Effective stunning before slaughter is one of the most important welfare interventions available for farmed fish. Understanding the methods, their efficacy, and the gaps in current practice is essential for improving fish slaughter welfare.
Fish slaughter welfare is one of the areas where the gap between scientific evidence and commercial practice is most pronounced. The capacity of fish to experience pain and distress is now supported by strong scientific evidence, yet the majority of commercially harvested fish worldwide — both wild-caught and farmed — are killed without any attempt at stunning. For farmed fish in regulated markets, stunning is increasingly required but implementation quality varies enormously: unstunned fish that regain consciousness during bleed-out, poorly calibrated electrical stunning that paralyses without rendering unconscious, and aversive CO2 methods that cause distress before narcosis all represent welfare failures within nominally compliant systems. The challenge is that effective stunning at commercial scale requires both appropriate equipment and trained, motivated staff. Economic incentives — where slaughter speed is prioritised over welfare quality — can undermine the welfare benefits of even well-designed stunning systems. Consumer demand for welfare-assured fish products and regulatory enforcement of stunning efficacy standards are the primary levers for improvement.