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Optical and acoustic camera observations of the behavior of the Kuril harbor seal Phoca vitulina stejnegeri after invading a salmon setnet

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Title: Optical and acoustic camera observations of the behavior of the Kuril harbor seal Phoca vitulina stejnegeri after invading a salmon setnet
Authors: Fujimori, Yasuzumi Browse this author →KAKEN DB
Ochi, Yousuke Browse this author
Yamasaki, Shintaro Browse this author
Ito, Ryohei Browse this author
Kobayashi, Yumi Browse this author
Yamamoto, Jun Browse this author →KAKEN DB
Tamaru, Osamu Browse this author
Kuramoto, Yousuke Browse this author
Sakurai, Yasunori Browse this author →KAKEN DB
Keywords: Fishery damage
Haul out site
Seal-fishery conflict
Dual-frequency identification sonar
Top predator
Chum salmon
Issue Date: Nov-2018
Publisher: Springer
Journal Title: Fisheries science
Volume: 84
Issue: 6
Start Page: 953
End Page: 961
Publisher DOI: 10.1007/s12562-018-1236-z
Abstract: It has previously been confirmed that Kuril harbor seals Phoca vitulina stejnegeri cause damage to the chum salmon Oncorhynchus keta setnet fishery along the east coast of Hokkaido, Japan, but the level of damage has increased markedly with the recovery of their population in recent years. In this study, we attached an optical camera (Trawl Camera) and a dual-frequency identification sonar (DIDSON) acoustic camera to a setnet to observe the behavior of seals as they invaded the setnet, and to determine the number of salmon inside the net, to help inform the development of modified fishing gear. Salmon were observed at all times during daytime with the Trawl Camera, while seals were only observed once. Observations using the DIDSON in its low-frequency mode confirmed that the behavior of seals became vigorous from around sunset to nighttime within the recording time (1530-2100 hours). Observations using the DIDSON high-frequency mode showed that the overall lengths and body widths of seals ranged from 1.0 to 1.6 m and 0.15 to 0.35 m, respectively, while their swimming speeds ranged from 0.4 to 2.6 m/s, increasing around sunset and declining into the night. These results imply that seals mainly invade the setnet from evening to nighttime to predate on salmon.
Rights: The final publication is available at
© [2018] 公益社団法人日本水産学会
© [2018] The Japanese Society of Fisheries Science
Type: article (author version)
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 藤森 康澄

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