Author(s): Kouki Onitsuka; Juichiro Akiyama; Bin Shiraoka; Kazuya Mihara; Hikaru Takeuchi
Keywords: Rest; Ordinary and dark muscle; Open-channel flow; Swimming behavior
Abstract: Takamizu (2007) showed two things in the open-channel and actual river. First, it was good for the fish behavior that the hydraulic functions of pile dyke is made of thinned wood. Second, the pile dyke has the effect of the reduction of velocity. 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. A circular wire net of 0.25m in diameter is set up 3m downstream from upstream edge and isolate Nipponocypris temminckii is inserted. After it is confirmed that the Nipponocypris temminckii settled down, the circular wire net is taken up. Further, trajectory of Nipponocypris temminckii was recorded with a digital video camera set up the above of the open-channel. 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 decreases with an increase of velocity, because the total time of the rest increases 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.