Sea lice infestations are one of the most significant welfare problems in farmed Atlantic salmon, causing tissue damage, behavioral changes, and stress that require careful management with welfare-conscious treatment choices.
Sea lice represent one of the most serious welfare problems in salmon aquaculture, combining the chronic discomfort of tissue damage with the acute stress of treatment interventions. Affected fish show behavioral changes including reduced feeding, abnormal swimming, and increased aggression, all consistent with chronic pain states. The treatment dilemma is that many effective interventions, including chemical baths and mechanical delousing, are themselves welfare-compromising events. The most welfare-positive approach to lice management combines preventive strategies through site selection and fallowing with biological controls using cleaner fish, minimizing the need for acute treatment events. Cleaner fish welfare itself requires attention, as wrasse and lumpfish have their own significant welfare needs that are not always well met on salmon farms.