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Effects of the Depth of the Pool in Pool-and-Weir Fishway on Migration Rate

Author(s): Kouki Onitsuka; Juichiro Akiyama; Saori Kuramoto; Koichiro Matsuda; Shohei Noguchi

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Keywords: Yu; Depth of the pool; Pool-and-weir fishway

Abstract: Fishways have been constructed to facilitate migration of fish past dams, waterfalls and rapids. The most of fishway in Japan is pool-and-weir fishway. One of the factors that influences on the migration rate in pool-and-weir fishway is the depth of the pool. Kubota pointed out that the migration rate of iwana was high when streamwise pool length was twice the length of iwana. Hayashida pointed out that swimming behavior depended on the flow patterns in the pool, and that it was important to design the pool length and depth to make the migration rates high. However, there is little information of the effects of the depth of the pool on migration rate. In this study, the depth of the pool in a pool-and-weir fishway was changed 0.2, 0.4, 0.6, and 0.8 m, and the discharge in each depth was changed 3,5, 7,9, and 11 l/sec in each depth. Pool-and-weir fishway that is connected three wooden pools that pool length L x =0.9m, width of pool B=0.8m, height from pool bottom to top of notch H t =0.9m, height from pool bottom to bottom of notch H u =0.7m, thickness of notchΔx=0.2m and headΔy=0.15m was used. The migration rates of ayu (Plecoglossus altivelis altivelis) were obtained with the aid of two sets of digital video cameras. The number of used fish is 50. Velocity measurements were conducted with a 3-D electromagnetic current meter. It was found that the migration rates of ayu took the highest value when the depth in a pool-and-weir fishway was 0.2 and0.4 m, and the migration rates were high in any depth when discharge was 5 l/sec.


Year: 2012

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