Fish hatcheries produce billions of fish for aquaculture and stocking programmes. The welfare conditions in early life stages have lasting effects on fish health and behaviour.
Hatchery conditions during early life stages are welfare-critical for fish. Crowding triggers chronic stress responses that suppress immune function, impair growth and increase aggression. Grading — the process of sorting fish by size — involves repeated handling and atmospheric exposure. Water quality fluctuations cause acute distress. Despite these challenges, welfare-conscious hatchery management is achievable: enriched environments with cover structures, appropriate light cycles, careful density management and minimised handling reduce stress indicators significantly. For wild-stocking hatcheries, welfare also intersects with conservation effectiveness — fish raised in enriched environments that simulate natural conditions survive far better upon release.