Sea lice are parasitic copepods that cause significant welfare harm to farmed salmon and pose a conservation threat to wild salmon populations. Developing effective, humane management strategies is one of the most pressing challenges in salmon aquaculture.
Sea lice management involves a genuine welfare conflict: chemical treatments reduce lice burden on farmed fish but cause acute stress, and some treatments also harm non-target crustaceans in the environment. Physical treatments including thermal and freshwater baths cause brief but significant acute stress. Cleaner fish used as biological controls face their own welfare challenges — wrasse in particular experience high mortality rates in salmon farms. The most welfare-positive approach involves integrated pest management that minimises all treatment events through prevention (site selection, stocking density, snorkel systems) rather than reactive treatment. Welfare-positive lice management is also better for sustainability and wild salmon conservation.