Methods to create aquatic environment with self sustenance on biotope functions under flooding

本研究的目的是建立日本宫崎县五濑河一部分北河中濒临灭绝的甲壳类动物，特别是日本大甲虫的保护方法。获得的结果包括科学基础结果和保护方法。科学基本结果如下：1）研究了日本甲壳虫的生命周期。为了使鉴定幼虫的种类成为可能，应用了基因技术。幼虫并未从河口转运至海洋；2)研究了日本竹节虫的抗性和偏好特性，并利用其结果对幼虫的转运进行了数值模拟。结果，日本石竹幼虫集中在盐楔上游端周围；3）日本石竹幼虫有点嗜盐，但成虫则不然。利用这一特性来减少幼虫被冲入海洋的情况； 4) D. japonicas 与其他竞争物种共享空间，例如 Sesarmops intermedium。生存空间可能存在重叠，但未发现严重竞争。保护粳稻的方法如下：5)人工水池对粳稻成虫的保护有效；洪水之下。泥沙输送，特别是沙子的输送，对粳稻造成严重损害。

The purpose of this study is to establish conservation methods of endangered species of crustaceans, especially Dairatonotus japonicas in the River Kita, a part of the River Gokase, Miyazaki Prefecture, Japan.The results obtained consist of scientifically basic ones and methods to conserve it.Scientifically basic results are as follows :1) The life cycle of D. japonicas is investigated. In order to make identifying species of larvae possible, a gene technology was applied. The larvae were not transported to the ocean from the estuary ;2) Characteristics of D. japonicas on resistance and preference ware investigated and by using its results, the transport of the larvae was numerically simulated. As a result, larvae of D. japonicas are concentrated around the upstream end of the salt wedge ;3) The larvae of D. japonicas are sort of halophilic, but the adults are, however, not. This characteristics are utilized to reduce washout of the larvae to the ocean ; and4) D. japonicas shares space with other competitive species, such as Sesarmops intermedium. Overlap of the living space may happen, but severe competition was not found.Methods to conserve D. japonicas are as follows:5) Artificial pools are effective to protect adults of D. japonicas; under flooding. Sediment transport, especially sand takes place severe damage to D. japonicas.