Sea lice infestation is the most significant welfare and production challenge in Atlantic salmon farming, with treatments including chemical, mechanical, and biological approaches that each carry welfare implications.
Sea lice management in salmon farming creates welfare challenges at multiple levels. The lice themselves cause tissue damage, pain, and chronic stress in infested fish. Treatment interventions — whether chemical, thermal, mechanical, or biological — impose additional acute welfare costs. Mechanical treatments like thermolicer (warm water bathing) can cause stress and injury including gill damage when poorly calibrated. Laser-based delicing systems reduce handling stress but require validation of efficacy and safety for fish welfare. Cleaner fish used for biological control face their own severe welfare challenges in salmon cage environments, including exposure to sea lice chemicals, difficulty accessing food, and high mortality rates. The integrated management of sea lice at good welfare standards for all species involved remains an unsolved challenge for the salmon farming industry.