Hundreds of billions of farmed fish are killed annually using methods that may cause significant suffering if fish are sentient.
Fish slaughtered by asphyxiation on ice or in CO2 take up to 10 minutes to lose consciousness, during which they experience hypoxia and potentially significant distress. Given emerging evidence of fish sentience and pain, these methods may cause enormous suffering at extraordinary scale. Percussive stunning followed by gill cutting is more humane but rarely used commercially.