Sea lice are the most significant health challenge in salmon aquaculture, and treatment methods have major welfare implications.
Sea lice represent a welfare crisis embedded in the standard model of open-net pen salmon farming. The parasites themselves cause tissue damage, secondary infection, and severe stress; the treatments used to control them — chemical, thermal, and mechanical — carry significant welfare costs of their own. Hydrogen peroxide bath treatments cause respiratory distress; thermal delousing burns fish when temperature control fails; mechanical brushing causes physical trauma. Cleaner fish represent a more welfare-positive biological control strategy but also raise welfare questions about the cleaner fish themselves. Systemic solutions — closed containment, selective breeding for resistance, and RAS — address sea lice at the source rather than treating consequences.