Sea pen salmon farming can achieve better welfare outcomes through improvements to stocking density, sea lice management, and slaughter methods while maintaining commercial viability.
Sea pen salmon welfare encompasses multiple interconnected challenges. Sea lice are perhaps the most significant welfare problem, causing painful skin lesions and immune compromise. The treatments for lice — including warm water baths, laser systems, and chemical treatments — all carry welfare costs requiring careful calibration. Stocking density management must balance commercial profitability against chronic stress from crowding. The welfare of cleaner fish used for lice control is frequently overlooked; wrasse and lumpfish mortality rates in commercial pens are extremely high and largely unregulated. A whole-system welfare approach addressing density, lice management, cleaner fish welfare, and slaughter simultaneously would deliver the greatest improvements.