The slaughter of farmed fish involves welfare challenges that are only beginning to receive regulatory attention, with most commercial methods causing prolonged stress and potential suffering before death.
The welfare case for improving fish slaughter rests on the same science that establishes fish sentience generally. Live chilling in ice slurry - used for billions of fish annually - does not cause rapid insensibility; fish remain responsive to stimuli for over 10 minutes in ice slurry in some species. Suffocation in air causes prolonged asphyxia in fully conscious fish. CO2 stunning causes aversive gill irritation before insensibility. These methods, applied to the enormous numbers of fish killed annually, represent a welfare problem of staggering scale if fish can experience suffering. Percussive stunning and electrical stunning cause near-instantaneous insensibility - the technology exists, but economic barriers slow adoption.