Age and Length Composition of Columbia Basin Chinook and Sockeye Salmon and Steelhead at Bonneville Dam in 2012
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 both spring and summer
Chinook salmon comprising, respectively, 86.1% and 61.7% of the runs. Three-year-olds were
the most abundant age class for the fall Chinook salmon making up 46.2% of the run. Four-yearolds
were the most abundant age group for sockeye salmon comprising 96.3% of the run, and
four-year-olds were the most abundant in the steelhead run comprising 48.7% of the run.
Steelhead data were analyzed for the salt years regardless of the freshwater phase, the
majority of steelhead had two-salt winters (57.3%) in 2012. Using adipose fin clips, scale
patterns, and dorsal fin condition for classification, the steelhead migration consisted of 66.3%
hatchery- and 33.7% natural-origin steelhead. A-run steelhead, less than 78cm in length,
comprised 85.3% of the steelhead run. B-run fish, equal to or greater than 78cm, comprised
14.7% 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 2012. Columbia River Inter-Tribal Fish Commission Technical Report 13-03. Portland, Oregon. 44p.