Wild Atlantic salmon populations have declined catastrophically over the past century from overfishing, habitat loss, and aquaculture interactions, with individual fish experiencing multiple welfare stressors.
Wild Atlantic salmon experience welfare challenges across their entire extraordinary life cycle. Smolts migrating to sea through salmon farm lease areas encounter dramatically elevated sea lice burdens that cause tissue damage, osmotic stress, and immune suppression. River dams block upstream migration, forcing fish to repeatedly attempt impassable barriers until they exhaust themselves. Thermal stress in warming rivers during summer low flows causes physiological distress and potentially lethal overheating. Predation pressure from recovering seal populations affects fish concentrated below migration barriers. Returning spawning adults that fail to reach natal streams after their exhausting oceanic migration die without reproducing. The cumulative welfare burden on a salmon navigating dam barriers, sea lice exposure, thermal stress, and predation is substantial for an animal undertaking one of the most energetically demanding migrations of any vertebrate.