Pre-slaughter stunning is critical for salmon welfare. Different stunning methods vary greatly in their humaneness, and improvement in industry practice is ongoing.
Slaughter represents the final welfare moment in a farmed salmon life and has historically received insufficient attention. CO2 narcosis, which involves immersing fish in carbon dioxide-saturated water, causes up to 4 minutes of distress before unconsciousness and remains in widespread use despite poor welfare outcomes. The contrast with well-applied percussive or electrical stunning, which achieves effective unconsciousness in seconds, is stark. Industry transition away from CO2 stunning has been driven by certification scheme requirements, regulatory change in Norway, and retailer procurement standards. Pre-slaughter crowding and pump transfer also impose welfare costs that can be reduced through refined handling practices. Consumer and retailer demand for products from better-welfare slaughter systems is a key driver of change in this sector.