Boreman et al. (1984) used a higher level of 

River below Bonneville Dam (Tracy & Wall 1993, 50% of maximum spawning stock biomass per 

DeVore et al. 1996); Atlantic sturgeon in the Hud- recruit as a target for rebuilding (rather than mainson 

River (Kahnle et al. 1992, Kahnle unpublished taining) populations of shortnose sturgeon along 

data); paddlefish in Lake Ponchartrain, Louisiana the Atlantic coast. If spawning stock biomass and 

(Reed et al. 1992); and shortnose sturgeon in the egg production are linearly related (fecundity is 

lower Connecticut River (Boreman 2 ). The fishery typically a linear function of female body weight), 

for white sturgeon in the lower Columbia River currently 

has minimum size limit of 112 cm and a maximum 

size limit of168 cm (DeVorepersonalcommunication), 

and the fishery for Atlantic sturgeon in 

2 

Boreman, J. 1992. Impact of added mortality on the reproductive 

success of shortnose sturgeon in the lower Connecticut River. 

Report prepared for the Northeast Regional Office, National 

Marine Fisheries Service. 14 pp. 

401 

then the same 20% and 50% target levels should 

3 Kahnle, A,, K. Hattala & K. McKown. 1992. Proposed New 

York State Atlantic sturgeon regulations. Prepared for the Atlantic 

States Marine Fisheries Commission, Atlantic Sturgeon 

Plan Review Team. 14 pp. 

4 

MAFMC (Mid-Atlantic Fishery Management Council). 1990. 

Fishery management plan for the bluefish fishery. Mid-Atlantic 

Fishery Management Council, Dover, Delaware. 79 pp.

402 

Figure 2. Effects of an increase in the current mortality rate (Z) 

of age 1 and older females on the corresponding percentage of 

the maximum lifetime egg production of an age 1 female for 

shortnose sturgeon in the lower Connecticut River and paddle- 

fish in Lake Ponchartrain. 

Figure I. Relationship between fishing mortality rate (F) and 

corresponding percentage of the maximum lifetime egg production 

of an age 1 female when F = 0 for white sturgeon in the Columbia 

River below Bonneville Dam and Atlantic sturgeon in 

the Hudson River. 

apply to potential lifetime egg production per minimum level of 20%. An estimate of the current 

recruit (EPR). 

fishing mortality rate for Atlantic sturgeon in the 

The fishing mortality rate corresponding to 20% Hudson River is unavailable. 

of EPR max for white sturgeon in the lower Columbia Mortality due to incidental capture in indirect 

River and for Atlantic sturgeon in the Hudson Riv- fisheries is probably incorporated in the current eser 

is F = 0.14 (Figure 1). A 50% level of EPR max timates oftotal mortality ( Z ) for both the shortnose 

would be achieved if the fishing mortality is F= 0.06 sturgeon populationin the lower Connecticut River 

for white sturgeon, and F = 0.05 for Atlantic stur- and the paddlefish population in Lake Ponchargeon. 

At the 1986-1990 average fishing mortality train. Increasing the total mortality rate on age 1 

rate of F = 0.37, lifetime egg production of age I fe- and older shortnose sturgeon from Z = 0.12 (curmales 

in the white sturgeon population is approxi- rent) to Z = 0.16 will reduce potential lifetime egg 

mately2% of EPR max –far below the recommended production of a female recruit to 50% of EPR max' 

Table I. Female life history characteristics for white sturgeon in the lower Columbia River, Atlantic sturgeon in the Hudson River, 

shortnose sturgeonin the lower Connecticut River, paddlefish in Lake Ponchartrain, striped bass in the Hudson River, winter flounder in 

Cape Cod Bay, and bluefish along the Atlantic coast. 

Characteristic White Atlantic Shortnose Paddlefish Striped bass Winter Bluefish 

sturgeon sturgeon sturgeon flounder 

Maximum age (years) 104 60 30 20 18 12 8 

Natural mortality (M) 0.09 0.07 0.12 0.30 0.15 0.35 0.25 

Length (cm) at oldest age 309 343 91 120 105 45 89 

Fecundity at oldest age 1 500000 1800000 66000 200000 3100000 2200000 5300000 

Age at first maturity (years) 16 11 5 9 3 2 2 

Age at full maturity (years) 35 21 17 10 9 6 3 

Years between successive 

spawnings 3 3 3 2 1 1 1 

Age at 50+% EPR max (years) 37 29 17 11 1 1 6 3 

Fishing mortality (F) 0.37 ? 0 0 0.39 1.07 0.80 

Ages in fishery 14-25 14+ 

– – 

2+ 2+ 

0+

and increasing total mortality to Z = 0.23 will reduce 

the EPR value lo 20% of EPR max (Figure 2). For 

paddlefish, increasing the total mortality rate from 

Z = 0.30 (current) to Z = 0.36 will reduce the EPR 

value to 50% of EPR max and increasing the rate to Z 

= 0.45 will reduce the value to 20% of EPR max (Figure 

2). 

As a group, chondrostean populations are more 

sensitive to loss in reproductive potential caused by 

increases in the mortality rate of age 7 and older females 

than are striped bass, winter flounder, and 

bluefish populations (Figure 3). The higher sensitivity 

of the chondrosteans to mortality in age 1 and 

older fish is due to a combination of characteristics 

that determine theirpopulation dynamics (Table 1). 

The chondrosteans are generally longer lived, are 

later maturing and have lower natural mortality 

rates than striped bass. winter flounder, and bluefish. 

The chondrosteans do not spawn every year 

once they reach sexual maturity and, except for Atlantic 

sturgeon and white sturgeon, have substantially 

lower fecundity than the other three species I 

examined. A life history characteristic that integrates 

individual fecundity, naturalmortality, age at 

maturity, and years between successive spawnings 

is the age at which at least 50% of the maximum 

lifetime egg production of an age 1 female is 

achieved when no fishing mortality occurs other sources 

(EPR max ) .For white and Atlantic sturgeons, this age 

is 3-10 times greater than the equivalent age for 

striped bass, winter flounder, and bluefish (Table 1); 

403 

Figure3. Effects ofincreasing the total mortality rate ( Z ) ofage 1 

and older females above the level when F = 0,on the correspond 

ingpercentage ofthemaximuin lifetime egg production ofan age 

I female for white sturgeon in the Columbia River below the 

Bonneville Dam. Atlantic sturgeon in the Hudson River short 

nose sturgeon in the lower Connecticut River, paddlefish in 

Lake Ponchartrain, striped bass in the Hudson Rivcr, winter 

flounder- in Cape cod Bay, and bluefish along the Atlantic coast. 

therefore, the probability of surviving from age 1 to 

the age of 50% of maximum lifetime egg production 

is reduced by a power of 3–10 for the sturgeons. 

Restricting fishing mortality to offset losses from 

For relatively long-lived species such as sturgeons 

and paddlefish, a small reduction in fishing mortality 

on the age groups vulnerable to harvest can offset 

the effects of a relatively large reduction in age 0 

Table 2. Reduction in fishing mortality rate (F) necessary to 

achieve equivalent lifetime egg production of an age 1 female 

survival. This relationship is possible because the 

white sturgeon in the Columbia River below Bonneyille Dam 

when the fraction of females surviving from egg to age 1 (S 0)is age 0 fish are exposed to the risk of reduced survival 

reduced. 

during only one year in their life; whereas, exposure 

to the risk of fishing spans many years. As an example. 

suppose the number of age 0 white sturgeon in 

Reduction in F needed to maintain Reduction in F 

S 0 (% ) equivalent lifetime egg (%) 

the lower Columbia River is reduced by 20% due to 

production 

contaminant toxicity. A 20% reduction in age 0 sur- 

0 0.370 0 vival implies that for every age 1 female that would 

5 0.364 2 have survived her first year of life, only 0.8 females 

10 0.358 3 are now surviving under the altered conditions. The 

15 0.352 5 

value for potential lifetime egg production from 0.8 

20 0.345 7 

age 1 females with the baseline fishing mortality 

25 0.339 8 

30 0.331 11 rate of F = 0.37 is equal to the lifetime egg production 

of one age 1 female and a fishing mortality rate

404 

that is reduced by 7%, from F = 0.37 to F = 0.345 

(Table 2). 

Even though fishing may not be the reason for an 

observed decline in abundance of sturgeon and 

paddlefish populations, reducing fishing mortality 

is an effective means of offsetting the effects on reproductive 

potential caused by other, often uncontrollable 

mortality sources,Restricting fishing mor- 

tality may be the only tool available to managers for 

restoring depleted populations. At a minimum, reducing 

fishing pressure on long-lived species allows 

managers time to detect and correct the true causes 

of population decline. This strategy is currently being 

employed to rebuild the population of white 

sturgeon in the lower Columbia River (Columbia 

River Management Joint Staff'). The strategy was 

also adopted by the Atlantic States Marine Fisheries 

Commission in the early 1980s to restore the de- 

pleted coastal migratory stock of striped bass 

(ASMFC 6 ) which is now producing year classes at 

record levels (Donald Cosden personal communcation). 


Special thanks go to the people who shared their 

information during the preparation of the manuscript, 

especially A. Kahnle, K. Hattala, J. Clugston, 

V. Birstein, J. DeVore,T. Cochnauer, P. B. Moyle, K. 

D. Keenlyne, and J. Waldman, to Brad McGowan 

for providing valuable assistance in locating references. 

and to John DeVore and an anonynmous reviewer 

for critically reviewing the paper. 


Baker, J.P. 1980. The distribution. ecology. and management of 

the lake sturgeon (Acipenser fulvescens Rafinesque) in Michgan. 

Mich. Dept. Nat. Res.. Fish. Div., Fish. Res. Rept. No. 

1883. 95 pp. 

Becker, G.C. 1983. Fishes of Wisconsin University of Wisconsin 

Press, Madison. 1052 pp. 


in need of conservation. Consv. Biol. 7: 773–787 

Boreman, J. & H.A. Austin. 1985. Production and harvest of anadromous 

striped bass stocks along the Atlantic coast. Trans. 

Amer. Fish. Soc. 114: 3–7. 

Boreman, J . S. J. Correia & D.B. Witherell. 1993. Effects of 

changes in age-0 surv ival and fishing mortality on egg producfion 

of winter flounder in Cape Cod Ray. Amer. Fish. Soc. 

Symp. 14: 39–45. 

Boreman, J., W.J. Overholtz & M.P. Sissenwine. 1984. 4 preliminary 

analysis of the effects of fishing on shortnose sturgeon. 

National Marine Fisheries Service. Northeast Fisheries Center. 

Woods Hole Laboratory Reference Document 84–17. 23 

pp.. 

Carlson, D.M. & P.S. Bonislawsky. 1981. The padddlefish (Polyodon 

spathula) fisheries of the midwestern United States. Fisheries 

(Bethesda) 6: 17–27. 

Cochnauer, T.G.. J.R. Lukens & F.E Partridge. 1985. Status of 

white sturgeon. Acipenser transmontanus, in Idaho. pp. 127– 

133. In: E.P. Binkowski & S.I. Doroshov (ed.) North American 

Sturgeons. Dr W. Junk Publishers, Dordrecht. 

Dadswell, M.J., B.D. Taubert. T.S. Squiers, D. Marchette & J. 

Buckley. 1984. Synopsis of biological data on shortnose sturgeon. 

Acipenser brevirostrum LeSueur 181. FAO Fish. Synop. 

No. 140, NOAA Tech. Rep. NMFS 14, US Dept. Commerce, 

Washington. DC. 45 pp. 

DeVore, J.D., B.W. James. C.A. Tracy & D.A. Hale. 1996. Dynamics 

and potential production of white sturgeon in the unimpounded 

lower Columbia River. Trans. Amer. Fish. Soc. (in 

press). 

Folz, D.J. & L.S. Meyers. 1985. Management of the lake sturgeon, 

Acipenser fulvescens, population in the Lake Winnehago system. 

Wisconsin. pp. 135–146. In:F.P. Binkowski & S.I. Doroshov 

(ed.) North American Sturgeons, Dr W, Junk Publishers, 

Dordrecht. 

Goodyear, C.P. 1988. Implications of power plant mortality for 

management of the Hudson River striped bass fishery. Amer. 

Fish. Soc. Monogr. 4: 245–254. 

Goodyear, C.P. 1993. Spawning stock biomass per recruit in fisheries 

management: foundation and current use pp. 67–81. In: 

S.J. Smith, J.J. Hunt & D. Rivard (ed.) Risk Evaluation and 

Biological Reference Points for Fisheries Management, Can. 

Spec. Publ. Fish. Aquat. Sci. 120. 

Kallemeyn, L. 1983. Status o fthe pallid sturgeon. Fisheries (Be- 

5 

Columbia River Management Joint Staff. 1993. Status report: 

Columbia River fish runs and fisheries 1938–1992.Prepared for 

Oregon Department of Fish and Wildlife and Washington Department 

of Fisheries. 257 pp. 

6 ASMFC (Atlantic States Marine Fisheries Commission). 1989. thesda) 8: 3–9. 

Amendment 4 to the Atlantic States Marine Fishcries Commission 

interstate striped bass management plan. ASMFC, Wash- 

the pallid sturgeon. Trans. Amer Fish. Soc. 122: 393–396. 

Keelyne, K.D. & L.G. Jenkins. 1993. Age at sexual maturity of 

ington, DC. 60 pp. 

Mason, W.T.. Jr. & J.P. Clugston. 1993. Foods of the Gulf stur-

405 

geon in the Suwanee River, Florida. Trans. Amer. Fish. Soc. 

122: 378–385. 

Reed, B.C., W.E. Kelso & D.A. Rutherford. 1992. Growth, fecundity, 

and mortality of paddlefish in Louisiana. Trans. Amer.Fish.Soc.121:378–384. 

Rieman, B.E. & R.C. Beamesderfer. 1990. White sturgeon in the 

lower Columbia River: is the stock overexploited? N. Amer. J. 

Fish. Manag. 10: 388–396. 

Rochard, E., G. Castelnaud & M. Lepage. 1990. Sturgeons (Pisces: 

Acipenseridae); threats and prospects. J. Fish Biol. 37 

(Supplement A): 123–132. 

Tracy, C.A. & M.F. Wall. 1993. Length at age relationships for 

white sturgeon, Acipenser tuansmontanus, in the Columbia 

River downstream from Bonneville Dam. pp. 185–200. In: 

R.C. Beamesderfer & A.A. Nigro (ed.) Status and Habitat Requirements 

of the White Sturgeon Populations in the Columbia 

River Downstream From the McNary Dam, Volume 2, Final 

Report to Bonneville Power Administration, Portland. 

Trautman. M.H. 1981. The fishes of Ohio. Ohio State University 

Press, Columbus. 782 pp. 

Williams, J.E., E.J. Johnson. D.A. Hendrickson & S. Contreras- 

Balderas. 1989. Fishes of North America endangered, threatened, 

or of special concern. Fisheries (Bethesda) 14: 2–20.

Sturgeons from the western and eastern north Pacific rim: the Sakhalin sturgeon,AcipenserMiikadoi, 102 cm TL from the Datta (Tumnin) 

River of the Russian far east, now residing at Propa-Gen International, Komadi, above a white sturgeon. A. transmontanus, 86 cm TL 

from western US stock, now at Szarvas, Hungary. Originals by Paul Vecsei, 1996.

Environmental Biology of Fishes 48: 407–417. 1997. 


Alternatives for the protection and restoration of sturgeons and their 

habitat 

Raymond C.P. Beamesderfer & Ruth A. Farr 

Oregon Department of Fish and Wildlife, 2501 Southwest First Avenue, P.O. Box 59, Portland, OR 97207, U.S.A. 

Received1.11.1994 

Accepted 18.3.I996 

Key words: Acipenseriformes, life history, population dynamics, harvest, culture, Columbia River, hydropower 

Synopsis 

This paper reviews the life history and habitat requirements of sturgeons, alternatives for their protection and 

restoration in North America, and a typical protection and enhancement program in the Columbia River. 

Sturgeon are uniquely adapted to mainstem river systems which are characterized by their large scale. diverse 

habitats. and dynamic nature. Adaptations include mobility, opportunistic food habits, delayed maturation, 

longevity, and high individual fecundity. Unfortunately these life history characteristics are now a handicap 

for sturgeon because of fragmentation and destruction of their habitat. A variety of habitat-related alternatives 

for the protection and restoration of sturgeon were identified in a review of the literature and a survey of 

sturgeon biologists and managers throughout North America. However, harvest restrictions and supplementation 

using aquaculture are much more likely to be implemented than the system-wide measures needed to 

affect sturgeon habitat. A program for white sturgeon protection and enhancemment in the Columbia River is a 

typical case where harvest management and supplementation measures are being used to optimize production 

of existing habitat but significant changes in water use and hydropower operation are needed to restore 

sturgeon to historic levels of production. 

