海域に流入する農業水路における淡水魚類の遡上と分布について

抄録

  Upstream migration and distribution of freshwater fishes are investigated in the lower reach of an agricultural canal flowing into the sea. The survey on upstream migration was conducted using two fixed nets installed at the drop structure nearest to the sea and the distribution survey was carried out using a cast net and two scrape nets in the basins and downstream areas of 19 drop structures including structures of groundsill, a vertical drop, multistep drops, and an inverted drop. During the surveys, a total of 1,136 freshwater fish belonging to 4 orders, 8 families and 17 species were captured by two fix nets, a cast net and two scrape nets. The distribution survey revealed that ayu, Plecoglossus altivelis altivelis, loach, Misgurnus anguillicaudatus and Japanese dace, Triborodon hakonensis were broadly distributed within the study area. Conversely, the habitats of Ayukake, Cottus kazika and Kajika, Cottus sp. were limited to the area near the sea and the growth of these fishes were inhibited in such a simplified habitat within the concrete flume.