Notwithstanding public perception, the great white shark is "extremely rare" in Maltese waters as are the basking shark and the devil shark, a scientific study concluded.

Although many publications on local fish feature long lists of sharks and rays, more often than not their compilers based them on information gleaned from previous publications without questioning their veracity, Patrick J. Schembri, of the Biology Department at the University of Malta, said.

This anomaly has now been put right following a four-year study by biologists Titian Schembri and Prof. Schembri in collaboration with Ian K. Fergusson, who is involved in shark conservation and is a producer of nature documentaries for the BBC.

The results of this study, called Revision Of The Records Of Shark And Ray Species From The Maltese Islands (Chordata: Chondrichthyes) have been published in the journal The Central Mediterranean Naturalist issued by Nature Trust (Malta).

The aim of the study was to put the list of the sharks and rays occurring in local waters on a sound scientific footing instead of being based on unsubstantiated records and mythology.

Twenty-four sharks and 14 rays along with two other species, whose presence is a distinct probability although not encountered during this study, were authenticated out of a former list of 37 shark species and 26 species of rays.

In reviewing the literature, the authors go as far back as Pehr Forsskål (1732-1763), a Swede who studied botany under Linnaeus.

In his Descriptiones Animalium, published posthumously in 1775, Forsskål listed 114 Maltese fish including 13 cartilaginous species apart from two cetaceans.

Prof. Schembri noted that some authors start out by uncritically accepting records in previously published works but then add tales recounted to them by fishermen and divers.

"For example, in the case of rays, in particular, there are instances when even experts find it extremely difficult to differentiate between one species and another," Prof. Schembri added.

The main reason for wanting to know which sharks and rays can be found in the sea around us is that several of these species of cartilaginous fish are endangered to such an extent that they are on the verge of extinction in some parts of the Mediterranean while others are quite common, at least in the central Mediterranean.

"One cannot protect these species unless one knows their population levels and unless one can distinguish them clearly.

"If you are exploiting a stock of fish commercially, you need to manage that stock, otherwise you will over-exploit, especially if the species are slow-growing as the majority of cartilaginous fish are.

"In order to manage that fish, you need to know what the species is and because there are species that look similar, equipped only with superficial knowledge, you might think you are managing one thing while in truth you will be dealing with something completely different.

"Basically, there was a mess in this sector and in order to unravel this mess, we looked at every single record in the scientific or semi-scientific literature and evaluated the historical records.

"We also examined as many specimen as we could from the fish markets in Valletta and Marsaxlokk and checked museum records and photographs people have donated.

"Our list only includes species which we could relate either to an actual specimen or to photographs taken in Malta and that show clearly the fish's distinguishing features that enable the identification of the fish."

Titian Schembri carried out the bulk of the checks at the fish markets, where he not only noted the species landed but also their abundance in the catches.

Mr Schembri warns, however, that such data is biased since it is based on what was landed at the market in a specific season.

Prof. Schembri explained: "Some fish caught as by-catch are thrown away while fishermen are still out at sea.

"It was particularly instructive to compare our findings with the records kept by Giuseppe Despott (1878-1936), a zoologist who was also superintendent of fisheries.

"We can compare our findings with Despott's records bearing in mind changes in the fishing gear along the years - to get an indication of whether some fish have become more common while others have become scarcer.

"This scientific paper establishes a base line from which other researches can go further.

"Other researchers can look closer to see whether certain species are rare because they are becoming scarce or because they are not caught."

He noted that the basking shark - gabdoll, great white shark - kelb il-bahar abjad, and devil ray - baqra, are protected locally and internationally.

"We have found these three species to be extremely rare in Maltese waters. Another 14 species - 12 sharks and two rays - are also listed in the Flora, Fauna and Natural Habitats Protection Regulations 2003 as species that require management, meaning their numbers are declining and need to be managed if they are to recover."