Crowding during management procedures — grading, harvesting, and treatment — is one of the most acute welfare events in salmon farming, causing severe physiological stress and injury.
Crowding is an unavoidable component of salmon farm management, but its welfare impact varies enormously with technique. Gentle pumping, minimum crowding duration, appropriate water temperature, and oxygen supplementation during crowding all reduce stress and injury. Operations that crowd rapidly, pump aggressively, and keep fish crowded for extended periods cause much greater welfare harm. Training operatives in welfare-conscious crowding techniques is one of the most impactful near-term welfare improvements in salmon aquaculture. Welfare protocols that specify maximum crowding density, duration, and pumping speed create enforceable standards for this high-impact procedure.