Yohei Iiguni

Effects of Transmitted Light and Bubbles in Open-Channel Flows on Fish Behaviors

Fish sometimes enters into an intake gate of dams. Some techniques with electricity, transmitted light and air bubbles have been developed to avoid fish from the intake gate. However, a lot of fisheries co-operative associations pointed out that most of such techniques have no effect. In this study, the color types of transmitted light are changed at both sides of a rectangular water tank and swimming area of Zacco platypus are observed. Further, the air bubbles are injected from the channel bottom and trajectories of fish are observed.

Effects of Notch Ratio on Migration Rate in Pool-And-Weir Fishways

Most of fishways constructed beside of weirs and dams in Japanese rivers belong to pool-and-weir type. Usually, a notch is placed at the weir. Ministry of Land, Infrastructure and Transport recommends that the ratio between the notch width and fishway one set in the range between 0.17 and 0.20 without any verification. In this study, the notch ratio in pool-and-weir fishway was changed in the range between 0.1 and 0.7 and migration rates of the ayu, Plecoglossus altivelis altivelis, were obtained with the aid of two sets of digital video cameras. Further, three components velocities were measured with a 3-D electromagnetic current meter.

Flow Stability in Pool-and-Weir Fishways, Plunging and Streaming Flows

In Japanese rivers, there are many river constructions, i.e., dams, weirs, drops, for the purpose of flood control. Fishways are river constructions which facilitate migration of fish past dams and weirs. There are a lot of fishway types such as pool-and-weir type, stream type, operation type and so on (see Nakamura, 1995). The pool-and-weir fishway is typical type in Japanese rivers. There are three types of flow regimes in pool-and-weir fishways such as a plunging flow, streaming flow and intermixed flow of plunging and streaming flows. Rajaratnam et al. (1988) proposed a prediction formula of these flow regimes. However, this formula has no physical meaning. Further the accuracy of formula is not high. In this study, the criterion formula, which can predict the flow regime in the pool-and-weir fishway, is suggested semi-theoretically. The experiments were conducted with changing the aspect ratio and discharge in the pool-and-weir fishway. The water surface profiles were measured with a point gauge and also two components velocities were measured with a 2-D electromagnetic current meter. A new criterion formula, which is able to predict the flow formation, is proposed.© 2007 ASME