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A study published in the December 14 edition of the prestigious peer-reviewed scientific journal Science concludes that sea lice from salmon farms have been driving a rapid decline in pink salmon populations in the Broughton Archipelago. The scientists expect that 99 per cent of the wild pink salmon will be gone in four years from today, or two generations, if sea-lice infestations continue.
The study was conducted by a team of six biologists, fisheries scientists, and mathematicians from Dalhousie University and the University of Alberta. The team analyzed Fisheries and Oceans Canada data on the number of pink salmon returning to rivers on the central coast of British Columbia from 1970 to 2006. They then organized the data into four groups according to whether or not the populations were exposed to salmon farms before and during the sea-lice infestations, and calculated population growth rates for each group. It is the first study to demonstrate the impact of sea-lice infestations on wild salmon populations and reveal their looming extinction.
"In light of these results, it is clear that governments must take immediate precautionary action to stop open net-cage salmon farming from harming wild salmon," said David Suzuki Foundation marine conservation specialist Jay Ritchlin. "The evidence continues to be published in the most respected scientific journals, and the B.C. legislature’s own Special Committee on Sustainable Aquaculture has called for a transition to closed systems. It is time to act."
Sea lice are natural parasites that feed on salmon skin, muscle, and blood. In high numbers they cause stress, osmotic failure (disturbed salt-water balance), viral or bacterial infection, and ultimately death. Numerous studies have shown that where there are no fish farms, wild juvenile salmon have almost no lice. Fish farms, however, amplify the parasite on wild salmon migration routes. In the Broughton Archipelago, the wild juvenile salmon must run an 80-kilometre gauntlet of fish farms before they make it to the open ocean.
"Recent efforts to use chemical treatment are apparently not enough for the wild fish. In Europe and South America, lice have already shown the first signs of resistance to these chemicals. Widespread use of chemical treatments just isn’t good environmental policy," Ritchlin noted. "The region needs to have the source of the lice infestations removed. We must get the open net-cage salmon farms out of the way of the juvenile salmon and ultimately into closed tanks."
The report notes that the impact of fish farms is far higher than that caused by commercial fisheries. Not only are the salmon and the ecosystem at risk, so too are the economies and cultures that depend on wild salmon.
The David Suzuki Foundation is a member of the Coastal Alliance for Aquaculture Reform, a nine-member coalition working to protect wild salmon, coastal ecosystems, coastal communities, and human health from destructive fish-farming practices.