Use of Rehabilitated Habitat by Brown Trout and Rainbow Trout in an Ozark Tailwater River

We evaluated instream and riparian habitat rehabilitation that was completed following catastrophic flooding in the White River, below Beaver Dam, Arkansas. Most rehabilitation structures were designed to stabilize the river banks and increase cover for trout (Salmonidae) during high flows associated with hydroelectric power generation. We quantified trout response to rehabilitation at two spatial scales—microhabitat and river reach. At the microhabitat scale, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss occupied the deepest habitats available and were randomly associated with cover at low flow (about 1 m3/s). Principal‐component scores describing physical characteristics of brown trout and rainbow trout microhabitats were significantly different from available‐habitat scores at high flow (about 215 m3/s), when trout were strongly associated with velocity refugia near the river margins—habitats similar to those created by rehabilitation structures. At the reach scale, trout population size and structure were estimated in modified (700‐m) and reference (800‐m) reaches before and after rehabilitation. Total trout density and biomass in the modified reach increased after rehabilitation relative to that of the reference reach, evidence that the modified reach supported more fish after rehabilitation. Analyses stratified by salmonid species and size indicated that the observed effect was primarily due to rainbow trout and small trout (10.0–19.9 cm) of all species shifting their distributions into the modified reach. Our results suggest that instream and riparian habitat rehabilitation structures commonly applied to small streams are a valid management technique for large tailwater rivers. However, implementation in each system should be carefully evaluated, and management expectations for large trout should be conservative. Because of the observed benefit for small trout, placement of rehabilitation structures near spawning areas should be considered when management for wild trout is a priority. Finally, we suggest integration of instream and riparian habitat rehabilitation into broader management plans when applied to regulated rivers.