Dolphinfish have explosive growth rates
Those who have followed the 15-year Dolphinfish Research Program by marine biologist Don Hammond knows that dolphin, also known as mahi mahi, have incredible growth rates.
The hundreds of recaptures from the thousands of dolphins tagged in Hammond’s study have revealed the accelerated growth, not to mention the oftentimes long-distance migrations of the species.
“We have spoken of conservative growth rates of 0.5 to 1.0 inch in length per week and gaining two to three pounds per month,” Hammond said in his December newsletter.
It means a 50- to 60-pound bull likely is less than two years of age.
But some anglers and even fishery managers have been skeptic, added Hammond who bases his study in Charleston, S. C.
To add credence that dolphins are voracious feeders and hence quick to grow during their short lives, Hammond outlined a documented case of one dolphin’s remarkable growth during a study by the University of Miami’s Rosenstiel School of Marine and Atmospheric Science’s aquaculture program.
Ron Hoenig, the hatchery manager for Rosenstiel’s aquaculture program, provided the details.
The study involved a male (bull) dolphin that was caught offshore Miami on Dec. 19, 2014, by Capt. Ray Rosher on the boat the Miss Britt, and immediately taken to the Rosenstiel’s experimental hatchery on Virginia Key as part of a captive breeding program.
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At its capture, the fish weighed approximately 5 to 6 pounds.
It was fed all the squid, sardines, herring and mackerel it wanted once a day, seven days a week. It lived under optimal conditions, with no predators to avoid, a situation expected to foster maximum growth rate.
After nine months, on Sept. 24, 2015, the dolphin weighed 56.4 pounds on digital scales, an increase of 50 pounds in the 279 days.
That relates to an overall average weight gain of 5.5 pounds each month. Hammond pointed out that such a growth rate would be unrealistic among wild fish, which are constantly on the move. Only a few other bull dolphin in the Rosenstiel program have shown similar growths. Females don’t grow as large.
“It does demonstrate the potential growth the species has,” Hammond said, adding that by releasing small fish, fishermen can earn dividends in short order in the form of bigger fish.
Unfortunately, Gulf of Mexico federal regulations do not protect small dolphin whereas Atlantic recreational fishermen off Florida, Georgia and South Carolina must observe a 20-inch fork length minimum, and a 10-fish per harvester daily limit. There’s no catch limit for commercial harvesters.
“Few Gulf anglers have been willing to tag their small dolphin for science in this region,” Hammond said. “This is probably because of the attitude set by the Gulf of Mexico Fisheries Management Council which views dolphin as a species that has no need of regulations, meaning there are no creel limit or size restrictions for dolphin in the Gulf. There is no reason for anglers to throw back their 12-inch fish.”
In the season-ending newsletter, Hammond said anglers tagged more than 1,600 dolphins in 2015, which is well above the 15-year average. A total of 36 tags were reported recovered during the year.
Financing for Hammond’s program is dependent upon donations and grants. The Florida Sport Fishing Association of Cape Canaveral, the Central Florida Offshore Anglers of Orlando, and the Sebastian Inlet Sportfishing Association of Melbourne have made financial contributions, along with individuals and businesses from Brevard County.
For more on the program visit www.dolphintagging.com
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Everglades Park plan
A new General Management Plan (GMP) by the National Park Service for the Everglades National Park will require boaters to complete a free online boating education course and they’ll need short-term or annual mandatory use permits for which fees will be charged.
The 1.5-million acre park includes major sections of Florida Bay and the Ten Thousand Islands in South Florida, two of the premier sportfishing areas in the state.
Changes also include poll and troll zones with mandatory-use access channels in 140,000 acres of protected shallow-water, peak season no-motor and slow speed segments, a new 120-mile Everglades Paddling Trail in the western section of the park called the Alternative Wilderness Waterway, and the opening of the Joe Bay area for public use for the first time in over 30 years, where paddling and catch-and-release fishing will be permitted.
In the East Everglades section, 27,300 acres will be open to private airboat use, and within that zone 16,400 acres will be available for concessioner airboat tours. Also the Marjory Stoneman Douglas Wilderness will be expanded by 85,000 acres.
The 20- to 30-year plan updates the 1979 Master Plan with the goal of improving habitat conservation while maintaining reasonable boating and fishing access.
The complete plan can be found at: http://parkplanning.nps.gov/evergmp.
Contact Bill Sargent at sargentwb@gmail.com.