What Are Sea Lice and What Role Do Salmon Farms Play?
Sea lice are natural parasites that attach to and feed on salmon, consuming mucus, skin, muscle, and blood. In high numbers, lice cause stress, osmotic failure (disturbed salt-water balance), increased susceptibility to viral or bacterial infection, and ultimately death. Sea lice are considered common and benign on adult salmon, but they are naturally rare on juvenile wild salmon. Where there are no fish farms, there are few sea lice on juvenile wild salmon, because the wild adult salmon that carry the parasite are offshore when juveniles enter the sea. Juvenile pink salmon infected with sea lice. Industrial fish farms, however, create densely packed host populations dangerously near B.C.’s wild salmon rivers. Because the farmed fish are held in net pens, they are exposed to parasites that infect wild fish or other nearby farms. Sea lice infect the farmed salmon, which then amplify the parasite in the surrounding environment. In B.C., wild juvenile salmon often migrate past several sal
