Recirculating aquaculture systems (RAS) are increasingly used for salmon farming. They offer environmental advantages but introduce unique welfare challenges that require careful management.
RAS offers compelling environmental advantages over sea cage salmon farming but is not inherently higher welfare. The controlled indoor environment eliminates sea lice and escapees but introduces new welfare challenges: extreme stocking densities, mechanical system dependency, gas supersaturation risk, and constant noise and vibration. Water quality in RAS is highly controllable but catastrophically collapses when systems fail — mortality events from ammonia spikes or oxygen crashes are documented. The welfare case for RAS depends on how facilities are managed: well-designed, carefully operated systems with appropriate density limits and rigorous monitoring can achieve good welfare outcomes; poorly managed high-density facilities may have worse welfare than well-run sea cages. Independent welfare assessment of specific RAS operations is essential.