Welfare of Farmed Salmon in Recirculating Aquaculture Systems

Recirculating aquaculture systems for salmon promise reduced environmental impact but present distinct welfare challenges related to high density, water quality management, and sensory environment.

Key Facts

RAS technology enables salmon farming in land-based tanks with minimal water exchange and waste discharge
Stocking densities in RAS can be even higher than sea cage systems due to precise water quality control
Salmon in RAS cannot engage in the depth-diving behavior they perform in sea cages, even if constrained
Water quality in RAS must be actively managed to prevent ammonia and CO2 accumulation
RAS proponents argue for welfare benefits from parasite-free, controlled environments but evidence is mixed

Welfare Considerations

Recirculating aquaculture systems represent a significant investment in sustainable salmon production, and their environmental credentials are genuine. Their welfare credentials are more contested. High stocking densities, lack of depth variation, constant artificial lighting, and the sensory monotony of a tank environment may represent welfare costs compared to sea cages, even as they eliminate sea lice and escapement. Welfare science for RAS salmon is developing, and the honest position is that RAS welfare is not automatically better than sea cage welfare — it is different, and requires its own evidence base.

What You Can Do

Choose salmon from RAS operations with documented welfare monitoring and evidence-based management
Support research into welfare indicators specific to land-based recirculating salmon production
Advocate for welfare standards to be developed alongside environmental standards for RAS certification
Ask seafood suppliers to provide evidence about welfare outcomes in RAS operations they source from