From Farms to the Wild: Sea Lice and Fraser River Sockeye

A new report “Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast” published¬†on Tuesday¬†in PLoS ONE¬†links sea lice from fish farms to wild Fraser River sockeye.

Looking at salmon migrations from the Skeena River populations versus those of the Fraser River populations, the study notes that Fraser River sockeye must swim by more fish farms during their life cycles than the Skeena River salmon do. The researchers suggest it is because of the concentrated populations of sea lice around the open net farms, and the fact the sockeye must swim past them as they migrate, that the infection of these fish is much greater. The Skeena River salmon are not exposed to open net farms during their migrations, therefore their sea lice counts are significantly lower than the Fraser River sockeye. Although the results of the study are significant, the impacts of the new findings require further study.

The study genetically identified 30 different stocks of infected Fraser sockeye that swim past open net-pen salmon farms in the Strait of Georgia, such as the endangered Cultus Lake stock.The researchers determined that parasitism of Fraser sockeye increased strongly after the juvenile fish passed by fish farms, and that the same species of lice were present in large numbers on the farms.

Further, after swimming past salmon farms, the juvenile Fraser sockeye hosted more sea lice than Skeena and Nass River sockeye that migrated along the north coast, which is free of farms. [Read full article].

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