UF experts hope to solve mysteries of sturgeon migration

October 24, 2001

GAINESVILLE, Fla. — It’s a migratory mystery.

Each fall, threatened Gulf of Mexico sturgeon swim south down the Suwannee River out into the Gulf of Mexico. In the spring, they return to the Suwannee, sometimes swimming as far north as the Florida-Georgia border. But where they go during the winter no one knows, and that’s what University of Florida researchers want to find out.

This year, UF researchers are monitoring the movements of individual sturgeon in the gulf to determine whether the fish remain in shallow coastal waters during the winter or migrate far offshore, she said.

“It’s surprising how little is known about these huge, primitive fish,” said Debra Murie, assistant professor of fisheries ecology with UF’s Institute of Food and Agricultural Sciences. “By studying their migrations we may be able to help protect them more effectively.”

Gulf of Mexico sturgeon are one of three sturgeon species native to Florida waters, Murie said. Weighing up to 250 pounds, they have remained largely unchanged since the Jurassic Period, about 195 million years ago. About 3,000 adult fish are believed to inhabit the Suwannee River during summer months. Classified as threatened, they are protected by state and federal law.

Last spring, Murie and her colleagues outfitted 18 sturgeon with ultrasonic tags called “pingers” that emit signals allowing researchers to locate the fish using underwater microphones. UF researchers currently are negotiating the Suwannee by boat, locating the tagged fish as they migrate south.

Sturgeon typically leave the river by Thanksgiving, according to observations by Doug Colle, senior scientific manager with the UF team.

As the fish reach the open waters of the Gulf of Mexico, locating them becomes more difficult, said Daryl Parkyn, a UF fish physiology research assistant professor who is leading the winter tracking project. Underwater microphones must be used from several angles to determine a sturgeon’s position relative to the boat, then researchers employ global positioning system technology to identify the boat’s location.

Parkyn and his graduate student, Julianne Harris, are mapping the sturgeons’ movements to identify habitat critical for the fish. He said they are particularly interested in monitoring sturgeon in estuaries, areas near river mouths where fresh and salt water mix.

“It’s believed that adult sturgeon don’t eat much during the six to eight months each year that they’re in the river, so they have to make up for it in the gulf,” he said. “We know that the Suwannee estuary contains large concentrations of clam-like shellfish called brachiopods, because we have been surveying food resources in the estuary.”

He said the UF research team often finds brachiopods in the stomachs of sturgeon captured in the Suwannee River during spring. Parkyn and Murie recently developed a new method to pump the stomachs of live sturgeon without harming the fish.

“If sturgeon migrating out of the river spend a lot of time in the estuary, then we would speculate that they are probably feeding in the area,” he said. “We will try to test this idea by examining their stomach contents. This would help to tell us how important brachiopods are as a food source for Suwannee sturgeon.”

Other fish species apparently consume the shellfish, he said. UF biologist Jamie Holloway has found brachiopods in the stomach contents of redfish, a popular saltwater game fish.

Parkyn said this winter’s sturgeon research may have immediate importance. In 2002, the U.S. Army Corps of Engineers is scheduled to dredge McGriff Channel, a sediment-clogged portion of the Suwannee River at the entrance to the gulf.

“The channel definitely needs to be cleared,” he said. “Our larger research boats occasionally run aground in that area at low tide. We’re just concerned about the possibility that the timing of the dredging may affect sturgeon feeding habitat or behavior at a critical moment.”

But Corps of Engineers spokesperson Don Fore in Jacksonville said the dredging should have little or no effect to the fish.

“The contractor will probably use a cutter suction dredge, which breaks up sediment with a cutting head and pumps it away immediately,” he said. “The cleared sediment will probably be placed upland about six miles away.”

Fore said dredging is expected to begin next summer, after sturgeon have returned to the Suwannee River. The Corps of Engineers is coordinating with the National Marine Fisheries Service and the U.S. Fish and Wildlife Service to determine the best window of opportunity to minimize effect on sturgeon.

“The Corps of Engineers respects environmental concerns, and we will do everything we can to avoid causing any problems,” he said. “We just need to dredge a minimal channel so people can navigate safely in recreational boats.”

The two-year study is funded by UF’s department of fisheries and aquatic sciences and the Sturgeon Production Working Group, which includes UF, the state Department of Environmental Protection, the state Fish and Wildlife Conservation Commission and a sturgeon aquaculture representative.