Atlantic halibut (Hippoglossus hippoglossus) is a high-value flatfish species with growing aquaculture production in Norway and Scotland. Its unusual biology — metamorphosing from symmetric pelagic larvae to asymmetric demersal adults — creates unique welfare challenges during farming.
Malpigmentation in halibut, caused by inadequate light conditions and diet during development, is both a welfare indicator and production issue: abnormal pigmentation is associated with impaired immune function. Crowding of demersal fish in round tanks prevents natural resting behaviour, causing chronic stress. Halibut appear highly sensitive to handling: removing them from water causes acute stress responses far exceeding those seen in salmonids. Welfare-conscious farms provide flat resting surfaces, individual grading procedures using minimally handling-intensive methods, and species-appropriate stocking densities below 15 kg/m2.