EFFECTS OF ENTRANCE LENGTH OF SIDE-POCKET IN OPEN CHANNEL FLOW ON EVACUATION BEHAVIOUR OF ZACCO PLATYPUS IN FLOODS

Abstract

 In the environmental field of river, there is a problem that evacuation space for fish is scant. By previous investigation, it is figured out that fish evacuate to the low velocity zone. But the relationship between evacuation behavior and river structure is not fully elucidated. The porpose of this study is to make clear that geometric structure of effective wando which is important as a evacuation space. Side-pocket was set up and the entrance length of it was methodically changed. The swimming behaviors of Zacco Platypus (Oikawa) in floods were recorded with digital video camera. Changes in behavior doe to the difference of the entrance length were investigated. It is found that Zacco Platypus aggressively evacuated when the entrance length was 8 times longer than Zacco Platypus.