改修された農業排水路における小型魚の移動について

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A peak runoff into an agricultural drainage channel around outskirts of cities often becomes larger and keener according with urbanization of its catchment. Then, the channel would be improved to convey increased runoff water smoothly downstream. It is, however, difficult to enlarge its cross-section and/or raise its embankment, because residential area spreads close to it in such a case. The only way left to this situation is to apply concrete lining so as to make the velocity faster. Additionally, eco-friendly works like fish pools and fish habitat blocks are required and also actually introduced with such improvement works in order not to damage the ecosystem in it. However, even if fish pools are introduced, they are located every several hundreds meters discretely in the channel. While the flow in the fish pools is calm enough for fishes to stay and live in, the velocity of flow in every reach between the pools might be too large to migrate through it. In this research migration of two kinds of small fishes, i.e., Pseudorasbora parve and Squalidus chankaensis sp. in the Ooe agricultural drainage channel that has been under improvement are investigated using fluorescent ink and RAPD markers. The following results are obtained; 1) Velocity in improved reaches is too large for small fishes to migrate, especially migrate upstream; 2) Migration is often taken during non-irrigation period. It might mean decrease of the discharge due to a kind of water management is an important and indispensable factor of the ecosystem dynamics; 3) There are several genetic types of Pseudorasbora parve in a single channel and the distribution of the types are dominated by hydraulic conditions.
日本雨水資源化システム学会の論文

改修された農業排水路における小型魚の移動について

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