Theses and Dissertations Collection

Kokanee Oncorhynchus nerka provide valued recreational fisheries, and also serve as a prey resource for economically, socially, and ecologically important fishes. As such, management of kokanee is a major focus of natural resource agencies. Despite considerable research over the last 60 years, several questions remain regarding the management of kokanee in Idaho. Specifically, uncertainty surrounding common sampling techniques for kokanee undermine confidence in population assessments for the species. Additionally, observed growth differences between kokanee breeding groups (e.g., early-run, late-run) raise questions about the potential influence of genetics and hatchery practices on the population structure of the species. Finally, the potential mechanisms underlying competitive interactions between kokanee and Opossum Shrimp Mysis diluviana (hereafter Mysis) are largely unresolved. In an effort to improve the understanding of the ecology and management of kokanee, we sought to 1) evaluate the size selectivity of different sampling techniques for kokanee, 2) evaluate the potential causes of growth disparities among kokanee breeding groups (early-run, late-run) in Idaho, and 3) investigate how ontogenetic shifts in diet in kokanee potentially influence competitive interactions with Mysis.