Comparison of Kokanee Breeding Groups In Lake Pend Oreille, Idaho

Kokanee Oncorhynchus nerka were introduced into Lake Pend Oreille (LPO) in the 1920s and rapidly became an important fixture in both the fish assemblage lake and the regional economy.  Prior to a substantial population decline, which began in the late 1960s, kokanee sustained Idaho’s largest recreational fishery, with harvest averaging over a million fish annually.  The Idaho Department of Fish and Game has made kokanee recovery in the system a priority for their socioeconomic benefit, and to benefit endangered bull trout Salvelinus confluentus in the system.  Kokanee spend the majority of their life history aggregated in the main body of the lake feeding on macrozooplankton, before dispersing at the time of spawning.  Spawners segregate among several of the lake’s tributaries and shoreline areas.  The nature and extent of this segregation has important implications for the current kokanee recovery strategy, which generalizes fecundity, age structure, and origin information (i.e., hatchery versus wild) information from a single tributary on the entire lake.  In this study, population dynamics and sexual characteristics were evaluated for segregated breeding groups within tributary and lakeshore spawning areas of LPO. Our analysis provides management recommendations for a more representative sampling among all breeding groups.