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Last Updated :2024/07/25

研究者情報

マスター

アカウント（マスター）

  • 氏名

    宮下　和士(ミヤシタ　カズシ), ミヤシタ　カズシ

所属（マスター）

  • 北方生物圏フィールド科学センター　水圏ステーション

所属（マスター）

  • 北方生物圏フィールド科学センター　水圏ステーション

独自項目

syllabus

  • 2021, 生物圏科学特別講義Ⅱ, Special Lecture in Biosphere Science II, 修士課程, 環境科学院, Aquatic Biology, Marine Ecology, Oceanography
  • 2021, 生物圏科学実習Ⅰ, Laboratory and Field Work in Biosphere Science I, 修士課程, 環境科学院, 精子、卵、発生、分化、受精、オルガネラ、生活史、個体群、群集、モニタリング、センシング sperm, egg, development, differentiation, fertilization, organelle, gamete, life history, population, community, monitoring, sensing
  • 2021, 生物圏科学実習Ⅱ, Laboratory and Field Work in Biosphere Science II, 修士課程, 環境科学院, 精子、卵、発生、分化、受精、オルガネラ、生活史、個体群、群集、モニタリング、センシング sperm, egg, development, differentiation, fertilization, organelle, gamete, life history, population, community, monitoring, sensing
  • 2021, 水圏科学特論Ⅱ, Advanced Course in Aquatic Biology II, 修士課程, 環境科学院, 水圏動物、頭足類、スルメイカ、バイオロギング、バイオテレメトリー、海棲哺乳類、高次捕食者、生物多様性、生物地理要素 Aquatic animals, bio-logging, bio-telemetry, cephalopod, Japanese flying squid, marine mammals, top predators, selective breeding, biodiversity, biogeological elements
  • 2021, ﾌｨーﾙﾄﾞ科学基礎論, Fundamental Course in Field Sciences, 修士課程, 環境科学院, 生物資源創成、共生生態系保全、持続的生物生産、生物多様性、生態系機能、生物群集生態 Bio-resources development, Ecosystem conservation, Sustainable bio-production, Biodiversity, Ecosystem function, Population and community ecology
  • 2021, 教科教育法（水産II）, Teaching Method of School Subjects(Fishery Ⅱ), 学士課程, 教育学部, 資源増殖、海洋漁業、海洋工学、情報通信、水産食品
  • 2021, 環境と人間, Environment and People, 学士課程, 全学教育, サケ、回遊、人工ふ化放流、分類、気候変化、資源変動、生活史、個体群密度効果、生物多様性、バイオロギング、母川回帰、嗅覚、物質循環、海水適応、ゲノム、性統御、始原生殖細胞、流通、食品，機能性素材、アスタキサンチン，考古学、先住民族、市民運動
  • 2021, 海洋資源科学実験Ⅲ, Laboratory Work on Marine Resources Ⅲ, 学士課程, 水産学部, 行動生態計測、衛星データ解析－マイクロ波リモートセンシング、海洋観測データ解析、魚類遊泳力学，魚類行動計測、水産海洋工学、数値流体解析
  • 2021, 国際交流Ⅱ, Arts and Science Courses in English 2, 学士課程, 国際本部, Ecosystem conservation, Sustainable bioproduction, Biodiversity, Material cycling, Harmonizable relation between human and environment
  • 2021, 英語演習, English Seminar, 学士課程, 全学教育, 生態系保全、持続的生物生産、生物多様性、物質循環、人間環境共生系
  • 2021, General Education Seminar, General Education Seminar, 学士課程, 総合教育部, 生態系保全、持続的生物生産、生物多様性、物質循環、人間環境共生系
  • 2021, General Education Seminar, General Education Seminar, 学士課程, 現代日本学プログラム課程, 生態系保全、持続的生物生産、生物多様性、物質循環、人間環境共生系
  • 2021, 北方生物圏生態科学, Aquatic Ecology in the Northern Biosphere, 学士課程, 水産学部, 生態系　生態　資源　計測　モニタリング 持続可能性
  • 2021, 環境と人間, Environment and People, 学士課程, 全学教育, 生物資源創成、共生生態系保全、持続的生物生産、生物多様性、生態系機能、生物群集生態

