Age and Length Composition of Columbia Basin Chinook, Sockeye, and Coho Salmon at Bonneville Dam in 2000

AUTHORS:	Denise A. Kelsey  |  Jeffrey K. Fryer
PUBLICATION DATE:	9 February 2001
REPORT #:	01-1

ABSTRACT:
Five-year-old fish (BY 1995) were estimated to comprise 2% of the spring chinook, 26% of the summer chinook, and 40% of the fall chinook salmon population. Three-year-old fish (BY 1997) were estimated to comprise 14% of the spring chinook, 42% of the summer chinook, and 17% of the fall chinook salmon population. The sockeye salmon population sampled at Bonneville was predominantly four-year-old fish (95%), and the coho salmon population was 99.9% three-year-old fish (Age 1.1). Length analysis of the 2000 returns indicated that chinook salmon with a stream-type life history are larger (mean length) than the chinook salmon with an ocean-type life history. Age classes 0.3 and 0.4 have no significant change over time and age 0.1 chinook salmon had a significant decrease in mean length over time. Based on three-year- old returns, the relationship predicts four-year-old returns of 325,000 (+ 111,600, 90% Predictive Interval [PI]) spring chinook and 27,800 (+ 29,750, 90% PI) summer chinook salmon. Based on four-year-old returns, the relationship predicts five-year-old returns of 54,300 (+ 40,600, 90% PI) spring chinook and 11,000 (+ 3,250, 90% PI) summer chinook salmon.

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