Salmon Smolt Welfare in Freshwater Hatcheries

Atlantic and Pacific salmon smolts raised in freshwater hatcheries face welfare challenges during their development before transfer to sea cages, including crowding, disease, and handling stress.

Key Facts

Salmon hatcheries raise smolts from egg to the point of smoltification — the physiological transition to saltwater tolerance
Freshwater hatchery phases typically last 12 to 18 months before smolts are transferred to sea cages
High stocking densities in hatchery tanks cause competition, injury, and chronic stress in developing fish
Sea lice exposure begins at transfer to sea cages, with hatchery conditions affecting lice susceptibility
Vaccination of smolts at hatchery involves handling and injection that causes acute stress
Water quality in recirculating hatchery systems requires careful management to avoid ammonia and oxygen stress
Mortality rates in the freshwater phase of salmon farming can be significant, representing welfare losses at scale

Welfare Considerations

Welfare during the freshwater smolt phase sets the foundation for salmon welfare throughout production. Fish that experience chronic crowding stress, disease, and poor water quality in the hatchery phase arrive at sea cages already immunocompromised and stress-sensitised. The vaccination handling event — necessary for disease protection but acutely stressful — represents a welfare trade-off where short-term discomfort serves longer-term health. Improving hatchery welfare through lower stocking densities, optimised water quality, and careful handling protocols during vaccination reduces the cumulative welfare burden of salmon production and likely improves production outcomes by reducing disease and mortality.

What You Can Do

Support salmon welfare certification schemes that audit hatchery conditions alongside sea cage welfare
Ask salmon producers about their hatchery welfare standards and stocking density management
Support research into lower-stress vaccination delivery methods for farmed fish
Advocate for welfare standards to apply throughout the full production cycle including the freshwater phase