Authors
Rian C. Hooff
Amy Ritchie
Jeff Fryer
John Whiteaker
Report Citation
Hooff, R.C., A. Ritchie, J. Fryer, and J. Whiteaker. 1999. Age and Length Composition
of Columbia Basin Chinook, Sockeye, and Coho Salmon at Bonneville Dam in 1999. Columbia
River Inter-Tribal Fish Commission Report reference #99-05, Portland, Oregon. (http://maps.critfc.org/tech_rep).
Publication Date
14 December 1999
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Age and Length Composition of Columbia Basin Chinook, Sockeye, and Coho Salmon at
Bonneville Dam in 1999
Abstract
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Representative samples of adult 1999 Columbia Basin chinook (spring, summer, and
fall), sockeye, and coho salmon populations were collected at Bonneville Dam. This
was the thirteenth year spring chinook salmon, the tenth year summer chinook salmon,
and the fifteenth year sockeye salmon were sampled in this study. It was the second
year for sampling fall chinook and coho. Fish were trapped, anesthetized, sampled
for scales and biological data, allowed to revive, and then released. The scales
were examined to estimate age composition. The results of this project contribute
to an ongoing database collection of Columbia Basin salmonid populations age class
structure. Based on scale analysis, four-year-old fish (from brood year 1995) were
estimated to comprise 70% of the spring chinook, 39% of the summer chinook, and
62% of the fall chinook salmon population. Five-year-old fish (BY 1994) were estimated
to comprise 7% of the spring chinook, 37% of the summer chinook, and 8% of the fall
chinook population. Three-year-old fish were estimated to comprise 23% of the spring
chinook, 21% of the summer chinook and 28% of the fall chinook salmon population.
Two and six-year-olds accounted for the remaining 1% of spring chinook, 3% of summer
chinook, and 2% of the fall chinook runs. The sockeye salmon population sampled
at Bonneville was predominantly four-year-old fish (83%), and the coho population
was entirely three-year-old fish (age 1.1). Differences in age class returns over
the past ten years were used to predict spring and summer chinook population sizes
for 2000. Based on a regression with three-year-old returns, the relationship predicts
four-year-old returns of 95,800 spring chinook and 14,900 summer chinook.
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