Sea lice infestation is one of the most significant welfare problems in Atlantic salmon aquaculture. The development of sea lice resistance and the welfare impact of treatments are key challenges for the industry.
Sea lice infestation and its treatments create a complex welfare problem with no simple solution. Untreated infestations cause chronic skin damage, immune activation, and debilitation - a direct welfare harm. Many treatments also impose welfare costs: hydrogen peroxide causes respiratory distress, thermal treatments cause acute thermal stress, and in-feed treatments may have side effects. Cleaner fish used to control lice have significant welfare needs including appropriate species-specific conditions, adequate shelter, and diet, but are frequently kept in conditions that cause high mortality. The development of genetic resistance offers the most promising welfare-positive long-term solution as it prevents infestation rather than treating it.