Sea lice infestations in farmed Atlantic salmon cause significant welfare problems, and the treatments used to control them carry their own welfare costs — creating a complex ethical landscape in which there is no simple solution.
Sea lice management represents one of the clearest examples of welfare dilemmas in aquaculture: both the infestation and the treatments cause suffering, and the choice is between different forms of harm rather than harm versus no harm. Crowding, chemical exposure, mechanical removal, and thermal treatment all cause measurable stress and sometimes death. The welfare case for reducing lice burden through preventive measures — lower stocking density, site fallowing, submerged cage designs, and selective breeding for lice resistance — is strong, as it reduces both the disease and the treatment burden simultaneously.