Age and Length Composition of Columbia Basin Chinook and Sockeye Salmon and Steelhead at Bonneville Dam in 2010
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. Based on scale pattern analysis of our sample, four-year-olds were the most abundant age group for spring Chinook salmon comprising 91.6% of the run. Four-year-olds were the most abundant age class for the summer Chinook making up 70.1% of the run, while three-year-olds were the most abundant for fall Chinook, at 53.6%. Four-year-olds were the most abundant age group for sockeye salmon comprising 92.9% of the run, and four-year-olds were the most abundant in the steelhead run comprising 44.2% of the run. The unageable freshwater-, but ageable saltwater-winters (r.X) steelhead were a large proportion of run at 22.7%. Using adipose fin clips, scale patterns, and dorsal fin condition for classification, the steelhead migration consisted of 64.1% hatchery- and 35.9% natural-origin steelhead. A-run steelhead, less than 78cm in length, comprised 80.2% of the steelhead run. B-run fish, equal to or greater than 78cm, comprised 17.8% 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 2010. Columbia River Inter-Tribal Fish Commission Technical Report #11-09, Portland, Oregon.