Aquaculture Slaughter Methods and Fish Welfare

The method used to kill fish at harvest is one of the most significant determinants of fish welfare in aquaculture. Current practices vary widely, and many standard methods cause prolonged suffering.

Key Facts

CO2 stunning — the most common method globally — causes aversion, distress, and a prolonged unconscious state before death in many species.
Electrical stunning followed by percussive killing is among the most humane methods currently available for farmed fish.
The RSPCA Assured standard requires that Atlantic salmon are stunned before slaughter using percussive or electrical methods.
Studies using brain activity (EEG) show that CO2 immersion does not render fish insensible rapidly; pain-related processing continues.
Norway, a leading salmon producer, has legislated requirements for effective pre-slaughter stunning.

Welfare Considerations

The scale of aquaculture slaughter is enormous — hundreds of billions of fish are farmed and killed annually. This makes slaughter method one of the highest-impact welfare interventions in the food system. Methods that cause prolonged suffering, such as CO2 narcosis, live chilling in ice water, or asphyxiation in air, remain widespread because they are cheap and convenient. Transitioning to humane slaughter methods requires investment in technology and regulatory will — but the welfare returns, measured in reduced suffering across a massive population, are correspondingly large.

What You Can Do

Choose seafood certified under welfare-conscious schemes that require humane slaughter (e.g. RSPCA Assured, ASC with welfare module).
Support organizations working to improve fish welfare standards in aquaculture.
Advocate for government regulation requiring effective pre-slaughter stunning for farmed fish.
Reduce consumption of farmed fish species raised in systems with no welfare oversight.