Abstract: The Xiangshan harbour is a typical aquaculture area in China. Vibrio is one of the most important pathogenic bacteria, which is the main cause of bacterial disease of marine fishes. In this study, seawater sample and fish (Pseudosciaena crocea) in the Xiangshan harbour aquaculture area were collected from Aug. to Nov., 2012. The number of Vibrio and total bacteria and the environmental parameters were monitored. Vibrio community structure changed significantly with time. Canonical correspondence analysis showed that temperature, TOC, PO3-4-P and NO-3-N were the most important environmental driver factors of the Vibrio community structure. The predominant bacteria of seawater sample and the fish were identified using 16S rDNA gene and rpoA gene. The result demonstrated that there was obvious difference between the cage-area and control area of Vibrio species component. The abundance of Vibrio harveyi increased suddenly when the fish disease outbreak occurred. Hence, the abundance of Vibrio harveyi can be an indicator of Xiangshan harbour fish illness. Moreover, Photobacterium angustum increased sharply as a result of antibiotic application after the outbreak.

Key words: Vibrio, community structure, fish diseases, environmental parameters