Wild salmon welfare is shaped by migration barriers, hatchery conditions, and the energetic demands of spawning migrations. Dam removal and passage restoration are the most impactful welfare interventions available.
Wild salmon welfare during spawning migration represents one of the clearest examples where habitat restoration directly improves welfare for millions of animals. A salmon that must negotiate multiple dam fish ladders arrives at its spawning ground with energy reserves depleted by the additional exertion, reduced reproductive success, and often fatal by the time spawning is complete. Gas bubble disease — caused by nitrogen supersaturation in water below dam spillways — causes fish to develop bubbles in tissues that disrupt function in a manner analogous to the bends in divers. Dam removal eliminates these welfare problems directly and durably. Hatchery salmon face different welfare challenges: crowding generates disease and aggression, feeding on artificial pellets may not prepare fish for wild foraging, and hatchery conditions select against behavioural traits that contribute to survival. The welfare case for wild salmon is inseparable from the ecological case for river connectivity.