Daniel Schramm

October 16, 2006

A study just out from the University of Alberta Centre for Mathematical Biology concludes industrial aquaculture is killing off massive numbers of wild salmon in Canada. Martin Krkosek, the study's lead author, found that when young pink and churt salmon swim past the net pens where adult salmon are raised and harvested, they pick up parasites that congregate around the nets. While the adults are not killed by the parasites, it only takes one or two of the lice to kill a juvenile. "We often worry about wildlife making humans sick, but here is a case where humans are making wildlife sick," says Dr. Mark Lewis, a co-author of the study who does interdisciplinary work in the fields of biology and mathematics.

The study found a direct correlation between levels of sea lice at the farms and rates of juvenile salmon die-off, which increased to 95% when levels of lice were at their peak in late spring. Only a small percentage of young salmon survive the migration to the ocean, so the impact of the lice could drive subpopulations of affected salmon into extinction. "It also raises a more distant specter," says Dr. Andy Dobson, an epidemiologist at Princeton. "When are we going to see the first human disease caused by aquaculture?"

The Aquaculture Association of Canada, an industry trade group based in New Brunswick, questions the study, as it has questioned previous studies linking aquaculture to negative environmental impacts. Chris Hendry, the Association's president, says "there is some uncertainty" about the link. Dr. Simon Jones, a government scientist for Fisheries and Oceans Canada, is cited at the Association's website as saying, "It's just too simplistic to say that salmon farms are the culprit for all sea lice infestations."

While this statement may technically be true, the new study refutes any claims that the sea lice infestations produced by the farms are not the primary threat to the salmon. Mr. Krkosek points out that only 5% of lice infestations of young salmon are due to sources other than aquaculture facilities. "The debate is over . . . . This paper brings our understanding of farm-origin sea lice and Pacific wild salmon to the point where we know there is a clear severe impact," says Alexandra Morton, another co-author. "The work is of an impeccably high standard, and will be very difficult to refute," says Dr. Dobson.

The question remains whether the industry will now take steps to isolate the aquaculture pens from wild salmon migratory routes.

Sources

Martin Mittelstaedt, Fish Farm Sea Lice Kill Up To 95% of Salmon, Team Finds, The Globe and the Mail, October 3, 2006, available at http://www.truthout.org/issues_06/100306EC.shtml.

Salmon Farms Kill Wild Fish, Study Shows, Biology News Net, Oct. 3, 2006, http://www.biologynews.net/archives/2006/10/03/salmon_farms_kill_wild_fish_study_shows.html.

Aquaculture Association of Canada, Aquaculture Association of Canada to Bridge the Communication Gap in Fish Farming Science, July 24, 2006, http://www.aquacultureassociation.ca/scienceadvisory.html.