Sea lice infestations are the most significant health challenge in Atlantic salmon farming, and the treatments used carry their own welfare costs alongside the parasites themselves.
Sea lice welfare impacts operate at two levels: the parasites themselves cause chronic pain through tissue damage and stress through impaired osmoregulation; and treatments - particularly crowding for bath treatments and the treatments themselves - cause acute additional stress. Hydrogen peroxide baths cause oxygen depletion and can cause eye and gill damage. The welfare ideal is prevention through containment technology or cleaner fish rather than reactive treatment of severe infestations. Industry is under pressure to move toward preventative approaches.