Sea lice are the most costly parasite problem in Atlantic salmon farming, and treatments used to control them carry significant welfare risks for the fish themselves.
Sea lice management presents a welfare dilemma: untreated infestations cause chronic suffering through tissue damage and immune stress, while treatments themselves cause acute distress. Thermal bath treatments require fish to be crowded into a vessel and exposed to temperature extremes. Mechanical snorkel systems and laser devices reduce chemical use but involve confinement stress. Cleaner fish used as biological control often receive inadequate welfare consideration as a secondary species. The welfare priority is to develop and use the least harmful effective treatment while addressing the husbandry factors — particularly stocking density and farm siting — that drive infestation severity.