Diet of and Prey Availability for Reintroduced Juvenile Lake Sturgeon (<i>Acipenser fulvescens</i>) in Ft. Loudoun Reservoir, Tennessee

After fifteen years of reintroducing juvenile Lake Sturgeon (Acipenser fulvescens) in the Upper Tennessee River Basin, fisheries biologists are researching basic ecological traits of subsistent organisms. I set out to seasonally assess whether Lake Sturgeon forage opportunistically or selectively in Ft. Loudoun Reservoir. After anesthetizing individual juvenile Lake Sturgeon caught on trotlines in a 13-km reach of the reservoir, I used colonic flush and gastric lavage techniques to describe diets quantitatively. I also used two methods to assess available prey items in the study area by 1) taking systematic benthic grabs along several transects across the width of the reservoir and 2) opportunistically deploying rock cages filled with various types of hard substrate to assess potential prey that colonize hard surfaces. After identifying macroinvertebrates to their lowest taxonomic level, the foraging modes of Lake Sturgeon were determined by comparing the relative abundances of invertebrate taxa in the gut contents of each sturgeon specimen to the relative abundances of the same invertebrate taxa collected from the resource base. Indices that quantify resource overlap or segregation were used to determine how selective Lake Sturgeon in Ft. Loudoun Reservoir were with respect to diet.

I conclude that Lake Sturgeon in Ft. Loudoun Reservoir forage primarily in the benthos where they utilize a relatively narrow niche consisting mostly of larval chironomids, some genera of which they prey upon selectively. Comprehensive conclusions regarding Lake Sturgeon foraging patterns, niche utilization, and selective predation can only be drawn if researchers a) determine the seasonally available prey base by identifying macroinvertebrates to genus/species level b) analyze diet composition (again, identifying prey items to genus/species) from both stomach and intestinal contents and c) use a combination of indices that determine how selective, if at all, Lake Sturgeon are when utilizing the available prey base.