Multiple sea lice treatment methods are available for farmed Atlantic salmon with significantly different welfare impacts that should guide selection decisions.
Sea lice treatment welfare assessment should be based on comparative stress indicators rather than assuming all licensed treatments are equivalent. Hydrogen peroxide treatment parameters must be strictly controlled — elevated temperature or extended exposure time causes acute gill and eye damage. Mechanical removal systems cause scale loss and handling stress even when properly operated. Freshwater treatment causes osmotic stress for marine-adapted fish. No treatment is without welfare cost — the management goal is minimizing treatment frequency through prevention, and choosing the lowest-welfare-impact treatment when treatment is necessary. Treatment protocol decisions should explicitly weigh welfare impacts alongside efficacy and economics.