Sea lice infestations are the primary welfare and economic challenge in Atlantic salmon aquaculture, and integrated pest management approaches offer welfare benefits over chemical treatments alone.
Sea lice cause chronic welfare harm through direct tissue damage, pain associated with lesions, and the secondary stress of chemical treatments. Fish treated with chemical baths show elevated cortisol, altered swimming behavior, and reduced feeding for days post-treatment. Integrated pest management approaches that combine lice monitoring thresholds, biological control, physical barriers, and selective use of treatments represent the welfare-optimal strategy. The welfare of cleaner fish used in biological control is an emerging concern, requiring adequate nutrition, refuge provision, and protection from salmon predation.