Atlantic halibut farming uses both traditional sea cage and land-based recirculating aquaculture systems, each with distinct welfare profiles that affect the quality of life for this large flatfish.
The welfare comparison between sea cage and RAS halibut production highlights different trade-off profiles rather than a clear winner. Sea cage production exposes halibut to natural photoperiod and temperature variation that may support circadian regulation, but also to sea lice, environmental pathogens, and the denial of substrate that these bottom-dwelling fish require for resting behavior. RAS production can provide substrate panels, controlled water quality, and freedom from external parasites, but the artificial environment requires careful management to avoid the chronic low-level stressors of suboptimal water chemistry. In both systems, substrate provision for resting is a key welfare feature for a species that naturally spends significant time on the seafloor. Halibut welfare science is less developed than salmon welfare science, and species-specific welfare indicators and standards lag behind the growth of the industry.