Sea lice are ectoparasites that cause significant suffering in farmed salmon and threaten wild salmon populations. Management strategies range from chemical treatments to biological controls with varying welfare implications.
Sea lice represent a major welfare burden for farmed Atlantic salmon. Heavy infestations cause tissue damage, osmoregulatory disruption, and secondary bacterial infections that cause chronic suffering. Treatments are themselves welfare-compromising — bath treatments cause acute stress responses, and mechanical treatments like hydrolicer can cause physical injury. Cleaner fish used for biological control — particularly lumpfish — are often kept in poor conditions with high mortality, trading one welfare problem for another. The most welfare-positive solution is the transition to closed containment systems that eliminate sea lice exposure, but this requires significant capital investment and changes to industry structure.