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Age and Length Composition of Columbia Basin Chinook and Sockeye Salmon and Steelhead at Bonneville Dam in 2015

Apr 25, 2017


The Columbia River Inter-Tribal Fish Commission (CRITFC) conducts a field study at Bonneville Dam which first began in 1985 to assess the age, length-at-age, and stock composition of adult Pacific salmon migrating up the Columbia River. Adult spring, summer, and fall Chinook Salmon (Oncorhynchus tshawytscha), Sockeye Salmon (O. nerka), and steelhead (O. mykiss) were collected, sampled for scales and additional biological data, PIT tagged, tissues collected for genetics, revived and released. Scales were examined to estimate age composition; the results contributed to an ongoing database for age structure of Columbia Basin salmon runs. Based on scale pattern analysis of our sample, four-year-olds were the most abundant age group for spring, summer and fall Chinook Salmon comprising, respectively, 88.4%, 47.5% and 41.3% of the runs.  Four-year-olds were also the most abundant age group for Sockeye Salmon comprising 93.7% of the run, and steelhead run comprising 43.2% of the run. Steelhead data were analyzed for the salt years regardless of the freshwater phase, the majority of steelhead had one-salt winters (52.6%) in 2015.  Using adipose fin clips, scale patterns, and dorsal fin condition for classification, the steelhead migration consisted of 65.9% hatchery- and 34.1% natural-origin steelhead. A-run steelhead, less than 78cm in length, comprised 94.7% of the steelhead run. B-run fish, equal to or greater than 78cm, comprised 5.3% of the run.



Chulik, C., A. Strong, J. FiveCrows, A. Ikemoto, A. Cate, J. Nowinski, J. Whiteaker, and J.K. Fryer. 2017. Age and length composition of Columbia Basin Chinook and Sockeye salmon and steelhead at Bonneville Dam in 2015. Columbia River Inter-Tribal Fish Commission Technical Report 17-02. Portland, OR. 32p.



Report No.


Media Type

CRITFC Technical Report