Interactions between farmed salmon and wild Atlantic salmon raise welfare concerns including sea lice transmission, genetic mixing, and competition from escaped fish.
Farm-wild salmon interaction represents a case where aquaculture welfare affects both farmed animals and wild populations. Sea lice transmitted from high-density farms to wild salmon migrating past farm sites cause welfare harm to wild fish — compromising immune function, damaging gills, and increasing mortality in small sea trout in particular. Genetic introgression from escaped farmed salmon reduces the fitness of hybrid wild fish over generations, with population-level welfare and conservation implications. Closed containment systems — land-based or enclosed sea cage systems that prevent lice spread and escapes — address these problems at source, representing the welfare-responsible future for salmon aquaculture.