Abstract:
Dr. David O. Alila (University of Dar es Salaam – Tanzania) will present a seminar titled “The Evolutionary Ecology of African Annual Killifish of the Genus Nothobranchius” The talk will examine how ecological and evolutionary forces shape the extraordinary life histories, adaptations, and diversification of Nothobranchius killifish, a group of short-lived species inhabiting ephemeral wetlands across sub-Saharan Africa. Drawing on extensive fieldwork and experimental studies in Tanzania, the global hotspot of Nothobranchius diversity, Dr. Alila will highlight how ecological pressures drive rapid evolution, niche partitioning and sympatric coexistence. Importantly, he will demonstrate how these evolutionary traits underpin the species’ exceptional potential as native biological control agents against malaria mosquitoes, linking fundamental evolutionary ecology to practical, sustainable applications for biodiversity conservation and public health.
The Encyclopedia of Theoretical Biology (Asakura Publishing) has been published.
IFB
Professor Hiroshi Hakoyama of the Institute of Freshwater Biology has contributed the following three entries to The Encyclopedia of Theoretical Biology (in Japanese) published by Asakura Publishing:
“Demographic and environmental stochasticity” pp. 50–51
“Optimal foraging” pp. 122–123
“Risk-sensitive foraging” pp. 124–125
Title: The Encyclopedia of Theoretical Biology
Publisher: Asakura Publishing Co., Ltd. (Tokyo)
Publication date: 13 November 2025
ISBN: 9784254172034
Publisher website: https://www.asakura.co.jp/detail.php?book_code=17203
Covering the whole field of biology, this encyclopedia provides an overview of theoretical ideas and mathematical methods that are useful for understanding the basic logic of biology, explained in a way that is accessible even to readers outside the field. It is organized into eight sections: Ecology & Environment, Evolution, Behavior & Society, Neuroscience, Development & Morphogenesis, Medicine, Systems Biology, and Biological Information. In addition, two chapters are devoted to common methodologies: mathematical modeling and data analysis.
The Chikuma–Shinano River Research Group presented at the 27th River Ecology Research Meeting
IFB
On November 13, 2025, at the Tokyo Stock Exchange Conference Center in Chuo-ku, Tokyo, the “27th River Ecology Research Meeting” (organized by the River Ecology Research Association and co-organized by the Japan Society on Ecological Engineering) was held. At this meeting, the “Chikuma–Shinano River Research Group,” led by Professor Hiroshi Hakoyama of the Institute of Freshwater Biology, Nagano University, gave a research presentation.
The Chikuma–Shinano River Research Group focuses on the importance of habitat connectivity in rivers and advances research on relationships between river ecosystems and river management using diverse approaches, including fish diversity, aquatic communities, channel morphology, and environmental DNA.
Oral presentation
“The importance of habitat connectivity in rivers — impact assessment and conservation measures for river ecosystems”
Presenter: Hiroshi Hakoyama (Representative, Chikuma–Shinano River Research Group)
Selected poster presentations
“The importance of habitat connectivity in rivers — impact assessment and conservation measures for river ecosystems”
Hiroshi Hakoyama
“Relationships between fish diversity and environmental variables in the Shinano River: towards understanding habitat connectivity”
Sakie Kodama, Takeru Kodama, Leanne Faulks, Alessandra Cera, Hiroshi Hakoyama
“River fragmentation at the local scale: effects on biodiversity”
Leanne Faulks, Alessandra Cera, Sakie Kodama, Hiroshi Hakoyama
“Spatial and temporal variations of community-level profile of epilithic biofilm for assessing disturbances”
Alessandra Cera
“Relationships among dams, water quality, microbial communities, and fish assemblages in the middle reaches of the Chikuma River”
Takeru Kodama, Mitsuki Ohara, Yoshinobu Hanaoka, Koki Hada, Sakie Kodama, Leanne Faulks, Hiroshi Hakoyama
“Estimating Fish Density from Downstream eDNA Reads in an Experimental Waterway”
Mitsuki Ohara, Takeru Kodama, Hiroshi Hakoyama
“Channel changes in the middle reaches of the Chikuma–Shinano River based on cross-section survey data and aerial photographs”
Fuka Iwai, Takato Izuchi, Masafumi Toyoda
“Analysis of fish–environment relationships using integrated river data from the Ministry of Land, Infrastructure, Transport and Tourism with dam location information”
Takeru Kodama, Sakie Kodama, Leanne Faulks, Masafumi Toyoda, Hiroshi Hakoyama
“Effects of ayu on river ecosystems”
Shun Kato, Leanne Faulks, Yuji Onishi, Shinji Takahashi, Hiromi Uno
For the detailed program and further information, please refer to the website of the River Ecology Research Association.
