Sea lice treatments in salmon farming impose welfare costs on both target lice and the fish being treated. Minimizing treatment stress while maintaining parasite control requires careful protocol design.
Sea lice treatment welfare involves competing welfare considerations — the welfare burden of untreated heavy lice infestation versus the welfare cost of treatment procedures. The optimal balance requires treatment when lice reach thresholds that cause significant welfare harm, using the most welfare-compatible treatment method available, with protocols that minimize the crowding, handling, and chemical exposure stress associated with treatment. Bath treatments impose acute stress through crowding during application and potential chemical irritation — minimizing exposure duration and optimizing crowding density are important welfare considerations. Mechanical treatments cause physical stress through pump transfer and temperature shock in thermal treatments. The development of laser-based non-chemical treatments represents a welfare advance over chemical approaches, though handling stress during laser system transit remains. Proactive lice management that reduces the frequency of intervention is welfare-beneficial.