This research was carried  out to  study  genetic  diversity of ampicillin-resistant Vibrio  from
various  stages of tiger  shrimp larvae  (Penaeus Monodon) development from,Tambak Inti Rakyat
hatchery, near Labuan, West Java, Indonesia. A total of 25 ampicillin-resistant Vibrio isolates were
isolated using thiosulphate  citrate bile-salt  sucrose  agar (TCBS-Agar) and seawater  complete
agar (SWC-Agar). Physiological and biochemical characterization showed that the isolates could be
grouped into only two species, i.e. V. harveyi from the egg stage; and V. metschnikovii from larvae
and post-larval stage (i.e nauplius, zoea, mysis, PLi, PL5, PL,0, and PL,5). These isolates were also
present in their respective rearing water  of  each stage  and  some natural feed.  Schizotyping
analysis employing restriction endonuclease Noll (5'-GC4GGCCGC) indicated that the isolates
could be grouped into  at least  13 different  genotypes.  Therefore,  schizotyping  was  more
discriminative than physiological characterization. This study showed that particular groups of Vibrio
colonized all stages of shrimp larvae and demonstrated closed phylogenetic relationship. These groups
of Vibrio might be  the dominant microbiota which could suppress the development of other Vibrio
including the pathogenic Vibrio.