The Sturgeon Makes a Decades-Long Comeback in the Tennessee River System

In Small Planet by Patrice Coleleave a COMMENT

They’re big, they’re ancient, they’re tasty, and they’re coming back after decades of extinction in this part of the world. Lake sturgeon, known in Latin as Acipenser fulvescens, is called a “living fossil” because it has changed little since swimming with the dinosaurs 140 million years ago, making it the most primitive bony fish alive today. The last time one was caught commercially from the Tennessee River was in 1961. Now it’s entirely possible to hook one from the river right here in Knoxville.

Tennessee is nearly the southern edge of the sturgeon’s native range that includes large parts of Canada and the Midwest. These fish get huge compared to other freshwater species, reaching a length of up to 9 feet and weighing as much as 275 pounds. They can also live longer than any other North American freshwater fish, up to 150 years. But they don’t start reproducing until the age of 15 to 20 years, and that makes them vulnerable as a species. Another vulnerability is that they taste good, and their eggs are prized caviar, so it’s no surprise that over-fishing led to their decline. Dam construction and water pollution helped finish them off in this region.

Water-quality improvements resulted from the Clean Water Act, and TVA efforts to improve reservoir habitat and re-establish sturgeon in the Tennessee River system began over 15 years ago. If fish could talk, our sturgeon might have Yankee accents, having come from the Great Lakes via the Wisconsin Department of Natural Resources. Eggs and sperm are collected in April from live, spawning fish, and the fertilized eggs are shipped to several hatcheries in the Southeast. Six months of meticulous care and feeding later, the young fish are at least 6 inches long and ready to face the realities of river life. At that size they are less likely to be eaten by other fish. The timing of the release in autumn also gives them the advantage of lower energy needs in colder water so they can adapt to this new situation before needing to eat a lot.

The releases occur at two sites on the French Broad River and one on the Holston. TVA’s tailwaters improvement program that began with Douglas Dam improved oxygen levels and water quality in the French Broad. Both tributaries of the Tennessee River have suitable sturgeon habitat in transition zones between deep pools and shallow gravel bars.

It takes a lot of team work to make this happen. The University of Tennessee’s Institute of Agriculture, TVA, Tennessee Wildlife Resources Agency, U.S. Fish & Wildlife Service, the Tennessee Aquarium, U.S. Geological Survey, Tennessee Technological University, Conservation Fisheries Inc., the Tennessee Clean Water Network, Wisconsin Department of Natural Resources, and the World Wildlife Fund are among the agencies and institutions that have contributed time, money, and expertise.

Much of the work occurs long after the little fish have swum out of sight. Scientists monitoring the program’s success go fishing every now and then to see where these fish end up and how they are faring, and there’s good news. Survivors of the earliest releases have been captured, and they are spreading upstream and especially downstream, even locking through dams. Sturgeon caught below Nickajack Dam near Chattanooga had to pass through four dams and swim 250 miles from their release site. Some sturgeon have turned the corner and gone up into the Clinch and Hiwassee Rivers.

Some monitoring is more high-tech than a trot line. A network of 29 sonic receivers tracks the movements of 57 tagged sturgeon between Knoxville and Chattanooga. Another receiver on a tugboat makes weekly trips to detect tagged fish between those stationary receivers.

The public can play a big role in monitoring the recovery of this endangered species. If you catch one of these fish you must release it, but snap a quick photo of it first and report the place caught and size of fish to any of the participating agencies or to iCaughtOne.org.

Since 2000, more than 150,000 lake sturgeon have been released to the Tennessee River, and the oldest survivors are nearing reproductive age. The next measure of success will be spawning activity, where males and females congregate in shallow water, and their shark-like tale fins thrash above the surface. A naturally reproducing population of lake sturgeon will be a big step toward getting it off the endangered list and maybe even achieving recreational harvest.

Early in the program some larger, older sturgeon were released with the expectation that their survival rate would be much higher compared to smaller fish. But the three to four years required to grow a 2-foot-long fish proved to be less effective than producing many more small fish in a much shorter time frame. And the little guys are surviving at a very high rate.

Still, it was an unforgettable moment arriving at Seven Islands Wildlife Refuge many years ago to see a TVA acquaintance dipping big fish out of a TWRA tank truck with a huge landing net and carrying them toward the boat launch. After getting to touch and examine a fish unlike any I’d ever seen, with shark-like skin and features (except for the almost imploring expression in its eyes), I was able to lower it into the water. It didn’t thrash or swim off right away. In fact, these newly-wild sturgeon lingered for a long time in the shallow water at the end of the boat ramp, as if reluctant to leave their caregivers and the safety of the hatchery.

Patrice Cole

Patrice Cole's Small Planet educates readers on local issues pertaining to environmental quality and sustainability. Topics include particular threats to natural resources, public policy with local impacts, and advances in environmental science. She has 25 years of professional experience in environmental science and sustainability. She has also taught biology, ecology, environmental planning, and sustainability at the University of Tennessee and Pellissippi State Community College. Cole earned a master’s degree in planning and a Ph.D. in ecology and evolutionary biology at UT.

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