Introduction 

grains for the nine endemic sturgeon species. In this 

paper, we discuss key characteristics ofsturgeon life 

Given their singular evolutionary, morphological history which constrain populations, alternatives 

genetic, and physiological traits (Grande & Bemis for protection and restoration of sturgeon and their 

1991, Bemis et al. 1997 this volume, Birstein 1993, habitats which have been identified for North 

Birstein et al. 1997 this volume), it is no surprise that American populations, and protection and enhansturgeon 

are also ecologically unique. However, life cement efforts for Columbia River white sturgeon 

history traits which have proven adaptive over the which typify the problems faced in many other poplast 

100 million years are now a disadvantage in the ulations. 

face of drastic habitat changes and overfishing during 

the last century. Sturgeon are presently depleted, 

threatened. or extinct almost everywhere they Life history and habitat requirements 

occur (Smith 1990, Birstein 1993). Biologists 

throughout North America are grappling with the 

difficulty of developing protection or recovery pro- 

Critical habitat requirements and effective protection 

and restoration measures can be inferred from

408 

sturgeon life history. Sturgeon are uniquely adapt- variety of prey and switch as prey availability 

ed to the large mainstem river systems upon which changes. These fish can also withstand long periods 

all species rely during all or part of their life cycle of starvation during periods of low food availability 

(Rochard et al. 1990). Rivers include diverse hab- or spawning migrations (Dadswell 1979, Mason & 

itats which are distributed in large scale patterns Clugston 1993). Sturgeon generally feed on invercorresponding 

to the surrounding topography. Typ- tebrates in the benthic food chain (Held 1969, Dadical 

transitions include headwaters through tribu- swell 1979, Carlson et al. 1985, Sandilands 1987, 

taries. mainstem, and estuary into an ocean, sea, or McCabe et al. 1993) where most production occurs 

large lake. In large basins, rivers may traverse many in large river systems (Sheehan & Rasmussen 1993). 

different regions and climatic zones. Rivers are also Fish may also be an important diet component of 

extremely dynamic habitats featuring large season- some sturgeon species (Semakula & Larkin 1968). 

al and annual variations in physical conditions and Large sturgeon can consume large prey. Pursuit and 

resource availability (Sheehan & Rasmussen 1993). capture of active prey belie an image of sturgeon as 

Seasonal cycles in weather and runoff drive changes sluggish bottom scavengers. 

in velocity. morphometry, temperature, substrate, Populations of sturgeon are buffered from anand 

turbidity. Conditions vary from year to year in nual variation in environmental conditions by deunpredictable 

patterns based on regional weather layed maturation, longevity, and high individual fepatterns. 

Periodic floods and droughts may radical- cundity. Delayed maturation (Roussow 1957, 

ly alter the riverine environment. Distribution and Sunde 1961, Dadswell 1979, Conte et al. 2 , Chapman 

abundance ofmany species of fishes and other orga- 1989, Guenette et al. 1992, Keenlyne & Jenkins 

nisms vary widely in response to spatial and tempo- 1993) speeds growth to large sizes as energy is deral 

patterns. For instance, anadromous fishes are voted to somatic rather than gonadal development. 

seasonally abundant as they move between spawn- Large size helps reduce predation. lowering natural 

ing and feeding areas in portions of many temperate mortality rate and increasing longevity. A long liferivers 

and estuaries. 

span (Pycha1956.Wilson 1987, Rien &Beamesder- 

Sturgeon have evolved life history characteristics fer 1994) allows fish numerous opportunities to 

which allow them to thrive in these large, diverse. spawn and reduces the need to spawn in years when 

and dynamic river systems. Individuals often range conditions are not suitable. Many species have been 

widely to take advantage of scattered and season- observed to resorb eggs under these conditions 

ally abundant resources. Regular migrations for (Artyukhinetal. 1979, Chapman 1989). Highfecunspawning 

and short-term movements for feeding dity associated with large size improves spawning 

have been observed for many species (Chadwick success in years when suitable conditions are en- 

1959, Miller 1972a, Haynes et al. 1978, Haynes & countered. 

Gray 1981, Smith 1985, Wooley & Crateau 1985, Many sturgeon species depend on free-flowing 

Sandilands 1987, Kempinger 1988, Odenkirk 1989, rivers and seasonal floods to provide suitable 

Hall et al. 1991, Mosindy & Rusak 1 , O’Herron et al. spawning conditions. Adhesive eggs are typically 

1993). Many species are euryhaline and move freely broadcast over rocky substrates in turbulent. highbetween 

freshwater, estuaries, and saltwater (Ro- velocity areas during high spring runoff (Magnin 

chard et al. 1990) to further broaden their resource 1966, Buckley & Kynard 1985, Smith 1985, Kempbase. 

Long-distance movements are facilitated by inger 1988, Hall et al. 1991, Mosindy & Rusak1, Latheir 

large size, shape, and swimming ability which Haye et al. 1992, Parsley et al. 1993). Recruitment 

allow them to move through heavy current. 

Sturgeon are opportunistic predators that eat a 

1 Mosindy, T. & J. Rusak. 1991. An assesment of lake sturgeon 

populations in Lake of the Woods and the Rainy River 1987–90 

Ontario Ministry of Natural Resources 66 pp. 

, 2 

Conte, F.S., S.I. Doroshov & P.B. Lutes. 1988. Hatchery manual 

for the white sturgeon Acipenser transmontanus Richardson 

with application to other North American Acipenseridae. University 

of California Cooperative Extension Publication 3322. 

104pp.

409 

has been widely correlated with spring and summer 

discharge (Stevens & Miller 1970. Khoroshko 1972, 

Votinov & Kasyanov 1979, Kohlhorst et al. 1991, 

Veshchev 1991). Flowing water provides oxygen, 

disperses eggs, and excludes egg predators. Seasonal 

floods scour substrates free ofsand and silt which 

might suffocate eggs. Seasonal floods and corresponding 

changes in temperature, velocity, and turbidity 

may also provide spawning cues (Kempinger 

1988, Kohlhorst et al. 1991, LaHaye et al. 1992). 

Unfortunately, many of these adaptations to 

large river systems are now detrimental to sturgeon. 

Availability of food and critical spawning areas are 

limited where construction of dams blocks movements 

among scattered areas and creates homogenous 

reservoirs which reduce habitat diversity. 

Dam and reservoir operation for hydropower generation, 

flood control, irrigation, and navigation reduce 

seasonal and annual variability in flow which 

provide suitable spawning and rearing conditions 

for sturgeon and many of their prey. Altered systems 

favor development of a new array of prey. 

predators, and competitors. Benthic feeding and 

delayed maturation increase vulnerability to bioaccumulation 

of toxic pollutants (Ruelle & Keenlyne 

1993). Longevity and delayed maturation make 

populations extremely susceptible to overexploitation. 

Large size and high fecundity increase the value 

of individual fish and provide incentives for excessive 

or illegal harvest. 

Because of the unique features of their large river 

habitats and adaptive life history characteristics, 

sturgeon require a much broader definition of habitat 

than is typically applied to fishes when alternatives 

for habitat improvement are considered. Fish 

habitats are often defined ill terms of Site-Specific 

conditions like depth,velocity, substrate, and cover. 

Sturgeon habitat must be defined in terms of sys- 

tem-wide conditions including large areas of diverse 

habitat; natural variation in flow, velocity, 

temperature, and turbidity; high water quality; a 

broad prey base; and free-flowing sections which 

provide suitable spawning sites (Carlson et al. 1985, 

Crance 3 , Mosindy 1937, Payne 1937, Curtis 1990, 

Taub 4 , Lane 1991, Pitmad, Beamesderfer 1993, 

Dryer & Sandoval 6 , USFWS & GSMFC 7 ). 

Alternatives for protection and restoration 

To help identify and assess the potential feasibility 

of alternatives for protecting and restoring sturgeons 

and their habitat, we recently conducted a 

mail survey of 268 sturgeon and paddlefish biologists 

and managers from throughout North America. 

One page questionnaires including a return address 

and postage were sent to each person identified 

in a ‘Summary of sturgeon and paddlefish researchers 

and managers’ developed by the United 

States Fish and Wildlife Service. While survey results 

from this sample cannot be construed as an unbiased 

indication of which measures are appropriate, 

results should be useful in identifying the range 

of alternatives available. 

Survey questions included ‘please list measures 

you believe to be potentially beneficial to the conservation, 

productivity, or diversity of sturgeon or 

paddlefish populations with which you are familiar’ 

and ‘which of the above alternatives have been implemented 

and proven beneficial to the targeted 

sturgeon or paddlefish species?’ In addition, each 

person was asked to (1) identify their experience 

with sturgeon or paddlefish (basic research, applied 

research, stock assessment/monitoring. habitat protection, 

fishery regulation, or aquaculture); (2) 

3 

Crance, J.H. 1986. Habitat suitability index models and instream 

flow suitability curves: shortnose sturgeon. U.S. Fish and 

Wildlife Service Biological Report 82 (10.129). 

4 Taub, S.H. 1990 Fishery management plan for Atlantic sturgeon 

(Acipenser oxyrhynchus oxyrhynchus) Atlantic States Marine 

Fisheries Commision Fisheries Management Report 17. 

73pp. 

5 

Pitman, V.M. 1992. Texas paddlefish recoveryplan. Texas Parks 

and Wildlife Department, Austin. 30 pp. 

6 Dryer, M.P. & A.J. Sandoval. 1993. Recovery plan for the pallid 

sturgeon (Scaphirhynchus albus). U.S. Fish and Wildlife Service, 

Denver. 55pp. 

7 

USFWS & GSMFC (United States Fish and Wildlife Service & 

Gulf States Marine Fisheries Commission). 1995. Gulf sturgeon 

recovery plan. Atlanta. 170 pp.

410 

Table 1. Specific alternatives identified as potentially beneficial to the conservation. productivity. or diversity of sturgeon or paddlefish 

populations in a survey of sturgeon and paddlefish biologists throughout North America. Each biologist developed a list of alternatives 

and ranked them according to potential benefit. 

Cat egory Number responses Number implemented Mean rank 

Specific response 

Habitats 

General (e.g. protect or restore critical habitat) 59 18 1.9 

Flow (e.g. restore hydrograph) 30 6 1.8 

Spawning habitat (e.g. protect) 15 10 2.9 

Dredging or channelization 9 4 2.4 

Control predators 3 0 5.7 

Dams 3 0 3.0 

Rearing habiiat 2 1 3.0 

Construct spawning habitat 1 I 5.0 

Harvest 

Partial size specific (e.g. protect broodstock) 37 31 2.2 

General (e.g. control harvest) 32 25 2.6 

Complete closure 17 11 1.8 

Enforcement (e.g. poaching and caviar sales) 14 7 3.0 

Commercial closure 10 5 1.8 

Bycatch control 2 0 3.5 

Research 

Stock assessment 20 6 2.9 

Aquaculture 18 5 2.4 

Genetics 17 6 3.1 

Life history 15 6 2.4 

Habitat requirement 24 5 2.6 

General 9 4 3.6 

Reproduction 9 4 2.2 

Monitoring 3 2 2.3 

Pollution 3 0 2.3 

Passage 1 0 3.0 

Culture stocking 

General 29 16 2.5 

To historic ranges 17 7 2.3 

Fingerlings 5 5 2.2 

Establish cryogenic stock reservoirs 4 3 2.5 

Young of the year 1 1 2.0 

Use as reservoir for genetic stock 1 1 2.0 

Passage 

Improve passage at dams 16 4 3.0 

Eliminate dams 12 1 1.7 

Run of the river- operations 6 6 1.8 

General 2 I 2.5 

Pollution 

General 19 5 3.1 

Contaminants 8 1 4.1 

Sediments 5 2 2.8 

Nutrient (e.g. feedlot runoff) 2 2 3.5 

Planning 

General (e.g. coordinate interstate efforts) 13 8 2.1 

Listing/legal protection 9 7 2.0 

Recovery plan 4 4 3.0 

Management plan 4 1 3.7 

Information and education 

Public outreach 15 5 3.I 

General 7 2 4.0

name the sturgeon or paddlefish species with which 

familiar; and (3) provide related articles or reports. 

Specific alternatives identilied in 1.51 responses 

were classified into 8 general categories (Table I), 

including general problem areas identified in the 

‘Framework for the management and conservation 

of paddlefish and sturgeon species’ prepared by a 

national steering committee of biologists for the 

U.S. Fish and Wildlife Service. The most frequently 

identified categories included habitat, harvest, and 

research (Figure 1). Average ranks based on order 

of listing were similar for habitat, harvest, passage, 

Figure 1 Potentially beneficial alternatives indentified and implemented 

for the conservation, productivity, or diversity of stur- 

culture/stocking, and planning (Table 1). 

Habitat-related alternatives most often involved geon or paddlefish Populations in a survey of sturgeon and pad. 

protection of critical habitat, especially for spawn- dlefish managers throughout North America. 

ing. Effects of the natural hydrograph, dredging or 

channelization, dams, and predators were also rec- but the low incidence where programs had been imognized 

(Table 1). Pollution- and passage-related plemented (35%). 

measures were tabulated separately although they The capture and harvest of sturgeon are restrictmight 

also be considered as habitat-related mea- ed almost everywhere they occur in North America. 

sures. Pollution-related alternatives mentioned Annual harvest rates greater than 5–10% are alcontaminants, 

nutrients, and sediments. Passage- most universally believed to exceed sustainable levrelated 

alternatives recognize the widespread con- els because of resulting low survival to large reprostruction 

of dams which are barriers to migration. ductive sizes (Semakula & Larkin 1968, Miller 1972, 

Harvest-related alternatives involved complete Huff , 8 Threader& Brousseau 1986, Nowak & Jesfishery 

closures, partial restrictions, and more in- sup 1987. Young et al. 1988, Rieman & Beamesdertensive 

enforcement of restrictions especially with fer 1990, Kohlhorst et al. 1991). Closed reasons. prorespect 

to caviar. Specific alternatives to culture- tected areas, size limits. bag limits, gear restrictions, 

stocking most frequently involved stocking juve- and catch-release regulations have all been used for 

niles to supplement or reestablish populations with- sturgeon and paddlefish (Cochnauer 1983, Cochin 

historic ranges. Research needs on all aspects of nauer et al. 1985, Foltz & Meyers 1985, Galbreath 

biology and management were noted. Frequent ref- 1985, Smith 1985. Hart1987, Debrot et al. 9 ,Scarnecerences 

to planning efforts recognize the wide- chia et al. 1989. Taub 4 . PSMFC 10 ). Significant fisherspread 

distribution of sturgeons across several ju- ies still occur for white sturgeon. Acipenser transrisdictional 

boundaries. Several responses also reit- montanus, and paddlefish, Polyodon spathula 

erated a need for public outreach programs. 

The most likely measures to be implemented involved 

planning (73%), harvest restrictions (70%), 

and aquaculture (58%). Although habitat protecquently 

recognized as potentially beneficial, they Marine Research Pubiication No. 16. 32 pp. 

8 

Huff, J.A. 1975. Life history of gulf of Mexico sturgeon, Acipention 

and enhancement measures were the most fre- ser oxyrhynchus desotoi, in Suwannee River, Florida. Florida 

9 

appeared least likely to be implemented in cases Debrot, A.O., H.A. Schaller & M.A. Matylewich. 1989. Estiwhere 

indentified Planning efforts were frequently mates of sustainable exploitation rates lor Columbia River landlocked 

white sturgeon: evaluating the importance of a maximun 

identified as beneficial, perhaps reflecting the rela- 

size limit. Columbia River Inter-Tribal fish Commission Tech- 

tively low cost of such efforts. A generally poor understanding 

of sturgeon biology is implied by the 

frequent mention of a need for additional research 

nical Report 88-4. 41 pp. 

411 

10 PSMFC (Pacific States Marine Fisheries Commission). 1992. 

White sturgeon management framework plan. Portland. 201 pp.

412 

(Galbreath 1985, Pitman 11 , Graham 1996). Small Habitat modifications to benefit sturgeon have 

fisheries remain for lake Acipenser fulvescens, rarely been implemented. The elimination of daily 

green Acipenser medirostris, AtlanticAcipenser ox- discharge fluctuation for hydroelectric power genyrinchus 

oxyrinchus, and shovelnose Scaphirhyn- eration at a dam in Michigan has increased spawnchus 

platorynchus sturgeons (Smith et al. 1984, Foltz ing activity of lake sturgeon (Auer 1996). Effects of 

& Meyers 1985, Thuemler 1985, Olver 1957, Smith experimental releases of water from a Montana res- 

1990, Michalenko et al. 1991). Fishing for shortnose ervoir on spawning success of white sturgeon are 

Acipenser brevirostrum, pallid Scaphirhynchus al- currently being tested (Marcuson 15 ). Dredge and fill 

bus, and gulf Acipenser oxyrinchus desotoi stur- operations have been modified or curtailed in 

geons has been curtailed by their federally-recog- spawning areas oflake sturgeon in the St. Lawrence 

nized status as endangered or threatened species. River (Dumont et al. 1987). Successful site-specific 

Alabama sturgeon Scaphirhynchus suttkusi are rare habitat alterations have improved spawning by lake 

and not subject to harvest. 

sturgeon in several areas where rock substrate was 

Culture of North America sturgeon currently re- limiting and introduced to stabilize shoreline (Folz 

lies on the capture of wild broodstock which are & Meyers 1985) or to increase current velocity (Rostimulated 

to spawn using hormones, although cap- chard etal. 1990. LaHayeet al. 1992). A fish elevator 

tive broodstock are being developed for several was operated sporadically from 1938–1969 to lift 

species (Smith 1990). Artificial spawning has been white sturgeon past Bonneville Dam on the Columdocumented 

for Atlantic, shortnose, pallid, lake, bia River (Warren & Beckman 16 ). 

and white sturgeons, and for paddlefish (Conte et The broad habitat needs of sturgeon suggest that 

al. 2 , Smith 1990). Success of several experimental only large-scale, system-wide habitat protection 

releases of lake sturgeon, shortnose sturgeon, and and improvemcnt programs can be expected to propaddlefish 

is currently being evaluated (Graham 12 , vide significant benefits for those populations that 

Anderson 1987, Pitman 11 , Smith &Jenkins 1991, La- are depleted or threatened by habitat alteration. 

Pan et al .l3 , Graham 1996). Stocking programs for Except in rare cases,site specific changes can be exwhite 

sturgeon have been restricted to release of pected to have little effect. Options for producing 

small numbers of juveniles in the Sacramento. system-wide changes to benefit sturgeon are limit- 

Snake, and Willamette rivers as partial mitigration ed because they involve complex issues of water difrom 

private hatchery operators for use of wild version, land use, and hydropower system developbroodstock. 