The 2025 Glass Eel and Yellow Eel Research Meeting Was Held
IFB
On October 31, 2025, the 2025 Glass Eel and Yellow Eel Research Meeting was held at the meeting room of the Institute for Freshwater Biology, Nagano University (Komaki 1088, Ueda City).
Participants reported on local glass eel surveys conducted across Japan and discussed future directions for data analysis and collaborative research.
Date: October 31, 2025 (Friday), 13:30–16:00
Venue: Meeting Room, Institute for Freshwater Biology, Nagano University (Komaki 1088, Ueda City)
Agenda:
0. Opening
1. Glass eel survey in Miyazaki – Tetsuya Matsunaga / Hidekazu Hayashida (13:30–13:50)
2. Glass eel survey in Wakayama – Yoshitsugu Kaji / Toshimitsu Tanaka (13:50–14:10)
3. Glass eel survey in Kagoshima – Hiroki Nakashima (14:10–14:30)
Break (10 min, 14:30–14:40)
4. Glass eel survey in Fukuoka – Noritaka Mochioka (14:40–15:00)
5. Glass eel survey in Chiba – Junichi Hirata (15:00–15:20)
6. Glass eel survey in Shizuoka – Takahiro Yamamoto (15:20–15:40)
7. General discussion (15:40–16:00)
8. Closing
Break (10 min, 16:00–16:10)
Data Analysis Discussion (16:10–18:00, with short breaks)
9. Time-series data analysis – Hiroshi Hakoyama (16:10–16:30)
10. Discussion on analysis of survey data from each JV (16:10–18:00)
Participants shared survey results from various regions and engaged in active discussions to strengthen collaboration for future eel resource management.
Professor Hakoyama Presented at the SEAFDEC/JAIF Project End Meeting on Tropical Anguillid Eel Management in Southeast Asia
IFB
On October 31, 2025, Professor Hiroshi Hakoyama attended the Project End Meeting on “Development of Stock Assessment Methods and Strengthening of Resources Management Measures for Tropical Anguillid Eel in Southeast Asia,” organized by Southeast Asian Fisheries Development Center (SEAFDEC) and supported by the Japan‑ASEAN Integration Fund (JAIF), held in Bangkok, Thailand. For details see https://www.seafdec.org/project-end-meeting-jaif-eel-2025/.
Professor Hakoyama delivered a presentation titled “Experience from Japan in Managing the Japanese Eel (Anguilla japonica): Implications for Tropical Anguillid Eels in ASEAN (Rev. 2),” under Agenda 7-2.
In his talk, he introduced Japan’s experience and lessons learned in the sustainable management of Anguilla japonica and discussed how these insights could be applied to improve regional management frameworks for tropical anguillid eels across ASEAN Member States.
The meeting brought together representatives from ASEAN Member States, SEAFDEC departments, and partner organizations to present project outcomes, share country experiences, and discuss future directions for regional cooperation in eel resource management.
Professor Hakoyama Participated in the 2025 Nagara River Field Study Tour Organized by the River Ecology Research Association!
IFB
On October 16–17, 2025, the Nagara River Field Study Tour, organized by the River Ecology Research Association, was held, and Professor Hakoyama participated as a member of the parent committee.
During the event, participants visited the study sites of the Nagara River Research Group, and on the second day, oral presentations of research results were given.
The 2025 General Meeting of the "Association for Restoring the Blessings of the Chikuma River" Was Held!
IFB
On October 7, 2025, the 2025 General Meeting of the “Association for Restoring the Blessings of the Chikuma River” was held in the training hall on the second floor of the Kamiko Fisheries Cooperative Hall.
Under the leadership of Chairman Yoichi Tsuchiya, the Association aims to “revive the Chikuma River as a mecca for ayu fishing.” Through efforts to create a river environment that is friendly to native fish species such as ayu and ugui, and beloved by local residents, the Association seeks to contribute to the promotion of fisheries and tourism industries, as well as to regional revitalization. The Institute for Freshwater Biology (IFB) cooperates as a member organization of this Association.
