The present survey was undertaken to investigate the distribution of Vibrio parahaemolyticus (FUJINO et al. 1951) SAKAZAKI et al. 1963 in the Seto Inland Sea in summer. The survey was carried out aboard the Toyoshio-maru, research vessel of Hiroshima University, in the eastern part of the Sea in September of 1963, and in the western part in September of 1964. The location of sampling stations is shown in Fig. 1 and Table 1.
A selective liquid medium was prepared with 3% NaCI containing arabinose ethyl-violet broth as described by HoRIE et aJ. 4 ) and a BTB teepol agar medium was used to detect the bacteria according to the official method10 ) of the Japanese Ministry of Health and Welfare.
Biotype I organisms (abbreviated I in Tables 2 and 3) of the bacterium, being believed to cause acute gastro-enteritis to man, were found to be widely distributed in Osaka Bay, Harima-nada, Mizushima-nada, and the southern part of Suo-nada as seen in Table 2.
As listed in Table 3, moreover, biotype I was isolated at high ratio from sandy sea bottom. Biotype 2 (abbreviated II in the Tables) was isolated from extensive areas of the Sea and irrespective of the depths from the surface. An allied species (abbreviated III in the Tables) was felt to constitute considerable proportions in both sea water and sea bottom.
In so far as this survey was concerned, the distribution of the bacteria had no relation to the values of such oceanographic properties as chlorinity, dissolved oxygen, or temperature.