Recirculating aquaculture systems (RAS) offer potential welfare improvements over open net pens but introduce specific challenges requiring careful management for optimal fish welfare.
RAS represents both an opportunity and a risk for salmon welfare. The elimination of sea lice — a major welfare burden in open net pen farming — is a genuine welfare gain. Controlled water quality allows optimal dissolved oxygen and temperature management. However, RAS failures — power outages, filtration collapse — cause rapid, catastrophic deterioration of water quality that can kill entire batches. CO2 accumulation in poorly managed systems causes aversive responses and chronic stress. Stocking density in some commercial RAS operations remains high enough to cause territorial conflict and injury. The welfare potential of RAS is significant but requires operational standards and monitoring that are currently inconsistent across the industry.