Sea lice infestations are a major welfare problem in Atlantic salmon farming, causing tissue damage and stress while posing risks to wild salmon populations.
Sea lice management in salmon farming involves complex welfare trade-offs across multiple species. Chemical bath treatments cause acute stress during application and may have incomplete efficacy leading to treatment repetition. Mechanical treatments using lasers (Stingray system) avoid chemical welfare impacts but cause handling stress. Cleaner fish — wrasse and lumpfish used as biological control agents — are often sourced from wild fisheries, transported, and housed in conditions causing high mortality, representing a significant secondary welfare concern. The intensity of sea lice pressure in open-net-pen farming creates chronic welfare compromise that closed containment systems can eliminate. Consumer demand for certified salmon products with sea lice management requirements in their standards is driving improvement in some markets.