Immunisation studies on an emerging pathogen, Serratia marcescens were conducted in commercially important marine ornamental fish, Amphiprion sebae. In vivo experiments were conducted using formalin killed cells (bacterin) of S. marcescens in the 3 months old juveniles of A. sebae from the same brood. Bacterin was administered at the rate of 105 cells per gram body weight of fish which was the lethal dose estimated from pathogenicity studies carried out earlier. After 15, 30 and 50 days of administration of bacterin, experimental fish were subjected to challenge studies. The relative percentage survival (RPS) rendered by administration of bacterin increased after 15th day and 100% protection was achieved from challenge on 35th and 50th days. 

Serratia marcescens, Amphiprion sebae, immunisation, bacterin, relative percent survival (RPS)