Sea lice infestations cause chronic pain, skin damage, and death in farmed salmon. They are the most significant welfare problem in open-sea salmon aquaculture and a major driver of wild salmon decline.
Sea lice cause ongoing, chronic suffering in farmed salmon. The parasites feed on skin and underlying tissue, creating wounds that expose salmon to secondary bacterial and fungal infections. Heavy infestations cause immunosuppression, anaemia, and emaciation. The treatments themselves impose additional welfare burdens: thermal delousing bathes salmon in heated water causing thermal stress; hydrogen peroxide treatments cause acute chemical irritation; mechanical delousing with laser systems is imprecise. The frequency of treatment cycles means farmed salmon experience repeated acute stressors on top of chronic parasite burden. The sea lice crisis represents a fundamental ecological incompatibility between open-water salmon farming and healthy coastal ecosystems.