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Abnormal Migration Timing and High en route Mortality of Sockeye Salmon in the Fraser River, British Columbia

Abnormal Migration Timing and High en route Mortality of Sockeye Salmon in the Fraser River,... Since 1995, several stocks of Fraser River sockeye salmon (Oncorhynchus nerka) have begun upriver spawning migrations significantly earlier than previously observed. In some years, the timing of peak migration has shifted more than 6 weeks. Coincident with this early migration are high levels of en route and pre‐spawning mortality, occasionally exceeding 90%. These phenomena pose risks to the perpetuation of these fisheries resources. At present, although there are many competing hypotheses (e.g., energetics, osmoregulatory dysfunction, oceanic conditions, parasites) that may account for early migration and high mortality, there are no definitive answers, nor any causal evidence that link these issues. With poor predictive ability in the face of uncertainty, fisheries managers have been unable to effectively allocate harvest quotas, while ensuring that sufficient fish are able to not only reach the spawning sites, but also successfully reproduce. If trends in mortality rates continue, several important sockeye salmon fisheries and stocks could collapse. Indeed, one sockeye stock has already been emergency listed as endangered under Canadian legislation. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Fisheries Wiley

Abnormal Migration Timing and High en route Mortality of Sockeye Salmon in the Fraser River, British Columbia

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References (48)

Publisher
Wiley
Copyright
© American Fisheries Society
ISSN
0363-2415
eISSN
1548-8446
DOI
10.1577/1548-8446(2004)29[22:AMTAHE]2.0.CO;2
Publisher site
See Article on Publisher Site

Abstract

Since 1995, several stocks of Fraser River sockeye salmon (Oncorhynchus nerka) have begun upriver spawning migrations significantly earlier than previously observed. In some years, the timing of peak migration has shifted more than 6 weeks. Coincident with this early migration are high levels of en route and pre‐spawning mortality, occasionally exceeding 90%. These phenomena pose risks to the perpetuation of these fisheries resources. At present, although there are many competing hypotheses (e.g., energetics, osmoregulatory dysfunction, oceanic conditions, parasites) that may account for early migration and high mortality, there are no definitive answers, nor any causal evidence that link these issues. With poor predictive ability in the face of uncertainty, fisheries managers have been unable to effectively allocate harvest quotas, while ensuring that sufficient fish are able to not only reach the spawning sites, but also successfully reproduce. If trends in mortality rates continue, several important sockeye salmon fisheries and stocks could collapse. Indeed, one sockeye stock has already been emergency listed as endangered under Canadian legislation.

Journal

FisheriesWiley

Published: Feb 1, 2004

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