Migratory salmon face barriers to their spawning runs that cause exhaustion, injury, and welfare harm. Fish passage infrastructure design profoundly affects salmon welfare.
Salmon welfare during migration is profoundly affected by the physical infrastructure they encounter on spawning runs. A salmon that encounters an impassable barrier must make repeated exhausting attempts to ascend, depleting the energy reserves it needs for spawning and exposing itself to prolonged predator risk. Poorly designed fish passes that are impassable to weak or smaller fish create selection effects and cause welfare harm for individuals who cannot pass. The welfare case for effective fish passage — and where barriers are obsolete, for dam removal — is compelling. The ecological restoration argument for dam removal is well established; the welfare argument adds another dimension to the case for prioritising barrier removal over fish pass retrofitting where both options exist.