Rainbow trout are among the most extensively farmed fish globally, and the methods used to slaughter them vary widely in their welfare implications, from acceptable to severely poor.
The welfare of rainbow trout at slaughter varies enormously across production systems. Carbon dioxide, despite its widespread use, is aversive and distressing for fish, which detect it as an acidifying agent and show escape behaviour and air-gasping before losing consciousness. This method fails basic welfare criteria yet remains standard practice in many operations. Electrical stunning systems that cause immediate loss of consciousness are available and affordable for commercial trout operations, but adoption has been slow without regulatory requirements. Consumer and retail pressure for humane slaughter standards, combined with certification schemes that require electrical or percussive stunning, represent the most effective pathway to welfare improvement for this large farmed fish population.