At the meeting, reports on this year’s activities were presented, along with research presentations. From IFB, Professor Hiroshi Hakoyama and Researcher Takeru Kodama gave presentations on IFB’s initiatives and topics related to the water quality of the Chikuma River.
Researchers from Indonesia’s BRIN Visit the Institute of Freshwater Biology
IFB
From September 29 to October 3, 2025, Dr. Arif Wibowo, Director of the Center for Aquatic Conservation Research, and Dr. Dwi Atminarso from Indonesia’s National Research and Innovation Agency (BRIN) visited the Institute of Freshwater Biology (IFB) at Nagano University.
During their stay, the two researchers held in-depth discussions with Professor Hiroshi Hakoyama and other IFB staff members on the future directions of collaborative research on eel resource management, river ecosystem conservation, and environmental DNA (eDNA) analysis in Southeast Asia.
They also toured IFB’s research facilities and exchanged ideas on data sharing and the establishment of a long-term research collaboration framework.
This visit was conducted as part of the activities of the Eel Task Team,
aimed at strengthening international collaboration toward the sustainable use and ecological conservation of tropical and temperate eel species.
Associate Professor Sakie Kodama Appointed as Advisor to the Newly Established "Insect Ecology Research Club" in 2025!
IFB
The Insect Ecology Research Club, a new student circle at Nagano University, was founded by students who bonded during the Laboratory Course in Freshwater Biology.
The club’s activities include raising insects (such as beetles, silkworms, and bell crickets), outdoor observation and identification, and ecological research.
Abstract:
The Japanese eel was classified as Endangered IB by the Ministry of the Environment in 2013. In response, the Fisheries Agency implemented the Eel Habitat Improvement Support Project from 2016 to 2023, installing stone basket reefs (Ishikura-kago) at 86 sites across 40 rivers and 2 lakes in 19 prefectures, ranging from Iwate to Kagoshima. The project was carried out based on the precautionary principle, with effect verification mainly conducted by Kyushu University. Using eight experimental ponds at the Kagoshima Prefectural Fisheries Technology Development Center, it was demonstrated that stone baskets help reduce damage from birds.
Furthermore, six stone baskets of varying stone sizes (long diameter 10, 20, 30 cm) were installed in the brackish zone of the Saigo River in Fukutsu City, Fukuoka Prefecture. It was revealed that yellow eels prefer stones of 10 cm in diameter, while silver eels prefer 20 cm, and that individuals with high-frequency use of stone baskets had better nutritional conditions compared to those with low-frequency use. Currently, stone baskets have been installed at four sites from the freshwater zone to the estuary of the Saigo River and the Arase River in Kagoshima Prefecture, in an effort to identify effective locations for protecting individuals undergoing silvering metamorphosis.
Workshop on Biodiversity Conducted at Ueda Nishi High School UNMP (9th)
IFB
On September 23, 2025, Associate Professor Sakie Kodama and Professor Hiroshi Hakoyama from the Institute for Freshwater Biology, Nagano University, conducted a workshop titled “Thinking About Biodiversity – A Workshop with the Institute for Freshwater Biology, Nagano University” as part of the 9th Ueda Nishi Mind Project (UNMP) held at Ueda Nishi High School.
The workshop aimed to help students deepen their understanding of biodiversity conservation and invasive species control while developing scientific inquiry skills through hands-on learning.
Participants conducted fieldwork in the Chikuma River, collecting and observing planarians (Dugesia japonica)—a freshwater species known as an indicator of clean water.
Following an ecological introduction by Associate Professor Kodama, students collected planarians in the river and then observed them under microscopes at the IFB.
They also performed flow cytometry to examine ploidy variation, discovering multiple individuals with different ploidy levels within the same population—a fascinating finding for the students.
Through this experience, they learned the importance of biodiversity conservation and gained a deeper appreciation of scientific observation and analysis.
R package “extr: Extinction Risk Estimation” Released on CRAN
IFB
On September 21, 2025, Professor Hiroshi Hakoyama of the Institute for Freshwater Biology, Nagano University, released his R package “extr: Extinction Risk Estimation” on the Comprehensive R Archive Network (CRAN).
This package implements a method for estimating extinction probabilities from population time-series data under the Wiener process with drift, and includes the newly proposed approach for constructing confidence intervals for extinction risk using the w–z method (Hakoyama, 2025, arXiv preprint).
