Farmed salmon infect wild stocks with sea lice, study finds

A new study of wild and farmed salmon in the Pacific Northwest reveals that farmed salmon breed parasitic sea lice that infect juvenile wild salmon swimming nearby and could affect stocks of other important commercial species. A Canadian research trio looked at some 5,500 young salmon as they swam through a narrow channel past a salmon farm, and they recorded unnaturally high rates of lice infestation as the small fish migrated through a cloud of lice stretching nearly 19 miles around the farm, which itself is only about one-eighth of a mile. “Conservatively, this means that the parasite footprint of the farm is 150 times larger than the farm itself,” said study coauthor John Volpe. But the troublesome parasites aren’t the only nasties to come out of fish farms; a study in the journal Science last year found more cancer-causing PCBs in farmed fish than in their wild-caught counterparts, and in Europe, chemicals used to control the parasites and dye the salmon pink have led enviros to encourage boycotts of farm-raised salmon.