Abstract
It is important to secure the rest area for fish. Fish has the ordinary and dark muscle. When fish uses ordinary muscle, fish got tired. In such a situation, fish needs a rest. In this study, rest characteristic of ayu (Plecglossus altivelis altivelis) with changing the width and the number of interception was researched. The migration rates of ayu were obtained with the aid of a digital video camera. It was found that the migration speed increased with an increase of flow velocity, because ayu swim in keeping with flow velocity for prevent to be drift towards downstream. The total time of the rest increases with an increase of flow velocity.