The method enables accurate extinction-risk estimation even with limited data, providing a statistically rigorous framework for validating Population Viability Analysis (PVA) and supporting IUCN Red List assessments.
Prof. Hakoyama Presents at the SEAFDEC Common Positions Meeting (Bangkok, Thailand)
IFB
The Regional Technical Consultation on Development of the ASEAN–SEAFDEC Common Positions on the Proposed Listing of Commercially-exploited Aquatic Species into the CITES Appendices (for CITES CoP20) was held in Bangkok, Thailand, on 16–18 September 2025 (organized by SEAFDEC with support from the Government of Japan Trust Fund).
Participants included country representatives from Indonesia, Japan, Lao PDR, Malaysia, Myanmar, the Philippines, and Thailand (with Brunei Darussalam, Cambodia, and Viet Nam joining online), FAO, academic experts, and SEAFDEC departments (Secretariat/TD/AQD/MFRDMD/IFRDMD).
Prof. Hiroshi Hakoyama (IFB) presented on Proposal 35—the Appendix II proposal concerning the genus Anguilla (including Japanese eel and American eel)—highlighting:
Japanese eel in East Asia forms a single panmictic population, with glass eels arriving from a shared spawning area via ocean currents; therefore, regional indices can represent the stock as a whole.
Based on IUCN Criterion E (probability of extinction), the estimated risk is below the thresholds for CR/EN, with narrow confidence intervals.
Accordingly, Japanese eel should be addressed as a regional fisheries management issue rather than a CITES listing issue.
The same reasoning can apply to other widely distributed marine species with large populations, where Criterion A (decline-based) assessments can overestimate risk.
During the RTC, 11 proposals for commercially-exploited aquatic species (CEAS)—including sharks and rays, sea cucumbers, and abalone—were discussed using FAO Expert Panel results and country information, and a draft of the ASEAN–SEAFDEC common/coordinated positions was compiled.
FAO Publishes Review of CITES Proposals for Aquatic Species
IFB
The Food and Agriculture Organization of the United Nations (FAO) has published the Expert Advisory Panel report reviewing proposals to list commercially exploited aquatic species under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The report compiles the Panel’s scientific and technical assessments conducted in July 2025.
Proposal No. 35 concerns the listing of eels (Anguilla spp.). Prof. Hiroshi Hakoyama of the Institute for Freshwater Biology contributed to the evaluation of this proposal as a member of the Expert Advisory Panel.
FAO EXPERT PANEL ASSESSMENT REPORT OF PROPOSAL 35: Japanese eel, Anguilla japonica, and American eel, Anguilla rostrata, plus all Genus Anguilla
This proposal is for inclusion of the Japanese eel, A. japonica and the American eel, A. rostrata in Appendix II, Under Annex 2 (a) criterion B.
It also includes all non-CITES species of the genus Anguilla in CITES Appendix II in accordance with Article II, Paragraph 2 (b) for reasons of similarity to $A. anguilla$, or to one of the species proposed (A. japonica and A. rostrata) in live or processed form.
EXPERT PANEL RECOMMENDATION
Japanese eel and other look alike eels
The Expert Panel assesses Proposal 35 not to meet the CITES listing criteria.
This conclusion is based on a comprehensive evaluation of the best available scientific data and technical information, which indicates that $A. japonica$ and related species exhibit medium inherent productivity, large effective population sizes above the Appendix II extent of decline threshold, and low extinction risk as demonstrated by Population Viability Analysis (PVA). Furthermore, the suggested direct linking of international trade to population declines across the genus is not well supported by the evidence. Existing regional and national management measures across Asia are extensive and demonstrably effective, particularly in eastern Asia where cooperative frameworks and practical species identification methods support sustainable use and trade monitoring.
While an Appendix II listing might offer some regulatory harmonization benefits, the risks of unintended negative consequences - including increased illegal trade, market distortions and the disruption of successful management cooperation - are considerable. Therefore, the Expert Panel expresses moderate to high confidence in the result of their evaluation, emphasizing that targeted conservation actions and strengthened species and region-specific management represent more effective pathways to sustainable conservation outcomes than a premature genus-wide listing.
Quantitative assessment of extinction risk requires not only point estimates but also confidence intervals (CIs) that remain informative even when data are limited.
However, their reliability has long been debated, since short observation spans tend to inflate uncertainty and reduce usefulness.