PositionHistory

  • 教育研究評議会評議員, 2022年4月1日, 2024年3月31日
  • 北方生物圏フィールド科学センター長, 2022年4月1日, 2024年3月31日

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プロフィール情報

学位

  • 博士（農学）（東京大学）

プロフィール情報

  • 姓

    宮下, ミヤシタ

  • 名

    和士, カズシ

  • ID各種

    200901007992614296

対象リソース

業績リスト

研究キーワード

  • 生態系サービス   スマート水産業   計量魚探   行動生態   バイオテレメトリー   バイオロギング   海洋生態系計測学   システム水産学   海洋生物資源計測学   音響生態学   海洋計量生態学   海洋生態系変動解析学   水産音響   Marine Acoustical Ecology   Marine Quantitative Ecology   Marine Echosystem Change Analysis   

研究分野

  • ライフサイエンス / 水圏生産科学
  • 環境・農学 / 環境動態解析

経歴

  • 2022年04月 - 現在 北海道大学 北方生物圏フィールド科学センター センター長・教授
  • 2011年07月 - 現在 北海道大学 北方生物圏フィールド科学センター 教授
  • 2007年04月 - 2011年06月 北海道大学 北方生物圏フィールド科学センター 准教授
  • 2002年04月 - 2007年03月 北海道大学 北方生物圏フィールド科学センター 助教授
  • 1998年03月 - 2002年03月 北海道大学 水産学部 助教授
  • 1997年04月 - 1998年03月 海洋水産資源開発センター 職員（技術系）
  • 1996年05月 - 1997年03月 東京大学 海洋研究所 日本学術振興会特別研究員
  • 1996年04月 - 1996年04月 東京大学 海洋研究所 農学特定研究員

学歴

  • 1993年04月 - 1996年03月   東京大学   大学院農学生命科学研究科   水圏生物学専攻（博士課程）
  • 1991年04月 - 1993年03月   北海道大学   大学院水産学研究科   漁業学専攻 （修士課程）
  • 1987年04月 - 1991年03月   北海道大学   水産学部   漁業学科

委員歴

  • 2022年03月 - 現在   音響水産資源調査研究会   会長
  • 2019年05月 - 現在   水産業の明日を拓く スマート水産業研究会 会長
  • 2016年04月 - 現在   北海道総合ICT水産業フォーラム   会長
  • 2014年04月 - 現在   日本バイオロギング研究会   幹事
  • 2013年04月 - 現在   水産海洋学会   評議員（幹事）
  • 2007年 - 現在   Asian Society of Fisheries Acoustics（アジア水産音響学会）   音響調査WG 座長   Asian Society of Fisheries Acoustics（アジア水産音響学会）
  • 2007年 - 現在   Asian Society of Fisheries Acoustics（アジア水産音響学会）   理事   Asian Society of Fisheries Acoustics（アジア水産音響学会）
  • 2016年04月 - 2022年03月   サケ学研究会   幹事
  • 2018年04月 - 2020年03月   サケ学研究会   会長
  • 2017年 - 2020年   北太平洋科学機構（PICES)   国際サケ年（IYS)日本代表委員
  • 2013年04月 - 2017年03月   北太平洋科学機構（PICES)   水産科学委員会委員（FIS)
  • 2011年04月 - 2017年03月   日本水産学会   学会誌編集委員   日本水産学会
  • 2003年04月 - 2008年03月   北太平洋科学機構（PICES)   MIE助言委員会委員   北太平洋科学機構（PICES)

