Salmon hatchery programs used to supplement wild populations involve intensive juvenile rearing conditions whose welfare implications affect both hatchery fish and the wild populations they interact with after release.
Salmon hatchery welfare involves an unusual dynamic: the welfare costs of intensive hatchery rearing affect both the fish themselves and the wild populations into which they are released. Hatchery fish released after intensive crowding rearing carry physiological and behavioral deficits that reduce their survival and may compete with wild fish. Supplementation hatcheries using lower densities, predator conditioning, and more natural feeding approaches produce fish with better welfare during rearing and better survival post-release. The welfare case for reforming hatchery practices thus aligns with the conservation case — better welfare during rearing produces better outcomes for conservation goals.