Assessment of Stocking Advanced Fingerling Brown Trout in a North Carolina Tailrace

Bridgewater Tailrace (BWTR) is a 29-km waterway extending from Lake James to Lake Rhodhiss on the Catawba River in western North Carolina. An 18-km reach of the stream is classified as Special Regulation Trout Waters by the North Carolina Wildlife Resources Commission (NCWRC)and is managed as a put-grow-and-take brown trout (Salmo trutta) fishery. Early studies demonstrated recruitment of stocked fingerling (25?75 mmTL) brown trout was highly variable and possibly impacted by elevated discharge water temperatures during late summer months. Recent upgrades to Bridgewater Hydro Station resulted in more consistent minimum flows and dissolved oxygen levels, which may help ameliorate historical recruitment issues. In 2011, the NCWRC initiated a multi-year study to evaluate annual stockings of 10,000 advanced fingerling (200?255 mm TL) brown trout that were stocked during late fall after the threat of elevated discharge water temperatures. Catch rates were variable among years, and several years showed significant differences between spring and fall surveys for CPUE and relative weight (Wr); however, temperatures appeared suitable for year-round survival so other mechanisms must be limiting recruitment. Age and length data suggested that recruitment to age 2 was extremely limited, and older fish were rare. A variety of factors not evaluated during this study may be preventing stocked fish from recruiting to older year classes, including flow alterations, habitat limitations, and excess angler harvest. Stocking advanced fingerlings in the fall appeared to establish a fishery composed primarily of age-1 brown trout. Nonetheless, trophy fish were present in low numbers, Wr was good, and growth rates were fast, suggesting that minor alterations to the current management approach, such as increasing the minimum size limit, may continue to enhance the fishery. Age-structured modeling simulations predicted that an increased minimum-length limit (MLL) of 356 mm to be the best regulation for optimizing structural size indices and yield .Based on this study, the NCWRC adopted a 356-mm MLL and two-fish creel limit per day for the BWTR on 1 August 2018.

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