受賞

  • 2019年03月 日本水産学会 水産学進歩賞
     
    受賞者: 宮下 和士
  • 2015年 北海道大学 総長賞（奨励賞）
     
    受賞者: 宮下 和士
  • 2011年 日本弁理士会会長奨励賞
  • 2009年 平成21年度（第16回）河川整備基金助成事業優秀成果
  • 2009年 平成21年度海洋音響学会論文賞
  • 2008年 平成20年度（第15回）河川整備基金助成事業優秀成果
  • 2006年 情報処理学会北海道支部技術研究賞

論文

  • Keizo Ito, Shiori Sonoki, Kenji Minami, Susumu Chiba, Hokuto Shirakawa, Toshifumi Kawajiri, Yanhui Zhu, Kazushi Miyashita
    Scientific Reports 14 1 2024年02月14日 
    Abstract Eelgrass beds provide a habitat for many high-value fishery resources, and provisioning services, one of the ecosystem services, need to be quantified. However, few examples have been evaluated spatially. We determined the distribution of eelgrass beds in Lake Notoro, a marine lagoon in Hokkaido, Japan, and quantified the provisioning services by the eelgrass beds in relation to Pandalus latirostris, a fishery resource. Acoustic measurement surveys of the eelgrass beds and catch surveys of the shrimp were conducted in July and August 2015. The relationship between catch per unit effort (CPUE) of shrimp and the distribution of eelgrass beds was shown. The estimated distribution area of eelgrass beds was 7.07 km2. Shrimp was frequently caught at water depths of 3–5 m, approximately 200 m from the edge of the eelgrass beds. The expected catch of shrimp in the fishing area of Lake Notoro in 2015 was 25.37 tons and US$ 463.6 thousand. Eelgrass beds were found to affect the fisheries production not only on the inside but also at the edge and outside. The entire coastal space should be evaluated, while considering the effect of the distribution of eelgrass beds, to quantify the provisioning services.
  • Yanhui Zhu, Keizo Ito, Kosuke Mizutani, Kenji Minami, Hokuto Shirakawa, Yohei Kawauchi, Yuka Iwahara, Kimiharu Nahata, Nobuhiko Sato, Kyosuke Seki, Mitsuki Kuroda, Kazushi Miyashita
    Fisheries Science 2023年12月01日
  • Kentaro Honda, Koh Hasegawa, Ikuo Ono, Kazushi Miyashita
    Environmental Biology of Fishes 2023年02月25日 [査読有り]
  • Xinyi Li, Hiroshi Yamaguchi, Hokuto Shirakawa, Kenji Minami, Nobuhiko Sato, Yanhui Zhu, Yasuyuki Miyakoshi, Kazushi Miyashita
    Journal of Marine Science and Technology 31 4 2023年01月01日
  • 名畑公晴, 黒川大智, 宮下和士
    日本水産学会誌 88 6 523 - 533 2022年11月15日 [査読有り][通常論文]
  • Yanhui Zhu, Kosuke Mizutani, Kenji Minami, Hokuto Shirakawa, Yohei Kawauchi, Huamei Shao, Makoto Tomiyasu, Yuka Iwahara, Tsutomu Tamura, Masahiro Ogawa, Kai Tatsuyama, Kazushi Miyashita
    Journal of Marine Science and Engineering 10 7 966 - 966 2022年07月14日 [査読有り]
     
