Pre-slaughter stunning of farmed salmon is now required in several jurisdictions, representing a major welfare advance for the billions of fish killed in aquaculture annually.
Unstunned salmon bled into ice slurry take minutes to lose consciousness while experiencing the physiological distress of blood loss. The evidence for fish pain and stress means this is not a trivial welfare concern at a scale of hundreds of millions of animals. Proper percussive or electrical stunning provides instantaneous unconsciousness before killing - a meaningful welfare improvement that is technically straightforward. The adoption of stunning requirements by Norway and the UK demonstrates that industry transition is feasible at commercial scale.