The hours immediately before slaughter are among the most welfare-significant in a farmed salmon's life. Crowding, air exposure, handling, and the slaughter method itself all carry significant welfare costs that evidence-based practices can reduce.
Pre-slaughter salmon welfare involves a cascade of stressors that compound each other. Crowding concentrates fish at high densities, causing oxygen depletion, physical injury from conspecific contact, and intense physiological stress. Pumping fish from cages to processing vessels causes additional trauma. On the kill floor, the time between first handling and effective insensibility determines the severity of the welfare insult. Methods that cause rapid, reliable unconsciousness with minimal aversion are demonstrably preferable. The transition from CO2 narcosis — which evidence suggests is aversive — to electrical or percussion stunning represents one of the most achievable and high-impact welfare improvements available to the salmon farming industry. Consumer and retailer pressure is increasingly driving this transition.