    The sandeel species (Ammodytes spp.) occupy a critical ecological position in connecting lower trophic levels to higher ones. However, they are strongly affected by the marine environment and their catch rates are trending downward. In this study, the target strength (TS) of sandeel species was measured in free-swimming specimens using a split-beam quantitative echo sounder with 38 and 120 kHz frequencies in a physically controlled environment. Parameters a and b used in the estimated TSmean–fork length (FL: 13.5–21.5 cm) equation were 53.7 and −124.3 dB at 38 kHz, and 71.3 and −153.2 dB at 120 kHz, respectively. The TS of the sandeel species were not proportional to the square of the FL but increased relatively rapidly with increasing body size. In addition, the mean and standard deviation of the swimming angle for the sandeel species from the acoustic data at 120 kHz were −2.2° and 7.7°, respectively, and most were in the −30° to 30°, range. Furthermore, TS was stronger at 38 kHz than at 120 kHz for all FL classes. The use of such frequency characteristics could facilitate the discrimination of fish species in the field and the sustainable assessment of sandeel species stocks.
  • 成層化したダム湖におけるウグイ（Pseudaspius hakonensis）の生息場と環境要因との関係の解明
    長岡祥平, 黒田充樹, 南憲吏, 沖津二朗, 白川北斗, 大杉奉功, 東信行, 上田健太, 朱妍卉, 中森陸, 佐藤信彦, 宮下和士
    Laguna 29 99 - 114 2022年05月 [査読有り]
  • 福島県さくら湖における計量魚群探知機を用いた藍藻類の音響計測の試み
    中森 陸, 南 憲吏, 白川 北斗, 朱 妍卉, 沖津 二朗, 大杉 奉功, 東 信行, 金 相曄, 谷田 一三, 黒田 充樹, 長岡 祥平, 佐藤 信彦, 宮下 和士
    Laguna 29 87 - 98 2022年03月 [査読有り]
  • Mitsuki Kuroda, Kazushi Miyashita
    Environmental Biology of Fishes 105 12 1845 - 1855 2022年02月01日 [査読有り]
  • Kenji Minami, Hokuto Shirakawa, Yohei Kawauchi, Huamei Shao, Makoto Tomiyasu, Yuka Iwahara, Yuichi Tsuda, Hideo Takahara, Yanhui Zhu, Kazushi Miyashita
    Canadian Journal of Fisheries and Aquatic Sciences 79 2 195 - 199 2022年 [査読有り]
     
    Although chum salmon (Oncorhynchus keta) is an important fishery resource in Japan, acoustic methods cannot be applied to biomass estimation because the target strength (TS) is unknown. This study clarified the TS for each fork length (FL: 5.5–33.5 cm) of young chum salmon inhabiting the Japanese coastal area to the Bering Sea by measuring free-swimming fish. The size dependences of the TS values were TSmean = 20 log10 FL – 68.0, for both 38 and 120 kHz. This facilitated the estimation of biomass of young salmon using acoustic methods.
  • Koki Tsujii, Mayuko Otsuki, Tomonari Akamatsu, Kazuo Amakasu, Minoru Kitamura, Takashi Kikuchi, Amane Fujiwara, Hokuto Shirakawa, Kazushi Miyashita, Yoko Mitani
    Polar Biology 44 12 2289 - 2298 2021年12月 [査読有り]
     
