Recirculating aquaculture systems (RAS) offer environmental advantages over open-cage farming. But their intensive nature creates specific welfare challenges requiring careful management.
RAS offers a genuine trade-off between environmental benefits and specific welfare challenges. The elimination of sea lice and reduced antibiotic use are clear welfare improvements over conventional sea cage farming. However, the extreme crowding possible in RAS — enabled by water quality control — creates high-density environments where fish are chronically stressed without adequate space for normal behavior. Equipment failures create acute welfare crises: oxygen supply failures can kill thousands of fish within minutes. The behavioral impoverishment of RAS — no current variation, no substrate, no spatial complexity — means fish spend their entire lives in an environment fundamentally unlike their natural habitat. Integrating habitat complexity into RAS design, including current generation, substrate areas, and refugia, is an emerging welfare improvement area.