Age and Length Composition of Columbia Basin Chinook and Sockeye Salmon and Steelhead at Bonneville Dam in 2007
The Columbia River Inter-Tribal Fish Commission conducted a field study at Bonneville Dam in 2007 to assess the age, length-at-age and stock composition of adult Pacific salmon migrating up the Columbia River. These data were then used to predict the 2008 Chinook Salmon run. Adult spring, summer and fall Chinook Salmon (Oncorhynchus tshawytscha), Sockeye Salmon (O. nerka) and summer-run steelhead (O. mykiss) were collected, sampled for scales and additional biological data, revived and released. Caudal fin clips were also taken from Chinook Salmon and steelhead for later 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 four-year-olds were the most abundant age group for both spring and fall Chinook Salmon comprising 52.4% and 46.2% of their respective runs. Three-year-olds were the most abundant age class for summer Chinook making up 37.4% of the run. Three-year-olds were also the most abundant age group for Sockeye Salmon and steelhead comprising 39.9% and 59% of their respective runs. Based on fin marks for classification, the steelhead migration consisted of 81.9% hatchery- and 18.1% natural-origin steelhead. A-run steelhead, less than 78cm in length, comprised 88.9% of the steelhead run. B-run fish, equal to or greater than 78cm, comprised 11.1% of the run.
Whiteaker, J. and J.K. Fryer. 2008. Age and length composition of Columbia Basin Chinook and Sockeye Salmon and steelhead at Bonneville Dam in 2007. Columbia River Inter-Tribal Fish Commission Report Technical Report 08-4. Portland, OR. 45p.