River Improvement and Survey for Biota in view of Ecological Environment

Water resources engineering in Hirai River considering ecology has been put througth two years ago. We investigated phase of fishes, benthos in Hirai River before and after the river improvement.Summary of results is shown as follows. We found in decreasing two kinds of fishes during one year at most deep stream (=abyss), decreasing fishes was kinds of inhabit river bed, but the same a kinds of fish at rapids stream, and benthos was increasing at rapids stream more than abyss.