To establish an appropriate measure for the prevention of food poisoning from raw fish flesh (sashimi), distribution and population density of Vibrio vulnificus were investigated as environmental factors were changed. The bacteria were detected only in August during the study period from February to November, 1989. The number of bacteria was $2.0~6.0/100ml$. In August, salinity and pH were low, but water temperature and COD were high as compared to the rest of months.