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Scientific Report

Identification of Columbia Basin Sockeye Salmon Stocks in 2003

Abstract

In 2003, samples of adult Columbia Basin sockeye salmon, Oncorhynchus nerka, were collected at Bonneville Dam as well as at Tumwater Dam on the Wenatchee River and Wells Dam in the mid-Columbia River downstream of the Okanogan River. Tumwater and Wells dams were chosen to provide samples of sockeye salmon from the two principle stocks of Columbia Basin sockeye salmon, which originate from the Wenatchee and Okanogan basins. Age composition was estimated from the sampled sockeye salmon passing the three dams. Five-year-old fish were estimated to comprise 28% of the Bonneville Dam mixed-stock, 16% of the Okanogan stock, and 92% of the Wenatchee stock. Four-year-old fish were estimated to comprise 38% of the mixed-stock sockeye salmon migrating past Bonneville Dam, 57% of the Okanogan stock migrating past Wells Dam, and 1% of the Wenatchee stock migrating past Tumwater Dam. Three-year-old fish were estimated to comprise 25% of the Bonneville Dam mixed-stock, 27% of the Okanogan stock and none of the Wenatchee stock. Six-year- old fish were estimated to comprise 8% of the Bonneville Dam mixed-stock, 3% of the Okanogan stock and 7% of the Wenatchee stock. For the first time in 18 years of CRITFC Columbia River sockeye salmon studies, the age composition of the Okanogan stock and Wenatchee stock differed sufficiently to differentiate stocks at Bonneville Dam by age alone rather than using scale pattern analysis techniques on common age classes. We estimated that 84% of the sockeye salmon passing Bonneville Dam were of Okanogan origin while 16% were of Wenatchee stock.

Authors

Citation

Fryer, J.K. 2004. Identification of Columbia Basin Sockeye Salmon Stocks in 2003. Columbia River Inter-Tribal Fish Commission Report reference #04-01, Portland, Oregon.

Date

Mar 18th, 2004

Report No.

04-01

Media Type

CRITFC Technical Report

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