How farmed salmon are stunned before slaughter has significant welfare implications for billions of fish annually. Evidence-based stunning methods can dramatically reduce suffering at the end of life.
Pre-slaughter salmon welfare is a frontier where the scale of impact is enormous and the improvement potential is significant. The choice of stunning method matters greatly: CO2 narcosis, while widely used due to its scalability, exposes fish to what evidence suggests is an aversive experience before unconsciousness — fish show escape behaviour and opercular movements indicating distress during the CO2 exposure period. Percussive stunning, when correctly applied, renders fish unconscious within milliseconds. Electrical stunning is effective but technically more demanding. The challenge for the industry is scaling welfare-positive stunning methods to the industrial volumes involved — Norwegian facilities handling hundreds of thousands of fish per day. Investment in automated percussion and electrical stunning systems is increasing, driven partly by welfare certification requirements from key export markets.