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2018 Fiscal Year Final Research Report

Habitat use of mother-calf pairs of finless porpoises

Research Project

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Project/Area Number 16K07854
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeMulti-year Fund
Section一般
Research Field Aquatic bioproduction science
Research InstitutionToho University

Principal Investigator

SHIRAKIHARA Miki  東邦大学, 理学部, 訪問研究員 (30449251)

Research Collaborator OHKOSHI Kenji  
SHIRAKIHARA Kunio  
NAKAHARA Fumio  
SHINOHARA Masanori  
Project Period (FY) 2016-04-01 – 2019-03-31
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
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.

Free Research Field

鯨類生態学

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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Published: 2020-03-30  

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