Design method of environment in rivers with self-repairing functions in habitat

为了保护日本环境省资料较少的一种小蟹——日本代龙蟹（Deiratonotus japonicus），我们在日本宫崎市谷川河水系北川对代龙蟹的现存数量和偏好进行了实地调查。自2002年以来，这一数字从350万下降到2005年的最低水平5万，之后略有增加。这似乎是由于自然波动，但捕食。我们利用生境评价程序调查了它们在河流中的偏好和行为特征。成虫喜欢直径10-15毫米、盐度高的大卵石。另一方面，它们的动物适应低盐度。光照强度没有变化趋势。从卵到幼体，有时到s型桡足动物的magalopa，它们的出血试验成功了。幼体喜欢高盐度，而成体则相反。为了使它们稳定地放血直到巨蛹，我们还需要进一步的工作来选择诱饵。我们还尝试用基因技术鉴定甲壳类动物的种类。壳的污染在分析上造成了严重的问题，因此必须考虑新的技术来避免污染。建立了一种模拟水流和盐度输运的新模型。利用它，分析了其动物的运动。因此，根据它们的偏好，估计它们存在于盐楔顶部附近。由于河流形态是盐楔顶部位置与沉积物大小关系的关键，因此我们必须注意河流的设计。

For the preservation of Deiratonotus japonicus, a small crab, which is a kind of less data species by Ministry of Environment, Japan, we conducted field surveys on the existing number and preference of it in the Kita River in the Gokase River System, Miyazaki, Japan. They had been decreasing from 3.5 millions since 2002 and hit the lowest, 50 thousands in 2005, and then slightly increases as of yet;. This seems due to natural fluctuation, but predation.We utilized the Habitat Evaluation Procedure for investigating their preference and characteristics on behavior in the river. Their adults prefer rather large pebbles with 10-15mm in diameter and high salinity. On the other hand, their zoeas do low salinity. No tendency was found on light intensity.Their bleeding was tried and succeeded in it from egg to zoea and sometimes to magalopa with S-type copepoda Its zoeas prefer high salinity, on the other hand its adults do opposite. In order to bleed them stably until megalopa, we need further work to choose baits.We also tried to identify the species of crustacean by use of a gene technique. Contamination by shell caused severe problems on analysis, so that we must consider new techniques to avoid contamination.A new model to simulate flow and salinity transport was developed. By using it, the movement of its zoeas were analyzed. As a result of it, its zoeas were estimated that they exist around the top of the salt wedge based on their preference. Because river morphology is a key in the relationship between the location of the top of the salt wedge and the size of deposits, we have to pay attention on the design of the river.