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Evaluation on naturally-recruited/stocked Japanese eel distribution based on otolith stable isotope ratios.

Research Project

Project/Area Number 18H02225
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Review Section Basic Section 39060:Conservation of biological resources-related
Research InstitutionChuo University

Principal Investigator

Kaifu Kenzo  中央大学, 法学部, 教授 (30615258)

Co-Investigator(Kenkyū-buntansha) 白井 厚太朗  東京大学, 大気海洋研究所, 准教授 (70463908)
Project Period (FY) 2018-04-01 – 2022-03-31
Project Status Completed (Fiscal Year 2021)
Budget Amount *help
¥17,030,000 (Direct Cost: ¥13,100,000、Indirect Cost: ¥3,930,000)
Fiscal Year 2021: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2020: ¥5,460,000 (Direct Cost: ¥4,200,000、Indirect Cost: ¥1,260,000)
Fiscal Year 2019: ¥5,850,000 (Direct Cost: ¥4,500,000、Indirect Cost: ¥1,350,000)
Fiscal Year 2018: ¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000)
Keywordsニホンウナギ / 放流 / 耳石 / 安定同位体比 / 安定同位体 / 資源保全 / ウナギ / 資源動態
Outline of Final Research Achievements

Carbon and oxygen otolith stable isotope ratios were measured for Japanese eels that were captured in Japanese rivers. Those eels were classified into naturally-recruited/farmed-and-stocked individuals based on a discrimination model we developed. Along with the previously reported data, we obtained ratios of naturally-recruited/farmed-and-stocked individuals for 21 water systems in 17 prefectures (876 individuals). Ratio of farmed-and-stocked individual were from 41.4% in total with a range from 0.0 to 100.0%. Farmed-and-stocked individuals were dominant in Japan Sea coast where few glass eels recruit. The ratio of farmed-and-stocked individuals tended to be greater in waters that have dams in their lower reaches, even though the water systems are flowing into the Pacific Ocean or the Seto Inland Sea.

Academic Significance and Societal Importance of the Research Achievements

環境省は2013年にニホンウナギを絶滅危惧IB類に区分した。この時の評価に用いられた主なデータは、日本の内水面ウナギ漁獲量である。しかしながら放流個体が再生産に参加する確証はないため、ニホンウナギの個体群動態を正確に理解するにあたり、放流個体の存在は一種のコンタミとなっている。本研究により、水系ごとに大きな違いはあるものの、日本の内水面漁場に生息するニホンウナギのうち、放流ウナギがかなりの割合を占めることが確認された。本研究で試行したように、今後は天然遡上個体が優占する水域でデータを得ることにより、より正確にニホンウナギの個体群動態を把握できるようになる。

Report

(5 results)
  • 2021 Annual Research Report   Final Research Report ( PDF )
  • 2020 Annual Research Report
  • 2019 Annual Research Report
  • 2018 Annual Research Report
  • Research Products

    (7 results)

All 2021 2019 2018

All Journal Article (6 results) (of which Int'l Joint Research: 1 results,  Peer Reviewed: 6 results,  Open Access: 3 results) Presentation (1 results) (of which Int'l Joint Research: 1 results,  Invited: 1 results)

  • [Journal Article] Management of glass eel fisheries is not a sufficient measure to recover a local Japanese eel population2021

    • Author(s)
      Kaifu Kenzo、Yokouchi Kazuki、Miller Michael J.、Washitani Izumi
    • Journal Title

      Marine Policy

      Volume: 134 Pages: 104806-104806

    • DOI

      10.1016/j.marpol.2021.104806

    • Related Report
      2021 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] Distribution of naturally recruited wild Japanese eels in Japan revealed by otolith stable isotopic ratios and document investigation2019

    • Author(s)
      YONETA AKIHITO、ITAKURA HIKARU、ARAI KOHMA、KAIFU KENZO、YOSHINAGA TATSUKI、MIYAKE YOICHI、SHIRAI KOTARO、KIMURA SHINGO
    • Journal Title

      NIPPON SUISAN GAKKAISHI

      Volume: 85 Issue: 2 Pages: 150-161

    • DOI

      10.2331/suisan.18-00038

    • NAID

      130007622909

    • ISSN
      0021-5392, 1349-998X
    • Year and Date
      2019-03-15
    • Related Report
      2018 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] Increasing or decreasing? - Current status of the Japanese eel stock2019

    • Author(s)
      Kaifu Kenzo、Yokouchi Kazuki
    • Journal Title

      Fisheries Research

      Volume: 220 Pages: 105348-105348

    • DOI

      10.1016/j.fishres.2019.105348

    • Related Report
      2019 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Challenges in assessments of Japanese eel stock2019

    • Author(s)
      Kaifu Kenzo
    • Journal Title

      Marine Policy

      Volume: 102 Pages: 1-4

    • DOI

      10.1016/j.marpol.2019.02.005

    • Related Report
      2018 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Depletion of naturally recruited wild Japanese eels in Okayama, Japan, revealed by otolith stable isotope ratios and abundance indices2018

    • Author(s)
      Kaifu Kenzo、Yokouchi Kazuki、Higuchi Tomihiko、Itakura Hikaru、Shirai Kotaro
    • Journal Title

      Fisheries Science

      Volume: 84 Issue: 5 Pages: 757-763

    • DOI

      10.1007/s12562-018-1225-2

    • NAID

      40021650810

    • Related Report
      2018 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Distribution of wild and stocked Japanese eels in the lower reaches of the Tone River catchment revealed by otolith stable-isotope ratios2018

    • Author(s)
      Itakura Hikaru、Arai Kohma、Kaifu Kenzo、Shirai Kotaro、Yoneta Akihito、Miyake Yoichi、Secor David H.、Kimura Shingo
    • Journal Title

      Journal of Fish Biology

      Volume: 93 Issue: 5 Pages: 805-813

    • DOI

      10.1111/jfb.13782

    • Related Report
      2018 Annual Research Report
    • Peer Reviewed / Open Access / Int'l Joint Research
  • [Presentation] Current status of Japanese eel stock.2019

    • Author(s)
      Kenzo Kaifu
    • Organizer
      The 3rd ISTEGA
    • Related Report
      2019 Annual Research Report
    • Int'l Joint Research / Invited

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Published: 2018-04-23   Modified: 2023-01-30  

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