On Thursday, July 31, 2025, 22 members of the Komaki Neighborhood Association participated in a guided tour of the Institute for Freshwater Biology. The visit began with a presentation by Professor Hiroshi Hakoyama on the institute’s initiatives and ecological research in the Chikuma River. In the second half of the visit, the group toured the facility. The weather was relatively cool, making it an ideal day for observing the outdoor research areas.
On July 26 and 27, 2025, Dr. Takeru Kodama from the Institute of Freshwater Biology, Nagano University, was interviewed by KBC Kyushu Asahi Broadcasting. In the segment, he shared insights from his student research and provided commentary on the ecology of cicadas in various natural habitats across Fukuoka Prefecture, including parks, mountains, and mountain streams.
The feature will be aired on KBC’s evening news and lifestyle program “Gyutto” on July 28, 2025.
Nagano University’s Institute of Freshwater Biology and the Iio Laboratory at Shinshu University’s Faculty of Engineering have launched a collaborative study to analyze the swimming cost of eels using a newly developed flow-through chamber. This study is part of a research project supported by the Eel International Resource Unit of the Fisheries Agency of Japan, which focuses on tracking downstream-migrating eels using satellite tags.
The primary aim of the research is to investigate the effects of satellite tag attachment on eels and quantify the energetic cost of swimming. By observing the behavior of eels swimming in the flow-through chamber while equipped with satellite tags, researchers will be able to examine patterns of tag detachment as well as potential medium- to long-term impacts on swimming behavior.
On July 25, 2025, Associate Professor Shoichiro Iio and his team from Shinshu University visited the Institute to install the newly developed flow-through chamber and conduct preliminary swim tests with eels.
The satellite tagging project is led by the Institute of Freshwater Biology at Nagano University and conducted in collaboration with Kyushu University, Shinshu University, Miyazaki Prefecture, and Kumamoto Prefecture, under the support of the Eel International Resource Unit of the Fisheries Agency.
Contact:
Institute of Freshwater Biology, Nagano University
Email: ifb@nagano.ac.jp
Phone: +81-268-22-0594
Contact person: Hiroshi Hakoyama
A new research article by Dr. Huỳnh Quang Thiện and colleagues of the Institute of Freshwater Biology has been published in the international journal Check List.
The study reports new findings on the distribution of freshwater fish in central Vietnam, including the southernmost known occurrence of the genus Pseudohemiculter and a new locality record of P. dispar within the country.
These discoveries contribute significantly to our understanding of fish biodiversity in central Vietnam and are expected to inform future conservation efforts and aquatic resource management in the region.
Citation
Ty Minh Nguyen, Xuan Bach Nguyen-Le, and Thien Quang Huynh
On the southernmost record of fish genus Pseudohemiculter Nichols & Pope, 1927 and new record of P. dispar (Peters, 1881) (Cypriniformes, Xenocyprididae) from Phu Yen Province, Vietnam. Check List, 21(4): 666.
DOI: https://doi.org/10.15560/21.4.666
On Sunday, July 13, 2025, the 3rd “Lake Nojiri Waterside Creature Observation Event” was held on the beach in front of Green Sports Club (GSC) by Lake Nojiri, organized by Professor Emeritus Masaru Tanaka (Kyoto University) and others. Professor Hiroshi Hakoyama of the Institute of Freshwater Biology, Nagano University, joined as a special guest.
Participants, numbering several dozen, learned about the creatures inhabiting the lakeside by identifying Japanese eels (Anguilla japonica), dace (Tribolodon hakonensis), and other species collected during the event, while also enjoying water play. Lake Nojiri is known as a place where released Japanese eels grow to large sizes.
On Saturday, July 12, 2025, from 13:30 to 16:30, a public symposium titled “Symposium on Exploring the ‘Feelings’ of Eels in Lake Nojiri” was held at Shinano Town Community Hall, organized by the Nojiri Highland University Village (Director: Professor Emeritus Masaru Tanaka, Kyoto University). Professor Hiroshi Hakoyama of the Institute of Freshwater Biology, Nagano University, delivered a lecture titled “Spawning Migration Tracking of the Japanese Eel.”
The symposium attracted nearly 80 participants, with three invited speakers presenting on a variety of topics related to the conservation and management of Japanese eel resources.
Lecture 1: High School Students’ Challenge to Restore Eel Resources with an Eye on Forests, Rivers, and the Sea
Shinji Koba (Teacher and One Health Club Advisor, Fukuoka Prefectural Yamakado High School)
Lecture 2: Spawning Migration Tracking of the Japanese Eel
Hiroshi Hakoyama (Professor and Director, Institute of Freshwater Biology, Nagano University)
Lecture 3: Thinking about Lake Nojiri from the Eel’s Perspective: What is Environmental DNA Analysis?
Satoshi Kameyama (Principal Researcher, National Institute for Environmental Studies)
Discussion and Open Forum
Why the Japanese Eel? Why Lake Nojiri?
Facilitated by Masaru Tanaka (Nojiri Highland University Village)
Photo: Takeshi Ozaki
On July 7, 2025, a research paper from the Institute of Freshwater Biology, Nagano University, was published in the international academic journal Fish and Fisheries, presenting a meta-analysis of the genetic population structure of the genus Anguilla (https://doi.org/10.1111/faf.70007).
