Salmon hatcheries for stock enhancement and aquaculture smolt production raise welfare questions around crowding, handling stress, and the appropriateness of releasing hatchery fish into challenging wild environments.
Hatchery salmon welfare depends on water quality management, stocking density control, and minimizing unnecessary handling stress. High-density rearing in poor water quality causes chronic physiological stress affecting immune function and behavior. Handling events are acutely stressful and handling mortality can be significant if water temperature and oxygen are not carefully managed. Welfare during the hatchery phase directly affects the health and survivability of released fish. Beyond production welfare, releasing hatchery fish into challenging wild environments where starvation or predation mortality is high raises broader welfare questions about the entire enterprise.