Aquaculture Recirculating Systems and Fish Welfare

Recirculating aquaculture systems (RAS) offer potential welfare advantages over traditional net pens, but their design and management are critical to whether fish welfare is genuinely improved.

Key Facts

RAS recycles up to 99% of water through filtration and UV treatment, reducing disease risk from wild pathogens
Higher water quality control in RAS enables consistent temperature, oxygen, and ammonia management — all key to fish welfare
Stocking density in RAS can still be very high, which is a primary welfare concern regardless of water quality
RAS eliminates sea lice exposure from wild populations, a major welfare benefit for farmed salmon
Crowding stress in RAS can cause fin damage, scale loss, and increased aggression among fish
Land-based RAS systems can be sited closer to markets, reducing live transport distance and associated welfare stress

Welfare Considerations

Recirculating aquaculture systems represent a significant technological advance with real potential welfare benefits — particularly elimination of sea lice and better water quality control. However, the welfare promise of RAS depends entirely on how the systems are managed. High stocking densities, inadequate enrichment, and poor husbandry can produce poor welfare outcomes even in technically sophisticated facilities. Welfare standards for RAS must address density, behavioral opportunity, and handling practices.

What You Can Do

Support aquaculture welfare certification schemes that audit RAS operations as well as net pen farms
Ask retailers about the production systems behind farmed fish products and whether welfare standards apply
Advocate for welfare standards specific to RAS that address stocking density and fish behavioral needs
Follow aquaculture welfare research to understand how land-based systems can best serve fish welfare