Authors
Jeffrey
Fryer
Report Reference
#06-4
Publication Date
5 April
2006
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Identification
Of Columbia Basin Sockeye Salmon Stocks In 2005
Abstract |
| In 2005,
samples of adult Columbia Basin sockeye salmon Oncorhynchus nerka
were collected at Bonneville Dam on the Columbia River as well as
at Tumwater Dam on the Wenatchee River, and Wells Dam in the mid-Columbia
River downstream of the Okanogan River. Tumwater and Wells dams were
chosen to provide samples of sockeye salmon from the two principle
stocks of Columbia Basin sockeye salmon, which originate from the
Wenatchee and Okanogan basins. Age composition was estimated from
the sampled sockeye salmon passing the three dams. Four-year-old fish
were estimated to comprise 89% of the mixed-stock sockeye salmon migrating
past Bonneville Dam, 89% of the Okanogan stock migrating past Wells
Dam, and 78% of the Wenatchee stock migrating past Tumwater Dam. Five-year-old
fish were estimated to comprise 8% of the Bonneville Dam mixed-stock,
6% of the Okanogan stock, and 22% of the Wenatchee stock. Three-year-old
fish were estimated to comprise 1% of the Bonneville Dam mixed-stock,
1% of the Okanogan stock and none of the Wenatchee stock. Scale pattern
analysis techniques were used to estimate that 32% of the sockeye
salmon passing Bonneville Dam were of Okanogan origin, 61% were of
Wenatchee stock, with the remaining 7% of unknown origin. This estimate
differed substantially from that derived from fish counts at mainstem
dams of 78% Okanogan and 22% Wenatchee stock. Low known-stock classification
accuracy (66%) due to the similarity of scale patterns on Okanogan
and Wenatchee Age 1.2 sockeye salmon is likely responsible for this
difference. |
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