Mapping Lake Sturgeon Spawning Habitat in the Upper Tennessee River using Side‐Scan Sonar

Abstract

AbstractThe 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 separated from each other by hydroelectric dams along the upper Tennessee River. 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. Using low‐cost, consumer‐grade, side‐scan sonar and a GIS, we mapped the substrate of four tailwaters that may be future spawning locations for Lake Sturgeon. 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 evaluate that aspect of the suitability of each of the tailwaters for Lake Sturgeon spawning. The revised maps showed that 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 tailwater, 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 that 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 tailwater areas with suitable spawning substrate.Received March 11, 2016; accepted May 30, 2016 Published online August 31, 2016