Salmon hatchery programs intended to support wild population recovery raise welfare concerns about the conditions in which juvenile fish are reared and the stress they experience during release and migration.
Salmon hatchery programs occupy a complex position: they are conservation interventions intended to support declining wild populations, yet the welfare of the millions of individual fish reared in them is frequently poor. High rearing densities in concrete tanks prevent normal social organization and territorial behavior. Chronic crowding causes persistent cortisol elevation, fin erosion and disease susceptibility. The handling and transport associated with release — netting, confinement in tanks during road transport, abrupt exposure to natural water conditions — causes acute stress at the moment when fish need maximum physiological reserves to begin their dangerous journey to sea. Welfare improvements including appropriate stocking densities, enriched rearing environments and low-stress release methods would benefit both individual fish welfare and hatchery program effectiveness.