An experimental hatchery program is ment or operation whose implementation is conalso 

being developed to supplement white sturgeon strained by economic and social considerations. 

in the Kootenai River which flows through British Our survey demonstrated that while several al- 

Columbia, Idaho. and Montana (Apperson & Wak- ternatives may be identified, effective options are 

kinen 1992, Kincaid 14) . 

limited. Managers have had to rely on harvest management 

and aquaculture because system-wide 

11 

Pitman, V.M. 1991. Synopsis of paddlefish biology and their uti- habitat protection and enhancement measures 

lization and management in Texas. Texas Parks and Wildlife De- have been extremely difficult to implement. These 

partment. Austin. 70 pp. 

measures have effectively maintained populations 

12 Graham, L.K. 1986. Reintroduction of lake sturgeon in Missouri. 

FinalRep., D.J. Proj. F-1-R-35, Study S–25. Missouri Dep. 

and provided fishery benefits where habitat degra- 

Conserv., Columbia. 11 pp. 

dation is not severe. However, efforts which do not 

13 Lapan, S.R., A. Schiavone, R.M. Klindt. W.F. Krise, M.N. Di- address habitat degradation have generally failed 

Lauro & K. Fynn-Aikins. 1994. Re-establishment of lake sturgeon 

in tributaries of the St. Lawrence River. 1993. Report to the 

Lake Ontario Committee. Great Lakes Fishery Commission. 10 

pp. 

14 

Kincaid, H.L. 1993. Breeding plan to preserve the genetic variability 

of the Kootenai River while sturgeon. Bonneville Power 

Admin., Portland. 18 pp. 

15 Marcuson, P. 1994. Koolenai River white sturgeon investigalions 

annual report. Bonneville Power Admin., Portland. 67 pp. 

16 Warren, J.J. & L.G. Beckman 1993. Fishway use by white sturgeon 

to bypass mainstem Columbia River Dams. U.S. Fish Wildl. 

Sea Grant Extension Proj., Col. R. Series WSG-AG 93-02. 12 pp.

413 

Figure 2. Abundance and productivity of the pristine (1890) and 

present impounded and unimpounded white sturgeon stocks in 

the lower Columbia River (Beamesderfer et al. 1995. DeVore et 

al.1995). 

Figure 3. Relations between river discharge, availability of 

spawning habitat, and annual recruitment (Bonneville Reservoir 

only) for while sturgeon in the lower Columbia River 

(adapted from Parsley & Beckman 1994). 

to restore sturgeon populations to historic levels of 

productivity. 

350 000 kg, and support 145 000 angler trips (De- 

Vore et al. 1995). 

Current sturgeon biomass in the unimpounded 

234 km of the lower Columbia River appears simi- 

A Columbia River example 

lar to levels during pristine conditions prior to significant 

exploitation in the late 1800s (Figure 2). 

The Columbia River white sturgeon populations Upstream from Bonneville Dam, a series of mainrepresent 

a typical situation where habitat changes stem dams have trapped stocks ofwhite sturgeon in 

have drastically affected the stock, harvest has been a series of reservoirs. Individual white sturgeon 

regulated, supplementation stocking is being con- range extensively throughout each reservoir but 

sidered, but only habitat changes can be expectedto rarely pass upstream or downstream dams (North 

restore sturgeon productivity to historic levels. et al. 1993). All reservoirs arc similar in that hydr- 

Only an accident of engineering prevented the Co- ologic retention times arc short, littoral zone is limlumbia 

River population of white sturgeon from ited, and current is measurable most of the year. 

joining the other threatened and endangered stur- However, reservoirs vary in size, depth, substrate, 

geon and paddlefish populations throughout the and length of the free-flowing portion in the tailworld. 

In 1983 Bonneville Dam was completed in water of the upstream dam. 

the gorge where the river cuts through the Cascade Columbia River reservoirs provide a laboratory 

mountain range. If this dam had been built at the for examining limiting factors for white sturgeon. 

bottom of the gorge just 5 miles downstream, it Each stock is presented with a different array of 

would have flooded or blocked access to critical habitat conditions which affect reproduction, 

spawning habitat and destroyed productive c o n - growth, and survival and in turn regulate populamercial 

and sport sturgeon fisheries in the lower riv- tion size and productivity. Fish that historically 

er which annually produce 45 000 fish, yield moved throughout this area to use scattered resources 

are now trapped in a reservoir which no

414 

longer furnishes optimal conditions for different intervals 

of the life cycle. In some areas recruitment is 

high but rearing habitat is limited. Elsewhere rearing 

habitat is abundant but spawning habitat is not. 

The net result is that biomass and potential yield are 

less in impounded stocks than in the unimpounded 

stock (Figure 2). 

Productivity of some impounded stocks is especially 

limited by poor recruitment resulting from 

lack of suitable spawning habitat. Columbia River 

white sturgeon spawn in areas of high velocity 

(> 0.8 ms –1 )over large rocky substrate now available 

only in riverine areas downstream from darns 

(Parsley et al. 1993). Availability of usable habitat 

increases with river discharge and recruitment is 

correlated with habitat availability (Figure 3). Discharge 

effects vary among areas as a result of differences 

in channel morphology, and some areas provide 

little habitat except at very high flows. Discharge 

regulation in isolated areas of the upstream 

Kootenai and Snake rivers has resulted in complete 

reproductive failure (Apperson & Wakkinen 1992, 

Marcuson 15 ). 

Harvest levels which could be supported by the 

productive unimpounded stock cannot be sustained 

by the impounded stocks (Beamesderfer et al. 

1995). As a result, fisheries for several impounded 

stocks collapsed in the late 1980s after a period of 

intense exploitation as sport andcommercial fisheries 

switched to sturgeon following declines of salmon 

fisheries. Hydropower system managers are now 

cooperating with government agencies and Indian 

tribes responsible for managing these fish to protect 

and enhance these impounded stocks. 

One element of this program is intensive harvest 

management. Before 1988sturgeonstocks throughout 

the lower Columbia River were managed with 

similar regulations and only a few key stocks were 

monitored. Fisheries are now being regulated with 

stock-specific regulations tailored to the unique attributes 

ofeach stock in an attempt to optimize fishery 

benefits. A more intensive monitoring program 

has also been undertaken to regulate harvest at optimumlevels. 

A second program element is evaluating transplants 

of juveniles from the large and productive 

unimpounded stock into reservoirs where poor 

recruitment appears to have understocked the 

available rearing habitat. We believe that production 

of sturgeon by the system will ultimately be 

limited by the carrying capacity of the rearing habitat 

and that peak production will result from full 

stocking of all areas. Survival, growth, and condition 

of transplanted fish will be monitored to determine 

the costs and benefits of this alternative. 

Transplants also provide a low-cost means of evaluating 

the potential for enhancement of reservoir 

stockswithout capital costs, geneticrisks, or disease 

problems ofa hatchery operation. Hatchery supplementation 

will be considered in more detail if transplants 

are not feasible or effective. 

A third program element is developing and supporting 

recommendations for hydropower system 

operation to optimize river discharge and velocity 

during spring periods when water temperature is 

suitable for spawning. However, the large social 

and economic costs of modifications in hydropower 

system operation arc likely to preclude changes in 

water allocation for the sole benefit of sturgeon. 

Program cooperators are therefore implementing 

intensive sampling designs for eggs, embryos and 

larvae in an attempt to identify effects of withinyear 

differences in flow and to develop recommendations 

for using available water to optimize 

spawning conditions within each year. 

Flow management is the only element in the lower 

Columbia River program which attempts to enhance 

sturgeon by directly modifying habitat. Intensive 

harvest management for each stock and 

supplementation recognize habitat limitations but 

maximize productivity of the existing habitat rather 

than producing habitat improvements. 

Conclusions 

The flexible and opportunistic life history style of 

sturgeons may help explain their persistence and 

success over the last 100 million years. However, 

system-wide changes in the large river systems they 

inhabit now pose serious risks to these remarkable 

creatures. The large scale of detrimental habitat 

changes make them extremely difficult to control 

for the sole benefit of sturgeon and so sturgeon

415 

managers and biologists have been forced to rely on 

harvest restrictions and aquaculture programs with 

limited success. 

Sturgeon provide obvious economic and scientific 

benefits. We believe that sturgeon also serve as 

very large canaries in the coal mine of riverine ecosystems. 

These fish are universally threatened because 

their large riverine habitats are on the verge 

of ceasing to function at the ecosystem level. Only a 

combination of alternatives integrating habitat protection 

and recovery with harvest restrictions and 

supplementation can be expected to sustain sturgeon 

populations that are anything more than museum 

pieces. The challenge of all who recognize 

these problems will be to push for fundamental 

changes in how we use these large riverine systems 

rather than settling solely for alternatives in the 

constrained sphere of our immediate influence. 


Many thanks to all the sturgeon researchers and 

managers who filled out and returned questionnaires 

and sent material. J. DeVore and M. Parsley 

provided unpublished information on white sturgeon 

recruitment in the Columbia River Research 

and recovery efforts for Columbia River white sturgeon 

are funded by the Bonneville Power Administration 

(Contract DE-A179-86BP63584), the Federal 

Aid to Fish Restoration Act, and the States of 

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Threatened fishes of the world: Scaphirynchus suttkusi Williams & 

Clemmer,1991(Acipenseridae) 

Richard L. Mayden & Bernard R. Kuhajda 

Department of Biological Sciences, Box 870344, University of Alabama Tuscaloosa, AL 35487–0344, U.S.A. 

Common names: Alabama shovelnose sturgeon, Alabama sturgeon(E). 

Conservation status: Recommended for protection (Ramsey 

1976, 1986). Proposed as Federally Endangered 15 June 1993 

(Federal Register 1993); listing postponed 21 June 1994 (Federal 

Register 1994a), listing withdrawn 15 December 1994 (Federal 

Register 1994b). Currently receives no protection. 

Identification: One of three species of Scaphirynchus distinguished by having orangish-yellow, brassy-orange, to brownish-tan head, 

body, and fin coloration in mature adults significantly larger orbit diameter; no sharp, retrose spiness on snout tip and anterodorsal to 

eye;and poorly developed squamation on venter. Other features include significantly different number of dorsal plates. anus to anal fin 

plates. plates posterior to anal fin. lateral plates anteriorto dorsal fin origin. dorsal fin rays, and 11 head, fin, and body proportions, relative 

to its sister species S. platorynchus. Complete description by Williams & Clemmer (1991) and Mayden & Kuhajda (1996). Photograph by 

John Caruso. 

Distribution: Endemic to larger rivers of Mobile Basin. Former distribution included Tombigbec, Alabama,Canada, Coosa, Alabama 

and Mississippi rivers. Recent collections are only from the Alabama River, Alabama below the lowermost two dams. Abundance: 

Species verey rare: only 36 specimens known from museum records or photo documentation. Contrary to decisions by the U.S. Fish and 

Wildlife Service (Federal Register 1994b), the species is not extinct: two adult specimens were captured in the Alabama River in Spring 

I995 and one in Spring 1996. All current data, extending from the general degradation of the Mobile Basin ecosystem (U.S. Fish and 

Wildlife Service 1994) to the paucity of records and specimens of the Alabama sturgeon. indicate that this is one of the most endangered 

species in the United States. However, this has not always been the case. as this species once maintained a healthy population size, but has 

declined in this century due to anthropogenic changes to the ecosystem. In a report to the U.S. Congress in 1898 (US. Commission of Fish 

and Fisheries 1898) the total catch of ‘shovelnose sturgeon’ from rivers in alabama was 19 500 kg. Of this, captures of the shovelnose 

sturgeon. S platorynchus, from the Tennessee River numbered only 500 kg, while captures of S. suttkusi from the Alabama and Black 

Warrior (Tombigbee) rivers numbered 19 000 kg. Given that an Alabama sturgeon averages 1 kg, this represents a substantial harvest of a 

species that is currently extremely rare. Habitatand ecology: Life history aspects of S. suttkusi are poorly known. Appears to prefer 

relatively stable substrates of gravel and sand in areas of current in large river channels, but will also occur over softer sediments. Its 

Spring diet is dominated by macroinvertebrates that typically bury in sandy substrates in both riffle and lentic depositional areas. Occasionally, 

small fish plant items. and some mollusks and snails associated with relatively stable and silt-free substrates occur in stomachs. 

Based on food items present in stomachs and lack of items (invertebrate taxa) indicative of certain habitats, Spring-collected Alabama 

sturgeon appear to feed in sandy depositional areas with very little silt and slow to moderate current (see Burke & Ramsey 1995, Mayden 

& Kuhajda 1996). Reproduction: Reproductive biology not well known; most information is inferred from its closest relative, S. platorynchus. 

Spawning season probably extends from February to July. Species of Scaphirynchus spawn in freshwater and are known to 

migrate upstream to spawning areas as ‘spawning runs’ that may be triggered by rising water levels in the Spring and early Summer. 

Probably spawns in larger rivers in swift current and coarse, rock or gravel substrates, but may also spawn over hard bottom substrates in 

main-channel areas or in tributaries to major rivers. Like other members of the family, individuals of this species probably do not spawn 

every year. Rather, following sexual maturity at five to seven years of age, spawning may occur every one to three years with a hiatus of 

even greater number of years possible. Although unknown for the Alabama sturgeon. eggs of shovelnose sturgeon are adhesive and 

require current for proper development, indicating that both a stable and silt-free, substrate is necessary for their successfull development. 

Hatching occurs in five to eight days under proper conditions (see Mayden & Kuhajda 1996) Threats: Recruitment of Alabama sturgeon, 

indicative of spawning success, has declined precipitously during this century. Because this species has not been sought in the 20th century 

in a commercial fishery, this decline can be correlated directly with habitat degradation, modifications of the rivers for navigational 

purposes, mining operations in and adjacent to the rivers, and the construction of dams in the Mobile Basin, all of which have flourished in 

this century. All of these changes result in increased siltation of benthic habitats, reduced overall current velocities, elimination of natural 

seasonal flooding of river flood plains, irregular flow regimes within the river channels, the loss of and/or change in structure of reverine

macroinvertebrate faunas, and obstruction of upstream migratory routes for migratory species. The latter constraint severely limits 

available spawning areas for the Alabama sturgeon; irregular flow regimes and flood/navigational controls eliminate natural signals to 

initiate spawning runs; and increased siltation and loss of stable substrate result in the loss of food sources and habitat appropriate for 

spawned eggs (current and clean surfaces). Macroinvertebrates found in the sturgeon’s diet are adversely impacted by the higher silt 

deposits occurring over stable substrates in low current areas, a consequence that will have an indirect, yet adverse impact on the survival 

of this sturgeon species. Conservation action: The U.S. Fish and Wildlife Service proposed this species for endangered status with critical 

habitat on 15 June 1993 (FederalRegister 1993). On 21 June 1994 (Federal Register 1994a), the Service postponed listing for six months to 

provide addditional time to assess the conservation status of the species through sampling. During this six month period no specimens of 

the sturgeon were captured. Consequently, the listing proposal was withdrawn by the Service on 15 December 1994 (Federal Register 

1994b) due to ‘insufficient information tojustify listing a species that may no longer exist’. On 2 December1993, less than one year before 

either the postponement or withdrawal of the listing, a mature male specimen of S. suttkusi was captured from the Alabama River. In 

April and May 1995 and April 1996, three additional specimens were discovered in the Alabama River. Currently, the Alabama sturgeon 

receives no protection and is not under official consideration by the Service. Conservation recommendation: There can be little doubt 

that the imperilment of the many sturgeon species worldwide is a direct result of the gross changes that have occurred in their natural 

habitats due to modifications of river channels and water flow patterns. The current predicament of the Alabama sturgeon is no exception. 

The protection and recovery of this sturgeon species, and others, will be a challenge, but one that can be accomplished through 

concerted and novel efforts. An effective recovery plan for the Alabama sturgeon most minimally includes efforts to (1) increase appropriate 

spawning habitats, (2) increase access to upstream and downstream river stretches across dams, (3) establish minimum flow 

regimes, and (4) decrease silt loads. As observed for some populations of shovelnose sturgeon (Cross 1967), the initiation of spawning 

activity of the Alabama sturgeon may be triggered by high-water conditions in the Spring. Should this be the case, an effective recovery 

program for the Alabama sturgeon must address the need for both irregular and high water flow in and downstream of spawning areas for 

this species. Critical habitat must be designated to assist in securing the species’ future. To compile additional biological information on 

this species, additional specimens need to be captured, radio-tagged, released and followed through telemetry studies. Finally, adults 

should be captured for a propagational program, as hasbeen developed for the endangered pallid sturgeon, S. albus,in the Missouri River 

drainage. Remarks: The listing of this species has been charged with abundant political and industrial opposition, actions due to potential 

environmental regulations that may be placed on existing hydroelectric dams and industrial users of the large rivers inhabited by this 

species. 

419 

Burke, J.S. & J.S. Ramsey. 1995. Present and recent historic habitat of the Alabama sturgeon, Scaphirhynchus suttkusi Williams and 

Clemmer, in the Mobile Basin. Bull. Alabama Mus. Nat. Hist. 17: 17–24. 

Cross, F.B. 1967. Handbook of fishes of Kansas. Misc. Publ. Mus. Nat. Hist., University of Kansas, Lawrence. 357 pp. 

Federal Register. 1993. Proposed endangered status and designation of critical habitat for the Alabama sturgeon (Scaphirynchus suttkusi). 

Vol.58,No. 113 (15June1993): 33148–33154. 

Federal Register. 1994a. Extension of the final decision to list the Mobile River System population of the Alabama sturgeon as an 

endangered specieswith critical habitat. Vol. 59, No. 118 (21 June 1994): 31970–31974. 

Federal Register. 1994b. Withdraw ofproposed rule for endangered status and critical habitat for the Alabama sturgeon. Vol. 59, No. 240 

(15 December 1994): 64784-64809. 

Mayden, R.L. & B.R. Kuhajda. 1996. Systematics, taxonomy, and conservation status of the endangered Alabama sturgeon, Scaphirhynchus 

suttkusi Williams and Clemmer (Actinopterygii, Acipenseridae). Copeia 1996: 241–273. 

Ramsey, J.S. 1976. Freshwater fishes. pp. 53-65.In: H.T. Boschung (ed.) Endangered and Threatened Plants and Animals of Alabama, 

Bull. Alabama Mus. Nat. Hist. 2. 

Ramsey, J.S. 1986. Alabama shovelnose sturgeon. pp. 18-19.In: R.H. Mount (ed.) Vertebrate Animals of Alabama in Need of Special 

Attention, Alabama Agricultural Experimental Station, Auburn University, Auburn. 

