Document Type

Thesis

Date of Degree Completion

Fall 2020

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Paul James

Second Committee Member

Clay Arango

Third Committee Member

Kristina Ernest

Abstract

This study examines an ecologically and recreationally important population of kokanee salmon (Oncorhynchus nerka) residing in Keechelus Lake and its tributary Gold Creek in the central Cascades of Washington State. This population of kokanee salmon is a vital food base for a population of ESA-listed resident bull trout. However, little is known about the early life history of this population and how it interacts with unique features in its rearing environment. With my research I described the early life history of kokanee salmon that spawn in the lake’s main tributary, Gold Creek, and proposed a framework to determine the natal origin of spawning adults. Monitoring in the spring of 2019 showed spawning adults produced viable eggs that survived the winter with young-of-year emerging episodically in mid-April. The majority of adults avoided spawning in Gold Creek itself, preferring a man-made outlet channel that had significantly higher water temperatures and a prominent beaver dam. Stock discrimination of sampled spawning adults suggest that 83% of adults are of wild origin and 17% are of hatchery origin. The conservation of the Gold Creek Pond outlet channel will be critical for kokanee salmon spawning and rearing habitat until habitat becomes more suitable in Gold Creek. With this research, future restoration efforts in the Gold Creek ecosystem can integrate the life history data of kokanee salmon as well as assess the contribution of hatchery-origin kokanee salmon to the ecosystem.

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