Habitat suitability and availability for Rainbow Trout (Oncorhynchus mykiss) in the Canyon Reservoir tailrace and evaluation of side scan sonar for habitat mapping in a semi-wadable river
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Rainbow Trout Oncorhynchus Mykiss are typically stocked in tailraces across the southeastern United States to mitigate fish habitat and assemblage alterations caused by large impoundments. Hypolimnetic discharges from Canyon Reservoir have created conditions suitable for a coldwater tailrace fishery and trout have been stocked there since 1966. Changes in habitat availability for adult Rainbow Trout with discharge rate were examined to provide flow and habitat improvement recommendations for the Canyon Reservoir tailrace. Physical habitat modeling incorporated habitat suitability information for trout coupled with hydraulic modeling to assess habitat quality and quantity at various flow rates. Habitat mapping included traditional surveying, remote sensing, bathymetric mapping, and side scan sonar. Side scan sonar was evaluated for efficiency and applicability to river systems similar to the tailrace. Results indicate that summer water temperature is likely the primary limiting factor for adult trout survival and could impose limitations on physical habitat during critical summer months. Modified flow rates and habitat improvement could cause a potential increase in adult trout abundance and assist put-grow-and-take strategies in the upper portion of the tailrace. Side scan sonar provided efficient mapping of non-wadable sections of the study area. Challenges related to water level, access, navigability, positional accuracy, and post-processing were overcome. Trial runs, training, map accuracy assessments, and technological development will improve the effectiveness of this technique.