| Project/Area Number |
16K07854
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Aquatic bioproduction science
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| Research Institution | Toho University |
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Principal Investigator |
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| Research Collaborator |
OHKOSHI Kenji
SHIRAKIHARA Kunio
NAKAHARA Fumio
SHINOHARA Masanori
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2018: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2016: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Keywords | スナメリ / 個体群 / 育児海域 / 飛行機目視調査 / 沿岸性鯨類 / 保全 / 飛行機調査 / 行動観察 / 出産期 / 生態学 |
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| Outline of Final Research Achievements |
We conducted aerial and land-based sighting surveys to estimate calving and nursing grounds for finless porpoises. Aerial surveys were conducted in the coastal waters < 20 m in depth between Takahagi, Ibaraki Prefecture and Onjyuku, Chiba Prefecture from spring to summer in 2017 and 2018 (sighting effort, 3600km). A total of 91 hours of land-based surveys were done from April 2016 to September 2017. Mother-calf pairs were not found at the north and south ends of the survey areas. The distribution was concentrated off Kashima and off Choshi, suggested the possibility that finless porpoises preferred certain areas as a nursing ground. Encounter rates of mother-calf pairs increased in May－June and the proportion of the pairs showed an upward trend from April to July in Kashima Nada and around Choshi. In the land-based surveys, mother-calf pairs were sighted in May－July and September and feeding behavior of the mothers were observed.
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| Academic Significance and Societal Importance of the Research Achievements |
スナメリは，沿岸域に生息するため，漁網による混獲，船舶との衝突，汚染物質の蓄積，埋め立てによる生息地の消失など人間活動の影響を強く受けている小型鯨類である．個体数減少が明らかにされている生息地もある．成熟メスの人為的死亡の増加は個体数の減少に結びつく可能性があるため，彼らにとって重要な保全すべき海域を明らかにすることは不可欠である．本研究は，野生のスナメリを上空から観察することにより，水深20ｍ以浅の特定な場所が育児海域となる可能性を示唆した最初の研究である．また通常は1～数頭の小さな群れを作るスナメリがある時期に大群を作るという新知見も得ることもできた．
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