Sea lice infestations in Atlantic salmon farms cause significant pain and tissue damage while requiring treatments that are themselves welfare-concerning; lice management is a central challenge in salmon aquaculture.
Sea lice represent a compounding welfare problem: the lice themselves cause tissue damage and immune suppression in infested fish, while chemical and mechanical treatments impose additional acute stressors. The welfare of wrasse cleaner fish — used as a biological control method — is often neglected, with high mortality from crowding, starvation, and disease in a species not adapted to pen conditions. A truly welfare-conscious salmon aquaculture industry must address lice management across all species involved.