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solonavi 14 December 2007 General 129 views No Comment Print This Post  Email This Post

reuters

Infestations of sea lice at salmon farms on Canada’s west coast are threatening local wild pink salmon populations and could result in their extinction in another four years, Canadian researchers said on Thursday.

They collected nearly four decades of data on the numbers of pink salmon in rivers along the central coast of British Columbia, comparing wild salmon populations exposed to salmon farms to those not exposed.

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The researchers believe their findings have implications beyond the region and fish populations they studied. They said their findings indicate that in certain situations fish farms can threaten wild fish populations by concentrating and spreading infectious diseases.

Sea lice are parasites that attach themselves to the skin of wild salmon in the open ocean, feeding on their skin and muscle tissue. Adult salmon can survive a small infestation, but juvenile salmon headed from the river to the sea are too vulnerable to withstand an infestation.

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In nature, juvenile salmon can avoid the problem because the infected adults are offshore. But salmon farms that feed into rivers through open net systems can expose young salmon swimming past them to the disease.

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While once rare, there are now more than 20 salmon farms in the area, creating a habitat for sea lice that will overwhelm the wild salmon if not addressed, the researchers said.

If infestations continue, they predict extinction of local salmon populations within the next two generations, or four years.

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A barrier would prevent transmission of lice in infested farms from reaching the juvenile salmon in the wild. This can be costly, Morton said, but so would the loss of wild salmon.