The river network is one of the key functions for maintaining riverine biodiversity. However, the location of most restoration projects was determined by only the site scaleʼs biodiversity status. Additionally, although the effect of large river restoration projects was often well assessed, most small stream restorations have been conducted without monitoring. In this study, to provide information for restoration prioritization, we clarified the influence of stream connectivity and stream restoration on the α and β diversity of freshwater fish based on the samples obtained from 21 small streams belonging to 1st to 3rd-order streams in Tokachi river, central Hokkaido, Japan. Here, we hypothesized that (a) small stream restoration could increase α diversity particularly at high connectivity stream, and (b) β diversity would increase at a lower connectivity stream but will be not changed by restoration. Results revealed that high α diversity was supported by restoration and proximity to the mainstem. Additionally, α diversity was higher at restoration sites (characterized by various stream widths and max water depth) than at non-restoration sites. In contrast, although β diversity was negatively influenced by dIIC, we could not find any relationship between restoration status (restored or not). Our results suggested that restoration sites should be selected based on the interaction of conservation target (α diversity or β diversity) and spatial position within stream network. For instance, small stream restoration nearby mainstem is a priority to conserve α diversity of freshwater fish. Additionally, given our results that stream restoration increased α diversity regardless of habitat connectivity and had no effect on β diversity, restoration at low-connectivity streams (i.e. high β diversity stream) may contribute to both α and β diversity conservation.

We conducted a systematic review of literatures on biodiversity in retarding basins to grasp the status of knowledge regarding effects of constructions and managements of them on biodiversity. Six taxonomic groups (birds, amphibians, fish, insects, shellfish, and plants) were included in the review to examine multi-taxonomic responses. Totally 9,183 literatures were reviewed, and 242 were selected for this systematic review. The total number of sites in the selected literature was 33, which cover only 22 ％ of the number of retarding basins in Japan. Birds were reported most frequently (94) whereas amphibians were most scarce (6). For all the taxa, reports on the occurrence of rare species or invasive species, and new record of species distribution, were common. Only 15 studies were based on the BACI design, suggesting a lack of scientific knowledge regarding biodiversity assessments in retarding basins. Thus, we could not fully clarify the effects of retarding basins on biodiversity. However, some studies suggested that the artificial disturbances, wetland creation, vegetation management, and soil excavation, had positive effects on many taxa.

The RTK-UAV survey has evaluated only a limited number of sediment excavation cases in a project governing the status of the natural environment in the habitat of endangered species. Therefore, this study focused on excavation projects carried out by the Civil Engineering Office, which was designed to be instrumental in preserving endangered species. The project site was situated along the A River, which traverses B area. To effectively evaluate the general condition of the extent of sediment excavation performed by the RTK-UAV, DSMs were created from images captured using the RTK-UAV in September 2021 and August 2022. Differential analyses between the two time periods were performed. Vegetation height was determined from the DSM and ortho-images, and the vegetation volume was calculated based on estimates. After subtracting the vegetation deposition from the channel excavation volume, the excavated sediment volume was found to be 8,851.08 m³. The local governmentʼs calculated volume of the excavated sediment (approximately 8,332 m³) agrees with the obtained result. Thus, the potential of RTK-UAV in estimating excavated sediment volume is promising and can be used for large-scale projects.

Pond drying, which has continued as a management method to maintain reservoir functions, improves reductive conditions of bottom sediment, and maintains the reservoir water quality thereby conserving and improving the aquatic habitats. Nevertheless, water discharged from reservoirs contains bottom sediments that cause turbidity, contributing to the downstream pollution load. Here, we monitored the runoff water quality in a reservoir that was pond dried after eight years. During the final stages of pond draining, turbidity increased, with COD temporarily exceeding 1,000 mg L^－1, TN of 200 mg L^－1, and TP of 7 mg L^－1. The total COD, TN, and TP loads were, 284.4 kg, 44.4 kg, and 1.5 kg, respectively, for the 12-hr period of increased turbidity. The NO₃-N concentration increased, before increase in turbidity, and remained high after the operation. This may be attributed to reduced reductive conditions at the pond bottom resulting in suppressed denitrification. Correspondingly, previously inhabited bivalves were not observed, possibly due to the progression of reductive conditions at the pond bottom caused due to the absence of pond drying for eight years.

