Sea lice are parasites that cause significant welfare harm to farmed salmon, and management approaches vary widely in their own welfare implications and effectiveness.
Sea lice management is one of the most complex welfare challenges in salmon aquaculture because the treatments themselves cause welfare impacts. Chemical bath treatments stress fish; mechanical removal systems can cause physical injury; freshwater immersion causes acute stress. The most welfare-positive approach is prevention through low-stocking density, strong fish immune systems, physical barriers, and selective use of cleaner fish. When treatment is unavoidable, careful selection and implementation of the least stressful effective option minimizes welfare harm. Transparency about sea lice burden and treatment methods is increasingly required by responsible retailers.