The methods used to treat sea lice in farmed salmon have significant welfare implications, with each approach carrying specific acute and chronic welfare costs that must be weighed against the welfare burden of untreated louse infestation.
Sea lice treatment welfare creates a compound welfare problem: treatment causes acute welfare harm, but failure to treat allows chronic welfare harm from louse burden to accumulate. The welfare-minimizing approach is to prevent infestation rather than treat it, through genetics, closed containment, and management practices that reduce louse pressure. Where treatment is necessary, the relative welfare costs of different methods must be assessed honestly: thermal delousing risks thermal shock; mechanical delousing risks physical injury; chemical treatment risks handling stress. Progressive producers have invested in treatment welfare improvement while simultaneously reducing treatment need through preventive approaches.