Many construction works in aquatic environments, such as pile driving, directly induce vibrations into the riverbed. Although benthic animals may be affected by these vibration, their impacts have not been adequately considered during construction works. This study aimed to examine mitigation measures for the rare bivalve species, Nodularia nipponensis, during pile driving activities in their habitat vicinity. Vibrations were measured on the riverbed near the construction site, and laboratory experiments were performed to understand the responses of N. nipponensis under different vibration acceleration levels and frequencies in a controlled environment. Long-term effects of continuous vibration exposure (33 days) were also examined. We found that the vibration threshold for N. nipponensis was within the vibration acceleration level of 80 to 90 dB, with strong reactions observed around frequencies of 40 Hz and 100 Hz. Considering the vibrations generated during pile driving (85 dB and 20-80 Hz at 5 meters from the source), it was inferred that individuals near the vibratory hammer were likely to respond to the vibrations during pile driving. In the long-term experiment with continuous vibration exposure, no significant difference in wet weight change was observed between the vibration-stimulated group and the non-stimulated group. Our results suggest that N. nipponensis responds to intermittent vibrations but not to continuous ones and that frequent intermittent vibration exposure may cause longer shell closure periods, potentially resulting in adverse effects on their growth. Therefore, vibratory-type machinery should be selected to reduce the impact of pile driving on N. nipponensis.

We investigated the potential of small pools on the sides of forest roads in the Shonai region of northeastern Japan as breeding habitats for the near threatened species Tohoku salamander (Hynobius lichenatus). We surveyed the presence of egg sacs of the salamander in pools from April to June 2022. The relationships between the number of egg sac pairs and environmental factors were analyzed using a Zero-inflated negative binomial model (ZINB). Furthermore, we conducted a population survey of the salamanders in pools where egg sacs were found during August to September 2022 before the metamorphosis of larvae, to determine their survival to larval stage at the egg-laying sites. Egg sacs were detected in 85 out of 250 surveyed pools, suggesting that pools on the sides of forest roads are used as egg-laying sites by the salamanders. The ZINB analysis revealed positive correlation of number of egg sacs with litter availability, water depth, low number of Japanese fire-bellied newts, proximity to forest, and lack of road pavement. Of the surveyed pools where egg sacs were identified, 75 were further examined for the presence of larvae and larvae were found at 20 sites. This suggests that larvae could not survive at many egg-laying sites on the sides of forest roads.

In Japan, animal experimentation is defined as the use of animals for educational, experimental research or production of biological products, or for other scientific purposes. The implementation system for animal experiments is based on the laws and regulations that have been revised or issued by 2006, such as the Act on Welfare and Management of Animals (Ministry of the Environment), Standards relating to the Care and Keeping and Reducing Pain of Laboratory Animals (Ministry of the Environment), Fundamental Guide-lines for Proper Conduct of Animal Experiment and Related Activities in Academic Research Institutions (Ministry of Education, Culture, Sports, Science and Technology), and Guidelines for the Proper Conduct of Animal Experiments (Science Council of Japan), etc. An institutional management system was established in which the head of the institution is ultimately responsible for the proper conduct of animal experiments, and the implementing institution prepares institutional regulations and conducts animal experiments in an appropriate manner. The framework of this institutional management is as follows: the researcher is responsible for planning and carrying out the experiment in consideration of animal welfare in order for the researcher to conduct free and creative scientific research; the head of the implementing institution should establish institutional regulations for animal experiments, set up an animal experiment committee, approve the animal experiment plan, and take necessary measures for the proper implementation of the animal experiment plan, such as monitoring the results of the animal experiment plan. The head of the implementing institution is responsible for the proper implementation of the animal experiment, as stated in the following: the head of the institution is responsible for the planning of the animal experiment plan and the execution of the experiment, and the head of the implementing institution is responsible for the planning of the animal experiment plan and the execution of the animal experiment. At universities, research institutes, and other institutions that conduct animal experiments, animal experiment plans are reviewed for appropriateness by the institutionʼs animal experiment committee under the aforementioned laws and regulations as well as the rules of the conducting institution, and animal experiments are conducted after receiving approval from the head of the institution. Often, experiments using wild animals other than laboratory animals or experiments conducted at locations other than animal experiment facilities are also applied for. The Animal Experiment Committee, which examines such plans, collects relevant information, and carries out various procedures and innovations to ensure the proper implementation of experiments that differ from those using laboratory animals or at animal experiment facilities. This paper presents examples of experiment plans consulted to the Education and Training Committee in charge of the Council for Animal Experimentation Facilities of National University Corporation (Kokudokyo), as well as examples of experiment plans at Niigata University. Specifically, (1) as examples of cases received by the ″Anything Goes Consultation Room″ of the Education and Training Committee of the National Association of University Animal Experimentation Institutes, responses to cases such as research using wild animals that were subject to capture of harmful birds and animals, and (2) research using seabirds (Black-tailed gull) living in the domestic ocean and research using the Japanese striped snakes living on islands as cases from Niigata University will be introduced.