Recirculating Aquaculture Systems (RAS) allow intensive fish production in land-based facilities with potential welfare benefits from better water quality control but new welfare challenges.
RAS represents a trade-off in aquaculture welfare. The technology offers genuine improvements in water quality management, disease control and avoidance of environmental welfare risks like sea lice. However, very high stocking densities in enclosed environments create crowding stress, and the artificial environment with constant noise and light may cause chronic stress. Individual fish welfare in RAS requires monitoring that goes beyond water quality to include behavioural indicators of stress, social aggression and stereotypic behaviour. The welfare potential of RAS is significant if density and environmental management match species needs.