ATHENS, Ga. -- A dramatic rescue mission that could save a river-dwelling fish from extinction takes a major step in mid-November, when scientists from the University of Georgia, the Georgia Department of Natural Resources and the U.S. Fish and Wildlife Service release some 15,000 fingerlings into northeast Georgia's Broad River. At stake is the future of the robust redhorse, a fish thought extinct until a few survivors were discovered in 1991.
The small fish, artificially bred from some of the 1,000-3,000 surviving members of the species found in Georgia's Oconee River, represents one of the most important reintroduction efforts ever conducted in the Southeastern United States. The fingerlings, each with a microwire tag that will provide crucial information when they are sampled later, will be released at seven sites on the Broad River in hopes that the robust redhorse will once again flourish.
"The Broad River is a good place to release these six- to eight-inch-long fingerlings," said Dr. Jay Shelton, a fisheries biologist in UGA's Warnell School of Forest Resources. "One of our main concerns is predators such as the flathead catfish, and the Broad River doesn't have large populations of these." The river also has a relatively undisturbed watershed, good water quality and acceptable habitat.
Also involved in the project from the University of Georgia is Dr. Bud Freeman, an ecologist who has been instrumental in finding appropriate locations on the Broad River for release of the fish.
The robust redhorse (Moxostoma robustum) was thought extinct for more than 100 years until Jimmy Evans, a biologist with the Georgia Department of Natural Resources, Wildlife Resources Division (WRD), discovered a population of the fish (most of which were over 15 years of age and reproducing poorly) in the Oconee River near the town of Toombsboro five years ago. He and technician Wayne Clark set about finding a way to save the redhorse, which was discovered during a survey of fish populations necessitated by the upcoming relicensing of the Georgia Power Company's Lake Sinclair Dam. The fish is a large species of redhorse sucker and has teeth located in its throat used to grind up the shells of clams and mussels.
Because efforts to save endangered species have touchedoff conflicts between environmentalists and industry, so Evans and others set out to avoid those problems. With the financial support of the Georgia Power Company, Evans coordinated the WRD's efforts to build a coalition of scientists and interested parties, all working together to save the robust redhorse.
The success of those efforts has been striking, but in the beginning, problems abounded. Particularly troubling was the issue of breeding the fish in large enough quantities to save the species from extinction. That was why Shelton came into the project in 1995. As a fisheries biologist who has spent years studying how fish can best be raised for commercial agriculture, he offered insights that proved crucial.
"We think one of the reasons the fish became threatened in the first place is that they are gravel substrate spawners, meaning fertilized eggs are deposited in the spaces between submerged gravel," said Shelton.
This behavior, perhaps developed over millennia in rocky-bottomed rivers, worked fine until the mid-19th century, when deforestation and intensive farming began to spill tons of silt into the rivers, covering up areas of gravel. (Atlantic slope rivers of Georgia and North and South Carolina seem to have made up the fish's original habitat.) With the increase of cotton farming after World War II, sediments poured into the Oconee River at record rates, not only burying the gravel beds (and often the fertilized embryos there) but also killing the mussels on which the fish feed.
Shelton came into the project to help find a way in which the remaining fish could be used to bring the species back from the brink of extinction. From the beginning, he and others working on the project were dubious about transporting fish from their native habitat to breeding areas, since mortality can be high, and the species had no margin for losing individuals. Instead, Shelton, the state WRD and scientists from the U.S. Fish and Wildlife Service set up a facility near the river where the fish lived.
During the fish's spawning months of April and May during 1995 and 1996, they introduced a portable hatchery system through which water from the Oconee River could be kept moving so that captured fish would be in conditions close to that of their own environment. The idea was to inject females with hormone treatments that would make them ovulate and release eggs, which could then be fertilized. But finding the right hormone "recipe" was difficult.
"With the assistance of graduate student Tim Barrett and U.S. Fish and Wildlife Service biologist Greg Looney, a hormone treatment was found that yielded superb results," said Shelton, "inducing 100 percent of the females treated to release `ripe' eggs in 1995 and 1996."
These eggs were released into a large bowl, where they were covered with milt from robust redhorse males. It was soon clear that this method was producing viable embryos, but transporting the embryos to rearing ponds and successfully growing new redhorses was difficult at best. Using three different facilities in the state (including one at the University of Georgia), the scientists worked hard in 1995 to grow the embryos to fingerlings but had limited success. Only about 10 percent survived, and at one facility, none survived at all.
With continued work, the researchers learned more and more about correct water temperature and about better ways of nurturing the embryos. By this year, a full 30 percent of the fertilized embryos survived to be stocked into rearing ponds, producing tens of thousands of finerglings. Shelton also points out that considerable care was taken to make sure that the newly produced fish are genetically diverse -- using as many different parents as possible -- to increase the population's vigor.
Oddly enough, the future of the robust redhorse may depend not on a native food source but on the exotic Asiatic clam, which is now common in Georgia's rivers and has largely replaced the dwindling native river mussels as the chief food source for the redhorse. And while natural predators such as the flathead catfish and largemouth bass will take some of the fingerlings, most should have a good chance for survival in the Broad River, due to their large size at stocking.
While the robust redhorse is on Georgia's State Protected Species List, the fish was not proposed for the national list, because a number of interested parties wanted to try a new strategy to speed the recovery process and perhaps avoid the bitter battles of years past. As a result, government agencies, power companies and conservation groups came together to form the Robust Redhorse Conservation Committee, a group dedicated to saving the fish and encouraging cooperation rather than confrontation.
"We are working closely with the endangered species experts in the U.S. Fish and Wildlife Service," said Shelton "The consensus is that this partnership is the best approach to protecting the future of this fish."
While the release of the 18-month-old fingerlings this month will give researchers a better idea how the fish will do when reintroduced into its native habitat, they are taking 1¦s—rAnÔCY46dm^ži