Stock composition of age-0 Chinook salmon rearing in nonnatal U.S. tributary streams of the Yukon River
Dates
Year
2011
Citation
Daum, Dave, and Flannery, Blair G., 2011, Stock composition of age-0 Chinook salmon rearing in nonnatal U.S. tributary streams of the Yukon River: U.S. Fish and Wildlife Service, v. FINAL REPORT TO YUKON RIVER PANEL URE-23N-10, p. 22-22.
Summary
Yukon River Chinook salmon Oncorhynchus tshawytscha are described as having "stream-type" life histories. After emergence from river gravel, juvenile Chinook salmon feed and grow in tributary streams of the Yukon River throughout their first summer, overwinter in freshwater, and usually leave rearing areas for marine waters during the second spring/summer. Previous life history and distribution studies have shown that some age-0 Chinook salmon leave their natal streams and colonize downriver, nonnatal habitats for rearing and overwintering. A pilot study in 2006–2007 documented rearing of Canadian-origin Chinook salmon in downstream U.S. waters. A comprehensive three-year distribution study was funded by the Alaska Sustainable Salmon [...]
Summary
Yukon River Chinook salmon Oncorhynchus tshawytscha are described as having "stream-type" life histories. After emergence from river gravel, juvenile Chinook salmon feed and grow in tributary streams of the Yukon River throughout their first summer, overwinter in freshwater, and usually leave rearing areas for marine waters during the second spring/summer. Previous life history and distribution studies have shown that some age-0 Chinook salmon leave their natal streams and colonize downriver, nonnatal habitats for rearing and overwintering. A pilot study in 2006–2007 documented rearing of Canadian-origin Chinook salmon in downstream U.S. waters. A comprehensive three-year distribution study was funded by the Alaska Sustainable Salmon Fund in 2008 to describe the extent of Chinook salmon rearing in nonnatal U.S. tributary streams of the Yukon River between the U.S.–Canada border and Tanana, Alaska, a distance of over 850 km. Juvenile Chinook salmon were captured in 44 of the 56 streams sampled. Genetic material was collected from all 616 fish captured and the stock composition results from the samples are presented in this report. Using genetic mixed-stock and individual assignment analyses, sample mixtures and individuals were assigned to regional stock groups and country of origin. Canadian-origin Chinook salmon contributed between 88% and 100% of the yearly mixtures and between 91% and 100% of the yearly assigned samples, with Canadian percentages decreasing with increased distance from the U.S.–Canada border. The Carmacks regional group, 470 to 590 km upstream of the border, made up the majority of mixtures and individual assignments throughout the study area. Other Canadian groups were under-represented, including the large-river stocks from the Stewart, Pelly, and Teslin rivers. The furthest travel distance was estimated to be over 1,300 km. The Upper USA stock group was identified in some downstream creeks below the Dalton Highway Bridge, but always in low numbers. The mechanism that causes this disproportionate number of Carmacks area juveniles to leave their natal streams for downstream rearing areas and the cost, if any, of this dispersal strategy are unknown.