Structure and viability of a finless porpoise population off Kujukuri- Kashima Nada

• Project/Area Number: 15K07541
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: The University of Tokyo
• Principal Investigator: Shirakihara Kunio 東京大学, 大気海洋研究所, 客員教授 (90196618)
• Co-Investigator(Renkei-kenkyūsha): SHIRAKIHARA miki
• Research Collaborator: NAKAHARA fumio ; SHINOHARA masanori
• Project Period (FY): 2015-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥5,070,000 (Direct Cost: ¥3,900,000、Indirect Cost: ¥1,170,000); Fiscal Year 2018: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000); Fiscal Year 2017: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000); Fiscal Year 2016: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2015: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
• Keywords: スナメリ / 出産期 / 出生率 / 個体群存続可能性 / 出世率 / 個体群構造 / 出産率 / 体長推定

Outline of Final Research Achievements

Population viability for finless porpoises off Kujukuri - Kashima Nada in Japan was evaluated. A birth rate estimate in one year, which was given as the maximum of the ratio of 0-year calves to all the members within the year, did not exceed 10% for the four years. We were not sure whether the population has the birth rate high enough to assure population recovery because of a possible underestimate of the birth rate. For example, turbidity observed especially near Tone River were likely to cause lower detectability of 0-year calves. Parturition in these waters was estimated to start in March and have its peak from May to July.

Academic Significance and Societal Importance of the Research Achievements

沿岸性鯨類スナメリは国際自然保護連合により絶滅危惧種に指定されている．東日本太平洋側に分布する本種の個体群は東日本大震災の後に個体数の減少が指摘されている．さらに本個体群は少なくとも２つの個体群に分割すべきとの見解が示されている．本研究は，九十九里～鹿島灘個体群の存続可能性を新生子割合の把握に焦点をあてた調査から検討しており，スナメリの保全を直視している．

Research Products

• [Journal Article] Abundance decline in the narrow-ridged finless porpoise population off the Pacific coast of eastern Japan (2018)
  • Author(s): Kunio Shirakihara, Fumio Nakahara, Masanori Shinohara, Miki Shirakihara,Kazuhiko Hiramatsu,Takahiro Irie
  • Journal Title: Population Ecology Volume: 印刷中 Issue: 3 Pages: 325-332
  • DOI: 10.1002/1438-390x.12003
  • Peer Reviewed
• [Journal Article] Habitat use by Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Amakusa, Japan (2017)
  • Author(s): Inoue K, Y. Terashima, M. Shirakihara, K. Shirakihara
  • Journal Title: Aquatic Mammals Volume: 43 Issue: 2 Pages: 127-138
  • DOI: 10.1578/am.43.2.2017.127
  • Peer Reviewed
• [Journal Article] Ecosystem dynamics in Tokyo Bay with a focus on high trophic levels using Ecopath with Ecosim (2017)
  • Author(s): Sakamoto A, K. Shirakihara
  • Journal Title: J Mar Sci Technol Volume: 22 Issue: 1 Pages: 1-10
  • DOI: 10.1007/s00773-016-0388-8
  • Peer Reviewed
• [Journal Article] Effects of bycatch on the population viability of the narrow-ridged finless porpoises in Ariake Sound and Tachibana Bay, Japan (2015)
  • Author(s): Hashimoto M., Shirakihara K. and Shirakihara M.
  • Journal Title: Endangered Species Research Volume: 27巻 Issue: 1 Pages: 87-94
  • DOI: 10.3354/esr00658
  • Peer Reviewed / Open Access / Acknowledgement Compliant
• [Presentation] スナメリの出生率と親子連れ利用海域の評価 (2016)
  • Author(s): 白木原国雄・中原史生・篠原正典・白木原美紀
  • Organizer: 日本水産学会
  • Place of Presentation: 東京海洋大学（東京都港区）
  • Year and Date: 2016-03-27
• [Presentation] A Versatile Method of Risk Evaluation Based on the Future Predictions for the Various Narrowridged Finless Porpoise Populations (2015)
  • Author(s): Hashimoto M, Shirakihara K
  • Organizer: IWMC Vth International Wildlife Management Conference
  • Place of Presentation: 札幌コンベンションセンター(北海道札幌市）
  • Year and Date: 2015-07-26
  • Int'l Joint Research