    The Chukchi Sea environment changes considerably in physical and biological conditions, driven by the expanding volume of warm Pacific summer water. These environmental changes can affect the migration timing of baleen whales in the southern Chukchi Sea. However, few studies have been conducted in this area to determine the migration timing of bowhead whales (Balaena mysticetus), the only baleen whale species endemic to the Arctic region. In this study, we conducted a fixed passive acoustic monitoring of bowhead whales in the southern Chukchi Sea from July 2012 to October 2015 and compared the occurrence patterns of vocalizations to physical and biological environmental factors. Bowhead whale calls were detected in fall/winter and spring during the ice-freezing and retreating periods, respectively. The fall migration timing of bowhead whales through the southern Chukchi Sea was delayed in the years when the timing of sea ice formation was late, and it formed increasingly later in the years 2013, 2014, and 2012, in that sequence. Moreover, the sea surface temperature decreased before freeze-up, which affected the timing of fall migration of bowhead whales. There was no clear relationship between the occurrence of bowhead whale calls and the abundance of prey, especially in spring, suggesting that most bowhead whales use the southern Chukchi Sea as a corridor during their spring northward migrations. However, the occurrence of bowhead whales and high abundance of zooplankton in October-November present the possibility that bowhead whales expand their feeding area in the southern Chukchi Sea.
  • Makoto Tomiyasu, Hokuto Shirakawa, Yuki Iino, Daichi Oshiyama, Masahiro Ogawa, Takashi Kitagawa, Hiromichi Mitamura, Nobuaki Arai, Yoshinori Miyamoto, Keiichi Uchida, Kenji Minami, Kazushi Miyashita
    Fisheries Research 242 106020 - 106020 2021年10月 [査読有り]
  • Kenji Minami, Chihomi Kita, Hokuto Shirakawa, Yohei Kawauchi, Huamei Shao, Makoto Tomiyasu, Yuka Iwahara, Hideo Takahara, Takashi Kitagawa, Kazushi Miyashita
    Fisheries Research 240 105955 - 105955 2021年08月 [査読有り]
  • Keiichi Fukaya, Hiroaki Murakami, Seokjin Yoon, Kenji Minami, Yutaka Osada, Satoshi Yamamoto, Reiji Masuda, Akihide Kasai, Kazushi Miyashita, Toshifumi Minamoto, Michio Kondoh
    Molecular Ecology 30 13 3057 - 3067 2021年07月 [査読有り]
  • Mitsuki Kuroda, Yoshinori Tatsu, Yuya Ueda, Hokuto Shirakawa, Kenji Minami, Kazushi Miyashita, Makoto Tomiyasu
    Journal of Marine Science and Technology (Taiwan) 29 2 158 - 167 2021年05月 [査読有り]
  • Development of a Biomass Assessment Method Using Fisheries Echo Sounder for Monit Sounder for Monitoring Whitebait Fisher oring Whitebait Fishery in Shizuoka Pr y in Shizuoka Prefecture, Japan
    Kenichi Kobayashi, Yanhui Zhu, Daichi Oshiyama, Kenji Minami, Hokuto Shirakawa, Kazushi Miyashita
    Journal of Marine Science and Technology (Taiwan) 29 2 168 - 174 2021年05月 [査読有り]
  • Seasonal dynamics in fish distribution and abundance revealed by an acoustic sur acoustic survey in coastal waters of the Suzu Ar y in coastal waters of the Suzu Area, Kochi Pr ochi Prefecture, Japan
    Yanhui Zhu, Kenji Minami, Yuka Iwahara, Kentaro Oda, Koichi Hidaka, Osamu Hoson, Koji Morishita, Sentaro Tsuru, Masahito Hirota, Hokuto Shirakawa, Kazushi Miyashita
    Journal of Marine Science and Technology (Taiwan) 29 2 146 - 157 2021年05月 [査読有り]
  • 浅井咲樹, 内田圭一, 宮下和士, 荒井修亮, 三田村啓理, 北川貴士, 白川北斗, 富安信, 笹倉豊喜, 宮本佳則
    日本水産学会誌 87 2 108 - 116 公益社団法人 日本水産学会 2021年03月15日 [査読有り]
     

    浮魚礁近傍のカツオの行動生態調査は超音波バイオテレメトリーにより行われてきたが，追跡範囲は制限されていた。そこで新手法として超音波受信システムとデータ通信端末を組み合わせた漁船搭載型受信システムを開発した。本研究では浮魚礁周辺で操業する漁船に開発したシステムを搭載し，カツオの行動生態調査における有効性を検証した。その結果，追跡範囲の拡大，GPSによる個体位置情報の取得，1年を超える長期間の追跡に成功した。また，携帯通信網を介したデータの自動収集によってデータ回収の効率化を実現した。

