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

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 …