Specimens were collected at 14 points of the.Japan Sea off Tottori Prefecture almost once a month over period from April, 1964, to November, 1965. The farthest point of the fourteen was located 28.0 kilometers off the shore. The specimens consisted of 657 water samples collected from zero-, ten-, and fifty-meter strata of the sea water and 209 plankton samples harvested from a vertical depth of water of 30 meters. They were examined for the presence or absence of
Vibrio parahaemolyticus.
1. The organism was detected from 61 water and 11 plankton samples, or from 8.3 per cent of the total specimens.
2. The distribution of the organism was higher in such points as located 10.1 to 28.0 kilometers off the shore than in points 2.7 to 8.7 kilometers far from the shore.
3. The organism was detected principally during a period from May to September of the year.
4. Frequency of detection was the highest in the water samples collected from the ten-meter stratum and the lowest in those from the fifty-meter one of all the water samples from the three strata.
5. When analyzed from chlorine ion concentration, the rate of detection was high from the sea water at a concentration of 17.1 to 17.5 per mille, moderate from that at 17.6 to 18.0 per mille, and low from that at 18.1 to 19.5 per mille.
6. Of the 72 strains isolated, 18 strains (25.0 percent) were classified into biotype 1 and the remaining 54 into biotype 2.
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