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Scientific Report

Age and Length Composition of Columbia Basin Chinook and Sockeye Salmon and Steelhead at Bonneville Dam in 2011


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, revived and released. Caudal fin clips were also taken from Chinook, steelhead, and sockeye for genetic analysis. 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 Chinook salmon comprising 65.7% of the run. Three-year-olds were the most abundant age class for the summer Chinook making up 44% of the run, while four-year-olds were the most abundant for fall Chinook, at 54.5%. Four-year-olds were the most abundant age group for sockeye salmon comprising 67.1% of the run, and three-year-olds were the most abundant in the steelhead run comprising 45.6% of the run. Steelhead data were analyzed for the salt years regardless of the freshwater phase, the majority of steelhead had one-salt winter (59%) in 2011. Using adipose fin clips, scale patterns, and dorsal fin condition for classification, the steelhead migration consisted of 69.8% hatchery- and 30.2% natural-origin steelhead. A-run steelhead, less than 78cm in length, comprised 90.7% of the steelhead run. B-run fish, equal to or greater than 78cm, comprised 9.3% of the run.



Nowinski, J., D. Kelsey, J. Whiteaker, and J.K. Fryer. 2013. Age and length composition of Columbia Basin Chinook and sockeye salmon and steelhead at Bonneville Dam in 2011. Columbia River Inter-Tribal Fish Commission Technical Report #13-01, Portland, Oregon.


Jan 23rd, 2013

Report No.


Media Type

CRITFC Technical Report

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