How crowding, transport, and handling during salmon harvest causes welfare harm, and evidence-based interventions to reduce pre-slaughter stress in farmed salmon.
The pre-harvest period in salmon aquaculture represents a critical welfare bottleneck: fish that may have been maintained at acceptable welfare standards throughout production are subjected to a cascade of acute stressors in the final hours of their lives that cause enormous suffering at scale. Crowding operations expose fish to the combined stressors of dramatically reduced space, competition, and hypoxia. Pump transfer subjects fish to water velocity, pressure changes, and physical trauma. Live chilling in ice slurry without prior stunning means conscious fish experience progressive cold-induced immobilization — a process that takes many minutes and does not reliably cause unconsciousness before pain capacity is lost. Percussion stunning, properly applied, achieves near-instantaneous unconsciousness with appropriate confirmation of effectiveness, but operator training and equipment maintenance are critical to consistent welfare outcomes. The regulatory and industry movement toward mandatory stunning before slaughter in salmon — progressing through Norwegian, Scottish, and other major producing country regulations — represents one of the most impactful welfare improvements available in aquaculture given the billions of fish affected annually.