Abstract
Fishways have been constructed to facilitate migration of fish past dams, waterfalls and rapids. Wada pointed out that the migration rate of ayu (Plecoglossus altivelis altivelis) was high value when the depth of the pool in a pool-and-weir fishway was shallow. However, in this study, the discharge is fixed. Therefore the influence of the discharge change is not taken into consideration. And the cause of the migration is ambiguous.
In this study, the depth of the pool in a pool-and-weir fishway was changed 0.2, 0.4, 0.6, and 0.8m, and the discharge in each depth was changed 3, 5, 7, 9, and 11 l/s. The migration rates of ayu (Plecoglossus altivelis altivelis) were obtained with the aid of two sets of digital video cameras. It was found that the migration rates of ayu take the maximum value when the depth in a pool-and-weir fishway is in the range of 0.2-0.4 m. However the migration rate is low when discharge is a few, or large. And it was found that the migration rates of ayu is high when the fish's angle has gathered.
