Authors
Jeffrey Fryer
Denise A. Kelsey
Report Reference
#03-2
Publication Date
20 April 2003
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Identification of Columbia Basin Sockeye Salmon Stocks Using Scale
Pattern Analyses in 2002
Abstract |
| In 2003, samples of adult Columbia Basin sockeye salmon,
Oncorhynchus nerka, were collected at Bonneville Dam 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. Five-year-old
fish were estimated to comprise 55% of the Bonneville Dam mixed-stock,
40% of the Okanogan stock, and 58% of the Wenatchee stock. Four-year-old
fish were estimated to comprise 40% of the mixed-stock sockeye salmon migrating
past Bonneville Dam, 44% of the Okanogan stock migrating past Wells Dam,
and 42% of the Wenatchee stock migrating past Tumwater Dam. Three-year-old
fish were estimated to comprise 1% of the Bonneville Dam mixed-stock, 2%
of the Okanogan stock and none of the Wenatchee stock. Six-year-old fish
were estimated to comprise 4% of the Bonneville Dam mixed-stock, 13% of
the Okanogan stock and <1% of the Wenatchee stock. For the first time
in 17 years of CRITFC Columbia River sockeye salmon studies, sockeye salmon
were estimated to have spent more than two years in freshwater. Sockeye
spending greater than two years in freshwater were estimated to comprise
11% of the Okanogan Lake, 4% of the Bonneville Dam mixed-stock, and none
of the Wenatchee stock. Scale pattern analysis techniques were used to
estimate that 72% of the sockeye salmon passing Bonneville Dam were of
Okanogan origin, 27% were of Wenatchee stock, with the remaining 1% of
unknown origin. |
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