Sea lice infestations are the primary disease challenge in Atlantic salmon farming, and the treatments used to control them cause significant additional welfare harm.
Salmon welfare is doubly harmed by sea lice — first by the parasites themselves causing lesions and immune compromise, then by treatments that cause thermal burns, chemical toxicity or intense handling stress. Repeated thermal or chemical treatments across a production cycle compound cumulative welfare costs. The ideal solution — closed containment systems that exclude sea lice entirely — is technically available but economically challenging at scale. Interim welfare improvements including reduced treatment frequency through better monitoring, gentler handling protocols, and lower stocking densities that reduce lice transmission rates are achievable within current open-cage systems.