  • 水産資源を可視化する～直接計測、遠隔計測からバイオロギングまで～（新たな海の探求技術）
    宮下和士
    海洋調査 142 20 - 26 2020年10月 [査読無し][招待有り]
  • Spatial niche partitioning among three small cetaceans in the eastern coastal area of Hokkaido, Japan.
    Yuka Iwahara, Hokuto Shirakawa, Kazushi Miyashita, Yoko Mitani
    Marine Ecology Progress Series 209 - 223 2020年03月 [査読有り][通常論文]
  • Mina Jimbo, Daisuke Mizuguchi, Hokuto Shirakawa, Koki Tsujii, Amane Fujiwara, Kazushi Miyashita, Yoko Mitani
    Polar Biology 42 10 1953 - 1958 2019年10月 [査読有り][通常論文]
  • 野外環境下における人工海藻と漁網のニシン Clupea pallasii の産卵床としての活用
    富安信, 白川北斗, 小川真拓, 押山大智, 飯野祐樹, 宮下和士
    水産工学 55 3 2019年02月 [査読有り][通常論文]
  • Minoru Sano, Kazushi Miyashita, Kenji Minami
    Nippon Suisan Gakkaishi (Japanese Edition) 85 2 221  2019年
  • Yohei Kawauchi, Kenji Minami, Hokuto Shirakawa, Kazushi Miyashita, Yuka Iwahara, Makoto Tomiyasu, Motoki Kobayashi, Takeshi Sakai, Huamei Shao, Masahiro Nakagawa
    Nippon Suisan Gakkaishi (Japanese Edition) 85 1 2 - 16 2019年 
    Target strengths (TSs), swimming angles and swimming speeds of free-swimming Japanese jack mackerels (JJMs) with extended body size range (fork length (L)＝12.5-27.5 cm) in an indoor large experimental tank were revealed, based on TS measurements using a split-beam scientific echosounder operating at 38 and 120 kHz. The swimming angles ranged from －35 to 30°, and had a peak of about 0°. Most of the swimming speeds were under 1.2 L/s. TScm, i.e. the mean TS normalized by the square of L, at 38 and 120 kHz were estimated as －67.7 dB and －69.5 dB, respectively. These swimming properties and TScm were similar to those of JJM and related species in previous literatures. Therefore, the present study revealed the practical TSs of JJMs based on actual measurements.
  • Huamei Shao, Kenji Minami, Hokuto Shirakawa, Yohei Kawauchi, Ryuichi Matsukura, Makoto Tomiyasu, Kazushi Miyashita
    Fisheries Research 214 110 - 116 2019年 [査読有り][通常論文]
  • Can Swimming Depth Data from Multiple Pacific Herring Individuals Be Used to Estimate Characteristics if Their School? Verification by Micro Bio-Loggers
    Makoto Tomiyasu, Yuki Iino, Hokuto Shirakawa, Kazushi Miyashita
    Journal of Marine Science and Technology 2019年 [査読有り][通常論文]
  • 屋内大型水槽を用いた自由遊泳するマアジのターゲットストレングス測定
    川内陽平, 南憲吏, 白川北斗, 宮下和士, 岩原由佳, 富安信, 小林基樹, 酒井猛, 邵花梅, 中川雅弘
    日本水産学会誌 85 1 2019年01月 [査読有り][通常論文]
  • Saki Asai, Keiichi Uchida, Kazushi Miyashita, Nobuaki Arai, Hiromichi Mitamura, Takashi Kitagawa, Hokuto Shirakawa, Yoshinori Miyamoto, Toyoki Sasakura
    2018 OCEANS - MTS/IEEE Kobe Techno-Oceans, OCEANS - Kobe 2018 2018年12月04日 
    We conducted an investigation for remaining period and behavioral ecology of skipjack tuna (Katsuwonus pelamis) around the fish aggregating devices (FADs) in the sea near Yonaguni Island, Okinawa, Japan. Skipjack is known that it is altitude migratory fish and stays around an island and artificial fishing reefs 1. The knowledge concerning skipjack ecology and behavior are still poor and the reasons for staying around FADs are unknown. Investigation of migratory fish has a wide movement range and it is difficult to track continuously long-term. For this reason, a method of attaching a data logger directly to a fish body and measuring behavior are mainstream. However, since this method requires recapture of fish for the data collection, the data collection rate is extremely low. In this study, we tried long-term research and improvement of data recovery rate using ultrasonic biotelemetry system and FADs dotted in the sea near Yonaguni Island, Okinawa, Japan. As a result of the investigation, it was possible to confirm received signals of 71 individuals out of the 181 individuals released. And it became clear that many of the received skipjacks stayed more than 10 days and stayed in the sea near Yonaguni Island. Furthermore, we were able to obtain about the migration between FADs and the diurnal behavior around the FADs.
  • 帰山雅秀, 荒木仁志, 宮下和士, 永田光博, 佐々木義隆, 浦和茂彦
    海洋と生物 40 5 459 - 466 生物研究社 2018年10月 [査読無し][通常論文]
  • Heterogeneous Wireless Sensor Networks for Underwater Biogeocenosis Monitoring
    Takahiro Fujiwara, Shinsuke Konno, Hitoshi Gotoh, Hiroyuki Kawai, Kazushi Miyashita, Takao Moriya
    Proceedings of the Workshop on Smart City Based on Ambient Intelligence (SCAI 2018) 2018年08月 [査読有り][通常論文]
  • 浦和茂彦, 荒木仁志, 宮下和士, 永田光博, 佐々木義隆, 帰山雅秀
    海洋と生物 40 4 315 - 318 生物研究社 2018年08月 [査読無し][通常論文]
  • Koji Miyoshi, Yasuhiro Kuwahara, Kazushi Miyashita
    Fisheries Science 84 2 349 - 355 2018年03月01日 [査読有り][通常論文]
     
