Sea lice infestations are the primary welfare and economic challenge in Atlantic salmon aquaculture. Managing lice while minimizing treatment welfare costs requires innovative integrated pest management approaches.
Sea lice infestations cause chronic suffering through mechanical tissue damage, immune stimulation, and the physiological stress of maintaining osmotic balance despite skin damage. Heavy infestations expose tissue and create pathways for secondary bacterial and fungal infections. Treatment methods themselves carry welfare costs: chemical bath treatments cause chemical stress; thermolicer treatment causes thermal burns to fin edges, eyes, and gills; and mechanical removal devices cause pressure injuries. The challenge is balancing infestation welfare costs against treatment welfare costs, while simultaneously managing wild fish welfare impacts from lice spillover. Biological control using cleaner fish (wrasse, lumpfish) offers a welfare-positive alternative when the cleaner fish themselves are well managed.