US. Commission of Fish & Fisheries. 1898. Statistics of the fisheries of the interior waters of the United States. A report to the 55th 

Congress, House of Representatives: 489-497,531-533. 

US. Fish & Wildlife Service. 1994. Mobile River Basin ecosystem recoveryplan. Unpubl. technical/agency draft. Jackson, Mississippi. 128 

PP. 

Williams, J.D. & G.H. Clemmer. 1991. Scaphirynchussuttkusi, a new sturgeon from the Mobile Basin ofAlabama and Mississippi. Bull. 

Alabama Mus. Nat. Hist. 10: 17–31.



Threatened fishes of the world: Scaphirhynchus albus (Forbes & 

Richardson, 1905) (Acipenseridae) 

Richard L. Mayden & Bernard R. Kuhajda 

Department of Biological Sciences, Box 870344, University of Alabama, Tuscaloosa, AL 35487-0344, U.S.A. 

Commonname: Pallid sturgeon (E). 

Conservation status: Listed under Endangered Species Act as 

Federally Endangered (Federal Register 1990). Currently receives 

federal protection; detailed recovery plan prepared by 

Dryer & Sandvol(1993). 

Identification: One of three species of Scaphirhynchus distinguished by having pallid cream, gray, or whitish head, body, and fin coloration 

in mature adults; very small orbit diameter; elongate and pointed snout: inner barbels positioned anterior to outer barbels; few to 

no sharp, retrose spines on snout tip and anterodorsal to eye; and poorly developed squamation on venter. Other features include 

different number of dorsal plates, anus to anal fin plates, plates posterior to anal fin. lateral plates anterior to dorsal fin origin, anal and 

dorsal fin rays, and head, fin, and body proportions, relative to its close relatives S. platorynchus and S. suttkusi. One of the most detailed 

morphological analyses currently available was presented by Bailey & Cross (1954); recent morphological comparisons and analyses 

presented by Keenlyne et al. (1994a) and Mayden & Kuhajda (1996). Illustration from Forbes & Richardson (1920). 

Distribution: Endemic to Mississippi River Basin but naturally limited to the Missouri and lower Mississippi river drainages (Bailey & 

Cross 1954). Historic range includes the Atchafalaya River, lower Mississippi River upstream to confluence with Missouri River, and 

Missouri River (Keenlyne 1995). The species has never been found to occur in either the Ohio or upper Mississippi rivers where the 

shovelnose sturgeon, S. platorynchus, typically abounds. Abundance: Species rare, abundance declined markedly following channelization 

and dam construction in the lower Mississippi and Missouri rivers. These activities not only limit migratory routes of the species 

but have largely curtailed natural Spring flooding periods that are thought to trigger spawning. Habitat alterations have also impacted the 

naturally turbid characteristics of the Missouri and lower Mississippi rivers to the extent that forage species are declining and the typical 

turbid, large-river habitat of the pallid sturgeon has declined. Riverine ecosystems historically occurring in these major waterways are 

being replaced with lentic habitats that are less turbid and with aquatic species adapted to these clear, lentic environments (Pflieger & 

Grace 1987). Dryer & Sandvol (1993) provide detailed account of the distribution and abundance of this species. Habitat and ecology: 

Life history aspects of S. albus are relatively poorly known. Species is found in large river channels with considerable diversity in microhabitats. 

They are usually associated with rapid current over sand, gravel or rocky substrates (Kallemeyn 1983, Carlson et al. 1985. 

Erickson 1992). Known to prefer turbid water conditions that historically characterized the Missouri and lower Mississippi rivers. Diet of 

adults is dominated by fishes, typically large-river minnows and shiners (Cyprinidae) (Erickson 1992). Based on observed food habits, the 

pallid sturgeon depends on the historical, naturally occurring turbid water conditions to conceal itself from prey items (Keenlyne 1995). 

The documented decline of many cyprinid species known to serve as regular food items for the pallid sturgeon is likely involved in its 

imperilment. Relative to the shovelnose sturgeon, growth is much more rapid throughout various age groups (Carlander 1969, Ruelle & 

Keenlyne 1993). Pallid sturgeon may weigh up to 45 kg (Brown 1971); males reach 39 years of age, while females may live as long as 

41 years (Ruelle & Keenlyne 1993). Reproduction: Reproductive biology poorly known. Spawning believed to occur between April and 

mid-June, depending upon latitude (Keenlyne & Jenkins1993). Males mature at 53 to 58 cm or 5 to 7 or 9 years, with 2- or 3-year intervals 

between spawning; size of females at maturity unknown, but estimated to occur by 9 to 12 or 15 to 20 years of age, with 3- to 10-year 

intervals between spawning (Kallemeyn 1983, Dryer & Sandvol1993,Keenlyne & Jenkins 1993). Like shovelnose sturgeon, pallid sturgeon 

have been observed to possess mature gametes during periods coinciding with high river flow levels, possibly indicating that onset of 

spawning is initiated by typical Spring flooding of rivers. Spawning habitat not known. Gross habitat modifications made to the large river 

habitats in the Mississippi and Missouri river drainages through channelization and dams for navigational purposes preclude an accurate 

appraisal of the natural spawning habitats of this rare species. Under natural conditions it likely spawns in fast-flowing sections of the 

main-stem portions of the rivers. Because very few records exist for the species outside of main rivers, this species may not ascend smaller 

tributaries to spawn as does the shovelnose sturgeon. Although unknown for pallid sturgeon, eggs of shovelnose sturgeon are adhesive 

and require current for proper development, indicating that both a stable and silt-free substrate is necessary for their successful development. 

Hatching probably occurs in five to eight days under natural conditions (see Mayden & Kuhajda 1996). Threats: The gross 

human-induced habitat modifications in the Missouri and lower Mississippi rivers are the primary factors involved in the decline of the 

pallid sturgeon. These alterations, made primarily under the guise of navigation and flood control, have resulted in regulated flow 

patterns of these major rivers and have created habitats more lentic than lotic. Both of these conditions differ radically from the natural 

habitats to which the pallid sturgeon is adapted (e.g., braided channels, irregular flow patterns, flooding of terrestrial habitats, extensive

microhabitat diversity, and turbid waters). These changes have also reduced the natural forage base of the pallid sturgeon, another likely 

reason for its decline. Purported cases of hybridization with the shovelnose sturgeon (incidentally or intentionally occurring) may also be 

detrimental to the pallid sturgeon populations. Conservation action: This species was listed as endangered by the U.S. Fish and Wildlife 

Service on 6 September 1990 (Federal Register 1990). A panel of scientists has been assembled to serve as an advisory group for the 

recovery of this species; they have developed a recovery plan that map eventually lead to downlisting the pallid sturgeon (Dryer & 

Sandvol 1993). The major elements in the recovery of the species include establishing three wild-caught broodstock populations in 

different hatcheries; captive breeding. propagation, and stocking; protection of wild individuals; and habitat restoration in designated 

areas of the Missouri and lower Mississippi rivers. Conservation recommendation: Restoration of natural habitat and migratory patterns 

are essential. The historic habitats in the Missouri and lower Mississippi rivers must be restored in sections of these systems to provide 

appropriate microhabitats for pallid sturgeon foraging, spawning, and migration. Natural migratory patterns may be reestablished for the 

pallid sturgeon with the development of novel structures associated with dams that assist this speciess and others with overcoming these 

barriers. Remarks:Considerable interest exists as to whether the pallid and shovelnose sturgeon are diferent species. Much of this 

concern stems from the genetic study by Phelps & Allendorf (1983) wherein ‘hybrid’ and parental sturgeon were examined and no genetic 

differences were detected for these species at 37 loci. This study is technically and theoretically flawed and should not be used as either a 

basis for the existence ofhybridization between these sturgeon species or for determining geneticvariation either within or between these 

species. Their study employed buffer media standard for salmonid fishes, did not provide an adequate examination of differing environmental 

conditions for electrophoretic examination of protein variation, and did not demonstrate any empirical evidence for the 

existence of purported hybrids between these species. Unfortunately, because of the above study and that by Carlson et al. (1985), some 

biologists and laypersons have preconceived notions that hybridization between the pallid and shovelnose sturgeon is common in the 

wild. However, there is no empirical evidence to support this premise. To the contrary, in addition to these species possessing different 

geographic distributions, there are abundant morphological, behavioral and ecological attributes that may be used to distinguish these 

species. 

421 

Bailey, R.M. & F.B. Cross. 1954. River sturgeons of the American genus Scaphirhynchus: characters, distribution and syhonymy. Michigan 

Acad. Sci. Arts and Letters 39: 169–208. 

Brown, C.J.D. 1971. fishes of Montana. Montana State University, Bozeman. 207 pp. 

Carlander, K.D. 1969. Handbook of freshwater fishery biology. Iowa State University Press, Ames. 752 pp. 

Carlson, D.M., W.L. Pflieger, L. Trial & P.S. Haverland. 1985. Distribution, biology and hybridization of Scaphirhynchus albus and S. 

platorynchus in the Missouri and Mississippi rivers. Env. Biol. Fish. 14: 51-59. 

Dryer, M.P. & A.J. Sandvol. 1993. Pallid sturgeon (Scaphirhynchus albus) recovery plan. U.S. Fish & Wildlife Service, Bismarck. 55 pp. 

Erickson, J.D. 1992. Habitat selection and movement ofpallid sturgeon in Lake Sharpe, South Dakota. M.S. Thesis, South Dakota State 

University, Brookings. 70 pp. 

Federal Register. 1990. Determination of endangered status for the pallid sturgeon. Vol. 55, No. 173 (6 September 1990): 36641–36647. 

Forbes, S.A. & R.E. Richardson. 1920. The fishes of Illinois. 2nd ed. Illinois Nat. Hist. Surv., Champaign. 357 pp. 

Kallemeyn, L.W. 1983. Status ofpallid sturgeon (Scaphirhynchus albus). Fisheries 8: 3–9. 

Keenlyne, K.D. 1995. RecentNorthAmerican studies onpallid sturgeon, Scaphirhynchus albus (Forbes and Richardson). pp. 225–234. In: 

A.D. Gershanovich & T.I.J. Smith (ed.) Proceedings of the September 6-111993 International Symposium on Sturgeons, Moscow- 

Kostroma-Moscow, VNIRO Publications, Moscow. 

Keenlyne, K.D. & L.G. Jenkins. 1993. Age at sexual maturity of the pallid sturgeon. Trans. Amer. Fish. Soc. 122: 393–396. 

Keenlyne, K.D., C.J. Henry, A. Tews & P. Clancy. 1994a. Morphometric comparisons of upper Missouri River sturgeons. Trans. Amer. 

Fish. Soc. 123: 779–785. 

Mayden, R.L. & B.R. Kuhajda. 1996. Systematics, taxonomy, and conservation status of the endangered Alabama sturgeon, Scaphirhynchus 

suttkusi Williams and Clemmer (Actinopterygii, Acipenseridae). Copeia 1996: 241–273. 

Pflieger, W.L. & T.B. Grace. 1987. Changes in the fish fauna of the lower Missouri River, 1940–1983. pp. 166–177. In: W.J. Matthews & D.C. 

Heins (ed.) Community and Evolutionary Ecology of North America Stream Fishes, University of Oklahoma Press, Norman. 

Phelps, S.R. & F.W. Allendorf. 1983. Genetic identity of pallid and shovelnose sturgeon (Scaphirhynchus albus and S. platorynchus). 

Copeia 1983: 696-700. 

Ruelle, R. & K.D. Keenlyne. 1993. Contaminants in Missouri River pallid sturgeon. Bull. Environ. Contam. Toxicol. 50: 898–906.

Labels from caviar jars bought in New York. The survey of the New York City area shops using the molecular method of species identification 

(DeSalle & Birstein 1 ) showed that currently the number of illegal replacements of commercial sturgeon species caviar (beluga, 

sevruga, and Russian sturgeon caviar or osetra) by the caviar of American or non-commercial Eurasian species is very high: in December 

1995 and April 1996, it was 17% and in December1996, it was already 32% (Birstein et al. 2 ). Such companies as Petrossian Inc. (the upper 

row) continue to sell excellent caviar without misrepresenting. 

1 

DeSalle, R. & V.J. Birstein. 1996. PCR identification of black caviar. Nature 381: 197–198. 

2 

Birstein, V.J., P. Doukakis, B. Sorkin & R. DeSalle. 1997. Population aggregation analysis of caviar producing species of sturgeons and 

implications for diagnosis of black caviar. Cons. Biol. (submitted).

Environmental Biology ofFishes 48: 423–426,1997. 


Sturgeon poaching and black market caviar: a case study 

Andrew Cohen 

U. S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries 

Service, Office of Enforcement, Seatte, WA 98115, U.S.A. 


Key words: Acipenser transmontanus, Columbia River, Lacey Act, beluga caviar, illegal harvesting, environmental 

crimes 

Synopsis 

This paper documents a recent United States Federal prosecution of members of a poaching ring that sold 

caviar derived from illegally taken Columbia River white sturgeon, Acipenser transmontanus. Experts estimated 

that over 2000 adult sturgeon were killed in the process of illegally harvesting the more than 1500 kg of 

caviar involved in the case. Case studies of illegal activities related to exploitation of natural resources are 

rare. These crimes are difficult to discover and prosecute, for secrecy is essential, and by the time the facts are 

publicly available, irreparable environmental damage may have already been done. Sturgeons and paddlefishes 

have long life spans but take many years to reach reproductive maturity; they reproduce infrequently 

and rely upon large, often urban rivers for their spawning migrations. These basic biological characteristics 

render these fishes especially susceptible to illegal exploitation, particularly when stocks have already been 

damaged by overfishing, dam construction or pollution (as has the Columbia River population of white sturgeon). 

Given the often exorbitant prices for sturgeon and paddlefish caviar, and the relative ease of capturing 

these fishes during their spawning migrations, persons may be tempted to circumvent state and federal regulations 

designed to protect acipenseriforms. Additionally, those involved in the distribution and sale of caviar 

can be motivated to fraudulently mislabel the product; for instance, in this case, white sturgeon caviar was 

marked as beluga caviar and sold at approximately five times the normal price of white sturgeon caviar. 

Despite the clear evidence of an environmental crime, the scale of the abuse, and the convictions, sentencing 

was light, a discouraging sign for those who hope to limit such destructive crimes in the future. 

Between 1985 and 1990 poachers in the Pacific 

Northwest shipped more than 3000 lbs (> 1352 kg) 

of high quality caviar made from the roe of white 

sturgeon, Acipenser transmontanus, to a caviar 

company in New Jersey. The poachers sent containers 

of caviar via the Federal Express shipping company, 

using a fictitious business name, and a variety 

of nonexistent return addresses. The president/ 

owner of the caviar company paid the poachers, 

whom he had never met in person, by mailing packages 

of cash to various post office boxes in Washington. 

The owner of the company, a well known fifth 

generation caviar merchant, has been profiled in 

both Playboy and People magazines, and is often 

quoted as an industry expert. 

How was this poaching ring finally cracked? The 

story began with a bank robbery in the rural southern 

Washington State town of Dollars Corner, not 

far from the Columbia River, near Portland, Oregon. 

During November 1990, a poacher and his confederate 

were producing high quality caviar in a

424 

Express office. The poachers then left, and the FBI 

agents soon lost the truck in traffic. The agents re- 

turned to the Federal Express Office and spoke to a 

clerk who showed them the airbills and the boxes. 

Both boxes were addressed to a caviar company in 

New Jersey. The Federal Express clerk told the 

agents that the man who shipped the boxes looked 

like a fisherman, and smelled like fish. The FBI 

agents thought that the case was looking less like a 

bank robbery with every new bit of information. 

Without a search warrant, they could not look in- 

side the boxes, so after recording the information 

from the shipping labels, theboxes were loadedon a 

plane bound for New Jersey. 

In the meantime, the motel manager was con- 

cerned about the poachers’ unusual request for no 

room service and the FBI’s interest in both the cash 

and the men. She took it upon herself to enter the 

room with a passkey. She had read that drug dealers 

sometime manufactured methamphetamines in 

motels, and suspected that perhaps that was occur- 

ring in her motel. To her surprise, she found no drug 

manufacturing paraphernalia, but lots of fishing 

gear, an outboard engine, and buckets ofbrine. She 

later testified in court that the whole place smelled 

likefish. 

The FBI agents soon realized that the suspects 

were not involved in the bank robbery. Neverthe- 

less, their actions were strange for a couple of buddies 

who were on a fishing holiday. They contacted 

the Washington Department of Fisheries and the 

National Marine Fisheries Service, two agencies 

who specialize in resource related crimes. Thus be- 

gan a two year investigation of an organized poaching 

ring that spread from the Columbia River to 

New Jersey. 

Evidence began to trickle in as a federal Grand 

Jury in Seattle issued more than 30 subpoenas for 

records from telephone companies, banks, the ca- 

viar company, accountants, auditors and others. No 

stone was left unturned; after obtaining one of the 

poachers’ one-gallon sized shipping containers, the 

agents contacted the plastic company thatmanufac- 

tured the jars to obtain a list of everyone who had 

ever purchased that type of container in quantity. 

The caviar merchant provided a few documents af- 

ter they were demanded by subpoena, however, he 

cheap motel room in Vancouver, Washington. 

Much of the caviar came from sturgeon caught by 

the poachers, and some ofit was made from roe illegally 

purchased from sport fishermen on the banks 

of the Columbia River. The poachers had paid the 

month’s rent, approximately $ 900, in cash, and 

then told the motel manager that they did not want 

any maid service. The manager thought that the request 

for privacy was unusual, and became suspicious. 

About the time the poachers were checking into 

the motel a bank robbery occurred in nearby Dollars 

Corner, Washington. The bank robbers escaped 

with a package of cash that contained an exploding 

dye pack. The pack detonated, spewing red ink 

and staining both the cash and the thieves. 

The day after the robbery another local bank received 

a cash deposit from the motel where the 

poachers had rented the room. This deposit included 

red dye stained money. The bank teller recognized 

the stains on the bills as stains from the dye 

pack and notified the FBI. The FBI went to the motel 

and asked the manager where she had obtained 

the cash. There were only two rooms paid for in 

cash, one of which belonged to the poachers. The 

manager then told the FBI about her suspicions. 

