Evaluation of release strategies for hatchery kokanee in Lake Roosevelt, Washington

Lake Whatcom kokanee have been stocked in Lake Roosevelt since 1988 with the goals of providing a hatchery kokanee fishery and establishing a returning run for egg collection. Harvest and escapement goals have not been achieved since the program began. Four experiments were designed to evaluate release strategies in an attempt to improve adult returns to release sites. Paired releases of kokanee were made to compare imprinted to non-imprinted, early run to middle run, early release to late release, and direct hatchery releases to three different net pen releases. Hatchery and tributary returns did not differ significantly between imprinted and non-imprinted fish; however, early run fish outperformed middle run, early release date outperformed the late release fish, and hatchery releases outperformed net pen releases. The total number of kokanee recovered during the spawning migration in 1998 and 1999 was low. A combination of entrainment, predation, and hatchery practices appear to be the limiting factors that contribute to the overall low performance of Lake Whatcom kokanee in Lake Roosevelt.