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

2018 Fiscal Year Final Research Report

• 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
• Keywords: スナメリ / 出産期 / 出生率 / 個体群存続可能性

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.

Free Research Field

鯨類個体群動態、水産資源解析学

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．