Current Continuity and Restoration of Process for Fish Habitat in Decreased Discharge

河流环境具有动态特性，通过流量的波动进行破坏和恢复的循环，典型的河流环境是由低水位到高水位的流量波动维持和形成的。根据新河的观测数据，估计栖息地变化和动植物繁盛状态的原因包括灌溉分布问题。并通过近40年的航拍资料对比，探讨了人为干扰对沙砾坝形态结构的影响。从而确定了与生境和动植物生长状况相关的宏观和微观形态尺度。利用温度数据测井系统对现场流动不连续区进行了局部观测。指出了水流不连续对河流生态系统的影响。“以自然为导向的河流作品展”在木索河的新酒井河支流下游300多米的河段建成。护脚工程采用天然材料和多孔混凝土砌块，并对传统的以自然为导向的方法，如稳定良好的抛石配木结构鹅卵石进行了试验施工。本文采用地形测量、水力测量和鱼类围捕等方法，对鱼类生境特征进行了研究。根据野外观测和估算结果，指出了以下几点：河道上游地形为单调的水平河线，底部坡度平缓。指出由于复杂的地形和植被覆盖，鱼类栖息地水流分布多样。水生鱼类主要分布在坡边剖面，以沟壑和水池为主；底栖鱼类主要分布在水田剖面，与滨水植物、沉水植物关系密切。研究了日本绒螯蟹（Eriocheir japonica）在长ara河口拦河坝的seseragi -鱼道内的定居和上游迁移。大鳞鱼幼虫在大鳞鱼道的上潮区定居并蜕变为蟹期。大鳞蝇幼虫主要在夏初（6月）和冬初（12月）定居。它们在7、8月份开始向上游的淡水地区迁徙。由于水温过低，大部分在冬季定居的幼虫无法存活并蜕变成蟹。由此可见，河口水温对日本绒螯蟹的生长和上游洄游具有强烈的影响。这种夏季和初冬两个高峰的定居模式反映了海洋中观测到的繁殖的时间格局。本研究阐明了塞塞拉吉-鱼道具有沉降和向上游迁移的功能，以补充河口带的减少。少

River environment is characterized as dynamic properties in which cycles of destruction and restoration through fluctuations in discharge, and typical river environment is maintained and formed by fluctuations in discharge ranging from low water to high water. It is estimated that causes of the changes of habitats and thriving state of fauna and flora based on observed data in the Neo-River where includes a irrigative distribution problem. Also, how morphological structure on gravel bars is changing under influence of human disturbances is discussed by comparing the aerial photograph data for forty years. As a result, macro and micro morphology scale related to habitats and thriving state of fauna and flora are defined. It is occurred partially to flow discontinuity zone in the site using temperature data logging system. It is pointed out that flow discontinuity impacts through river ecological system.The "nature-oriented river works exhibition" has been constructed at downstream reach … More for three hundreds meters in the Shin-Sakai River branch of the Kiso River. The foot-protection works are using of natural materials and the porous concrete blocks, and the traditional nature-oriented method such as the well-stabilized riprap with wooden-framed-cobbles are constructed experimentally. This study has been conducted to investigate characteristics of fish habitats using by topographical survey, hydraulic measurement and fish trappings. As results of the field observation and estimation, it is pointed out as follows. The topography of upstream reach from the calvert is monotonous horizontal river line with a gently bottom slope. It is pointed out that fish habitat have diversified flow distributions caused by complicated topography and vegetation cover. The nektonic fishes inhabited mainly in the slope side section and preferred to riffle and pool, while the benthonic inhabited mainly in the paddy field section and were closely related with riparian plants, submerged plants.Settlement and upstream migration in the Japanese mitten crab (Eriocheir japonica) was investigated in the Seseragi-fishway in the Nagara estuary barrage. Megalopa larvae settled and metamorphosed to crab stage in the upper tidal zone in the Seseragi-fishway. Settlement of megalopa larvae occurred mainly in early summer (June) and early winter (December). Their upstream migration to the freshwater area began in July and August. The majority of larvae that settled in winter did not survive and metamorphose to the crab stage due to low water temperatures. Thus, the growth and upstream migration of the Japanese mitten crab seemed to be strongly influenced by water temperature in the estuary. This mode of settlement with two peaks in summer and early winter reflected the temporal pattern of reproduction observed in the sea. In this study, it is clarified that the Seseragi-fishway have a function of settlement and upstream migration for supplement of decreased estuary zone. Less