The FBI immediately began to conduct surveillance 

of the poacher’s activities, suspecting that 

they were the bank robbers. 

Forthenextfew days theFBI agents hid in anearby 

motel room and watched the suspected robbers 

through the window blinds. They looked like a pair 

of fishing buddies, with their ragged clothes and 

small boat trailered behind an old red pickup truck. 

At one point, the agents observed one of the poachers 

deposit a bag of trash in the motel dumpster. An 

agent casually took a look at the garbage, and found 

an empty salt box. Although the agent did not know 

it at the time, he had discovered an important piece 

of evidence; salt, of course, is a major ingredient in 

caviar. 

The next day the fisherman left the motel room 

with two large boxes. They loaded the boxes into 

the back of the red pickup truck and drove to a FederalExpress 

office in Portland, Oregon. The agents 

followed the truck as it crossed the state line, and 

watched the driver mail the boxes at the Federal

425 

denied any contact with the poachers to occur before 

1990. Agents later learned that the records of 

over 50 earlier shipments had been destroyed. Fortunately, 

copies of the early records had been secreted 

away by a company employee and were discovered 

during the execution of a federal search 

warrant. When all of the evidence was compiled, 

the agents determined that at least 67 shipments 

had taken place. The poachers had been paid an estimated 

$247 176 tax free dollars for 1462 kg of 

American sturgeon caviar. The poaching ring had 

been active for over five years. 

Seized records and court testimony indicated 

that when the caviar company repacked the illegally 

harvested product for resale, much of it was labeled 

as imported beluga or osetra caviar. Although 

the poachers’ caviar was of high quality, it 

was still merely American sturgeon caviar, which 

sells for about $89 wholesale and about $130 per 

pound (0.454 kg) retail. Imported beluga caviar can 

sell for as much as $600 per pound. During trial in 

federal court, the president of the caviar company 

testified that he sold the American caviar as imported 

caviar to customers such as the Rainbow Room, 

the Waldorf Astoria and Pan American Airlines. 

He stated, in substance, that he would not sell the 

mislabeled caviar to those customers whom he 

thought would recognize the subtle differences in 

American, beluga and osetra caviar, however he 

thought that the mislabeled caviar was acceptable 

for some restaurants and other commercial or institutional 

customers. If all of the poachers’ caviar 

was resold as beluga, then it was worth almost two 

million dollars. 

The caviar company’s records indicated that the 

poachers were paid up to $100 a pound for the illicit 

caviar. The poachers did not pay income tax on his 

profits from the unlawful sales. It is impossible to 

distinguish a male from a female sturgeon in the 

field, without first killing the fish. Therefore, it must 

be assumed that the poachers probably killed as 

many adult male sturgeon as female in their search 

for the valuable eggs. Of course, only a fraction of 

adult female sturgeon will be ripe at any particular 

time, and those fish would also have to be killed and 

eviscerated to determine if they contained roe. Caviar 

experts estimated that during the process of 

transforming sturgeon roe into caviar, about forty 

percent of the original weight of the eggs is lost. The 

Washington Department of Fisheries estimated 

that to obtain 3220 pounds of finished caviar, approximately 

two thousand male, female, ripe, and 

unripe sturgeon were killed in a five year period. 

That figure represents a significant part of the sturgeon 

population in the lower Columbia River, 

where the poachers were operating. 

After a two and a half week trial, a federal jury 

found the owner of the caviar company guilty of 

conspiracy to violate the Lacey Act. That statute 

prohibits the interstate transportation, purchase, 

sale or possession of fisheries products, like caviar, 

if the product was taken in violation of any state law. 

He was also found guilty of four misdemeanor 

counts of the Lacey Act itself, and one felony count 

of Obstruction of Justice. The Obstruction charge 

stemmed from the destruction of documents that 

were under grand jury subpoena, and then lying to 

the grand jury to hide his involvement. He was sentenced 

to eighteen months in federal prison, $4175 

in fines and penalties, three years probation, plus 

the costs of his imprisonment and probation. 

The caviar company itself was charged as a separate 

defendant, and was also found guilty of criminal 

Conspiracy and four misdemeanor counts of the 

Lacey Act. Fines and penalties ($20 625) were assessed, 

along with three years’ probation, although 

$10 000 of the fine was suspended by the judge. 

One of the poachers plead guilty to a Conspiracy, 

four felony Lacey Act counts and one felony income 

tax count. His plea-bargain arrangement included 

testimony against the other defendants at 

trial, in return for a lesser sentence. He was sentenced 

to eight months in federal prison and $2675 

in fines and penalties. 

The resale of the American caviar mislabeled as 

imported beluga and osetra caviar was not charged 

in the indictment. Nevertheless, when the caviar 

company president took the witness stand, he testified 

that the mislabeling took place. 

When a consumer pays several hundred dollars a 

pound for a product, there is a presumption that he 

or she is buying credibility. After all, ‘you get what 

you pay for’. At the same time, most consumers can 

not afford to eat top of the line caviar often enough

426 

to truly develop an educated palate, and rely on the 

caviar tin’s label and the brand name to ensure 

quality. Had it not been an unrelated bank robbery, 

this cycle of wholesale commercial poaching and 

product mislabeling might still be going on. 

The jury returned the guilty verdicts on 22 October1993, 

exactly eight years to the day after the first 

known shipmentbetween the poachers and the caviar 

company.’ 

1 Convicted were: Hansen Caviar Co. Inc.; Mr. Arnold Hansen- 

Sturm, the president of Hansen Caviar Co. Inc.; and Mr. Stephen 

Gale Darnell, the lead poacher (the second poacher served as a 

witness for the prosecution). This case was documented by the 

commercial news media at the time of the indictments, trial and 

convictions (e.g. Anonymous 1993,1994, Boss 1994, Houtz 1994a, 

b, O’Neill 1993) but this and other poaching cases are little 

known to the scientific community. In part, we think that this 

may stem from general unfamiliarity with (or unwillingness to 

recognize) the catastrophic biological impact that can be made 

by small numbers of environmental criminals. If we are to have 

any impact in reducing environmental crime, better awareness 

and swifter condemnation by biologists seem essential (editors’ 

note, March 1996). 


Anonymous. 1993. New Jersey firm guilty in roe case. The New 

York Times, 24 October. 

Anonymous. 1994. Caviar cons. Seafood Leader 14. 

Boss, K. 1994. Caught fishing. Pacific Magazine. 13 March: 12-20 

(prepared by Seattle Times). 

Houtz, J. 1994a. The courts. U.S. District Court, Seattle. The 

Seattle Times. 14 February: B2. 

Houtz, J. 1994b. Man gets 8 months for selling caviar from protected 

sturgeon. The Seattle Times, 15 January. 

O’Neill, M. 1993. Caviar distributor and 2 fishermen charged 

with evading limits on scarce U.S. roe. The New York Times, 4 

April: 40.



The threatened status of acipenseriform species: a summary 

Vadim J. Birstein1, William E. Bemis 2 & John R. Waldman 3 

1 

The Sturgeon Society, 331 W 57th Street, Suite 159, New York, NY10019, U.S.A. 

2 



3 Hudson River Foundation, 40 West 20th Street, Ninth Floor, New York, NY 10011, U.S.A. 


Key words: IUCN, CITES, listing, overfishing, pollution, dam construction, sturgeons, paddlefishes 

. . . increased demand has recently driven the price of black market smoked sturgeon 

as high as $26 a kilogram. With poachers standing to gain roughly a third of this price 

[besides the much higher price of caviar], a large fish could be worth thousands of 

dollars. 

Gary Hamilton 

in Canadian Geographic, July/August 1996, p. 62 

Papers in this volume describe many factors that expose 

acipenseriform fishes to particular risks of 

population decline and extinction. These range 

from such basic problems as how to define species 

boundaries and recognize different species of sturgeons, 

factors that necessarily impact all regulatory 

and law enforcement efforts. Other factors concern 

the extreme sensitivity of sturgeons to overfishing, 

their dependence on large, often polluted urban river 

systems for spawning, and migration routes 

blocked by hydroelectric dams. The value of the 

traditional reaction to such problems - stocking 

hatchery reared fish - is increasingly debated, particularly 

if the stocking occurs ‘on top of’ a remnant 

population of sturgeons. The prognosis for most 

species is extremely bleak, and has worsened during 

the few years that we have been recording information. 

Technical developments - such as the use of 

genetic markers to recognize different species of 

sturgeons (and their caviar) - may offer some new 

regulatory tools. Improved basic knowledge - especially 

behavioral and ecological data obtained by 

telemetry of wild fish - may help governments to 

protect sensitive and important sites, particularly 

spawning areas. 

Stocking can be a mixed blessing, though it certainly 

helped historically to sustain some species, 

such as Huso huso in the Volga River and Caspian 

Sea. Reintroduction to portions of ranges from 

which a species has been extirpated may seem to be 

a laudable goal, although this has not yet been 

achieved for any acipenseriform species. As in cases 

of attempted restorations of salmoniform fishes, serious 

questions surround the choice of stocks that 

might be used for reintroduction. Given the short 

time during which we can hope to act to preserve 

the global biodiversity of sturgeons and paddlefishes, 

greater international awareness, better regulation 

and stricter enforcement of existing laws are 

essential. It seems especially important that all interested 

persons act to assemble the best possible 

data on the current status of their local species of 

sturgeons and paddlefishes. 

Most species and many populations of sturgeons

428 

I 

pre-barbel length (measureto more anterior barbel base and note whether it is inner or outer barbel) 

pre-oral length 

inner barbel length 

outer barbel length 

head length (measured to the posterior edge of opercular flap) 

pre-orbital length (to anterior edge of orbit) 

count number and note 

arrangement of scutes just 

anterior to anal fin 

pre-pectoral length 

pre-pelvic length 

I 

I 

I 

pre-dorsal length 

pre-anal length 

standard length (SL; to 

end of last keeled 

scute on lateral surface) 

fork length (FL) 

total 

length 

(TL) 

Figure 1. Standard measurements for sturgeons: a - Ventral view of mouth based on an illustration of Scaphirhynchus platorynchus 

modified from Bailey & Cross (1954). b - Lateral view of body based on an illustration of Acipenser oxyrinchus (518 mm TL) modified 

from Vladykov & Greeley (1963). A color photograph including a metric scale bar should be made showing the ventral view of the head 

(as in a) and lateral view of the body (as in b) All measurements should be recorded from each specimen, together with date and exact 

locality data, water condition, observers name and institution, and late of the specimen.

429 

and paddlefishes, particularly anadromous forms, 

are in trouble (Birstein 1993, Bemis & Findeis 1994, 

Waldman 1995). Declines of sturgeon and paddlefish 

populations are described in many papers in this 

volume (e.g., Bacalbasa-Dobrovici 1997, Graham 

∨ 

1997, Hensel & Holcík 1997, Khodoreskaya et al. 

1997, Krykhtin & Svirskii 1997, Ruban 1997, Wei et 

al. 1997, Zholdasova 1997). Like other anadromous 

fishes, such as salmonids, sturgeons are extremely 

sensitive to overfishing (Boreman 1997, this volume). 

Overfishing, including unprecedented levels 

of poaching, is the main threat to sturgeon survival 

in Europe (especially in Russia), Siberia and China 

(Birstein 1993, 1996, Dumont 1995, Anonymous 

1995a, De Meulenaer & Raymakers 1996, Ruban 

1996). Poaching also plagues certain populations in 

the United States, such as Columbia River white 

sturgeon (Cohen 1997 this volume). Other factors, 

including pollution, at present play a less important 

role in the decline of populations (for instance, 

Khodorevskaya et al. 1997, Ruban 1997). Even species 

that are not fished for either caviar or meat, 

such as all three species of Pseudoscaphirhynchus, 

have declined, in this case primarily in response to 

the drying of the Aral Sea (Zholdasova 1997). 

Persistent problems in identifying species of Acipenser 

outside of their supposedly native ranges 

cause us to make two practical suggestions. First, 

document by photography and measurement external 

features of live wild sturgeons. Intraspecific variation, 

particularly in wide ranging species such as 

Acipenser ruthenus, is extremely confusing and no 

single researcher is ever likely to have access to all 

river systems in which such species occur. Figure 1 

proposes a series of measurements to be recorded, 

together with locality data including water flows, 

associated fauna, etc. These data will be most valuable 

when coupled with color photographs of the live 

specimen showing its natural coloration. Second, 

systematics cannot be stronger than the specimens 

and collections upon which it is based. Voucher 

specimens, especially large fish and ontogenetic series 

- even partial or salvaged specimens - with 

good locality data are needed for many species of 

acipenseriforms from many areas of the world, so 

we must take active roles in the growth and maintenance 

of sturgeon materials in permanent natural 

history collections. (As an aside, Grande & Bemis 

1991, found it easier to find museum specimens of 

the Eocene Green River paddlefish, Crossopholis 

than the extant Chinese paddlefish, Psephurus gladius, 

which is quite the reverse of most paleoichthyological 

experience.) 

For many years, stocking of artificially reared 

young has been used to maintain populations of acipenseriforms 

in the former Soviet Union (e.g., the 

three main commercial species of Caspian Sea sturgeons, 

Huso huso, A. stellatus, and A. gueldenstaedtii, 

Khodorevskaya et al. 1997) and in the United 

States (e.g., Polyodon, Graham 1997). The fragility 

of this approach is well-illustrated by events in Russia 

since the late 1980s, when stocking of Caspian 

Sea sturgeons began to decrease (Khodorevskaya 

et al. 1997). Not only do fewer hatcheries now operate 

on the Volga River, but also they are unable to 

catch enough brood stock, so that the beluga, H. huso, 

has become extremely threatened. Because of 

dam construction, beluga lost access to practically 

all of the spawning grounds in the Volga River. In 

1995, the number of females caught in the Volga 

River delta was insufficient for artificial breeding. 

Therefore, in 1995 there was no natural or artificial 

reproduction of H. huso in the Volga River. The situation 

on the Danube River is similarly discouraging, 

for the two dams at the Iron Gates now prevent 

the historic migration of beluga between the Black 

Sea and the middle reaches of the Danube River. 

Artificial breeding of H. huso in the Danube River 

(in the Serbian part of the river) has also been unsuccessful, 

and there is no indication that the situation 

will improve in the near future. We must make 

the case throughout the world that even the very 

best stocking programs can only provide short-term 

solutions unless they are coupled to plans for protecting 

and increasing levels of natural reproduction. 

Technology may aid in enforcing existing regulations 

and learning what to protect in nature, but 

our efforts as scientists must be focused not only on 

what we can learn about sturgeons and paddlefishes 

but also how to translate that knowledge into practical 

measures (Wirgin et al. 1997, this volume). For 

example, it is now possible to identify the caviar of 

certain species of sturgeons using species - specific

430 

Table 1. Threatened status of acipenseriforms 

Species English name Distribution Status (national listing or latest IUCN listing CITES 

studies) 1996 

1991 1996 2 

Status 1 References 

FamilyAcipenseridae 

Acipenser baerii Siberian sturgeon Main Siberian rivers VU 

A. baerii baerii Siberian sturgeon Ob River basin EN Ruban 1996, 1997 EN 

A. baeri stenorrhynchus Lena River Basins of the East Siberian rivers VU Ruban I997 VU 

sturgeon Yenisey, Lena, Indigirka, Kolyma, 

and Anadyr 

A. baerii baicalensis Baikal sturgeon Lake Baikal (Siberia) VU RSFSR Red Data EN 

Book 1983, Pavlov 

et al. 1985, 1994 

A. brevirostrum 3 Shortnose River, estuaries and ocean along T (Canada & USFWS1967, VU (Canada VU Appendix I 

sturgeon east coast of North America from USA) Williams et al. & USA) 

Indian River (Florida) 10 Saint 

1989, Manci 1993 

John River (New Drunswick) 

V (Canada) Campbell 1991 

A. dabryanus Yangtze or Yangtze River system EN (category Wei et al 1997 CR 

Dabry’s sturgeon 

1 of state 

protection) 3 

A. fulvescens lake sturgeon Great Lakes and lakes of T(Canada & Williams et al VU (Canada VU 

southern Canada USA) 1989 Manci 1993 & USA) 

A. gueldenstaedtii Russian sturgeon Black, Azov, Caspian seas and VU Lelek 1987 EN 

rivers entering into them 

Caspian Sea population H Khodorevskaya et EN 

al. 1997 

Black Sea population 

EX 

Danube River population, EN Guti 1995 

Hungary 

Danube River population. VU 

∨ ∨ 

Banarescu 1995 

Romania 

Dnepr River population (Black EN Gringevsky 1994 

Sea) 

Sea of Azov population VU. H Volovik et al 1993 EN 

A. medirostris Green sturgeon Pacificcoast of North America V (Canada) Campbell1991 VU 

from Aleutian Islands and Gulf of 

Alaska to Ensenada, Mexico 

T(USA) Moyle et al 1994 

A. milkadoi Sakhalin sturgeon Pacific Ocean from Amur River EN USSR Red Data EN 

to northern Japan, Korea. and 

Book 1984 Pavlov 

Bering Sea, Tummin (Datta) River 

et al. 1994 

A. naccarii Adriatic sturgeon Adriatic Sea, Po and Adige Rivers VU Lelek 1987 VU 

A. nudiventris Ship sturgeon Aral Caspian. Black seas and EN 


Caspian Sea and rivers entering EN Pavlov et al 1985 EN 

into it Lelek 1987 

H 

Sokolov & Vasiley 

1989 

Black Sea and rivers entering EN Pavlov et al. 1985. EN 

into them (Russia, Ukraine) 

H 

1994 

Sokolov& Vasiley 

1989 

Danube River population 

CR 


H un gar y 

Danube River populalion, EX 

∨ ∨ 


Romania 

Aral Sea (Central Asia) EX Zholdasova 1997 EX

431 

Table 1 Continued. 

