Fish hatcheries produce billions of juvenile fish annually for aquaculture and wild stock enhancement, with welfare during early life stages having lasting effects on health and behaviour.
Hatchery fish welfare is a frontier welfare issue with two distinct audiences: commercial aquaculture, where better hatchery welfare improves grown-out survival, and wild stock enhancement, where better hatchery welfare improves post-release survival in the wild. The evidence that early experience shapes stress axis sensitivity and behavioural flexibility throughout a fish lifetime means hatchery conditions are not merely a start-of-life welfare concern but a determinant of lifetime welfare trajectory. Enriched early environments -- more complex than bare fibreglass tanks -- require relatively modest investment and produce lasting welfare and performance benefits.