Wild salmon undertaking spawning migrations face extraordinary physiological demands and multiple welfare threats. Pacific salmon (Chinook, coho, sockeye) stop feeding after entering freshwater and rely entirely on stored energy reserves for migrations of 100-3,000 km. Warming river temperatures - particularly devastating in Pacific Northwest rivers where summer temperatures now exceed lethal thresholds - cause thermal stress, disease vulnerability, and mass mortality before spawning. Research documents stress responses in salmon attempting passage through poorly designed fish ladders and culverts. Sea lice from aquaculture facilities infest juvenile salmon migrating to sea, causing welfare harm and mortality. Predation by recovering populations of California sea lions at dam fish ladders causes significant mortality and welfare concern. Hatchery supplementation programmes aim to support populations but hatchery fish show welfare disadvantages including poorer navigation and disease resistance. Dam removal restoring natural passage represents the most comprehensive welfare-positive intervention.