Disease is a major welfare concern in aquaculture, with crowding-induced outbreaks causing mass mortality and suffering in farmed fish populations that can be reduced through better management.
Aquaculture disease creates welfare problems at two levels: the individual suffering of diseased fish, and the management interventions used to address outbreaks. Fish experiencing bacterial infections, parasitic infestations, or viral disease face pain, immune disruption, and death. Treatment interventions including bath treatments and handling during treatment add additional acute stress. Prevention through vaccination, lower stocking densities, improved water quality, and genetic selection for disease resistance addresses welfare far more effectively than treatment. The welfare-optimal approach minimizes disease pressure through management while ensuring that sick fish are detected early and treated or humanely euthanized.