Sea lice treatments for Atlantic salmon include thermal, fresh water, and chemical options with markedly different welfare profiles that are increasingly evaluated by regulators.
Sea lice treatment welfare for salmon is a complex and increasingly studied area. Thermal treatments using hot water cause acute stress and can cause serious injuries including cataracts and internal haemorrhage if water temperature or exposure duration is poorly controlled. Hydrolicer systems combining fresh and warm water are considered more welfare-positive when properly operated. Chemical bath treatments cause acute stress during crowding and bathing operations. Cleaner fish use avoids chemical and thermal treatment stress for salmon but raises welfare questions about the cleaner fish themselves, which are often housed in poor conditions. The welfare of each treatment option must be evaluated against the welfare cost of the sea lice infestation it treats.