A major bottleneck to the projected expansion of the aquaculture industry is disease outbreaks caused by bacterial pathogens. Fish diseases caused by Flavobacterium pathogens are persistent in salmonid aquaculture, and treatment is limited to antimicrobials, which contaminate the aquatic environment and promote antimicrobial resistance. Bacteriophages (phages) are viruses that naturally kill bacteria, and Flavobacterium ‐infec...