Abstract
The water includes turbidity during and after the flood. Almost fish uses eyes and lateral line during swimming, so that the turbidity may effect on the swimming behavior of school of fish. However, there are few study on relations between the turbidity and swimming behavior of school of fish. In this study, the swimming behaviors of school of ayu, Plecoglossus altivelis altivelis, by changing turbidity and the number of fish in static water, were recorded with a digital video camera. It was found that the fish school is divided to some fish school with an increase of turbidity. This is because ayu can not find the other individual by view due to turbidity. In addition, the distance between each ayu and school of fish radius decrease with an increase of turbidity.
