Sea lice infestations are the leading welfare and economic challenge in Atlantic salmon farming, causing painful tissue damage and requiring treatments that themselves carry welfare costs.
Salmon with heavy sea lice infestations experience chronic pain from tissue lesions, impaired osmoregulation, and secondary bacterial infections. Treatment interventions carry their own welfare costs — thermal treatment causes acute thermal stress and elevates cortisol significantly. Wrasse used as cleaner fish suffer high mortality from salmon feed competition, inappropriate temperatures, and inadequate hiding structures. The welfare burden of sea lice management is a major unresolved challenge in salmon aquaculture that requires both better prevention and more welfare-conscious treatment protocols.