Mapping Lake Sturgeon ( Acipenser Fluvescens ) Spawning habitat in the Upper Tennessee River Using Side Scan Sonar
The Lake Sturgeon Acipenser fulvescens is a fish species that was once dispersed widely throughout the Mississippi River drainage but was largely extirpated from the southern portions of its range by overfishing and habitat degradation. There is an ongoing restoration effort to reestablish the Lake Sturgeon to rivers of the Southeastern United States. Reintroduced juvenile Lake Sturgeon now occupy several reservoirs along the Upper Tennessee River that are separated from each other by hydroelectric dams. To complete their life history, Lake Sturgeon will migrate upriver from reservoir habitats to more lotic habitats and spawn over coarse rocky substrate, even in the tailwaters of impassable dams. We mapped the substrate of four tailwaters that may be future Lake Sturgeon spawning locations using low-cost, consumer-grade side scan sonar and a GIS. We used video imagery collected from random locations within the mapped areas to validate our digitization of sonar imagery. We calculated the area of four substrate classes displayed in the maps to assess the suitability of each of the tailwaters for Lake Sturgeon spawning. The best spawning substrate (unembedded, coarse, rocky substrate 6 – 25 cm in diameter) comprised 17.0 – 30.5% of the total area mapped at each dam, while the least suitable substrate class (fine sediment <0.2 cm in diameter) comprised 6.2 – 30.7% of the mapped areas. Our results suggest any future spawning events by Lake Sturgeon below each of these dams are likely to encounter some suitable spawning substrate patches, while management opportunities exist to supplement other tailwater areas with suitable spawning substrate.