The hours before slaughter are among the most welfare-significant in a farmed salmon's life. Crowding, transfer, and stunning methods determine whether millions of fish die with or without significant suffering.
Pre-slaughter welfare for farmed salmon has received more attention than almost any other farmed fish welfare issue, driven by the scale of production and advocacy by organisations like Humane Society International and RSPCA. The key welfare intervention is electrical stunning — delivering current through water to render fish unconscious before gill cut or bleed-out. When correctly implemented, the time from full consciousness to unconsciousness is measured in milliseconds. CO2 stunning, still used in some Norwegian facilities, causes an aversive, distressing response before unconsciousness and should be phased out. Welfare-certified salmon products increasingly specify pre-slaughter stunning as a requirement, creating consumer-driven incentives for the entire industry.