The period immediately before slaughter is among the most stressful for farmed salmon. Crowding, air exposure, and poor stunning practices cause significant suffering that better protocols can reduce.
Pre-slaughter is a welfare crisis point in salmon farming. Fish that have been growing for 2-3 years experience their most acute suffering in the final hours of life. Crowding triggers physiological stress responses, depletes oxygen, and increases aggression and injury. Transfer via pumps and conveyors is mechanically traumatizing. The widespread use of CO2 stunning is particularly problematic: fish exposed to carbon dioxide show aversive avoidance behaviors and take 3-4 minutes to lose consciousness, a period of significant distress. Higher-welfare alternatives are available — percussive stunning renders fish immediately insensible — but industry adoption remains incomplete. Consumer and regulatory pressure is the most effective lever for change.