The method of killing farmed fish at slaughter has major welfare implications; many conventional methods fail to produce rapid insensibility, causing significant suffering in enormous numbers of animals.
Aquaculture slaughter welfare is an area where the gap between best practice and common practice has enormous welfare implications given the numbers involved. Asphyxiation in air, one of the most common slaughter methods globally, involves prolonged consciousness and distress as fish experience the physiological crisis of hypoxia. Research shows fish can remain conscious for 10 minutes or more under these conditions. Ice slurry immersion causes cold stress before insensibility and its timeline to unconsciousness is species-dependent. The gold-standard methods, percussion stunning followed by immediate brain destruction or electrical stunning with immediate killing, produce near-instantaneous insensibility and are commercially feasible at scale. The Humane Slaughter Association and equivalent bodies in other countries provide guidance on fish slaughter that, if implemented, would dramatically reduce suffering at this final stage.