EFFECTS OF AIR BUBBLES ON PLECOGLOSSUS ALTIVELIS ALTIVELIS AND NIPPONOCYPRIS TEMMINKII BEHAVIOR

摘要

Fish sometimes enter into an intake gate of weirs and dams, so that a lot of released larval ayuand salmon are lost. Some techniques with air bubbles, electricity and transmitted light havebeen developed to avoid fi sh from the intake gate. However, a lot of fi sheries co-operativeassociations pointed out that most of such techniques have no effect. Generally, it is knownthat fi sh avoid the area which has air bubbles. In this study, the air bubbles are injected fromthe pool bottom and trajectories of fi sh are observed. It was found that air bubbles almostdo not effect on the swimming behavior of ayu, but they effect on the swimming behavior ofkawamutsu. With the increase of air quantity, kawamutsu swim to avoid the bubble area andalso their swimming distance and speed increase when they swim in the bubble area.