In this study, a new method is developed for constructing confidence intervals of the extinction probability $G$ under the Wiener process with drift, a canonical model of population viability analysis (PVA).
The proposed approach uses correlated noncentral-t distributions for the transformed statistics $\hat{w}$ and $\hat{z}$, derived from the estimators of drift and variance, and exploits the geometric properties of $G(\hat{w},\hat{z})$ in parameter space.
Monte Carlo experiments show that the proposed intervals maintain nominal coverage while achieving narrower widths than conventional methods such as the delta method, moment-based approaches, and bootstrap.
A key result is that even with short time series, extinction probabilities that are very small or very large can be estimated reliably, resolving the long-standing concern that PVA fails under data scarcity.
Applying the method to three 64-year catch series for the Japanese eel (Anguilla japonica) as abundance indices, the estimated extinction risk was found to be well below the IUCN Criterion E thresholds for Critically Endangered (CR) and Endangered (EN), with sufficiently narrow and statistically precise confidence intervals.
Although the Japanese eel is currently listed as Endangered (EN) under Criterion A (population decline), this analysis demonstrates that decline-based assessments substantially overestimate extinction risk in large populations.
These findings show that even under limited data conditions, extinction-risk confidence intervals can be constructed both rigorously and practically, providing empirical support for the reliability of PVA in IUCN Red List evaluations.
SEAFDEC Trainee (Dr. Dwi Rizki Septiana) Received at IFB
IFB
From September 8 to 12, 2025, the Institute for Freshwater Biology (IFB), Nagano University, welcomed Dr. Dwi Rizki Septiana from the Inland Fishery Resources Development and Management Department (IFRDMD) of the Southeast Asian Fisheries Development Center (SEAFDEC) for a technical training program titled “Learning Environmental DNA (eDNA) Analysis and Biomass Estimation Methods for Tropical Eels.”
Under the guidance of Dr. Mitsuki Ohara, the training focused on both experimental and analytical aspects of environmental DNA research — including DNA extraction, quantification, and analysis techniques, as well as statistical approaches to estimate biomass from eDNA concentration data.
This program was organized as part of the SEAFDEC Eel Task Force activities and the ongoing Memorandum of Understanding (MOU) between Nagano University and SEAFDEC.
It contributes to international capacity building toward the implementation of eDNA-based methodologies for the sustainable use and management of tropical eel resources.
Eel Swimming Experiment Featured in the Tōshin Journal and Shinshū Minpō
IFB
An article titled “Institute for Freshwater Biology, Nagano University – Observing Mid- to Long-Term Effects of Eel Swimming: Joint Study with Shinshu University Faculty of Engineering” appeared in the Tōshin Journal on September 2, 2025.
A follow-up feature titled “Nagano University’s Institute for Freshwater Biology Announces Two Studies on Eels – Flow Chamber Experiments and Swimming Analysis” was published in the Shinshū Minpō on September 6, 2025.
Both articles introduced the joint research project between the Institute for Freshwater Biology, Nagano University, and the Faculty of Engineering, Shinshu University, focusing on experiments observing the mid- to long-term effects of swimming behavior and tag attachment in eels.
The study aims to understand eel behavior and migratory adaptation, as well as to improve tagging and tracking technologies, combining hydrodynamic analysis and device design by the Faculty of Engineering with behavioral observation and data analysis by the Institute for Freshwater Biology.
These collaborative efforts provide fundamental insights into quantifying physiological impacts and refining tagging techniques, contributing to the sustainable use of eel resources and the conservation of aquatic ecosystems.
Study on Eel Population Structure Featured in the Shinano Mainichi Shimbun
IFB
On August 2, 2025, the Shinano Mainichi Shimbun published an article titled “Eels Mostly Reproduce as a Single Population,” followed on August 3 by a detailed feature titled “Half a Century of Eel Research Reveals: Many Individuals Belong to a Single Reproductive Population – Study by Nagano University Professor’s Team.”
The articles introduce the findings of a research group led by Professor Hiroshi Hakoyama of the Institute for Freshwater Biology, Nagano University, which analyzed data spanning over half a century and revealed that most East Asian eels, including the Japanese eel (Anguilla japonica), form a single panmictic population.
This finding deepens our understanding of the genetic population structure underlying extinction-risk assessments and resource management, and provides important insights for future conservation policies and international management discussions.
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.
Dr. Takeru Kodama Featured on KBC Kyushu Asahi Broadcasting!
IFB
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.
