Salmon Crowding Stress During Harvest and Slaughter

Pre-slaughter crowding of farmed Atlantic salmon causes acute stress and welfare harm - understanding and mitigating this is a priority for aquaculture welfare.

Key Facts

Farmed Atlantic salmon are harvested by crowding fish with nets before pumping to kill boats
Crowding triggers acute cortisol stress response measurable in plasma within minutes
Stress impairs fish welfare and negatively affects flesh quality and fillet colour
Optimal crowding protocols include minimising crowding duration, avoiding crowding in warm water
Electrical stunning (AQUI-S or Sterilair systems) followed by cerebral spiking is considered best practice
Some farms use CO2 anaesthesia which is aversive - fish show avoidance behaviour

Welfare Considerations

Pre-slaughter handling is a major welfare bottleneck in salmon farming. Fish experiencing acute crowding stress show physiological and behavioural indicators of suffering - elevated cortisol, opercular rate changes, abnormal swimming behaviour. The welfare cost of poor pre-slaughter procedures is substantial given the scale of salmon production (hundreds of millions of fish annually). Industry leaders are increasingly adopting electrical stunning protocols and minimising crowding duration. Consumer pressure and welfare certification schemes drive further improvement.

What You Can Do

Choose salmon certified to RSPCA Assured or equivalent welfare standards covering slaughter practices
Reduce farmed salmon consumption where possible
Support aquaculture welfare organisations pushing for improved slaughter standards
Engage with retailers about their salmon supplier welfare requirements
Advocate for mandatory welfare-positive slaughter requirements in aquaculture regulation
Follow developments in fish welfare science and aquaculture best practice