Fraser River Sockeye collapse
by Mike Price
Biologist, Raincoast Aquaculture Campaign
September 2009
The headlines continue to blare across local, regional, and national newspapers: 11 million Fraser River sockeye missing; poor early marine survival blamed.
Earlier this summer, Raincoast Conservation Foundation’s aquaculture field crew was searching the waters among the Discovery Islands at the northern end of Georgia Strait for juvenile sockeye. An unexpectedly beautiful and rich waterway off Vancouver Island’s east coast, the Discovery Islands host one of the largest salmonid migrations on the planet. It is also now home to BC’s highest concentration of salmon farms. There is growing concern that farm-origin sea lice are infecting migrating juvenile sockeye from the Fraser River; hence, our study.
The now missing Fraser sockeye were on course to migrate through this region in the summer of 2007, the first year of Raincoast’s sockeye project. Roughly 60% of the sockeye smolts we sampled that spring were of Fraser River origin, with Chilko and Quesnel stocks dominating the samples. Chilko is the largest producer of sockeye salmon in the Fraser River, and over 78 million fry left the lake in the spring of 2007 heading towards the Discovery Islands.
Even at a low survival rate, the return from these fish alone should have been 1,000,000 sockeye. Since ocean conditions were considered favourable for marine survival during the 2007 out-migration, DFO predicted high spawner returns of over 10 million sockeye. Yet, these fish have failed to show.
Could sea lice infection be the reason so many sockeye of Fraser origin failed to return, just as pink salmon populations have shown declines in another farm region? We are currently trying to answer this. One idea emerging from the scientific community is not that juvenile salmon necessarily die as a direct result of being infected by lice, but rather indirectly. For example, juveniles infected by lice show slower swimming speeds and ‘loner’ behaviour, two characteristics that encourage increased predation risk; more juveniles infected with lice from farms, more food for natural predators, less returning salmon.
Poor early marine survival is the likely cause for the missing Fraser sockeye – question is, are salmon farms the culprit. At Raincoast, we hope our Discovery Islands sea lice research will shed some light on the Fraser sockeye issue.
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