Rainbow trout are one of the most widely farmed fish species, but bacterial and viral diseases cause significant welfare harm and economic loss in aquaculture systems worldwide.
Disease management in trout farming is directly linked to welfare: sick fish suffer from the disease process itself, and treatment often involves additional stressors like crowding and bathing. Prevention through biosecurity, vaccination, and good husbandry protects welfare better than treatment. The relationship between welfare and disease is bidirectional - stressed fish get sick more easily, and sick fish are stressed. High-welfare husbandry that minimises crowding, maintains water quality, and reduces handling stress is also good disease prevention.