Sea lice infestations are a major welfare and production problem in Atlantic salmon aquaculture, requiring integrated management to protect fish health.
Sea lice management in salmon aquaculture illustrates the welfare complexity of disease control in intensive aquaculture. The lice themselves cause welfare harm through tissue damage and physiological stress — heavy infestations produce wounds comparable to severe dermatological disease in vertebrate terms. The treatments — chemical, mechanical, thermal, and biological — also carry welfare costs, ranging from drug-induced stress to physical injury from mechanical removal systems. The welfare calculus requires choosing between the harm of uncontrolled infestation and the harm of each treatment modality. This is further complicated by resistance development that has reduced the efficacy of pharmacological options, requiring more frequent or higher-intensity treatments. Integrated lice management combining biological controls, strategic treatment, and genetic selection for lice resistance represents current best practice from both welfare and sustainability perspectives.