Rainbow trout are the most commonly farmed fish in the UK and Europe, and their slaughter welfare has received increasing attention as fish sentience research advances.
The welfare of fish at slaughter is an area where both scientific understanding and practical implementation have improved significantly. Properly applied percussive stunning - a firm blow to the top of the head - renders trout immediately insensible if done correctly, but requires skill and is difficult to scale for high-throughput operations. Automated percussive and electrical stunning systems improve consistency. Carbon dioxide, widely used in salmon but also trout farming, causes significant aversion and is not considered humane. The evidence base for fish pain and distress at slaughter is now sufficiently strong to justify mandatory humane slaughter requirements.