Abstract
Fish has the ordinary and dark muscle. When fish uses ordinary muscle, fish gets tired. In such a situation, fish needs a rest. In this study, some spur dykes were established at both banks in open-channel flows and flow velocity was changed. The trajectories of Nipponocypris temminckii's were observed. It was found that the total time of the rest increases with an increase of aspect ratio and also velocity. The migration speed decrease with an increase of velocity, because the total time of the rest increase with an increase of velocity. After the rest, some fishes start to swim to the upstream and the other start to swim to the downstream.
