Recirculating aquaculture systems represent the most controlled and potentially highest-welfare approach to salmon farming, but also introduce unique welfare challenges from the technology itself.
Recirculating aquaculture systems offer a genuinely promising approach to salmon farming from both welfare and environmental perspectives. The ability to precisely control water quality, temperature, lighting, stocking density, and feeding parameters allows welfare optimisation that is simply not possible in open net pen systems. RAS eliminates sea lice, prevents escapes, removes effluent from the marine environment, and can be sited near markets. However, RAS also introduces specific welfare risks: the engineered water quality that sustains high-density farming can fail catastrophically, with rapid deterioration causing mass mortality; and the artificial environment removes the environmental variation that may be behaviourally important. Early welfare assessments of RAS salmon are promising but the technology is maturing rapidly and welfare standards specific to RAS production systems are needed. The welfare potential of RAS is significant if the technology continues to develop with welfare as a design criterion.