The final stages of Atlantic salmon production involve crowding, pump transfer and killing that impose severe welfare costs. Pre-slaughter welfare is a critical and often overlooked component of farmed salmon welfare.
Pre-slaughter crowding of Atlantic salmon causes acute physiological stress that represents a significant welfare cost even when slaughter is subsequently humane. Crowded fish show rapid cortisol elevation, scale loss from contact with each other and the net, and physical injury from the pump transfer process. Fish that enter the slaughter facility already highly stressed from crowding may show poorer stunning effectiveness. The cumulative welfare burden of a harvest process that begins with crowding, continues through pumping, and ends with a stunning and killing procedure means that the welfare cost of the final hours of a farmed salmon's life can be substantial even on well-managed farms.