Sea lice infestations in Atlantic salmon farming cause severe welfare harms, and the treatments used to control them impose additional physiological stress with their own welfare implications.
Sea lice on farmed salmon represent a welfare problem with no easy solution. The lice themselves cause genuine suffering through tissue damage and immune suppression. Yet the treatments available — chemicals, thermal stress, mechanical handling — all impose their own welfare costs. The biological solution of using cleaner fish is more humane but requires keeping wrasse in good welfare conditions, which presents its own challenges. Addressing sea lice welfare requires investment in better prevention through lower stocking densities, genetics, and selective breeding for lice resistance.