Gill disease is one of the most significant welfare and production challenges in Atlantic salmon aquaculture. Multiple pathogens and environmental factors combine to cause chronic respiratory distress.
Gill disease causes respiratory distress - the fish equivalent of breathing difficulty. Salmon with severely compromised gills must work harder to extract oxygen from the water, causing exhaustion and reducing all other activities. The treatments themselves carry welfare costs: freshwater baths, hydrogen peroxide treatments and mechanical lice removal all cause acute handling stress. Managing gill health requires a systems approach - reducing crowding, optimising water quality, timing treatments appropriately and investing in genetic resistance. The welfare case for gill health investment aligns directly with the production case, but prevention is far less costly to both than treating established disease.