A. oxyrinchus Atlantic sturgeon Atlantic Ocean (Canada and USA Lr (nt) 

A. oxyrinchus desotoi 5 Gulf sturgeon 

east coast) 

Gulf of Mexico and northern coast T Williams et al. VU 

of South America 

1989 USFWS 

1990bManci1993 

A. o. oxyrinchus Atlantic sturgeon River estuaries and ocean SC (USA) Williams et al VU (Canada LR Appendix 

along east coast of North America 1989 & USA) (nt) II 

A. persicus Persian sturgeon 

from the St. Johns River (Florida) 

to Hamilton Inlet (Labrador) 

Caspian and Black seas and EN Lelek 1987 EN 


Caspian Sea population 

VU 

Black Sea population R Pavloy et al. 1994 EN 

A. ruthenus Sterlet Drainages of main rivers EN Lelek1987 

VU 

entering the Caspian and Black 

seas (Volga, Danube) 

Volga River population 

Danube River population 

LR (1c) 

VU 

Danube River population, VU Guti 1995 

Hungary 

Danube River population, VU 

∨ ∨ 

Banarescu I995 

Romania 

Dnepr River population EN Gringevsky 1994 

Oh. Irtysh, Yenisey rivers (Siberia) 

VU 

A. schrenckii Amur River Amur- River system (Siberia) T Manci 1993 VU (China EN 

sturgeon 

& Russia) 

EN Kryktin & 

Svirskii 1997 

A. sinensis Chinese sturgeon Yangtze River system (China) EN, H Wei et al. 1997 EN 

(category) I 

of state 

protection) 4 

A. stellatus Stellate sturgeon Caspian Azov Black and Aegean EN 

or sevruga seas and rivers entering into them 

Caspian Sea populalion 

V U 

H 

Khodorevsskayaet 

al. 1997 


EN 

Dnepr River population (Black EN Gringevsky 1994 

Sea) 


Hungary 

Danube River population, EN 

∨ ∨ 


Romania 

Sea of Azov VU ,H VoIovik et al. EN 

I993 

A sturio Atlantic (Baltic) Baltic, Eastern North Atlantic, EN 6 USSR Red Data EN CR Appendix I 

sturgeon Mediterranean and Black Sca Book 1984 Lelek 

∨ 

1987. Holcik et al. 

1989 

A. transmontanus White sturgeon River and Pacific coast of V (Canada) Campbell 1991 LR (nt) 

North America from the Gulf of 

Alaska to Baja California 

V (California. Moyle 1994 

USA) 

Kootenai River and Kootenai EN USFWS 1994 7 EN 

Lake in Idaho, Montana and 

British Columbia downstream of 

Libby Dam in Montana

432 

Table 1. Continued. 

Huso dauricus Kaluga sturgeon Amur River system EN Krykhtin & EN EN 

Svirskii 1997,Wei 

et al. 1997 

H. huso Giant sturgeon Caspian, Black, and Adriatic VU Lelek 1987 EN 

or beluga 

seas and rivers entering into them 

Caspian Sea population 

H 

Khodorevskaya et 

al. 1997 


Dnepr River population EN Gringevsky 1994 

(Black Sea) 


Hungary 

Danube River population. VU 

∨ ∨ 


Romania 

Azov Sea population EN Pavlov et al. 1994 CR 

Adriatic Sea population 

EX 

Pseudoscaphirhynchus Syr-Dar Syr-Darya River (Kazakhstan, EN USSR Red Data CR 

fedtschenkoi shovelnose Central Asian) Book 1984 

sturgeon 

EX Pavlov et al. 1985, 

1994 

P. hermanni Small Amu-Dar Amu-Darya River EN USSR Red Data CR 

shovelnose (Uzbekistan, Central Asia) Book 1984 

sturgeon 

EX Pavlov et al. 1985 

P. kaufmanni Large Amu-Dar Amu-Darya River EN USSR Red Data EN 

shovelnose (Turkmenistan,Uzbekistan & Book 1984 

sturgeon Tadjikistan, Central Asia) 

CR Zholdasova 1997 

Scaphirhynchus albus Pallid sturgeon Missouri and Mississippi EN 8 Williams et al. EN EN 

River basins 

1989,USFWS 

1990b,Manci 1993 

S. platorynchus Shovelnose Missouri and Mississippi E Williams et al. 1989 VU 

sturgeon River basins 

S. suttkusi Alabama sturgeon Mobil basin in Alabama and EN 9 Williams et al. EN CR 

Mississippi 

1989,Williams& 

Clemmer 1991, 

Manci 1993,1994 


Polyodon spathula North American MississippiRiver system, SC (USA & Williams et al. VU (USA) VU Appendix 

paddlefish particularly Missouri and its Canada) 1989 II 

tributaries 

Psephurus gladius Chinese Yangtze River system EN (category Wei et al. 1997 VU CR 

paddlefish 

I of state 

protection) 2 

1 Categories are given in the new IUCN system (IUCN Red List Categories 1994): EX = extinct; CR = critically endangered; EN = endangered: W = 

vulnerable: LR = low risk; LR(nt) = near threatened: LC(lc) = least concern: or in the US Office of Endangered Species system: E = endangered; T = 

threatened; SC = special concern. H (Hatcheries) designates species whose natural reproduction is limited: such species are artificially bred and juveniles 

obtained are released into their natural habitat. 

2 Proposals of the Sturgeon Specialist Group. IUCN 

3 All populations of A. brevirosrrum along the east coast of the USA and Canada are listed as endangered by the USFWS, Title 50, parts 17.11,17.12 (USFWS, 

1967;DOI,1973). 

4 A list of wild animals by the states special protection in category I and 11.14 pp. (in Chinese). 

5 Populations of A. oxyrinchus desotoi are listed as endangered in AL, FL, GA, LA, and MS by the USFWS, Title 50. parts 17.11,17.12; federally threatened 

status from September 30,1990 (USFWS 1990b). 

6 According to the IUCN Red List (1994). the status of A. sturio is different in different countries: Albania (EN). Algeria (EN), Belgium (EX?), Finland 

(EX?), France (EN), Germany (EX?). Greece (EN). Iceland (EX?), Ireland (EX?). Italy (EN), Morocco (E). Netherlands (EX?), Norway (EX?), Poland 

(EX?). Portugal (EN). Romania (EN). Russia (EN), Spain (EX?). Switzerland (?),Turkey (EN). Ukraine (EN). United Kingdom (EN), Yugoslavia (EX?). 

The status of A. sturio for Spain and Netherlands should be considered as E since in 1992 sturgeons were caught in both countries (Volz & DeGroot 1992, 

Elvira & Almodovar 1993). In 1995. a few live A. sturio were caught in Albania (Tamas Gulyas personal communication). 

7 Kootenai River population of A. transmontanus is listed as federally endangered from 6 September. 1994 (USFWS 1994). 

'Populations of S. albus are listed as endangered in AR. IA, IL. KS, KY, LA, MO, MS, MT, ND, NE, SD and TN by the USFWS, Title 50, parts 17.11,17.12; 

federally endangered status from September 6,1990 (USFWS 1990a). 

9 Proposed listing of S. suttkusi as endangered has been withdrawn (Federal Register 59, No. 240: 64794–6409 (1994)). For the present, USFWS has placed this 

species in Category 2 (those species for which insufficient information is available to determine whether to proceed with a proposed rule to list or to consider 

the species extinct). At its meeting in Edmonton (Canada), 15-19 June 1995. the American Society of Ichthyologists and Herpetologists urged USFWS to list 

S. suttkusi as an endangered species (Anonymous 1995b. Mayden & Kuhajda 1996). 

EN 

EN

DNA primers (DeSalle & Birstein 1996). This may gladius) are already critically endangered, will be 

help law enforcement agencies to detect violations destroyed. Plans to develop oil fields in the northof 

CITES and other regulations, and coupled to the ern part of the Caspian Sea in Kazakhstan and 

development of this technology must be increased Turkmenistan (Sager 1994, Dumont 1995) threaten 

willingness to speak publicly on matters concerning the future of all sturgeons in the Caspian Sea. But 

enforcement of environmental laws. As another ex- even without these fundamental environmental 

ample of technology and efforts to conserve stur- changes it is evident that we may soon lose at least 

geons, radio telemetric studies revealed the spawn- some of the Eurasian sturgeon species. ‘Like the 

ing sites of shortnose sturgeon in the Connecticut Californian condor, the sturgeons only chance of 

River (e.g., Buckley & Kynard 1985). One of these survival may be in captivity’ (Dumont 1995). 

sites lies just below Holyoke Dam, Holyoke, Mas- The status of the American species of Acipensesachusetts, 

where the river passes through a highly riformes is comparatively much better than that of 

disturbed urban environment. Knowledge of the the Eurasian species (Table 1). Considering the 

existence of this spawning site enables public util- many ongoing recovery programs for almost all 

ities and state highway officials to limit their further American species (partly described in this volume 

impact on this portion of the river, particularly dur- by Bain 1997, Beamesderfer & Farr 1997, Graham 

ing the spring spawning season. In the future, it may 1997, Kynard 1997, Smith & Clugston 1997), the fubecome 

necessary to seek specific regulations pro- ture of American species seems to be much better 

tecting individual spawning sites from dredging or than that of the Eurasian ones, especially those with 

other destructive impacts. 

many extirpated populations. But as suggested 

The highly threatened status of all extant acipen- above, we must be careful not to become so reliant 

seriform species is summarized in Table 1, which upon artificial stocking of certain species that we nedates 

information given by Birstein (1993). Data for glect to develop ways to encourage - or at least to 

the main basins inhabited by sturgeons are given permit - natural spawning to play as large a role as 

separately. For the Danube River, evaluations are possible in maintaining populations. 

shown for both the middle (Slovak-Hungarian) and Clearly, Table 1 presents an initial step of the evallower 

(Romanian) reaches. Restocking efforts are uation of the status of acipenseriforms; a complete 

also mentioned in Table 1. The international eval- picture of the status of the group revealed river by 

uation of status is given for 1994 (IUCN Red List) river in each basin will take much effort and time. 

and 1996. Data for 1996 were collected by the Stur- But it seems that this effort is necessary if we are to 

geon Specialist Group created within the Species understand what is really left of the former range of 

Survival Commission of IUCN in 1994 (Birstein the extant acipenseriform species. Time is short, 

1995). The last column of Table 1 shows the present and we will be grateful for any forthcoming imlistings 

of species of sturgeons on the Appendices I provements to our data base. 

or II of CITES (Convention on International Trade 

in Endangered Species of Wild Fauna and Flora). 

It is evident from Table 1 that all European and Acknowledgements 

Asian sturgeon species are in trouble. For various 

reasons, however, only the European Atlantic sturgeon, 

A. sturio, attracts serious international attention 

to its conservation (Elvira & Gessner 1996, Williot 

et al. 1997, this volume). Meanwhile, the situation 

We thank the many readers and contributors to The 

Sturgeon Quarterly,which since its inception in 1993 

has helped to keep all of us aware of the global circumstances 

of sturgeons and paddlefishes. 

for many other species worsens. The construc- 

tion of Three Gorges Dam on the Yangtze River 

continues. When it is completed, the spawning References cited 

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Williot, P., E. Rochard, G. Castelnaud, T. Rouault, R. Brun, M. 

Lepage & P. Elie. 1997. Biological characteristics of the European 

Atlantic sturgeon, Acipenser sturio, as the basis for a 

restoration program in France. Env. Biol. Fish. (this volume). 

Wirgin, I.I., J.E. Stabile & J.R. Waldman. 1997. Molecular analysis 

in the conservation of sturgeons and paddlefish. Env. Biol. 



Env. Biol. Fish. (this volume).

Portraits of juvenile Acipenser gueldenstaedtii from the Black Sea stock, 71 cm TL armored form above a 77 cm rare naked form; the same 

individuals as on the frontispiece photographs. Originals by Paul Vecsei, 1996.

Species and subject index* 

12SrDNA(mitochondrialgene) 141-144 life history 324-328, 331-332, 348-353 Acipenser gueldenstaedtii (Russian sturgeon) 

I6S rDNA(mitochondrial gene) 141-144 in MerrimackRiver 324-325 208, 220 

I8SrDNA(nucleargene) 141-142, 146 

migration323-325, 328-330,349, in the Caspian Sea 209, 214 

Acipenser 351-353 in the Danube River 185,193, 208 

biogeography 41, 43, 128, 158, 169, palatquadrate shape 47 fishery 193,210,214 

174 inthe Pee DeeRiver 323, 330 reproduction 214–215 

in the Caspian Sea 215-216 phylogeny 45 status 203, 206 

feedingadaptations 119 population size321-323, 330 taxonomy 158 

fossil forms 174 

locomotion adaptation 121 

molecular phylogeny 147-148 

in the Potomac River 322 

predation on 331 

quadratojugal bone 47 

in the Volga River 209, 214–215 

Acipenser kikuchii (=A. sinensis), taxonomy 

159 

molecular variation in 159 

morphological characters 78, 81, 83, 

reproduction 324-327, 352-353 

in the Saint John River 322, 324-325, 

Acipenser medirostris (green sturgeon) 

fishery 412 

86-7.89-91.93.95-6,99, 101, 104, 331 spawning rivers169 

106-7,114-6 inthe Santee-Cooper River323-324 systematics 41 

osteological methods 77 

phylogeny 43, 64, 116, 128, 145, 

147-149, 171, 180 

in the Savannah River 322-324, 330 

spawning 324-326, 328-331, 350, 352 

status 319,322,356 

taxonomy 158-159 

in the Tumnin River 158 

Acipensermikadoi (Sakhalin sturgeon) 406 

polyploidy in 136 stocking 323 

in the Amur River 231–232 

range31 inthe SusquehannaRiver 322 spawningrivers 169 

rostralexpansion 120 taxonomy 159 systematics41 

speciation 128, 148 Acipenser dabryanus (Dabry’s sturgeon) taxonomy 158 

systematics 26, 39, 41-44, 147 

taxonomy157-160,386-388 

artificial reproduction 262 

biogeography257–258 

Acipenser multiscutatus (=A. schrenckii), 

taxonomy 159 

Acipenser baerii (Siberian sturgeon) 43, 223, compared to Acipenser sinensis 259 Acipenser naccarii (Adriatic sturgeon), 

230 distribution 259 taxonomy 160 

anthropogenic impacts 221 fishery 262 

Acipenser nudiventris (ship sturgeon) 208 

fishery 226-227 natural history 259-262 in the Aral Sea 378 

naturalhistory 180,221-228 

status258,433 

dams, impact of 374 

andpollution227 taxonomy 158,257 

in the Danube River 185, 196–197 

status 226 in the Yangtze River 177, 180,246, fishery 197 

taxonomy 158,225-226 253,257-263, 433 natural history 196, 378 

Acipenser brevirostrum (shortnose sturgeon) Acipenser fulvescens (lake sturgeon) 43 status39, 199–197,203,373 

43, 184 anthropogenic impacts 303-304, taxonomy 158 

andAcipenseroxyrinchus356-357 303-305 Acipenseroxyrinchus (American Atlantic 

inAltamaha River 322-323,331 

biogeography181,300–303,311 

sturgeon) 35, 43, 184, 310, 384 

artificialreproduction323 conservation recommendations 316 and Acipenser brevirostrum 356–357 

inAtlantic Coastal Rivers319 dams, impact of 303 

and Acipenser sturio 386 

biogeography319-320 distribution 299–301 anthropogenicimpacts339-341 

inthe Cape FearRiver 322-323 fishery302 -303.307 -308,313-316. artificialreproduction 343–345 

inChesapeake Bay 322 412 biogeography 181,336 

in the Connecticut River 318,321, genetics 301-302, 308,386,389-390 fishery 338- 343,411 

324-325,329-330 habitat 303 genetics 336,386-387,393-394 

dams, impact on 318, 323-324, 

328-329 

in Delaware River 322, 325, 330 

feeding 327, 351, 353 

fishery 332 

in Manitoba 307 

in the Menominee River 311–316 

in Ontario 307 

population status 305–308, 313–316 

in Quebec 305,308 

in the Hudson River 347–357 

natural history 336–338, 345, 354-356 

population structures 337 

in the Saint John River 340 

in the St. Lawrence River 310,340, 

freshwater amphidromy 178 spawning 180 384 

growth 324,350,352–353 status 305–309 Status 335, 340, 347-348,356 

habitat327–328 stockidentification388-390 inthe Suwannee River345 

in the Hudson River 220,321,324, taxonomy 159 taxonomy 159,386 

347-357 Acipenser oxyrinchus desotoi (Gulf sturgeon) 

* Prepared by Alice G. Klingener, University of Massachusetts, Amherst, MA 01003, U.S.A.

