Fish farms make louse-y migration routes

Raincoast biologist Mike Price discusses Fraser River sockeye and the role sea lice might play in their survival

Notes from the Field - A conservation update from the Great Bear Rainforest

 

 

 

by Michael Price, Biologist, Wild Salmon Program.

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Spring is early this year, and signs of its bloom abound. Life on the coast races against time to proliferate before summer sun fades to dark. Less  visible are the millions of young sockeye salmon migrating out of their ice-free lakes on route to a salty existence. The majority are travelling down  the Fraser River, Canada’s largest salmon producer. Some have travelled 500 km since the ice retreated; others, 1,000. Their journey has just begun.

Raincoast is in its fourth year examining the health of juvenile sockeye in Georgia Strait. We’ve noted that these fish are more heavily infected with sea lice than pink and chum salmon, and infection of the young salmon increases as they pass salmon farms. We’ve documented the release of blood, tissue, and live sea lice in the effluent from a fish farm processing facility in the region. Although we have yet to understand just how detrimental these factors are in terms of disease and parasite transfer to juveniles, they are clearly not beneficial.

Photo: Juvenile sockeye are infected with sea lice when they migrate past fish farms in the Discovery Islands.

Fraser River sockeye returned in record low numbers last fall, one percent of what they were a century ago. Fishing pressure has not helped. Low ocean productivity may be partly at fault. Loss of habitat and pollution have surely been detrimental. But what exactly has caused the sharp decline in Fraser sockeye, no one can say with certainty. It may be that the resilience and buffering capacity that allowed populations to recover from harsh and unforeseen events in the past, has been exhausted from a century of human abuse. All we really know, and all that matters, is that they are at the tipping point in their existence.

I am new to parenthood, and all my partner Clare and I think of is how to ensure our son is shielded from as many harmful stressors as possible – instinctively, we know this will improve his chances of living a full life. We can’t protect him from everything, but we can avoid the harmful ones. When it comes to salmon, and particularly vulnerable young Fraser River populations, should we not provide them the same protection? If we are serious about salmon conservation, and wish to ensure our children’s children inherit plentiful returns of salmon, we must begin by alleviating as many human-induced stressors as possible.

Compared to the far-reaching threat of changes in ocean productivity associated with climate warming, risks to wild salmon posed by industries such as salmon farming are far more easily mitigated. One way is to simply remove net-cage salmon farms from the migration routes of juvenile salmon.

The challenge for our generation is to act.

Investigate. Inform. Inspire.

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