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Age and Length Composition of Columbia Basin Chinook and Sockeye Salmon and Steelhead at Bonneville Dam in 2009

Nov 16, 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 Chinook, steelhead and sockeye, revived and released. Caudal fin clips were also taken from Chinook, steelhead and sockeye for genetic analysis. Scales were examined to esti¬mate age composition; the results contributed to an ongoing database for age structure of Columbia Basin salmon runs. A new Bonneville Dam fish trap configuration biased our Chinook sample in 2009 resulting in the proportion of smaller one-ocean Chinook sampled being higher than in the population as a whole. It is unknown whether the trap configuration affected other age classes or other species. Based on scale pattern analysis of our biased sample, three-year-olds were the most abundant age group for spring Chinook salmon comprising 48.5% of the run (see trap bias section). Three-year-olds were the most abundant age class for the summer Chinook making up 37.3% of the run, while four-year-olds were the most abundant for fall Chinook, at 57.5%. Three-year-olds were the most abundant age group for sockeye salmon comprising 79.8% of the run, and three-year-olds were the most abundant in steelhead comprising 50.8% of the run. A large percentage of the steelhead run (23.0%) had scales that could only be aged for saltwater winters. Using adipose fin clips, scale patterns, and dorsal fin condition for classification, the steelhead migration consisted of 73.8% hatchery- and 26.2% natural-origin steelhead. A-run steelhead, less than 78cm in length, comprised 92.2% of the steelhead run. B-run fish, equal to or greater than 78cm, comprised 7.8% of the run.



Kelsey, D., H. Ballantyne, J. Whiteaker, and J.K. Fryer. 2011. Age and length composition of Columbia Basin Chinook and sockeye salmon and steelhead at Bonneville Dam in 2009. Columbia River Inter-Tribal Fish Commission Technical Report 11-08 for U.S. Dept. of Energy Bonneville Power Administration Project 2008-518-00. 41p.



Report No.


Media Type

CRITFC Technical Report