438 

fishery 340 natural history 361-367 phylogeny 51-53, 171 

Gulf Sturgeon Recovery/Management restoration 367 systematics 50-53 

Plan 343 in the Rioni River 359,365 Actinopterygii 

mtDNAvariation391 status 203, 359, 361, 364-365, 367 morphological characters 46-49, 52, 58 

natural history 336-338 taxonomy 154, 159 phylogeny 32 

pollution341 Acipenser transmontanus (white sturgeon) systematics 33 

status 336, 343,394, 412 43,406 Alabama sturgeon see Scaphirhynchus 

stock identification 390-391 caviar poaching 423-426 suttkusi 

taxonomy 159,386 in the Columbia River 390,413-414 Alabama River 418-419 

Acipenser oxyrinchus oxyrinchus (Atlantic fishery 411,414 

Alazeya River, Acipenser baerii in 225 

sturgeon) 159,336,386 in the Fraser River 390 Altamaha River 

Acipenser persicus (Persian sturgeon) 220 

in the Caspian Sea 209 

gametogenesis 269-271 

hormones and reproduction 275 

Acipenserbrevirostrun in322-323, 

330 

taxonomy158 mtDNAgenome386 dams329 

Acipenser ruthenus (sterlet) 39, 43,72 natural history 179, 265–276 American shovelnose sturgeons see 

inthe AmurRiver 231-232 

neurendocrine control of reproduction Scaphirhynchus pp. 

intheDanubeRiver 185, 192-195 273–275 Amia 

fishery195 stockidentification 389-390 morphologicalcharacters52,86-87, 

natural history 169, 177,195 taxonomy 159 90,93 

spawningrivers 169 Acipenseridae as outgroup 142 

status 195 anatomical studies of 39 variation in 29 

systematics41 benthicadaptation 118-121 Amiidae (bowfins),systematics33 

taxonomy41, 158 biogeography118, 179 amphidromy 177-178,323 

Acipenser schrenckii (Amur sturgeon) 156, in the Black Sea 201, 205 

ampullary bones 107 

240 

in the Caspian Sea Basin 216-217 ampullary organs 64, 121 

inthe AmurRiver 231-232, 244 

characteristics and extinction status Amu-Darya River 

fishery231-232,237 356 Acipensernudiventris in 378 

natural history 236-237,244-245, cladistic analysis 41,74, 116-123 anthropogenic impacts 374-375, 377 

250-251 evolutionary interrelationships 74,76, dams 374 

status232,237,253 122-124 Pseudoscaphirhynchus in44-45 

taxonomy 158–159 fossil history 26 Amur River 

Acipensersinensis (Chinesesturgeon)241, morphological characters 50-52, 

Acipenser schrenckii in 128, 156, 158, 

243 54-58,77-116 177, 231-238, 240, 244-245, 

conservation efforts 253 

naturalhistory 119,407-409 248-250 

natural history 248-252 osteological studies 46-58, 77-116 

conservation efforts in 245-246 

taxonomy 158 paedomorphosis 118, 122-123 dams 250-251 

inthe Yangtze River 158,177,251-253 pectoral fin spines of 121 

fishery 41, 232-232,245 

Acipenser spp. pelvic fin origination 50 geography 233-234,244 

in the Hudson River 356 peramorphy 122-123 

Huso dauricus in 128,231–238 

status 400 phylogeny 64–65,74, 116-124, 128, Huso spp. in 180 

taxonomy 158-160 137-139, 149, 171 relict fauna 19 

Acipenserstellatus (stellatesturgeon)208 primitive condition 75 

spawning in 234-236, 245 

biogeography 180 reproduction 408–409 sturgeons in 231-232 

in the Caspian Sea 209,214 

respiratoryadaptation120 

anadromy 61, 177-180 

in the Danube River 185, 195-196,203 rostral expansion 120-121 

see also under natural history of 

fishery 196,210,213-214 soft-tissuecharacters 77 individual taxa 

naturalhistory 196,213 synapomorphy 46 

anamestic bones 83, 101, 114, 123 

status 196, 203 systematics 17-18, 26-45, 64-65, 74 Androscoggin River, dams 340 

stockidentification389-390 Acipenseriformes anteriorceratohyalbone92 

taxonomy 158 biogeography 34,62–63 anthropogenic impacts 409,411 

inthe Ural River213 cladistic studies28,45-48 Acipenser baerii 221 

inthe VolgaRiver209, 213 fossil history26-39, 179-180 Acipenser brevirostrum 322 

Acipenser srurio (European Atlantic molecular analysis 144, 385-396, Acipenser fulvescens 303-305 

sturgeon) 43, 184,364 421-422 bycatch 322, 332, 339 

anthropogenic impacts 360, 364, 366 morphological characters 46-58 Central Asia 44 

artificial reproduction 361-363, osteology32,46-58 comb jellyfish invasion 206 

365-367 phylogeny 26, 29, 33-34,45-48, dams 191, 209, 251, 263, 322, 340, 

biogeography180-181 122-123,127-133,144,171 348, 360, 364, 409, 412-413, 

in the Danube River 185,203 reproduction 265 418-421, 427, 433 

distribution 359-361 systematics 25–45, 47 in the Danube region 203-204 

fishery364 taxonomy 64 deforestation 203 

inFrance 359-367 Acipenserinae,jaws 119 dredging 322, 331 

geneticvariation 387 Acipenseroidei eutrophication in the Black Sea 205 

in the Gironde River 359, 363-364 morphological characters 46, 51-53, 55 gravel excavation 204, 360

439 

hypoxia 206 

irrigation 204,374,409 

oil fields 433 

overfishing 262-263, 340, 360, 409, 

427 

pesticides in the Caspian Sea 216 

poaching 216, 322, 332, 396, 409, 

423-426 

pollution 204-205, 215-216, 227, 

262-263, 322, 340-341, 364, 366, 

374-375, 377, 396, 409, 427 

Polyodon spathula279, 282-287 

and population vulnerability 399, 427 

Scaphirhynchusplatorynchus 296 

sea levels in the Caspian 216 

trawling for fish 205 

in the Volga River 209, 215-216 

VolgogradDam209 

water losses 204, 374-376, 382, 429 

antorbital bone 55, 83 

Apalachicola River, dams in 340 

aquaculture 

conservationrecommendations 411, 

415 

see also under reproduction; natural 

history in individual taxa 

Aral Sea 

Acipenser spp. 158, 378-379 

fishery379 

hydrological changes 374-376, 382, 

429 

Aral Sea ship sturgeon see Acipenser 

nudiventris 


Acipenser brevirostrum323 

Acipenser dabryanus 262 

Acipenser oxyrinchus 343-345 

Acipenser sinensis 243 

Acipenser sturio 361-363, 365-367 

Acipenser transmontanus 266-269 

in Delaware River 343 

hatcheries in the Caspian Basin 215 

and inbreeding 395 

Psephurus gladius 267 

Pseudoscaphirhynchus kaufmanni 378 

in the VolgaRiver 215 

Asia, biogeography ofAcipenseriformes 62 

ASMFC (Atlantic States Marine Fisheries 

Commission)recommendations and 

regulations343-345 

Atlantic region, speciation ofAcipenser 128 

Atlantic States Marine Fisheries 

Commission see ASMFC 

Atlantic Sturgeon Aquaculture and Stocking 

Committee 344 

Atlantic sturgeon seeAcipenser oxyrinchus; 


barbels 49, 63 

basipterygial process 58, 90 

basitrabecular process 49, 93-95 

beluga see Huso huso 

benthic adaptation 

of Acipenseridae 75, 118 

feeding 59, 119 

of Pseudoscaphirhynchus 123 

scales 119, 121 

of Scaphirhynchus 123 

benthophagy, evolution of 59 

Berg, L. S., career of 15-20 

bester 72 systematics 35 

biofiltration, in the Danube Delta 204 

biogeography 19, 34, 167-181, 174-175 

Acipenser 41, 43, 128,158 

Acipenser brevirostrum 319-320 

Acipenser fulvescens 300-303, 311 

of fossil forms 171-174, 179 

and phylogenetic analysis 62-63, 149 

see also biogeography; natural history 

under individual taxa: 

feeding adaptations 119 

locomotion adaptation 121 

morphological characters 46-52, 

54-55, 58, 78, 83, 85-87, 89-93, 

101-104, 107, 115-116 

† Chondrosteusacipenseroides35 

†Chondrosteushindenbergii 35 

chromosomes see karyotype 

circumorbital bones 114 

CITES (Convention onInternational Trade in 

Endangered Species of Wild Fauna and 

Flora) 429, 433 

cladistic characters see morphological 

characters under individual taxa 

cladistic studies 28, 45-48, 76, 145-157 

clavicle 89, 114 

cleithrum 55, 116 

Columbia River, Acipenser transmontanusin 

† Birgeria33 

biogeography 171, 173, 179 

morphological characters 46-47, 52 

synapomorphy 46-47 

systematics 34, 47 

390, 413-414 

Black Sea 

comb jellyfish see Mnemiopsis leidyi 

Acipenser spp 159 

Congaree Riverdams 340 

anthropogenic impacts 205-206 Connecticut River 

comb jellyfish, invasion of 206 

Acipenser brevirostrum in 321, 

geology 180, 204 324-325, 329-330 

the northwestern shelf 205 

dams 329, 340 

spawning in 179 

conservation 409-414 

border rostral bones 99-100 

bowfins seeAmiidae 

branchial skeleton 58, 105 


branchiostegals 50-52, 54-58, 86, 114-115 Acipenser dabryanus 263 

bycatch 332, 339 Acipenserfulvescens 316 

Canada, fishery regulation inAcipenser 


oxyrinchus 343 Acipenser sinensis 253 

Cape Fear River, Acipenser brevirostrum in 

322-323 

cardiac shield 55, 87 

Caribbean Conservation Corporation 345 

Caspian Sea 

Acipenser persicus in 158 

anthropogenic impacts 210, 214-217 

Acipenser sturio 367 

in the Amur River 245-246, 253 

applied technology 429 

aquaculture 411, 415 

ASMFC 344-345 

and dams 414 

in the Danube River 206 

reproduction 214-216 and fisheries 404, 411, 415 

sturgeons in 209, 310, 433 

flow management 414 

caudal peduncle 115 

habitat protection 411-412, 415 

caviar 422 

museum collections 429 

economics 342 

planning 411 

poaching 423 - 427 Psephurusgladius 267-268 

Central Asia, anthropogenic impacts 44 

species identification 429 

cheek bone loss 60 

stocking 429 

in the Yangtze River 253-254 

†Cheirolepis 33, 47, 52 

chemoreceptors, evolution of 63 

continental drift 169 

Chesapeake Bay, Acipenser brevirostrum in coracoid shelf89, 116 

322 

†Crossopholis magnicaudatus (Green River 

China-western North America, speciation of paddlefish) 28, 38 

Acipenser 128 

biogeography 171 

Chinese paddlefish see Psephurusgladius 


Chinese sturgeon see Acipenser sinensis 

morphological characters 50, 78, 

chondrichthyans, relationship to sturgeons 26 

85-87, 89, 91-3, 101, 103 

†Chondrosteidae 174 systematics 36, 38-39 

biogeography 169, 179 

morphological characters 51 

phylogeny 26, 171 

systematics 35, 51, 74 

† Chondrosteus 26,35 


culture see artificial reproduction 

cytochrome b (mitochondrial) gene 141-144 

dams 318, 409, 427 

in the Altamaha River 329 

in the Amu Darya River 374 

in the Amur River 250-251

440 

in the Androscoggin River 340 

in the Apalachicola River 340 

in the Columbia River 413-414 

in the Congaree River 340 

in the Connecticut River 329, 340 

in the Danube River 185, 191-192, 

195-197,203-204 

in the Delaware River 329 

in the Dordogne River 364 

in the Garonne River 364 

in the Hudson River 318, 328, 348 

impact on Acipenser brevirostrum 318, 

323-324, 328-329 endangered status see status 

impact on Acipenser fulvescens 303 

impact on Acipenser nudiventris 374 

impact on Acipenser oxyrinchus 340 

impact on Acipenser oxyrinchus epizootics 379 

desotoi 340 

in Irtysh River 223 

in the Kennebec River 329, 340 

in the Menominee River 312 

in the Merrimack River 329, 340 

in the Ob River 223 

in the Pearl River 340 

in the Pee Dee River 328, 340 

in the Santee-Cooper River system 

323-324, 329 

in the Savannah River 340 

in the Volga River215-216 

in the Wateree River 340 

in the Yangtze River 247-248, 

individual taxa 

250-251, 253, 261, 263, 433 extrascapular bone 55 

in the Yenisey River 224 

faunas, regional 28 

Danube River 9-11, 72, 208 

fecundity see under reproduction: also 

Acipenser ruthenus in 177 

under natural history in individual 

conservation recommendations 206 

taxa 

dams 185, 191-192, 195-197, 203-204 feeding 

and deforestation 203 

benthic adaptation 119 

Delta and the Black Sea 204 

migration 175 

Delta as a biofilter 204 

see also under natural history in 

fishery 202-203 


geography 185-186, 201 systems 59-61 

overfishing 9-11, 185, 206 

spawning in 61, 179 

status of sturgeons 185-197,201-206 

sequencing 141 

see also mtDNA; nDNA 

Dordogne River, dams 364 

dorsal rostral shield 99 

dredging, impact on Acipenser brevirostrum 

322, 331 

East China Sea, Psephurus in 177 

Eastern Atlantic, regional faunas 28 

eastern North America, speciation of 

Acipenser 128 

eggs-per-recruit (EPR) 400-403 

electroreceptors 63-64 

endocrines see hormones 

environmental threats see anthropogenic 

impacts 

EPR (eggs-per-recruit)and reproductive 

potential 400-403 

ethmoid expansion, in Acipenseridae 81 

ethmoid ridges 99, 106 

ethmoid shelf 105-107 

European Atlantic sturgeon see Acipenser 

sturio 

European freshwaters, regional faunas 28 

eutrophication, in the Black Sea 205 

evolutionary relationships see phylogeny; 

systematics; 

exploitation see fishery 

extinction see status; also under 

fenestra longitudinalis 54 

filter feeding, evolution of 59-61 

fin spine see pectoral fin spine 

Delaware River fishery 202-203 

Acipenser brevirostrum in 322,325, 

Acipenser baerii 226-227 

330 Acipenser brevirostrum 332 

Acipenser oxyrinchus in 343 


dams 329 Acipenserfulvescens 302-303, 

demersal spawning, evolution of61 307-308, 313-316, 412 

dermal bone, in fin rays 78 Acipenser gueldenstaedtii 193, 210, 

dermopalatine shelf 102- 103 214 

dermopalatine-ectopterygoidfusion 116 Acipenser medirostris 412 

development, Acipenser dabryanus261-262 Acipenser oxyrinchus 338-343, 411 

see also growth 

Acipenser ruthenus 195 

diadromy 177 Acipenser schrenckii 231-232, 237 

distribution 159-160, 168-169 Acipenser stellatus 196, 210, 213-214 

see also under biogeography; natural Acipenser sturio 364 

history; range in individual taxa 

Acipenser transmontanus 411, 414 

diversity 179 see also variation 

in the Amur River 41, 232-232, 245 

DNA 

in the Aral Sea 379 

content 133,136-137,139 


and phylogenetic analysis 142 

economics 341-342 

in the Great Lakes 302 

Huso huso 191,202-203, 210-212 

methods 339 

in Ontario 307 

Polyodon spathula 282-288, 411 

population impact 399-404 

in Quebec 308 

regulation in Acipenser oxyrinchus 

342-343 

regulation in the Columbia River 414 

restrictions 400, 403-404 


294-296, 412 

in the Volga River 210-211 


FMP(Fishery ManagementPlan)Acipenser 

oxyrinchus 343 

see also under ASMFC 

fossilhistory 26-39, 179-180 

biogeography 171-174 

Fraser River, Acipenser transmontanus in 12, 

390 

gametogenesis, inAcipenser transmontanus 

269-271 

Garonne River, dams 364 

gars see Lepisosteidae 

gene flow 395 

Acipenser oxyrinchus desotoi 393-394 

genetics 

analysis 336 

differentiation and variation 386-395 

and inbreeding 395 

see also mtDNA; nDNA; karyotype; 

haplotypes;alsounderspecific 

genes 

genotype see haplotypes 

geographic ranges see range; distribution 

also under individual taxa 

geological history, Black Sea 204 

gill rakers 113-115 

gill trematode see Nitzschia sturionis 

gill-arch dentition 47 

Gironde River, Acipenser sturio in 359 

glaciation, and biogeography 181 

gonadal cycles see under reproduction 

gonadal development,Acipenser 

transmontanus 269-270 

gonadotropins 273-274 

gravel excavation, in the Danube River 204 

Great Lakes, fishery 302 

Green River paddlefish see† Crossopholis 

magnicaudatus 

green sturgeon see Acipenser medirostris 

growth 

Acipenser brevirostrum 324, 350, 

352-353 





in Acipenseridae 408 


Scaphirhynchus platorynchus 293

441 

Gulf Sturgeon Recovery/Management Plan 

343 

† Gyrosteus mirabilis 35, 92 

habitat 


Acipenser fulvescens 303 

Acipenseridae 407-409 


Pseudoscaphirhynchuskaufmanni 377 

see also anthropogenic impacts 

haemal spine loss 105 

haplotypes 

of Acipenser fulvescens 301-302,308 

ofPolyodon spathula 389 

ofScaphirhynchus spp 389 

harvestsee fishery 

hatcheries seeartificial reproduction 

heavy metals, in the Caspian Basin 216 

Hell Creek formation 37 

Holarctic history 179 

Holarctic range, of Acipenseriformes 32 

homing 

fidelity and genetic variation 393-394 

spawning biology 171 

hormones 

gonadotropins 273-274 

and reproduction in Acipenser 

transmontanus 275 

Hudson River 

Acipenser spp. in 177, 179, 321, 324, 

347-357, 393 

dams 328, 348 

Huso 74 



locomotion 121 


86-87, 89-91, 93, 95, 99, 101-103, 

105-107, 113-116 


pelagic habit 121, 123 


rostral expansion 120 

systematics 39, 41, 117, 147 

Huso dauricus (kaluga) 

in the Amur River 231-238, 244-245 

fishery 231-232 

natural history 234-236, 244-245 

status 41, 232, 236-238, 253 

systematic relationships 41 

taxonomy 160 

Huso huso (beluga) 72, 156, 310 

in the Black Sea 205 

in the Caspian Sea 209, 213-214 

in the Danube River 185-186, 

202-203,206 

fishery 191,202-203, 211-212 

natural history 61, 186, 189, 211-213 

overfishing 189 

systematics 41, 45 

taxonomy 160 

in the Ural River 212-213 

in the Volga River 209, 211-213 

winter race 189 

hybridization 29, 72, 386 

Acipenser dabryanus and A. sinensis 

262 

Acipenser sturio and A. baerii 366 


Huso dauricus and Acipenser 

schrenckii 245 

Huso huso and Acipenser ruthenus 72 

Scaphirhynchus albus and S. 

