Sea lice infestations are a major welfare and production challenge in salmon farming, with treatments ranging from chemical baths to mechanical removal carrying their own significant welfare costs.
Sea lice represent a genuine welfare dilemma in salmon farming: untreated infestations cause chronic pain and debilitation, while most treatments cause acute welfare impacts. Chemical bath treatments involve crowding fish into small volumes of medicated water — a highly stressful experience. Mechanical delousing systems, while reducing chemical use, cause significant physical trauma to individual fish. The scale of treatment — hundreds of thousands of fish per treatment event — means even low mortality rates represent large numbers of deaths. Prevention through engineering solutions (deeper pens to avoid surface lice concentrations, snorkel feeding below the lice zone) offers better welfare outcomes than repeated treatment. Consumer choice of welfare-certified salmon is the primary market lever for improvement.