Authors
John Whiteaker
Jeffrey K. Fryer, Ph.D.
Jeremiah Doyle
Report Reference
#06-2
Publication Date
6 April
2006
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Age
And Length Composition Of Columbia Basin Chinook And Sockeye Salmon And
Steelhead At Bonneville Dam In 2005
Abstract |
| In continuation
of the Stock Assessment Project, the Columbia River Inter-Tribal Fish
Commission (CRITFC) conducted a field study at Bonneville Dam in 2005
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 2006 Chinook salmon run. Adult spring, summer and fall
Chinook salmon (Oncorhynchus tshawytscha), sockeye salmon
(O. nerka) and summer-run steelhead (O. mykiss)
were randomly 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 esti¬mate age composition; the results contributed
to an ongoing database for age structure of Columbia Basin salmon
populations. Based on scale pattern analysis four-year-olds (from
the 2001 brood year [BY]) were the most abundant age group for all
three races of Chinook salmon, comprising 74.2% of the spring Chinook
migration, 57.6% of the summer Chinook migration, and 55.4% of the
fall Chinook migration. Five-year-old fish (2000 BY) were second most
abundant, comprising 15.7% of the spring Chinook, 31.7% of the summer
Chinook, and 36.3% of the fall Chinook. Three-year-old fish (2002
BY) were third most abundant, comprising 5.6% of the spring Chinook
migration, 7.7% of the summer Chinook migration, and 5.7% of the fall
Chinook migration. The largest proportion of the sockeye salmon migration
through Bonneville Dam was four-year-old fish 89.9%. The steelhead
migration consisted of 33.4% four-year-old fish and 25.9% three-year-old
fish. Based on fin marks for classification, the steelhead migration
consisted of 86.9% hatchery- and 13.1% natural-origin steelhead. A-run
steelhead, less than 78cm in length, comprised 70.1% of the steelhead
run. B-run fish, equal to or greater than 78cm, comprised 29.9% of
the run. A year-class regression over the past 17 years of data was
used to predict spring, summer, and bright fall Chinook salmon population
sizes for 2006. Based on three-year-old returns, the relationship
predicts four-year-old returns of 75,700 (± 63,700, 90% predictive
interval [PI]) spring Chinook, 13,200 (± 32,600, 90% PI) summer,
and 80,700 (± 126,400, 90% PI) bright fall Chinook salmon for
the 2006 runs. Based on four-year-old returns, the relationship predicts
five-year-old returns of 23,900 (± 42,700, 90% PI) spring,
31,000 (± 8,500, 90% PI) summer, and 105,700 (± 48,500,
90% PI) bright fall Chinook salmon for the 2006 runs. |
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