Disease management in rainbow trout aquaculture has direct welfare implications for hundreds of millions of fish annually.
Trout disease management is a welfare domain where prevention is both more effective and more welfare-positive than treatment. Mass mortality events, while dramatic, represent the end stage of welfare failures that began with disease exposure and chronic stress. The shift to vaccination over antibiotic treatment in progressive aquaculture systems represents a significant welfare improvement, reducing antibiotic selection pressure while protecting fish from disease. Behavioral monitoring for early disease detection — recognizing changes in swimming pattern, aggregation behavior, and feeding response — enables faster intervention that reduces suffering duration. Water quality management that supports immune function is foundational to disease prevention.