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Hasegawa Kohei

Faculty of Fisheries Sciences　Marine Bioresource and Environmental Science　Marine Environment and Resource SensingAssistant Professor

Researcher basic information

■ Degree
  • 工学博士, 東京海洋大学
■ URL
researchmap URLホームページURL■ Various IDs
J-Global ID■ Research Keywords and Fields
Research Field
  • Natural Science, Atmospheric and hydrospheric sciences, Fisheries acoustics
■ Educational Organization

Research activity information

■ Awards
  • May 2025, Marine Acoustics Society of Japan, Paper award
    Measurements and theoretical model simulation of target strength of Pacific chub mackerel for use in a quantitative sonar
  • Nov. 2019, Asian Fisheries Acoustics Society, Young Fisheries Acoustician Award
    Kohei Hasegawa;Tohru Mukai;Naizheng Yan, 50144254
■ Papers
  • Repeated narwhal interactions with moorings challenge safety assumptions of passive acoustic monitoring in the Arctic
    Evgeny A. Podolskiy; Monica Ogawa; Mayuko Otsuki; Kohei Hasegawa; Shin Sugiyama
    Communications Biology, 8, 1, Springer Science and Business Media LLC, 12 Nov. 2025, [Peer-reviewed]
    English, Scientific journal
  • Changes in the coastal environments and their impact on society in the Qaanaaq region, northwestern Greenland
    Shin Sugiyama; Atsushi Yamaguchi; Tatsuya Watanabe; Yasumasa Tojo; Naotaka Hayashi; Jean-Baptiste Thiebot; Makoto Tomiyasu; Kohei Hasegawa; Yoko Mitani; Mayuko Otsuki; Yuta Sakuragi; Monica Ogawa; Kenzo Tanaka; Kaisei Sakurai; Kohei Matsuno; Naoya Kanna; Evgeny Podolskiy; Ryo Kusaka; Yefan Wang; Takuro Imazu; Kaho Watanabe; Ken Sato; Shinta Ukai; Soratakato Yamada; Ken Kondo; Shintaro Yamasaki; Kazutaka Tateyama; Kazutoshi Sato; Jun Inoue; Taro Mori; Tatsuya Fukazawa; Aqqalu Rosing-Asvid; Kirsty Langley; Andrea M.U. Gierisch; Jenna Sutherland; Toku Oshima
    Polar Science, Elsevier BV, Apr. 2025, [Peer-reviewed]
    English, Scientific journal
  • Broadband characteristics of Pacific herring (Clupea pallasii) and Pacific chub mackerel (Scomber japonicus) target strength identified using the tether method
    Zi Wang; Naizheng Yan; Tohru Mukai; Kohei Hasegawa; Jun Yamamoto
    Fisheries Research, 283, 107306, 107306, Elsevier BV, Mar. 2025, [Peer-reviewed]
    English, Scientific journal
  • Broadband Characteristics of Target Strength of Pacific Chub Mackerel
    Kohei Hasegawa; Naizheng Yan; Tohru Mukai; Yoshiaki Fukuda; Jun Yamamoto
    Fishes, 10, 2, 51, 51, MDPI AG, 28 Jan. 2025, [Peer-reviewed], [Lead author]
    English, Scientific journal, Broadband backscattering measurements of Pacific mackerel (Scomber japonicus) can improve acoustic surveys of the species for the management of its fisheries throughout the Pacific Ocean. The determination of its target strength (TS), the logarithmic form of the backscattering cross-section, is the aim of this work. It was measured for fourteen individual specimens, eight in a freshwater tank and six in a seawater tank, using calibrated broadband echosounders spanning the frequency band 24–84 kHz. The TS is expressed as a function of frequency and tilt angle, with fish length as a parameter. The individual broadband TS patterns with the tilt angle of fish showed size and frequency dependencies. The fish length-normalized TS of mackerel decreased with increasing fish length-to-acoustic wavelength ratio (l/λ) in the small l/λ range (approximately 2–6) but was flat in the larger l/λ range (>6). This variation in the normalized TS indicates that a pair of regression equations is necessary to span the range of commercially important mackerel relative to the acoustic wavelength. The relative l/λ characteristic of the normalized TS showed constant values with tilt-angle distributions over a large l/λ range and can be used as a characteristic of acoustic backscattering for discrimination among species.
  • Association of density and sound-speed contrast with maturity stage of Antarctic krill in the eastern Indian sector of the Southern Ocean
    Ryuichi Matsukura; Hanae Doiguchi; Natsuki Yamamoto; Koki Abe; Kazuo Amakasu; Yoshiaki Fukuda; Kohei Hasegawa; Tohru Mukai; Hiroto Murase
    Fisheries Science, Springer Science and Business Media LLC, 20 Sep. 2024, [Peer-reviewed]
    English, Scientific journal
  • Broadband target strength of arabesque greenling, Pacific sand lance, and pointhead flounder
    Naizheng Yan; Tohru Mukai; Kohei Hasegawa; Jun Yamamoto; Yoshiaki Fukuda
    ICES Journal of Marine Science, 81, 1, 195, 203, Oxford University Press (OUP), 12 Dec. 2023, [Peer-reviewed]
    English, Scientific journal, Abstract

