Disease prevention through vaccination and good husbandry is far more welfare-positive than reactive treatment in trout aquaculture, with significant advances in vaccine development.
Vaccinated trout experience brief handling stress at vaccination but are protected from diseases causing significantly more severe and prolonged welfare harm. The welfare calculus strongly favors vaccination over reactive antibiotic treatment. Stressed sick fish suffer before treatment is administered, while antibiotics cause additional welfare impacts. Disease prevention through biosecurity, husbandry quality, and vaccination represents the highest welfare-to-cost ratio interventions in trout aquaculture.