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

摘要本研究旨在探讨日本宫崎县谷濑河段北河中濒危甲壳类物种的保护方法，特别是日本虾蛄。所得结果包括科学的基本结论和保存方法。科学基础研究结果如下：1)研究了日本田鼠的生活史。为了使鉴定幼虫种类成为可能，应用了基因技术。幼虫没有从河口被运送到海洋；2)调查了日本吉吉虫的抗性和偏好特征，并利用其结果对日本吉吉虫幼虫的迁移进行了数值模拟。结果表明，日本夜蛾幼虫主要集中在盐楔上游；3)日本纹夜蛾幼虫有一定的嗜盐性，而成虫则不嗜盐。利用这一特性可以减少幼虫被冲到海洋中；4)与其他竞争物种（如Sesarmops intermedium）共享空间。生活空间可能会出现重叠，但没有发现激烈的竞争。养护日本仓鼠的方法如下：5)人工水池对日本仓鼠成虫的保护效果较好；在洪水。泥沙输运，尤其是沙粒输运，对日本金针菇的危害较大。

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.