Slaughter methods for farmed salmon vary widely in their welfare implications, with stunning effectiveness determining the quality of the fish final moments.
Salmon slaughter welfare is an area where the gap between best practice and common practice remains significant, and where the aggregate welfare impact of improvement would be enormous given the hundreds of millions of individuals involved. The welfare science is reasonably clear: percussive stunning applied correctly renders fish unconscious rapidly and is the gold standard. CO2 stunning causes distress before loss of consciousness and is inferior on welfare grounds. Live chilling causes prolonged cold stress in conscious fish and should be replaced. The challenge is industrial: slaughter lines operating at high speed under economic pressure are not conducive to careful welfare practice, and the invisibility of fish suffering means that consumer and regulatory pressure has been slower to develop than for terrestrial species.