The treatment of sea lice infestations in farmed salmon involves methods that are themselves welfare-compromising, creating a compound welfare problem in the industry.
Sea lice treatment welfare represents a true compound problem: the lice cause welfare harm, and the treatments cause additional welfare harm. Hydrogen peroxide baths cause respiratory distress and scale loss; thermolicers cause thermal shock; even laser systems involve crowding and handling stress. Cleaner fish — themselves sentient animals — are often housed inadequately and die at high rates. The welfare solution is to prevent lice burdens from reaching treatment thresholds through lower stocking densities, genetic resistance, and vaccination rather than treating high burdens reactively. Prevention is both better welfare and better economics.