Atlantic halibut farmed in advanced recirculating aquaculture systems can achieve higher welfare standards than sea cage production, but water quality precision and behavioral needs management remain critical challenges.
RAS halibut production represents one of the more welfare-promising developments in premium flatfish aquaculture because the controlled environment can in principle be optimized specifically for halibut welfare requirements. The elimination of sea lice removes one of the most significant welfare challenges of sea cage production. Precise temperature control maintains fish within their optimal physiological range. Substrate provision — panels on tank floors that mimic the seafloor environment halibut naturally rest on — supports natural resting behavior. The critical welfare challenges in RAS are water quality maintenance, particularly biofilter stability that prevents ammonia accumulation, and stocking density management that prevents the behavioral suppression of high-density crowding. When these parameters are well-managed, RAS halibut welfare may exceed that achievable in sea cage production. When water quality deteriorates — a risk in complex biological filtration systems — welfare consequences can be rapid and severe.