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Released November 7, 2003

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OCEAN SPRINGS - Marine biologists at The University of Southern Mississippi are tracking red snapper this fall to find out what happens to hatchery-raised fish released on offshore reefs.

Researchers released radio-equipped fish this week in the Gulf of Mexico, about 20 miles southeast of Horn Island this week.

The radio tracking experiment is part of a program to determine if using hatchery-raised fish is an option to enhance depleted marine fish populations in the gulf and what techniques will make it work best. Forty-five fish from a total of about 1,500 released over a three-week period have been tagged with the thimble-sized transmitters.

The snapper were all spawned, hatched and reared at the Gulf Coast Research Laboratory here. The Southern Miss lab is headquarter for the U.S. Gulf of Mexico Marine Stock Enhancement Program, in its sixth year through the support of the National Marine Fisheries Service, an agency of the National Oceanic and Atmospheric Administration.

"Stock enhancement has never been done before for offshore marine fish," said Dr. Reg Blaylock, one of the project's principal investigators. "In addition to developing the technology to grow the fish and release the fish, we are developing the techniques to assess the effect of the release."

The program has chalked up a host of firsts for rearing, tagging and release of the species that is in high demand and is designated by the federal government as overfished in the gulf.

Blaylock said the stock enhancement research team has used radio tagging with larger snapper, but never before with hatchery-raised fish so small - four to six inches.

"We are using routine technology to address a specific question about red snapper stock enhancement: What happens to the fish after they are released?" he said. "With stock enhancement programs, you have to make sure that the fish live and that you are supplementing the wild population instead of replacing it."

Blaylock said five acoustic receivers were tethered to the gulf bottom prior to the first release in October and left to float in the water column about 10 feet off the bottom. The battery-powered receivers will record data for two to three months.

To tag the fish with the radio equipment, researchers make a slit in the fish's abdomen, insert the tag and stitch up the incision. The fish do well and within a couple of days are ready for release. The snapper are transported out to the reef in tanks. Then they are flushed through a hose that delivers them to the reef about 70 feet beneath the water's surface.

Mississippi Gulf Fishing Banks, Inc., built the reef specifically for the laboratory's snapper research and development work, Blaylock said.

"As a fish passes within range, the receiver records a beep. You can then go retrieve the information and download data. The information will identify which individual is going where."

Monday's release is the third and final in this year's tagging experiment. Each release has placed on the reef approximately 500 snapper that were spawned, hatched and raised at GCRL. Fifteen from each release carry the radio acoustic tags. The research team tagged all 1,500 with a wire tag that is coded with information plus a color-coded elastomer tag - a polymer of different neon colors injected into fin and tail.

Blaylock noted that stock enhancement for marine fishes is more complicated than applying the well-developed technology used for enhancing populations of freshwater species and species such as salmon that spend part of the their lives in freshwater and part in saltwater.

"There is a great deal to be learned about the fundamentals of the process," he said. "It is even more complicated for the hatchery phase. What works to grow one species in culture may not work at all for another species. We have to do very basic research on growing the fish as well as basic research on the effects of the releases."

The Southern Miss lab has been a pioneer in marine research and education in the northern Gulf of Mexico since 1947. Institutions working with the GCRL on the stock enhancement program are Oceanic Institute of Hawaii, Mote Marine Laboratory of Sarasota, Fla., and Jackson State University.



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April 20, 2004 4:48 PM