Identification of Columbia Basin Sockeye Salmon Stocks in 2006
In 2006, samples of adult Columbia Basin Sockeye Salmon (Oncorhynchus nerka) were collected at Bonneville Dam on the Columbia River 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 principal stocks of Columbia Basin Sockeye Salmon, which originate from the Wenatchee and Okanogan basins. Age composition was estimated using scale pattern analysis from the sampled Sockeye Salmon passing the three dams. Four-year-old fish were estimated to comprise 65% of the mixed-stock Sockeye Salmon migrating past Bonneville Dam, 74% of the Okanogan stock migrating past Wells Dam, and 36% of the Wenatchee stock migrating past Tumwater Dam. Five-year-old fish were estimated to comprise 34% of the Bonneville Dam mixed-stock, 24% of the Okanogan stock, and 63% of the Wenatchee stock. Three-year-old fish were estimated to comprise 1% of the Bonneville Dam mixed-stock, 1% of the Okanogan stock and none of the Wenatchee stock. Scale pattern analysis techniques were used to estimate that 52% of the Sockeye Salmon passing Bonneville Dam were of Okanogan origin, 13% were of Wenatchee stock, with the remaining 34% not classified as to origin. The high estimate of unclassified stock is due to the high percentage of five-year-old fish combined with low sample sizes at Wells Dam making it not possible to differentiate these fish using scale patterns. A companion PIT tagging project estimated that 72.8% of the Sockeye Salmon passing Bonneville Dam were of Okanogan origin, with the remaining 27.2% of Wenatchee origin.
Fryer, J.K. 2007. Identification of Columbia Basin Sockeye Salmon stocks in 2006. Columbia River Inter-Tribal Fish Commission Technical Report 07-3. Portland, Oregon. 29p.