Atlantic halibut is a high-value aquaculture species with specific welfare challenges from its flatfish physiology, territorial behaviour, and sensitivity to environmental conditions.
Atlantic halibut welfare presents unique challenges arising from their flatfish anatomy and territorial behaviour. Lying on one side, halibut require appropriately designed tank surfaces — smooth, solid floors with adequate area for full body extension without forced overlap. Overcrowding causes competition-related aggression including fin-biting and physical injury, with visible wounds representing ongoing pain and infection risk. Cannibalism during early rearing is a welfare emergency: juvenile halibut in hatcheries will consume smaller pen-mates, necessitating careful size-grading and density management. The slow growth trajectory means welfare management must be sustained over years rather than months. Handling stress during grading events — necessary to prevent size-based cannibalism — must be minimised through anaesthetic use and rapid, skilled protocols. Water quality parameters are critical: halibut are sensitive to dissolved oxygen levels, temperature fluctuations, and water flow patterns, and deteriorating conditions produce rapid welfare decline before obvious mortality signals.