Interactions between farmed salmon and wild salmonid populations create welfare concerns for wild fish through disease transmission, genetic introgression, and ecological competition.
Wild fish welfare is affected by salmon farming through multiple pathways that extend welfare concern beyond the farmed fish themselves. Sea lice infestations transferred from farm fish to wild juvenile salmon cause tissue damage, osmotic stress, and mortality — significant welfare impacts on wild sentient fish. Genetic introgression from escaped farmed salmon reduces local adaptation in wild populations, creating persistent welfare effects across generations. Antibiotic-resistant pathogen transfer from farm environments creates treatment challenges for wild fish disease management. These interactions mean that salmon farm welfare considerations cannot be evaluated in isolation — the welfare burden extends to surrounding wild fish populations. Closed containment systems that physically separate farmed and wild fish populations represent the most welfare-positive solution but have not yet been adopted at commercial scale.