    Measurement of target strength (TS) is important for estimating the abundance of species using fisheries acoustics. However, most researchers have only used a limited number of representative frequencies for acoustic measurements of fish without a swim bladder (bladderless fish). Here, we measured the broadband TS of three bladderless fish species, arabesque greenling (Pleurogrammus azonus), Pacific sand lance (Ammodytes personatus), and pointhead flounder (Cleisthenes pinetorum), using two broadband echosounders. TS measurements were conducted in a seawater tank over frequency ranges of 45–90 and 80–120 kHz using a tether method. Higher TS and directivity were observed at higher frequencies than at lower frequencies for pointhead flounder and arabesque greenling. However, the TS for Pacific sand lance was relatively flat over the measured frequency spectra. Additionally, the TS of pointhead flounder and Pacific sand lance could be expressed as a function of body length and the TS of arabesque greenling could be expressed as a function of body length and frequency, which could be used in fish species discriminations and size estimations.
  • Measurements and Theoretical Model Simulation of Target Strength of Pacific Chub Mackerel for Use in a Quantitative Sonar
    Naizheng YAN; Tohru MUKAI; Kohei HASEGAWA; Kohji IIDA; Naotaka TSURUTA
    The Journal of the Marine Acoustics Society of Japan, 50, 4, 107, 122, The Marine Acoustics Society of Japan, 31 Oct. 2023, [Peer-reviewed]
    Japanese, Scientific journal
  • A Prototype Target Strength Measuring System for Small Organisms Using an Acrylic Water Tank
    Yoshiaki FUKUDA; Kohei HASEGAWA; Tohru MUKAI; Tomohito IMAIZUMI
    The Journal of the Marine Acoustics Society of Japan, 49, 2, 37, 45, The Marine Acoustics Society of Japan, Apr. 2022, [Peer-reviewed]
    Japanese, Scientific journal
  • In situ broadband acoustic measurements of age-0 walleye pollock and pointhead flounder in Funka Bay, Hokkaido, Japan
    Kohei Hasegawa; Naizheng Yan; Tohru Mukai
    Journal of Marine Science and Technology, 29, 2, 135, 145, National Taiwan Ocean University, May 2021, [Peer-reviewed], [Lead author]
    English, Scientific journal
  • Acoustic discrimination between juvenile walleye pollock and pointhead flounder
    Naizheng Yan; Tohru Mukai; Jun Yamamoto; Kohei Hasegawa
    Fisheries Research, 224, 105434, 105434, Elsevier BV, Apr. 2020, [Peer-reviewed]
    English, Scientific journal
  • Influence of behavioral patterns of several fish species on their radioactive cesium concentrations revealed with a biotelemetry system after the nuclear accident caused by the 2011 Great East Japan Earthquake
    Keiichi Uchida; Kohei Hasegawa; Yoshinori Miyamoto; Hisayuki Arakawa; Seiji Akiyama; Naoto Hirakawa
    Oceanography Challenges to Future Earth: Human and Natural Impacts on our Seas, 29, 44, Springer International Publishing, 15 Feb. 2019, [Peer-reviewed]
    English, In book
  • 3. Development of monitoring technique for estimating zooplankton density by size using multi-frequency profiler
    SAWADA KOUICHI; MATSUURA TOMOHIKO; MUKAI TOHRU; FUKUDA YOSHIAKI; HASEGAWA KOHEI; ABE KOKI; SASAKI KEI; YAMADA YUICHIRO
    NIPPON SUISAN GAKKAISHI, 84, 5, 947, 947, The Japanese Society of Fisheries Science, 2018
    Japanese, Symposium
  • Development of an online multi-frequency profiler for monitoring zooplankton
    Kouichi Sawada; Tomohiko Matsuura; Kohei Hasegawa; Tohru Mukai; Matt Stone; Kei Sasaki; Hideki Nikaido
    2018 OCEANS - MTS/IEEE KOBE TECHNO-OCEANS (OTO), 2018
    English, International conference proceedings
  • Monitoring the behavior of young bluefin tuna Thunnus orientalis and yellowtail Seriola quinqueradiata in set nets using ultrasonic biotelemetry
    Keiichi Uchida; Hiromichi Ogawa; Kohei Hasegawa; Yoshinori Miyamoto; Hideki Noro; Yuka Wada; Seiji Akiyama
    Nippon Suisan Gakkaishi (Japanese Edition), 84, 1, 14, 22, Nihon Suisan Gakkai, 2018, [Peer-reviewed]
    Japanese, Scientific journal
  • Evaluation of reflection error using ultrasonic telemetry system
    K. Hasegawa; K. Uchida; Y. Miyamoto
    The Journal of the Marine Acoustics Society of Japan, 44, 1, 1, 12, 海洋音響学会, Jan. 2017, [Peer-reviewed], [Lead author]
    English, Scientific journal
  • Prototype of a simple acoustic survey system for attachment to a GPS plotter echo sounder
    Y. Miyamoto; K. Uchida; K. Amakasu; K. Hasegawa; Y. Theparoonart; M. Anongponyoskun; S. Ishikawa; Y. Minlee; T. Sasakura
    The Journal of the Marine Acoustics Society of Japan, 43, 2, 71, 78, The Marine Acoustics Society of Japan, Apr. 2016, [Peer-reviewed]
    Japanese, Scientific journal,

