Aeromonas (A. hydrophila, A. salmonicida etc.) are well known as being Vibrio associated with food poisoning or diseases among humans, fish including ayu (sweetfish) and other animals. The summer in 1978, a large number of Ayu died of illness in the Ohta river.
At that time we examined and discussed the distribution of Aeromonas in the Ohta and Oda rivers.
1) Larger quantities of Aeromonas were distributed in algae which are Ayu and other fishes food than in the surface water itself.
2) The distribution of the Aeromonas depended on the water temperature largely. In 80% of the algae tested, the number of Aeromonas was 10^3 cells per ml in the temperature range of over 27°C. This number decreased gradually as the temperature decreased.
3) The decreasing tendency of Aeromonas was notable in the surface water. The number of Aeromonas per ml was less than 10 cells in the temperature range of below 20°C.
4) The haemolytic activity of the isolated Aeromonas also depended on the water temperature. Especially, in the temperature range, of over 29°C, 60-80% of the isolated Aeromonas had strong haemolytic activity which is connected with the cause of food poisoning or diseases among humans, fish and other snimals.
5) However, as the temperature decreased, the isolated Aeromonas had weak haemolytic activity. Still others had no haemolytic activity increased tendencies.