Stocking density in fish aquaculture is the single most influential management variable affecting welfare, with crowding causing documented physiological and behavioral harm.
Fish crowding is both a welfare harm and a biosecurity risk — dense populations spread disease more rapidly and require more antibiotic treatment. The economic argument for welfare-positive density reduction is strengthened by the disease and productivity losses from overcrowding. Certifying schemes that require density documentation enable consumer preference to drive market incentives for welfare improvement.