Sea lice are the greatest welfare and economic challenge in salmon aquaculture. Treatment methods themselves cause significant stress and injury to farmed salmon.
Salmon lice management creates a welfare dilemma: the lice themselves cause chronic pain and immune suppression, while the treatments involve acute stressors including handling, temperature shock, or chemical exposure. Thermal delousing at 34C kills lice but causes thermal stress to salmon; pressure-based mechanical separation causes physical injury including descaling. Cleaner fish — often wild-caught or poorly reared — suffer high mortality in lice removal roles. The search for treatment methods that minimize both lice-caused and treatment-caused welfare impacts is one of the most active areas of applied aquaculture welfare research.