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Tohru Mukai
Hokkaido University
PhysicsAcousticsTarget strengthFisheryBiology
74Publications
11H-index
388Citations
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Publications 76
Newest
#1Naizheng Yan (Hokkaido University)
#2Tohru Mukai (Hokkaido University)H-Index: 11
Last. Kohei Hasegawa (Hokkaido University)
view all 4 authors...
Abstract When using acoustic methods to investigate fish biomass, it is important to distinguish the target species from other organisms. Previous limitations to acoustic information in surveys meant it was not possible to discriminate juvenile walleye pollock from their predator, pointhead flounder, in Funka Bay, Japan, possibly leading to overestimates in population size. Thus, here, an acoustic method was developed to distinguish the two species based on relative frequency response. This meth...
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#1Naizheng Yan (Hokkaido University)
#2Tohru Mukai (Hokkaido University)H-Index: 11
Last. Naoyuki Kudo (Hokkaido University)
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The acoustic characteristics of bladderless fishes were examined by measuring the target strength (TS) of three species, pointhead flounder (flat-shaped), Arabesque greenling (spindle-shaped) and sandeel (cylinder-shaped). TS measurements were collected in a seawater tank (10 × 6 × 5 m) using the EK80 echo sounder (Simrad, Norway) and ES70-7C transducer (Simrad) over a frequency range of 45–90 kHz with a tether method. After TS measurement of the whole fish, we separated the flesh from the body ...
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#1Naizheng Yan (Hokkaido University)
#2Tohru Mukai (Hokkaido University)H-Index: 11
Last. Kohei Hasegawa (Hokkaido University)
view all 4 authors...
Source
#1Tohru Mukai (Hokkaido University)H-Index: 11
#2Naizheng Yan (Hokkaido University)
Last. Kohei Hasegawa (Hokkaido University)
view all 4 authors...
Source
#1Kouichi SawadaH-Index: 9
#2Tomohiko MatsuuraH-Index: 1
Last. Yuichiro Yamada (Kitasato University)H-Index: 4
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#1Kouichi SawadaH-Index: 9
#2Tomohiko MatsuuraH-Index: 1
view all 7 authors...
The density of zooplankton within bays and in inshore areas is an important environmental parameter for determining the optimal release timing of juvenile salmon (Oncorhynchus keta) from hatchery stations. This is because the juveniles remain in these areas for 1 month, during which time they feed upon zooplankton before they begin their journey to the ocean. We monitored zooplankton, water temperature and salinity from 2013 to 2017 in Yamada Bay, Iwate Prefecture, Japan, using a multi-frequency...
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#1Naizheng Yan (Hokkaido University)
#2Tohru Mukai (Hokkaido University)H-Index: 11
Last. Jun Yamamoto (Hokkaido University)H-Index: 9
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This study addresses the methods for distinguishing the pointhead flounder Cleisthenes pinetorum from the juvenile walleye pollock Gadus chalcogrammus in and near Funka Bay, Hokkaido, Japan. Acoustics data of th Gadus chalcogrammus e fish were monitored using a Simrad EK60 (38, 120, 200 kHz) split-beam echo sounder, and biological samples were collected using a rod for the pointhead flounder and a frame-type midwater trawl for the juvenile walleye pollock. The pointhead flounder schools presente...
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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
A multi-frequency acoustic zooplankton fish profiler (AZFP, ASL Environmental Sciences) with temperature-salinity and depth sensor was moored at 10 m from the bottom (ca. 30 m) at the mouth of Yamada Bay in Iwate Prefecture, Japan, from 14 January to 16 June 2015 in order to measure volume backscattering strength profiles from the transducer surface to the water surface at four frequencies (125, 200, 455, and 769 kHz). Zooplankton density by size was estimated from the measured volume backscatte...
1 CitationsSource
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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