The river improvement effects on endangered freshwater fishes and plants of the upper reach of The Muko-River, Hyogo Prefecture, Japan.

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Upper reach of the Muko-River is high-biodiversity reach inhabited by many species of endangered freshwater plants and animals. This point is characterized by low altitude and low gradient of stream bed, so this area show tendency of sandy-mad accumulation on stream bed like as lower reach of other streams. In the same time, this stream character arise frequent flood caused by high deposition rate of sandy-mad. The Hyogo Prefecture river section began the river improvement that centered on the soil excavation of the riverbed and the riverside in the Muko-River upstream region to achieve the flood control target of 1/2 probabilities in 2003.A physical impact by this river improvement aims at the influence given to a endangered freshwater fish that lives in this area and it has aimed to understand the influence of the river improvement by monitoring a long term, and to present the reduction plan of the influence in addition. After 2003 doing the test excavation in the first, the fish cro … More wd to this change is continuously analyzing the investigation how it reacts until 2009 as the transition of a physical, environmental condition such as depth and the bottom sediments in the standard investigation section.The width of the river channel, depth, and the flow velocity distribution are made monotonous by digging, an especially deep point disappears, and the area of the mud bottom has reduced. These habitat elements have not returned completely at point that eight years passed after it digs up the examination. White and brown bitterling, Acheilognathus tabira and Tnanakia limbata, having misgivings for fishes captured by the trap net corresponding to this, especially keep decreasing capture number from 2005 continuing to 2009 though it increased once why in 2003/2004.In this river improvement, if the river channel section made to flow as the water level of planned high water was safe was able to be secured, the deep pool and the meander reach that set up the obstacle in the river channel. Local deep pool, the revival of the shelter that accompanies it, and the reproduction of the sedimentary environment are expected centering on the meander point and the obstacle it. However, an original state of habitat-mosaic to bring up various aquatic animals and plants might not be created again in this river improvement method making the constant river bed gradients by such a long distance. Less