Fish are typically killed by methods that would be unacceptable for other vertebrates. Evidence-based humane slaughter methods can significantly reduce fish suffering at the point of death.
The slaughter of farmed fish in most commercial operations involves methods that cause prolonged suffering. Live chilling in ice slurry causes fish to remain conscious in severe cold-induced distress for up to 20 minutes before losing consciousness. CO2 euthanasia causes distress through acidification of blood. Neither is acceptable by the standards applied to other farmed vertebrates. Effective alternatives exist: electrical stunning renders fish immediately insensible; percussion stunning is effective for larger species; ike jime achieves instantaneous death. The welfare case for mandatory humane slaughter of farmed fish is equivalent to that for other farmed vertebrates.