platorynchus 29, 296, 388-389,421 

hydroelectric generation seedams; 

anthropogenic impacts 

hydrography, impacts 411 

hydrological changes 

Aral Sea 375-376 

see also anthropogenic impacts, water losses 

hyoid arch 58 

hyomandibular shape 49, 91-92 

hypobranchial skeleton 92-93 

hypoxia, in the Black Sea 206 

impoundments see dams 

Indigirka River, Acipenser baerii in 225 

infraorbital canal 48, 81-83 

interhyal-posterior ceratohyaljoint 104-105 

Iron Gates Dams see Danube River, dams 

irrigation, and the Danube. River 204 

lrtysh River, dams 223 

jaw 

evolution ofprotrusion 59-60, 122 

feeding adaptations 119-120 

shape 102 

jugal shape 112-113 

jugal anterior process 58, 81-83 

vs infraorbital canal 81-83 

juveniles see under life history in individual 

taxa 

kaluga see Huso dauricus 

karyological and molecular systematics 124 

karyotype 132-139, 386 

Kennebec River, dams 329, 340 

Khatanga River, Acipenser baerii in 224 

Kolyma River, Acipenser baerii in 225 

Korean Peninsula, Acipenser mikadoi in 159 

Lacey Act, prosecution under 425 

Lake Baikal 

Acipenser baerii in 224 

Acipenserfulvescens in 43 

Lake Erie, Polyodon spathula in 39 

lake sturgeon see Acipenser fulvescens 

Lake Winnipeg, fishery 302 

lateral ethmoid shelf see ethmoid shelf 

lateral extrascapulars clustered 114 

lateral line scales 50 

Latimeria chalumnae, karyotype 137 

Lena River, Acipenser baerii in 224, 227, 230 

Lepisosteidae, systematics 33 

Lepisosteus, morphological characters 86, 

90, 93 

life history 10, 168-169, 175-179 

Acipenser brevirostrum 324-328, 

331-332, 348-353 

Acipenser oxyrinchus 336-338, 345, 

353-356 

Acipenser oxyrinchus desotoi 337 

Acipenser sturio 361-363 

Acipenseridae 407-409 

and vulnerability to anthropogenic 

impacts 399,427 

locomotion, benthic adaptation 119, 121-122 

macrochromosomes see karyotype 

management see conservation 

mandibular canal 53 

Manitoba 

Acipenserfulvescens in 305 

fishery 302 

Meckel’scartilage55, 102-103 

medial opercular wall 87 

median extrascapular bone 83 

Mediterranean, regional fauna 28 

Menominee River, Acipenser fulvescens in 

311-316 

Merrimack River 

Acipenser brevirostrumin 324-325 

dams 329,340 

microchromosomes seekaryotype 

migration 169, 175-179 

Acipenser baerii 224 


328-330, 349, 351-353 


Acipenser nudiventris 378 

Acipenser oxyrinchus 336-337, 

353-356 

Acipenser schrenckii 237 

Acipenser sinensis 248 


Acipenseridae 408 

in the Connecticut River 329 

Huso dauricus 235 

Huso huso 186 

in the Yangtze River 248 

† Mimia33 


83, 86-7, 89, 93 

Mississippi River 

Polyodon spathula in 39 

Scaphirhynchus spp. in 388,420-421 

Missouri River, Scaphirhynchus spp. in 389, 

420-421 

mitochondrial DNA seemtDNA 

Mnemiopsis leidyi (combjellyfish), invasion 

of the Black Sea 206 

molecularanalysis 143-144, 148, 159-160, 

385-396, 421-422, 429 

molecular phylogeny 139-148 

morphological characters see under 


morphological studies 74 

mortality, fishing impact 399-404 

†Moythomasia 33 


mtDNA 386 

in Acipenser spp. 140,300, 336, 386, 

389-391, 396 

and phylogeny 149 

and RFLP (restriction fragment length 

polymorphism) 389-391, 393-394 

in Scaphirhynchus spp 388-389

442 

variation 386,390-391 status of Acipenseridae in 248 

muscle atrophy, in Caspian Sea sturgeon pectoral fin spines 55, 78, 87, 121 

215-216 

pectoral girdle 58 

myodomes 49 pectoral scales 93 

nDNA 

Pee Dee River 

evolution 132 

Acipenser brevirostrum in 323, 330 

genetic differentiation in 388-389 

dams 328, 340 

in taxonomic study 396 

† Peipiaosteidae 

neopterygians, supraneural bones 86 

neurendocrine control of reproduction, 


neurocranium, of Acipenseridae 81 

biogeography 169, 174 

morphological characters 50-51 

systematics 35-36, 51, 74 

† Peipiaosteus 28,34 

Nitzschia sturionis (gill trematode), in the antorbital bone 55 

Aral Sea 379 

basipterygial process 58 

nomenclature 13, 64, 77,118,225 basitrabecular process 49 

Acipenser 157-160 biogeography 174 

see also taxonomy 

North America, biogeography 62 

North American paddlefish see Polyodon 

branchiostegal reduction 52 



spathula 54-55, 58, 78, 83, 86-87, 89-93, 

North Atlantic, regional faunas 28 101-104, 107, 115-116 

nuclear DNA see nDNA 

systematics 35-36, 51 

Ob River 

pelvic fin origination 50 

dams 223 peramorphy 118, 122- 123 

spawning of Acipenser baerii 223 pesticides, in the Caspian Basin 216 

occipital canal, commissure 93 

†Pholidurusdisjectus, systematics 39 

Olenek River, Acipenser baerii in 224 

photoperiod, and reproduction in Acipenser 

olfactory system location 54 

Ontario, Acipenser fulvescens in 305, 307 


ontogenetic studies, in Acipenser 124 

opercular bones 46, 52-53, 55, 58 

76, 127-149 

osteology 32, 46-58, 74-116 137-139, 149 

outgroup taxa 32-34 

overfishing 

phylogeny 16-17, 26, 28-29, 33-34, 45-48, 

of Acipenser 64-65, 74, 116-123, 

of Acipenser brevirostrum 45 

of Acipenseridae 64-65,74, 116-124, 

128, 137-139, 149, 171 

ofAcipenseriformes 26, 29, 33-34, 

45-48, 122-123, 127-133, 144, 171 

and biogeography 149 

and hybridization 29 

and molecular analysis 139-144, 

ofAcipenser oxyrinchus 340 

in the Caspian Sea basin 216-217 

in the Danube River 185,206 

ofHuso huso 189 

of Psephurus 37 

in the Volga River 217 

see also anthropogenic impacts 

146-147 

Pacific rim, biogeographic regions 180 

of †Protoscaphirynchus 45 

paddlefishes see Polyodontidae; Polyodon 

of Scaphirhynchini 118 

paedomorphosis of Scaphirhynchus platorynchus 45 

in Acipenseridae 75,118, 122-123 

pineal bones 101-102 

and feeding system 59 

plesiomorphy 52, 59, 86, 92, 102, 107, 118 

and phylogeny 62 

poaching 

and skeletal development 49, 61-62 

palatal complex 58, 90-91 

palatopterygoid shape 51 

palatoquadrate bone 47, 95-96 

phylogenetic significance of protrusion 

26 

paleonisciforms 33 

†Paleopsephurus wilsoni 36-37,39, 174 364, 366 


91-3, 101, 104, 116 

pallid sturgeon see Scaphirhynchus albus 

parabasal canal 49 

parasphenoid process 46, 50 

PCR (polymerase chain reaction) 388-89 

Pearl River 

Acipenser sinensis in 158 

dams 340 allometry 29 

in Acipenser brevirostrum 332 

in Acipenser transmontanus 423-426 

in the Caspian Sea Basin 216 

and caviar 423-426 

and molecular analysis 396 

pollution 205, 262-263, 409, 427 

and Acipenser spp 227, 322, 340-341, 

in the Amu-Darya River 374-375, 377 


in the Caspian Sea 215-216 


and molecular analysis 396 

in the Volga River 215-216 

Polyodon spathula (North American 

paddlefish) 

anthropogenic impacts 279, 282-287 

biogeography 38-39 

fishery 282-288, 411 

genetic differentiation 389 


92-93, 99, 102-103, 105, 116 

population status by state 281-287 

range280-281 

status 279-280 

stock identification 389 

systematics 26, 36, 39 

† Polyodon tuberculata39 

Polyodontidae 


fossil history 28 


50-55, 58, 78, 83, 85-87, 89, 93, 

95-96, 99, 101, 105-106 


potamodromy 177 

synapomorphy 46 

systematics 36-39, 54, 74 

polyploidy 136-139, 148-149,386 

Polypteridae, systematics 32 

Polypterus 


86-87, 90, 93 

as outgroup 142 

Ponto-Caspian region 


geological change 180 

spawning 179 

speciation of Acipenser 128 

population 

Acipenser brevirostrum 321-323, 330 

Acipenser fulvescens 305-308, 

313-316 

Acipenser oxyrinchus 337 

Acipenser sturio in the Gironde River 

363-364 

in the Amur River, Acipenser 

schrenckii 236, 244-245, 248-250 

in the Aral Sea, Acipenser nudiventris 

318 

in the Caspian Sea 210, 216-217 

dynamics 400-404, 414 

Huso dauricus 234-236, 244-245 

Polyodon spathula 281-287 


Scaphirhynchus platorynchus 296 

in the Yangtze River, Acipenser 

sinensis 248-250 

posttemporal bone 52,54 

potamodromy 61, 177-178, 180 

Potomac River, Acipenser brevirostrum in 

322 

prearticular bones 103-104 

predation, on Acipenser brevirostrum 331 

premaxillary and maxillary bones 48-49 

preopercular canal 48 

proline gene, in Acipenser 141 

propterygial bone 87, 89 

protein evolution 133 

protein variation 388-389

†Protopsephurus 


branchiostegal number 58 

Jurassic paddlefish 28, 32 

morphological characters 53-54, 58 

systematics 36, 39, 53-54 

† Protoscaphirhynchus28 


systematic relationships 39 

† Protoscaphirhynchus squamosus 

phylogenetic analysis 45 

systematics 45 

protractor hyomandibularis muscle 59 

Psephurus gladius (Chinese paddlefish) 26, 

36-37, 246, 253, 433 


conservation efforts 267-268 


91-93, 95, 99, 102-103, 105, 114, 

116 

natural history 177, 247 

phylogenetics 119 

status 247 



Pseudoscaphirhynchus 74 

and Aral Sea drying 429 

benthic adaptation 123 


morphological characters 81, 86-87, 

90, 101, 107, 112-116 


peramorphy in 123 


status 381-383 

systematics 39,43-44, 117, 147 

Pseudoscaphirhynchus fedtschenkoi 

(Syr-Dar shovelnose sturgeon) 26,373, 

382 

morphotypes 77 

status 44, 373, 382 

Pseudoscaphirhynchus hermanni (small 

Amu-Dar shovelnose sturgeon) 

description 381-382 

distribution 382 

extinction of 373 

status 44,382 

Pseudoscaphirhynchus kaufmanni (large 

Amu-Dar shovelnose sturgeon) 

artificial propagation 378 

natural history 376-377, 381 

status 44,373,376,381 

† Pteronisculus, morphological characters 86 

Pyasina River, Acipenser baerii in 224 

quadratojugal bone 47, 53 

Quebec, Acipenser fulvescens in 305,308 

races, winter and vernal 18, 178 

ram ventilation, and filter feeding 60-61 

range see biogeography; distribution also 

under natural history in individual taxa 

regulations, of fisheries, see under fishery 

reproduction 265 

in Acipenser baerii 227-228 

inAcipenser brevirostrum 324-327, 

352-353 

in Acipenser oxyrinchus 354, 355 

in Acipenser schrenckii 236,250-251 

in Acipenser sinensis 250-251 

in Acipenser sturio 364-365, 367 

in Acipenser transmontanus 265-276 

in Acipenseridae 408-409 

in the Amur River 235-236,250-251 

and eggs-per-recruit (EPR) 400-401 

and fishing mortality 400-403 

in Huso dauricus 235 

in Psephurus gladius 247 

in Pseudoscaphirhynchus kaufmanni 

377 

in Scaphirhynchw platorynchus 

293-293 

threats to 429 

in the Yangtze River 247, 250-252 

see also artificial reproduction; spawning 

respiration 

adaptation for feeding 120-121 

evolution of 59-61 

respiratory shunt 120 

restocking see stocking 

restoration see stocking or under individual 

taxa 

RFLP (restriction fragment length 

polymorphism) 

in Acipenser fulvescens 390 

in Acipenser oxyrinchus 336, 393-394 

in Acipenser transmontanus 390 

in mtDNA analysis 389-391, 393-394 

and stock identification 391 

Rioni River, Acipenser sturio in 359, 365 

Romania, sturgeon fishery 203 

rostral bones 49,52-53,99, 101, 107 

see also border rostral bones; dorsal 

rostral shield; ventral rostral bone 

rostral canal shape 53,55,85-86 

rostrum expansion 52, 120-121 

benthic adaptation and 119 

Russian sturgeon see Acipenser 

gueldenstaedtii 

Saint John River 

Acipenser brevirostrum in 322, 

324-325,331 

Acipenser oxyrinchus in 340 

Sakhalin sturgeon see Acipenser mikadoi 

salinity 



and Huso dauricus 234 

tolerance in Acipenseridae 408 

Santee-Cooper River 

Acipenser brevirostum in 323-324 

dams 323-324,329 

† Saurichthys33 


relationship to Acipenseriformes 34 

Savannah River 

Acipenser brevirostum in 322-324, 

330 

dams 340 

443 

scalation 51, 121 

benthic adaptation 119, 121 

scales 47, 78 

Scaphirhynchinae, phylogeny 128 


benthic adaptation 119-120, 122 



93, 95-96, 99, 103, 105, 107 




Scaphirhynchus 74 

benthic adaptation 119-123 


distribution 292-293 

genetics 388-389 

habitat 45 

locomotion, adaptations 121 

in the Missouri River 389 


86-87, 89-90, 101, 107, 113, 

115-116 



status 395 

systematics 26, 39, 44, 117, 147 

taxonomy 388,395 

variation in 29,395 

Scaphirhynchus albus, status 45,388,412, 

420-421 

Scaphirhynchus platorynchus (shovelnose 

sturgeon) 45, 290, 292-296, 412 

Scaphirhynchus suttkusi (Alabama 

shovelnose sturgeon) 45, 292, 387-388, 

412, 418-419 

scapulocoracoid bone 74.78, 87, 89, 116 

scutes 54, 77-78 

sea level, of the Caspian Sea 214,216 

Sea of Azov, Acipenser spp. in 158 

Sea of Japan, Acipenser mikadoi in 159 

sensory systems, evolution of 63-64 

see also ampullary organs; barbels; 

visual systems 

shortnose sturgeon see Acipenser 

brevirostrum 

shoulder girdle denticles 50 

Siberian sturgeon see Acipenser baerii 

skeleton see osteology 

skull expansion see rostrum expansion 

Soviet Union (former)regional faunas 28 

spawning 169, 178-179, 408-409 


328-331, 350, 352 

Acipenser dabryanus 261-262 

Acipenser gueldenstaedtii 214 

Acipenser nudiventris 378 

Acipenser oxyrinchus 336-337, 354 

Acipenser schrenckii 236 

Acipenser sinensis 251-252 

Acipenser stellatus 196, 213 

Acipenser sturio 361, 364 

in the Amur River 234-236, 245 

in the Caspian Sea 214, 216

444 

evolution of61 † Strongylosteus, biogeography 173 in Acipenser 118 

Huso dauricus 234-236, 245 

sturgeons see Acipenseridae 


Huso huso 211-213 subopercle bone 47- 48, 53-54 

genetic 132, 386-390 

Psephurus gladius 267 supracleithrum 54-55, 58, 86-87, 89 

molecular 133, 143, 148, 160, 389 

Scaphirhynchus platorynchus 293-294 supraneural bone 58, 86 

in morphological characters 124 

stock levels 401-402 

Susquehanna River, Acipenser brevirostrum in phylogenetic studies 29 

in the Ural River 209-210 

in 322 

in systematic studies 65 

in the Volga River 209-210, 213, 216 Suwannee River, Acipenser oxyrinchus in see also under individual taxa 

in the Yangtze River 251-252, 267 

spawning rivers 159, 168-169, 174, 180 

spawning rivers see also under individual 

345 

Syr-Darya River, Pseudoscaphirhynchus in 

44 

ventral rostral bone 101, 107 

vernal race see races 

visual systems, evolution of 63 

rivers systematics 28-29, 31, 33-45, 47 vitellogenesis 269, 271-272 

speciation, in Acipenser 128, 138-139, 148 see also under individual taxa Volga River, sturgeons in 61, 179, 209-216 

†Spherosteus36, 174 taxonomy 64, 77, 118 

water losses see under anthropogenic 

St. Lawrence River, Acipenser oxyrinchus in 

340 

see also under individual taxa 

Teleostei, systematics 33 

impacts; hydrological changes 

Wateree River, dams 340 

status216-217, 423-429, see also under 


temperature, and reproduction in Acipenser 


white sturgeon see Acipenser transmontanus 

winter race see races 

stellate bones 53 

stellate sturgeon see Acipenser stellatus 

Tethys Sea 128 

threats, see under anthropogenic impacts; 

Yana River, Acipenser baerii in 225 

YangtzeRiver 

sterlet see Acipenser ruthenus 

specific threats Acipenser dabryanus in 177, 180, 246, 

†Stichopterus 28, 35-36, 50- 51, 74 Three Gorges Dam see Yangtze River, dams 253, 257-263, 433 

stock enhancement see artificial reproduction threonine gene, in Acipenser 141 

Acipenser sinensis in 158, 177, 

stock identification (genetic) 389-393, 395 tooth loss 49-50 248-251 

Stocking 367,409-413,427 trabecular process 101 dams 247-248, 250-251, 253-254, 261, 

Acipenser brevirostrum (shortnose trunk scalation 51 263, 433 

sturgeon) 323 Tumnin (Datta) River, Acipenser medirostris fishery 252-253 

in the Aral Sea 379 in 158,406 geography 246-253 

in the Columbia River 414 

Ural River, spawning in 179, 209-210, 

Psephurus gladius in 37, 246, 253 

dangers of333 212-213 † Yanosteus 36, 174 

stocks see fishery variation Yenisey River, Acipenser baeriiin 224

Sturgeon biodiversity and conservation

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