    The Northern Pacific sea star Asterias amurensis has a major negative impact on scallop mariculture. In northern Japan, fishermen clean up sea stars before releasing young scallops in the mariculture field however, new sea stars constantly invade the field from outside areas to feed on scallops. Thus, it is important to determine the migration speed and seasonal behavioral patterns of the Northern Pacific sea star to implement effective density control measures. Here, we set out to quantify these parameters using acoustic telemetry. In a rearing experiment, acoustic transmitters were retained on sea stars for up to 71 days using nylon fishing line. In the field experiment, we showed that the moving distance of the Northern Pacific sea star over a 1-week period was significantly further in spring (90.9 ± 49.9 m) than in summer (25.1 ± 18.9 m), and that the moving speed was significantly faster in spring (18.1 ± 15.2 m/day) than in summer (4.3 ± 9.1 m/day). Our results are the first to present the two-dimensional movement of Northern Pacific sea star individuals in spring and summer. We suggest that sea star extermination practices should be extended beyond the immediate culture area.
  • Makoto Tomiyasu, Hokuto Shirakawa, Yuki Iino, Kazushi Miyashita
    Fisheries Science 84 1 79 - 89 2018年01月01日 [査読有り][通常論文]
     
    Pacific herring Clupea pallasii inhabiting around Japan migrate to coastal areas to spawn and are often caught by gill and set nets of coastal fisheries. For sustainable resource management, it is necessary to understand the behavioral patterns of such spawning migration in coastal spawning grounds. In this study, the migration of herring found in the Akkeshi region in eastern Hokkaido was revealed using acoustic telemetry. Individuals showed two movement patterns, viz. migration to Akkeshi Lake and remaining in Akkeshi Bay. For those migrating, most individuals entered the lake within 12–48 h. Two individuals reached the end of the lake within 1–3 days, and herring eggs and individuals in the process of spawning were found there. Consequently, this migration is likely related to spawning in the lake. The timing of migration to the lake appeared to be related to tidal dynamics. For those remaining in the bay, pings were detected at several locations, but none in any area beyond the relatively short period of 1–4 days. It is therefore possible that individuals moved more widely and quickly than the detection range of the receiver and the frequency of the survey in the bay.
  • Midori Ishii, Hiroto Murase, Yoshiaki Fukuda, Kouichi Sawada, Toyoki Sasakura, Tsutomu Tamura, Takeharu Bando, Koji Matsuoka, Akira Shinohara, Sayaka Nakatsuka, Nobuhiro Katsumata, Makoto Okazaki, Kazushi Miyashita, Yoko Mitani
    Mammal Study 42 4 191 - 199 2017年12月01日 [査読有り][通常論文]
     
