Sea lice infestation is a major welfare and production challenge in salmon farming. The treatments used to control lice carry their own welfare implications that must be weighed carefully.
Sea lice welfare management in salmon farming involves navigating trade-offs between the welfare harm of lice infestation and the welfare harm of treatment. Heavy lice burdens cause skin damage, stress, compromised osmoregulation, and in severe cases secondary infections that cause significant suffering. However, treatments also carry welfare costs: chemical baths cause acute physiological stress; thermolicer treatment exposes fish to 34-degree water that causes thermal shock; and mechanical brush systems abrade skin. Cleaner fish used as biological controls often fare poorly in salmon farm tanks, kept in conditions unsuited to their welfare needs. Integrated lice management that combines prevention, monitoring, and targeted treatment — using the least harmful effective method — represents the welfare-optimal approach.