    Biological production is thriving in the coastal areas of Southeast Asia. However, resource evaluation has not progressed. In addition, the valid acoustic research needed for resource assessment is not being conducted or disseminated. Therefore, we developed a simple measurement system to perform acoustic investigations and provide basic education. We then conducted a field test in an effort to understand the distribution of fish schools in Tateyama bay, Chiba, Japan. Depth of the target research area was about 20 m. The acoustic device was composed of a GPS plotter and echo sounder (FURUNO GP1670F)+ Interface Box and PC. The concept has been used previously. However, the equipment is simple and easy to use in collecting acoustic data. First, we assumed the amount of resources for recreational boats to measure the distribution of fish using the fish finder. Results confirmed that the system was sufficiently effective.

  • Development of a real-time depth monitoring system for small fishing gear using an acoustic telemetry technique
    Kohei Hasegawa; Yoshinori Miyamoto; Keiichi Uchida
    FISHERIES SCIENCE, 82, 2, 213, 223, Mar. 2016, [Peer-reviewed], [Lead author]
    English, Scientific journal
  • Position accuracy of ultrasonic biotelemetry system using "Inverse cross bearing"
    K. Hasegawa; Y. Miyamoto; K. Uchida; T. Kakihara
    The Journal of the Marine Acoustics Society of Japan, 39, 4, 163, 172, The Marine Acoustics Society of Japan, Oct. 2012, [Peer-reviewed], [Lead author]
    Japanese, Scientific journal, Tracking system, one of the biotelemetry systems, detects signals from pingers using a receiver located on an observation boat. This system can be used without location constraints, unlike monitoring systems and positioning systems for which a receiver must be installed in the actual sea. But such a system cannot measure the pinger position in detail. In order to measure the pinger position in greater detail using a tracking system, a new method using "inverse cross bearing" was developed. This method determines the horizontal pinger position using the intersection point of more than two bearing lines from as many observation points. The vertical position of the pinger is measured by a depth sensor on the pinger itself. This system calculates the relative azimuth of the pinger using the receiving time differences among the four transducers. The GNSS compass, to convert the absolute azimuth of the pingers relative azimuth, measures the ships heading. To estimate the theoretical error factors, experiments were conducted in actual seas. The estimation results were compared to the results of the field experiments. In certain conditions, the estimated positioning accuracy was 14 m, and the measured value was 21 m. This discrepancy may be due to factors such as agitation of the ship.
■ Other Activities and Achievements
■ Books and other publications
  • Guide to operation of acoustic data collection system (AQFI-1301) for shallow waters
    Y. Miyamoto; K. Uchida; Y. Theparoonrat; M. Anongponyoskun; K. Thongsila; Y. Minlee; T. Sasakura; K. Hasegawa
    Research Institute for Humanity and Nature, Feb. 2017, 9784906888351, English, [Joint work]
■ Lectures, oral presentations, etc.
  • タチウオ曳縄漁業を対象にした漁具深度モニタリングシステムの開発
    長谷川浩平
    令和3年度日本水産学会春季大会第72回漁業懇話会講演会, Mar. 2021, Japanese
  • In situ broadband acoustic measurements of 0-age walleye pollock and pointhead flounder in Funka Bay
    長谷川浩平
    The 13th Annual Meeting of Asian Fisheries Acoustics Society, Nov. 2019, English
  • 遺伝的アルゴリズムを用いた広帯域送受波器の素子配列の最適化
    長谷川浩平
    海洋音響学会2019年度研究発表会, May 2019, Japanese
  • 不規則配列を適用した送受波器のビーム特性シミュレーション
    長谷川 浩平
    海洋音響学会2017年度研究発表会, 24 May 2017, Japanese, Oral presentation
    [Domestic Conference]
■ Syllabus
  • Introduction to Fisheries Sciences Ⅱ（水産科学汎論Ⅱ）, 2024年, 修士課程, 水産科学院
  • 大学院共通授業科目（一般科目）：自然科学・応用科学, 2024年, 修士課程, 大学院共通科目
  • 科学・技術の世界, 2024年, 学士課程, 全学教育
  • 海洋資源科学実験Ⅰ, 2024年, 学士課程, 水産学部
  • 水産科学英語Ⅱ, 2024年, 学士課程, 水産学部
  • 沿岸実習Ⅰ, 2024年, 学士課程, 水産学部
  • 沿岸実習Ⅱ, 2024年, 学士課程, 水産学部
  • 海洋資源科学洋上実習Ⅰ, 2024年, 学士課程, 水産学部
  • 海洋資源科学洋上実習Ⅱ, 2024年, 学士課程, 水産学部