Conducted a literature review of 66 studies on the genetic structure of Anguilla eels and performed a meta-analysis by extracting the means and standard deviations of pairwise genetic differentiation indices such as FST.
Confirmed panmixia (a single interbreeding population) for most Anguilla species except Anguilla marmorata, although further research is required for some understudied species.
Through meta-regression, examined how genetic marker types, differentiation indices, sample sizes, and sampling ranges influenced the detection of genetic differentiation, and emphasized the importance of ensuring sufficient sample sizes and representative sampling areas in future studies.
Eels of the genus Anguilla are widely distributed in rivers and coastal areas worldwide and are important fishery resources in terms of food culture and economy. In particular, the Japanese eel (Anguilla japonica) has faced severe declines in catch volume, posing a major issue both domestically and internationally. A fundamental component of eel resource management is understanding whether populations are structured into multiple subpopulations or form a single stock shared across national and regional boundaries.
This study aimed to statistically synthesize and analyze results from previously published genetic studies using meta-analysis techniques, and to systematically review and test whether the genus Anguilla exhibits panmixia (a single genetic stock). The goal is to strengthen the scientific basis for sustainable freshwater eel resource management.
A total of 66 relevant domestic and international studies were reviewed, extracting FST values and other indicators of population genetic structure. Meta-analyses were conducted to estimate overall effects and test heterogeneity, considering factors such as genetic marker types and the geographic scope of sampling.
The analysis confirmed that most Anguilla species form genetically mixed, panmictic populations. In particular, the Japanese eel (Anguilla japonica) can be managed as a single stock across its entire distribution, including rivers and coastal areas within and outside Japan. Conversely, Anguilla marmorata showed clear regional genetic differentiation, indicating the presence of subpopulations. The study also highlighted the lack of research on tropical eel species and emphasized the importance of representative and extensive sampling to detect genetic differentiation accurately.
This research, published in the internationally recognized journal Fish and Fisheries, makes a significant scientific contribution to advancing our understanding of the genetic structure of Anguilla eels. The confirmation of panmixia provides a stronger scientific foundation for managing eels as a single international stock. Future research is expected to address gaps in data for tropical eel species, clarify their genetic diversity and distribution patterns, and incorporate new technologies such as environmental DNA surveys. Continued monitoring, especially in the context of potential range expansions due to climate change, is also recommended.
The Institute of Freshwater Biology, Nagano University, serves as a core institution for large-scale projects funded by the Fisheries Agency, promoting research aimed at the sustainable use and conservation of eel resources, including the Japanese eel. Its initiatives encompass extinction risk assessments, analysis of genetic diversity, satellite tagging of spawning migrations, and field surveys on yellow and silver eels’ sex ratios. The Institute will continue collaborating with domestic and international research institutions and fisheries stakeholders to propose and implement evidence-based resource management strategies, further advancing research on the conservation and management of Japanese eels.
This research was conducted under the Fisheries Agency’s Fisheries Resource Survey and Assessment Promotion Project (Eel Unit).
Institute of Freshwater Biology, Nagano University
Email: ifb@nagano.ac.jp
TEL: +81-268-22-0594
FAX: +81-268-22-0544
Contact: Hiroshi Hakoyama
The 4th Eel Scientific Meeting was held in Hamamatsu, Japan, on June 16-17, 2025. This international meeting, hosted by Japan, brought together researchers and government officials from Japan, China, South Korea, and Chinese Taipei to discuss the sustainable management of eel resources. Professor Hiroshi Hakoyama and Researcher Huỳnh Quang Thiện from the Institute of Freshwater Biology (IFB) presented three research papers during the meeting, along with other contributors from the participating countries and regions.
Additionally, Dr. Shannan Crow from the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, as an invited speaker, delivered a special talk on “Eel Recruitment Patterns at Hydroelectric Stations Across New Zealand”.
The meeting aimed to provide scientific advice on the sustainable use of eels in the context of the “Informal Consultation on International Eel Resource Conservation and Management” (Informal Consultation).
On Friday, June 6, 2025, researchers Takeru Kodama and Huỳnh Quang Thiện from the Institute of Freshwater Biology participated in a yellow eel collection survey at the mouth of the Miyakoda River in Hamamatsu City, Shizuoka Prefecture. The survey was carried out jointly with researchers from the Lake Hamana Branch of the Shizuoka Prefectural Fisheries and Marine Technology Research Institute.
The Lake Hamana Branch regularly conducts these surveys to collect morphological and ecological data, such as body size and sex ratios of wild yellow eel populations, as well as genetic information, including DNA and RNA samples. At the Institute of Freshwater Biology, we will analyze this data to develop a practical method for determining the sex of eels based on RNA analysis. The foundation of this method was developed in recent years by Hsu et al. (2023).
On Thursday, June 5, 2025, 16 first-year students from the Faculty of Environmental Tourism visited the Institute of Freshwater Biology as part of Professor Kazuaki Takahashi’s first-year seminar. They learned about local nature and issues, the Institute’s efforts, and research on the fragmentation of the Chikuma River. The students toured the facility and learned about a universal projector that magnifies fish scales and determines their age from tree rings, as seen in the photo. The Institute of Freshwater Biology will continue to contribute to educational activities like this one.
