Sea lice are the most significant health challenge in Atlantic salmon farming. The treatments used to control them carry their own welfare costs, creating a difficult management challenge.
Sea lice management involves an unavoidable welfare trade-off: untreated lice cause chronic suffering through skin damage and immune suppression; treatments cause acute stress and sometimes mortality. Thermal treatments in particular can cause scale loss, fin damage, and internal bleeding when improperly calibrated. Cleaner fish welfare is a largely unaddressed issue — wrasse are removed from complex wild reef environments and placed in salmon cages with no species-appropriate enrichment. Genetic selection for lice resistance, vaccines, and closed-containment farming offer routes out of this cycle but require sustained investment. Minimizing chemical and mechanical treatment frequency while maintaining low lice burdens requires careful, site-specific management.