  • 海洋音響学, 2024年, 学士課程, 水産学部
■ Research Themes
  • Acoustic monitoring of Arctic top predators under abrupt climate change
    科学研究費助成事業
    01 Apr. 2024 - 31 Mar. 2028
    Podolskiy Evgeny; 三谷 曜子; 杉山 慎; 深町 康; 長谷川 浩平
    日本学術振興会, 基盤研究(B), 北海道大学, 24K02093
  • 計量魚群探知機を用いた北海道噴火湾に生息する海洋生物の音響判別手法の開発
    科学研究費助成事業
    01 Apr. 2022 - 31 Mar. 2025
    長谷川 浩平
    日本学術振興会, 若手研究, 北海道大学, 22K14931
  • Research for migration and distribution of pointhead flounder in Funka Bay, Hokkaido using acoustic methods
    Grants-in-Aid for Scientific Research
    01 Apr. 2019 - 31 Mar. 2022
    Hasegawa Kohei
    To estimate predation pressure of pointhead flounder on juvenile walleye pollock in Funka Bay, Hokkaido, We investigated the distribution of the both species in the area. Surveys were conducted from April to June when the both species appears in the area. Relative large school of pointhead flounder and walleye pollock was observed and the distribution of the both species overlapped. The overlapping gradually became smaller in scale in May and in June. The results implied that the predation pressure of pointhead flounder on juvenile walleye pollock was largest in April.
    Japan Society for the Promotion of Science, Grant-in-Aid for Early-Career Scientists, Hokkaido University, 19K15891
  • Elucidation of acoustic characteristics of the "floating pointhead flounder" by field and tank experiments and realization of acoustic survey of fisheries resources
    Grants-in-Aid for Scientific Research
    01 Apr. 2019 - 31 Mar. 2022
    MUKAI Tohru
    The acoustic characteristics of pointhead flounder were investigated by field surveys and tank experiments to realize their acoustic resource survey. We accumulated basic information necessary for acoustic resource surveys and identified the optimum survey season. First, in the field survey, we examined the characteristics of the fish schools of pointhead flounder captured by the quantitative echo sounder, and found that they were patchy in the mid-water layer. Next, tank experiments were conducted to investigate the acoustic characteristics and differences in their behavior during the day and night, as a result, acoustic surveys of pointhead flounder should be conducted during the daytime. Finally, we investigated the differences in the frequency characteristics and the echo shapes by the quantitative echo sounder in field surveys of other fish species and zooplankton overlapping with pointhead flounder, and proposed the method for discriminating these species.
    Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 19K06201
  • 道南沿岸域に生息する動物プランクトンの音響散乱特性の解明
    公益財団法人南北海道学術振興財団助成事業
    Apr. 2020 - Mar. 2021
    公益財団法人 南北海道学術振興財団, Principal investigator
  • Development of the design method of 3 in 1 fisheries broadband transducer for acoustic survey
    Grants-in-Aid for Scientific Research
    Jun. 2017 - Mar. 2020
    Sawada Kouichi; Tohru Mukai; Tomohiko Matsuura; Kohei Hasegawa
    By using multiple frequencies, it is possible to distinguish between zooplankton such as euphausiids and fish and to estimate the body length. But until now, it was difficult to introduce them in fishing boats because its cost and space for several transducers to be installed. Previous research has revealed that newly developed broadband transducer can transmit and receive multiple frequencies with a single transducer. However, it takes much time to calculate the layout of many elements (array layout) which satisfies the required performance at each frequency. Therefore, we introduced a genetic algorithm used to obtain optimal values in other fields, developed a method for performing the array layout calculation in a short time, and confirmed it through experiments. To verify the design parameters, we have developed a method to reduce the measurement error in the experiment.
    Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Exploratory), Fisheries Research and Education Agency, Coinvestigator, 17K19303
  • 噴火湾に分布するスケトウダラ仔稚魚を対象とした自然状態での広帯域音響散乱特性の解明
    2019年度笹川科学研究助成
    Apr. 2019 - Feb. 2020
    公益財団法人 日本科学協会, Principal investigator