Survival of Puget Sound chinook salmon ( Oncorhynchus tshawytscha) in response to climate-induced competition with pink salmon ( Oncorhynchus gorbuscha)
We tested for competition between pink salmon (Oncorhynchus gorbuscha) and chinook salmon (Oncorhynchus tshawytscha) originating from rivers in the Puget Sound area using coded-wire-tagged subyearling hatchery chinook salmon. Following a 2-year life cycle, many juvenile pink salmon enter Puget Sound...
Published in: | Canadian Journal of Fisheries and Aquatic Sciences |
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Main Authors: | , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
Canadian Science Publishing
2004
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Subjects: | |
Online Access: | http://dx.doi.org/10.1139/f04-112 http://www.nrcresearchpress.com/doi/pdf/10.1139/f04-112 |
Summary: | We tested for competition between pink salmon (Oncorhynchus gorbuscha) and chinook salmon (Oncorhynchus tshawytscha) originating from rivers in the Puget Sound area using coded-wire-tagged subyearling hatchery chinook salmon. Following a 2-year life cycle, many juvenile pink salmon enter Puget Sound in even-numbered years, whereas few migrate during odd-numbered years. During 19841997, juvenile chinook salmon released during even-numbered years experienced 59% lower survival than those released during odd-numbered years, a trend consistent among 13 chinook salmon stocks. Lower even-numbered-year survival of chinook salmon was associated with reduced first-year growth and survival and delayed maturation. In contrast, chinook salmon released into coastal streams, where few pink salmon occur, did not exhibit an alternating-year pattern of survival, suggesting that the interaction occurred within Puget Sound and the lower Strait of Georgia. Unexpectedly, the survival pattern of Puget Sound chinook salmon was reversed prior to the 19821983 El Niño: chinook salmon survival was higher when they migrated with juvenile pink salmon during 19721983. We hypothesize that chinook salmon survival changed as a result of a shift from predation- to competition-based mortality in response to recent declines in predator and prey abundances and increases in pink salmon abundance. Alternating-year mortality accounted for most of the 50% decline in marine survival of chinook salmon between 19721983 and 19841997. |
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