Fish slaughter methods vary enormously in humaneness, with most commercial operations still using methods that cause prolonged suffering — but effective stunning technologies exist and are increasingly being adopted.
Fish slaughter welfare is one of the most tractable improvements available in aquaculture — the technology for humane stunning exists, has been validated, and is commercially deployed in some sectors. The welfare case for improving slaughter methods rests on evidence that fish respond to noxious stimuli with physiological and behavioural changes consistent with pain and distress: asphyxia in air causes gill movements, escape attempts, and elevated stress hormones that persist for many minutes. Transitioning to electrical or percussive stunning before exsanguination eliminates this prolonged suffering at a relatively modest capital cost. Consumer and retailer pressure for certified humane slaughter has driven adoption in the salmon sector; similar pressure could accelerate uptake across other farmed species.