Authors
Donette P. Miranda
John Whiteaker
Jeffery K. Fryer, Ph.D.
Report Reference
#04-2
Publication Date
31 March 2004
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Age and Length Composition of Columbia Basin Chinook, Sockeye, and Coho
Salmon at Bonneville Dam in 2003
Abstract |
| In continuation of the Stock Assessment Project, the
Columbia River Inter-Tribal Fish Commission (CRITFC) conducted a field
study at Bonneville Dam in 2003 to assess the age, length-at-age and
stock composition of Pacific salmon migrating up the Columbia River,
and to predict the 2004 Chinook salmon run. Adult spring, summer and
fall Chinook salmon (Oncorhynchus tshawytscha), sockeye salmon
(O. nerka) and coho salmon (O. kisutch) were randomly
collected, sampled for scales and additional biological data, revived
and released. Caudal fin clips were also taken from Chinook salmon
for later genetic analysis. Scales were examined to estimate age composition;
the results contributed to an ongoing database for age class structure
of Columbia Basin salmon populations. Based on scale analysis of Chinook
salmon, five-year-old fish (from brood year [BY] 1998) comprised 53.9%
of the spring Chinook, 50.5% of the summer Chinook, and 26.9% of the
bright fall Chinook salmon migration. Fouryear- old fish (BY 1999)
comprised 38.5% of the spring Chinook, 32.5% of the summer Chinook,
and 60.4% of the bright fall Chinook salmon migration. The largest
proportion of the sockeye salmon migration through Bonneville Dam
was four-year-old fish (38.4%). The coho salmon migration consisted
of 93.1% three-year-old fish. A year-class regression over the past
14 years of data was used to predict spring, summer, and bright fall
Chinook salmon population sizes for 2004. Based on three-year-old
returns, the relationship predicts four-year-old returns of 191,300
(+ 67,400, 90% predictive interval [PI]) spring Chinook, 60,400 (+
23,400, 90% PI) summer, and 98,200 (+ 149,400, 90% PI) bright fall
Chinook salmon for the 2004 runs. Based on four-yearold returns, the
relationship predicts five-year-old returns of 25,600 (+ 44,100, 90%
PI) spring, 38,400 (+ 7,000, 90% PI) summer, and 182,900 (+ 89,600,
90% PI) bright fall Chinook salmon for the 2004 runs. The 2004 run
size predictions should be used with caution; some of these predictions
are well beyond the range of previously observed data. |
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