The duration of pre-slaughter crowding in salmon is one of the most important but least visible welfare variables. Longer crowding times cause progressive welfare deterioration.
Pre-slaughter crowding duration is a welfare variable that is almost entirely invisible to consumers but enormously important to fish welfare. Salmon crowded for hours in depleted oxygen experience physiological stress, physical injury from collisions, and compromised immune function. The welfare cost is directly proportional to duration - every additional hour of crowding represents additional suffering. Systemic improvements requiring maximum crowding durations, better coordination between harvest vessels and processing plants, and weather contingency protocols could significantly reduce crowding-related welfare harm at scale.