Recirculating Aquaculture Systems: Welfare Implications of RAS Salmon Farming

Recirculating aquaculture systems (RAS) are revolutionising salmon farming by bringing production onshore. These closed systems offer welfare benefits over sea cages but introduce new challenges.

Key Facts

RAS technology recycles up to 99% of water used, dramatically reducing environmental footprint compared to sea cages.
RAS eliminates sea lice infestations — one of the most significant welfare problems in conventional open-net salmon farming.
Water quality parameters in RAS can be precisely controlled, reducing welfare risks from temperature fluctuations and low oxygen.
High stocking densities in some RAS facilities can still cause crowding-related stress and fin damage.
Gas supersaturation — excess dissolved gases in RAS water — can cause gas bubble disease in fish, a painful welfare condition.
RAS requires significant energy input; welfare and sustainability must be evaluated together for a complete picture.
Several large-scale land-based RAS salmon farms have experienced significant mortality events during operational incidents.

Welfare Considerations

RAS salmon farming represents a genuine welfare improvement in some dimensions — the elimination of sea lice and their treatments, better control of environmental conditions, and removal of predation risk. However, new welfare risks have emerged. High stocking densities, if not carefully managed, cause chronic stress. Gas supersaturation incidents can cause acute suffering. System failures — power outages, pump malfunctions — can rapidly deteriorate water quality with catastrophic mortality events. The welfare assessment of RAS must be honest about both its advantages over sea cage systems and its specific risk profile. As the technology matures, welfare standards specifically designed for RAS environments are being developed by regulators and certification bodies.

What You Can Do

Ask retailers whether their salmon comes from RAS or sea cage production and research the specific farm's welfare record.
Support the development of RAS-specific welfare certification standards.
Advocate for mandatory environmental monitoring and emergency protocols in RAS facilities.
Stay informed about RAS welfare research through organisations like the Fish Welfare Initiative.
Reduce salmon consumption overall or shift to lower-sentience or better-managed seafood options.