Effective stunning before fish slaughter is the most important single welfare intervention at the end of a farmed fish's life. Methods vary enormously in welfare outcome, and the evidence base for species-specific efficacy is growing rapidly.
The welfare significance of slaughter stunning cannot be overstated: the few minutes between stunning and death represent the welfare ceiling for millions of individual fish per day. Poorly applied or absent stunning means fish experience the full aversiveness of being removed from water, handled, and bled while conscious. Electrical stunning, when correctly calibrated for species size and conductivity, produces immediate insensibility — the most humane commercially feasible method for most species. The principal barriers to adoption are cost of equipment, training requirements, and the complexity of maintaining calibration across varying fish sizes within a production batch. Welfare certification schemes that mandate effective stunning for specific species, with third-party audit, are the most reliable mechanism for closing the gap between best practice and typical commercial reality.