Authors
Jeffrey
Fryer
Report Reference
#07-03
Publication Date
27 February
2007
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Identification of Columbia
Basin Sockeye Salmon Stocks Using Scale Pattern Analyses in 2006
Abstract |
| In 2006,
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 using
scale pattern analysis from the sampled sockeye salmon passing the
three dams. Four-year-old fish were estimated to comprise 65% of the
mixed-stock sockeye salmon migrating past Bonneville Dam, 74% of the
Okanogan stock migrating past Wells Dam, and 36% of the Wenatchee
stock migrating past Tumwater Dam. Five-year-old fish were estimated
to comprise 34% of the Bonneville Dam mixed-stock, 24% of the Okanogan
stock, and 63% 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 52% of the sockeye salmon passing Bonneville
Dam were of Okanogan origin, 13% were of Wenatchee stock, with the
remaining 34% not classified as to origin. The high estimate of unclassified
stock is due to the high percentage of five-year-old fish combined
with low sample sizes at Wells Dam making it not possible to differentiate
these fish using scale patterns. A companion PIT tagging project estimated
that 72.8% of the sockeye salmon passing Bonneville Dam were of Okanogan
origin, with the remaining 27.2% of Wenatchee origin. |
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