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Kazuo Amakasu
Tokyo University of Marine Science and Technology
OceanographyPhysicsGeologyAcousticsTarget strength
50Publications
7H-index
155Citations
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Publications 49
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#1Tetsuro Tsuru (Tokyo University of Marine Science and Technology)H-Index: 17
#2Kazuo Amakasu (Tokyo University of Marine Science and Technology)H-Index: 7
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Owing to the strict restrictions on the use of air guns in marine seismic surveys due to concerns about their potential impact on the marine ecosystem, there have been several cases where seismic surveys were not permitted. This tendency has been particularly significant in coastal waters where fishing activity is flourishing, which creates blank zones in seismic surveys. The authors, therefore, adopted underwater speakers as environment-friendly seismic sources that can be used under such restr...
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#1Tetsuro Tsuru (Tokyo University of Marine Science and Technology)H-Index: 17
#2Jin-Oh Park (UTokyo: University of Tokyo)H-Index: 29
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#1Masahiko Furusawa (Tokyo University of Marine Science and Technology)H-Index: 12
#2Kazuo Amakasu (Tokyo University of Marine Science and Technology)H-Index: 7
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#1Kazuo Amakasu (Tokyo University of Marine Science and Technology)H-Index: 7
#2Tohru Mukai (Hokkaido University)H-Index: 11
Last. Masato Moteki (National Institute of Polar Research)H-Index: 2
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Abstract Antarctic krill, Euphausia superba, were observed using a broadband echosounder and their length-density distribution was inferred from the echo data through a least square inversion. The observation was conducted in the Indian Ocean sector of the Southern Ocean in January 2014. The transmit signal was a 10-ms linear frequency-modulated signal with a frequency sweep of 20–200 kHz. A large aggregation of Antarctic krill was observed at a sampling station over the continental shelf. The v...
3 CitationsSource
#1Minoru KitamuraH-Index: 9
#2Kazuo AmakasuH-Index: 7
Last. Motoyo ItohH-Index: 21
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#1Minoru Kitamura (JAMSTEC: Japan Agency for Marine-Earth Science and Technology)H-Index: 9
#2Kazuo Amakasu (Tokyo University of Marine Science and Technology)H-Index: 7
Last. Shigeto Nishino (JAMSTEC: Japan Agency for Marine-Earth Science and Technology)H-Index: 21
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Abstract To understand the seasonal dynamics of zooplankton in the southern Chukchi Sea, we use observations from a moored multi-frequency echo-sounder from July 2012 to July 2014. Zooplankton biomass, as indicated by area backscattering strength, was high during autumn and low in early spring; the seasonal peak in zooplankton biomass did not coincide with the spring phytoplankton bloom. This suggests that the seasonal zooplankton dynamics in the southern Chukchi Sea are less influenced by local...
1 CitationsSource
We have developed a free-fall multi-parameter profiler (YODA Profiler) to measure various physical and biological parameters in coastal ocean. We found internal bores create a strong mixing event. Sediment resuspension is associated with the mixing event and also AZFP detected fish school at the front of bore. We have deployed a cable observatory system (Oshima Coastal Environment data Acquisition Network System, OCEANS) in a coastal area to monitor coastal ecosystem continuously. OCEANS can mea...
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Walleye pollack (Gadus chalcogrammus) resources are abundant around Hokkaido in Japan. The acoustic survey of the walleye pollack using the quantitative echo-sounder has been performed around Hokkaido since 1995. The quantitative echo-sounder that is mainly used for this survey is the EK60 system consisting of GPT + ER60 software made by Simrad. On the other hand, EK80 system using the WBT has been released in 2015, and the acoustic survey will be conducted by EK80 system from now. Therefore, it...
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Walleye pollock (Theragra chalcogramma) is one of very important fisheries resources in Japan. The acoustic-net surveys have been conducted around Hokkaido since 1995. To improve the present resource management, the estimation of the standing stock of juvenile walleye pollock is necessary. The target strengths of juvenile walleye pollock at 38 kHz have been well-studied through measurement. However, there are little knowledge of the target strengths at frequencies other than 38 kHz. In this stud...
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To assess how seasonal and ice-associated whales differently respond to the Arctic climate changes, understanding the relationships among their presence and environmental conditions is necessary. We examined the seasonal acoustic presence of fin Balaenoptera physalus and bowhead whales Balaena mysticetus in relation to prey abundance and oceanographic conditions in the southern Chukchi Sea from July 2012 to July 2014 using passive and active acoustic methods. Oceanographic conditions obtained we...
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