Sea lice infestations cause significant welfare harm to farmed Atlantic salmon. Genetic approaches to resistance are emerging as a long-term welfare solution alongside treatment improvements.
Sea lice welfare harm is multi-layered: the infestation itself causes direct tissue damage and pain; treatments cause additional handling stress; and stressed fish have reduced immune function that compounds their vulnerability. Genetic resistance breeding offers the prospect of a welfare solution that eliminates the harm without repeated stressful interventions. Cleaner fish welfare (wrasse and lumpfish used to eat lice) adds a further species-level welfare consideration - their welfare requirements are significant and often inadequately met on farms.