Brackish Lake Shinji, Japan, has been designated for conservation efforts by the Law Concerning Special Measures for the Conservation of Lake Water Quality. Although the amount of loads flowing into this lake is decreasing, the chemical oxygen demand （COD） is increasing in this lake. To determine the cause of the increase of COD, we applied a multiple regression analysis using the environmental factors that might affect COD of lake water. By multiple regression analysis, only Chl-a concentration was extracted as a factor influencing the COD concentration. And extracted as a factor influencing the Chl-a concentration were taking out by fishing and TP concentration. COD concentration and Chl-a concentration decrease of the catch of Corbicula japonica was suggested to be most effective on the increase of COD and Chl-a in lake water. Reduce of the nutrient loads to the lake has been regarded as the primary measure to decrease COD in the lake. However, COD and Chl-a removal from the system as the fishery of Corbicula japonica has improved the lake water quality. It is, therefore, necessary to consider the influence of the food web and material flow in the ecosystems to effectively manage and conserve the water quality of lakes.

To determine the suitable sites and timing for temporary relocation toward land readjustment, the growth, survival, and disappearance of three species of lotic freshwater unionid mussels were investigated for two years after pilot relocation. Higher growth and survival and lower disappearance of the relocated mussels were observed in the irrigation pond, indicating that this is the most suitable site for relocation. Higher growth, survival, and disappearance were observed in the branch canal, indicating that the branch canal can be used as a relocation site if prevention measures are taken against hydraulic displacement of mussels. In the main canal, mussel growth was limited and showed lower disappearance but lower survival, indicating that the main canal is the least suitable relocation site. However, appropriate flow management can facilitate mussel relocation to the maincanal. Higher growth and mortality were observed in the warm season （May-October） and higher displacement in the typhoon season （August-October）, suggesting that mussel relocation should be implemented in winter. General recommendations for temporary relocation of lotic mussels are also suggested based on our results.

We analyzed whether the relationship between population density and urban land use rate differs depending on the region by the third mesh unit. When calculating the number of urban meshes based on population density and land use criteria, the number of urban meshes based on population density criteria was slightly larger than the number based on criteria of land use in many prefectures. However, in Hokkaido, there was atendency that the number of urban mesh is small with criteria based on population density. Pearsonʼs correlation coefficients between population density and urban land use rate were calculated for each prefecture, and as a result, a high value of 0.82 on average wasobtained, but relatively low values of around 0.6 were obtained in Hokkaido and Iwateprefecture. We analyzed whether these differences influence the prediction model of the number of woody plants in Kanto district and Hokkaido. Population density was estimated as a significant variable in the prediction model of Kanto district, but in the Hokkaido the opposite result to the Kanto model was obtained. When population density and urban land use rate are used as an index of urbanization, it will be necessary to recognize that therelationship has regional differences.

To clarify movement patterns of freshwater fish inhabiting restoration areas in agricultural channels in relation to effectiveness for fish conservation, we conducted fish samplings at five study stations with different types of restoration method (wooden raft walkway, fish nursery blocks, and deep water) in an agricultural channel (areas that did not dry-up even in the non-irrigation period), southern Okayama, western Japan in July and October 2014 and January, July, October and December 2015. In the samplings,we carried out mark recapture investigations on six fish species (Carassius sp., Tanakia limbata, Acheilognathus rhombeus, Candidia sieboldii, Misgurnus anguillicaudatus and Odontobutis obscura) to evaluate the habitat utilization and seasonal movement within the restoration areas. In the restoration areas, we recaptured 133 marked fish individualsincluding all six species during the investigation period. Of the fish, 114 and 19 individuals were recaptured at the same and different study stations where the fish were released,respectively, indicating that many fish individuals continuously inhabit the same restoration area. These results indicate that the restoration areas can provide suitable habitats for fish in this study channel.

The Wada Biotope in the town of Takahama in Fukui Prefecture, Japan was developed for the purpose of creating various wetlands environments, i.e., a freshwater pond, a brackish pond and paddy fields. As a result of a physical environmental survey after the Biotopeʼs development, salt water moved up to the brackish pond and did not run up to the freshwater pond. As a result of a fish survey after the Biotopeʼs development, freshwater fishes, marine fishes and amphidromous fishes were captured in the brackish pond. Thus, freshwater fishes, marine fishes and amphidromous fishes coexisted in one biotope. Challenges for the future are: (1) establishing ex-ante and ex-post assessment systems, regular monitoring, and adaptive management for the biotope development project, and (2) enabling Oryzias sakaizumii to overwinter in the freshwater pond with the introduction of a year-round water flow from the Katama River to the freshwater pond.

Discharge and water quality were measured during times of normal flow and flooding for eleven years, from 2006-2016 in Kochi River, Wakasa Town, Fukui Prefecture, Japan. Results revealed that both inorganic matter （soil particles） and organic matter （phytoplankton, nitrogen compounds and phosphorus compounds） flowed down in large amounts during flooding compared to normal flow. Organic and inorganic matters generally flow down the upper, middle and lower stream areas and are finally supplied to Obama Bay, an area of enclosed coastal seas. To investigate the influence of the Kochigawa Damon the downstream river and Obama Bay, future challenges include: (1) carrying out adischarge observation and water quality analysis before and after the dam; and (2)monitoring the sediment load to the dam.