The method of slaughter for farmed fish determines whether the animal loses consciousness rapidly or experiences a prolonged period of distress. Improving slaughter methods is one of the highest-impact welfare interventions available in aquaculture.
Fish slaughter welfare sits at the intersection of scale and scientific uncertainty. The evidence that many fish species are sentient is sufficient to generate serious moral concern about slaughter methods that may cause prolonged distress. Ice slurry chilling — one of the most widely used methods — produces a slow decline in consciousness during which fish actively attempt to escape, suggesting they experience the process as aversive. Electrical stunning produces rapid unconsciousness and is considered more humane, but requires capital investment and maintenance. The welfare case for transitioning from ice slurry to electrical or percussion stunning is strong, and the transition is economically feasible as demonstrated by the salmon industry in Norway and Scotland where electrical stunning is increasingly standard.