Rainbow trout slaughter welfare has improved significantly in some markets through adoption of percussive and electrical stunning, but conventional live CO2 narcosis remains widespread.
Trout slaughter welfare progress has been driven by retailer certification requirements in welfare-conscious markets. The shift from CO2 narcosis, which causes an aversive drowning-like experience before insensibility, to percussive or electrical stunning represents a significant welfare improvement for individual fish. Quality-conscious producers have adopted humane slaughter partly for welfare reasons and partly because stressed fish show reduced fillet quality, aligning commercial and welfare incentives. Extending these welfare improvements to all farmed trout globally requires both certification pressure from premium markets and regulatory requirements in larger volume markets.