Net pen salmon farming involves welfare challenges from sea lice, crowding, and disease, with significant welfare improvements possible through better management and technology.
Net pen salmon welfare is characterized by a persistent sea lice welfare problem that has defied resolution despite decades of effort. Salmon with heavy sea lice burdens experience tissue damage equivalent to serious wounds on their heads - painful open lesions that impair feeding and immune function. Chemical treatment causes acute stress and disorientation during application. The fundamental challenge is the open-water environment that exposes fish to wild sea lice from surrounding waters. Land-based closed containment systems solve the sea lice problem entirely but face economic viability challenges. The welfare pressure from sea lice has driven significant technological innovation.