The period immediately before slaughter is critical for fish welfare. Crowding, handling, and stunning methods all affect the level of suffering fish experience.
Fish slaughter methods vary enormously in their welfare implications. Asphyxiation in air, commonly used for tilapia and carp, can take 4-15 minutes to cause unconsciousness during which fish experience severe distress. CO2 stunning, while used widely, causes aversive effects during induction similar to carbon dioxide's aversive properties in mammals. Best practice involves rapid percussive stunning or electrical stunning to immediate unconsciousness followed by immediate killing. Consumer demand for welfare-certified products is beginning to drive meaningful improvements as certification schemes develop fish-specific welfare standards.