Atlantic halibut farming in recirculating aquaculture systems versus sea cages presents different welfare trade-offs that are beginning to be systematically evaluated.
Welfare comparison between RAS and sea cage halibut farming reveals different profiles of risk rather than a clear superior system. RAS provides consistent water quality and temperature control, reducing the risk of environmental stress events, but limits behavioral repertoire and natural light cycles. Sea cages allow greater behavioral freedom and natural environmental variation but expose fish to storm stress, sea lice, and temperature fluctuations. Halibut welfare indicators — ambicoloration rates, fin condition, wound prevalence, and appetite scores — are beginning to be used as standardized monitoring tools that can compare systems objectively. The welfare priority for both systems is pre-slaughter stunning: halibut are commonly harvested by air exposure and spiking without prior anesthesia, causing prolonged distress.