Stocking density in salmon aquaculture is a fundamental determinant of fish welfare. Overcrowding causes chronic stress, increases disease susceptibility, and leads to aggression and injury.
Stocking density is among the most straightforward welfare variables to regulate in aquaculture — and among the most frequently compromised for economic reasons. The relationship between crowding and stress is well-documented: above certain thresholds, cortisol rises, immune function falls, aggression increases, and feeding behavior is disrupted. The welfare costs of chronic crowding are real and accumulate over the months-long grow-out period. Regulatory maximum densities exist in some jurisdictions but are often set at levels that welfare science suggests are too high. Consumer pressure through certification choices creates economic incentives for lower-density production.