The slaughter of farmed fish is one of the most significant and least-regulated welfare issues in food production — affecting tens of billions of fish annually with inadequate welfare standards.
Fish slaughter welfare is perhaps the most significant unresolved welfare issue in animal agriculture by number of individuals affected. Tens of billions of fish are killed annually by methods that cause potentially prolonged suffering — CO2 narcosis is aversive, ice slurry causes gradual hypothermia, and live chilling means fish remain conscious. The technology for humane slaughter exists: electrical stunning followed by rapid killing. The barrier is economic and regulatory — investment in stunning equipment and mandatory standards are needed to drive adoption at scale. This is one of the highest-priority welfare improvements available.