Nocardia seriolae , a gram‐positive branching filamentous bacterium, is the causative agent of fish nocardiosis. It mainly infects fish through gills, anus, lateral line or surface injury, resulting in a large number of white nodules in visceral organs and skin ulcerations. N. seriolae can infect about 42 species of fish and severely harm the aquaculture industry in many regions, particularly in Asia. Aiming to have a more com...