Recirculating aquaculture systems (RAS) offer potential welfare improvements over open-net pen farming, but introduce their own welfare challenges requiring careful management.
RAS represents a welfare trade-off rather than a simple improvement over traditional aquaculture. The elimination of sea lice exposure, escape risk, and wild population contamination are genuine welfare advances. However, high stocking densities, CO2 accumulation, and the chronic noise and turbulence of water circulation systems create new welfare challenges. Fish welfare in RAS is best assessed using behavioral indicators — schooling cohesion, feeding response, surface activity — alongside water quality parameters. The welfare potential of RAS is highest when stocking densities are maintained below stress thresholds and water quality is actively managed for fish welfare rather than just production metrics.