Salmon hatchery programs raise welfare and conservation concerns as hatchery conditions alter fish behavior and physiology in ways that impair survival after release.
Hatchery salmon welfare encompasses both conditions during rearing and the welfare consequences of reduced survival fitness after release. Fish raised in crowded, stimulus-poor hatchery environments experience behavioral and physiological changes that impair their welfare prospects after release — reduced anti-predator responses and altered stress physiology leave them less equipped to survive in natural environments. The welfare paradox is that hatchery programs often cause harm both to individual hatchery fish and to the wild fish they are intended to supplement, through competitive interactions and genetic effects. Improved hatchery practices that reduce crowding, increase environmental complexity, and provide naturalistic feeding experiences improve both rearing welfare and post-release survival.