Sea lice are the most significant parasite challenge in Atlantic salmon farming. Treatment methods have major welfare implications, and less harmful alternatives are being developed.
Sea lice treatment is a significant welfare event for farmed salmon. Crowding during the collection process required to move fish through delousing equipment causes acute stress. Thermal treatment at temperatures that kill lice also causes physiological stress in salmon and results in mortality of weakened fish. Chemical bath treatments cause acute toxicity-related stress. The more sustainable approaches - cleaner fish, snorkel barriers, laser removal - have more favorable welfare profiles but are not universally available or effective. The welfare cost of repeated treatments over a salmon's 18-month sea water phase is cumulative and significant. The industry's progress toward non-chemical, lower-stress delousing represents genuine welfare improvement, but implementation across all facilities varies considerably.