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Study Suggests Big Risks with Fish Farms

by Ellen Hardy
14 December 2007, at 12:00am

CANADA - A study published in the journal Science has issued a warning that disease could spread from farmed fish to wild stocks.

The article shows that rather than benefiting wild fish, industrial aquaculture may contribute to declines in ocean fisheries and ecosystems.

Farm salmon are commonly infected with salmon lice (Lepeophtheirus salmonis), which are native ectoparasitic copepods, says the reports authors Martin Krkoek, Jennifer S. Ford, Alexandra Morton, Subhash Lele, Ransom A. Myers and Mark A. Lewis1.

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“If outbreaks continue, then local extinction is certain.”

Report author Martin Krkoek

"We show that recurrent louse infestations of wild juvenile pink salmon (Oncorhynchus gorbuscha), all associated with salmon farms, have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction. The louse-induced mortality of pink salmon is commonly over 80 per cent and exceeds previous fishing mortality," says Martin Krkoek.

"If outbreaks continue, then local extinction is certain, and a 99 per cent collapse in pink salmon population abundance is expected in four salmon generations.

"These results suggest that salmon farms can cause parasite outbreaks that erode the capacity of a coastal ecosystem to support wild salmon populations."

The researchers studied a 400-square-mile area along the coast of British Columbia where wild salmon migrate past salmon farms when traveling from inland streams to the open ocean. Using government data on adult fish returning from the ocean, the study finds that in some years more than 80 per cent of the pink salmon were killed by sea lice.

 

Ellen Hardy