The welfare of farmed salmon at slaughter depends critically on the stunning method used — science demonstrates significant variation in effectiveness and humaneness.
The welfare of farmed fish at slaughter has historically received less attention than the welfare of terrestrial livestock, despite the enormous scale of the industry. Fish welfare science has established that salmon experience stress and likely pain during ineffective slaughter methods. Carbon dioxide immersion causes severe physiological stress responses including frantic swimming and rapid opercular beating before unconsciousness. Water-to-air asphyxiation imposes prolonged distress. Mechanical percussion stunning when properly calibrated produces immediate loss of consciousness with minimal distress. The challenge is ensuring consistent effectiveness across high-throughput commercial operations where quality control is difficult. Norway regulatory requirements demonstrate that welfare standards are achievable at scale.