    In this study, we investigated the diving behavior of sei whales relative to the vertical distribution of their potential prey in the western North Pacific during the summer of 2013. Acoustic time-depth transmitters were attached to two sei whales for 10.2 and 32.0 h, respectively. The vertical distribution and density (expressed as the volume backscattering strength, SV) of their potential prey were recorded by an echosounder. Diving behavior was classified into two shapes: U-shaped and V-shaped. For both individuals, U-shaped diving was associated with higher SV values than V-shaped diving and the frequency of U-shaped diving increased from late afternoon until sunset. During the daytime, dense scattering layers (presumably zooplankton) were distributed at approximately 40 m and they then migrated toward the surface around sunset. The diving depth of the whales followed the diel migration of the scattering layers and the diving was concentrated in these layers when the density became high. The results of this study indicate that sei whales change their diving depth and shapes in response to the diel vertical migration of their potential prey.
  • Yuka Iwahara, Yoko Mitani, Kazushi Miyashita
    PACIFIC SCIENCE 71 3 303 - 318 2017年07月 [査読有り][通常論文]
     
    Hydrographic, hydroacoustic, and cetacean visual surveys were conducted using a quantitative echosounder to estimate environmental factors influencing migration timing and distribution of Pacific white-sided dolphins (Lagenorhynchus obliquidens) in the Tsugaru Strait (nonbreeding area) and Funka Bay (breeding area) near Hokkaido, Japan. Higher numbers of dolphins were observed in the Tsugaru Strait during May and June and in Funka Bay during June, July, and August. Potential prey were observed in the Tsugaru Strait in May, June, and August, but they may not have been of a suitable size in August, which may explain absence of the dolphins in that month. In Funka Bay, potential prey were abundant in May, but dolphins may have been absent because of small prey size and low water temperature. In a smaller-scale analysis, the -relationship between dolphins and prey was different in the two areas, with -dolphin distribution more closely associated with prey distribution in the Funka Bay breeding area. This difference may have resulted from mothers needing to feed more frequently during lactation. These data should serve as an important foundation for estimating environmental factors impacting small cetaceans around Japan as well as changing environmental factors during the cetacean life cycle.
  • Kentaro Honda, Nobuyuki Takahashi, Keiichi Yamamoto, Haruka Kagiwada, Yuichi Tsuda, Yoko Mitani, Kazushi Miyashita
    ICHTHYOLOGICAL RESEARCH 64 3 357 - 364 2017年07月 [査読有り][通常論文]
     
    Behavior of adult Parahucho perryi was examined using bio-logging and acoustic telemetry concurrently in the Bekanbeushi River system, eastern Hokkaido, Japan, in 2009 and 2010. Based on 46.1-87.9 h data from five P. perryi (69.0-80.0 cm fork length) caught from Lake Akkeshi, they used upstream (n = 2), midstream (n = 3), and downstream (n = 4) habitats. Large variability in diel activity and depth occupation existed in each stream habitat; however, fish in the downstream habitat tended to be more active than those in the upper habitats and mainly occupied shallower depths than mean bottom depth in this habitat.
  • Huamei Shao, Kenji Minami, Hokuto Shirakawa, Takashi Maeda, Toshiaki Ohmura, Yoshikazu Fujikawa, Norishige Yotsukura, Masahiro Nakaoka, Kazushi Miyashita
    JOURNAL OF MARINE SCIENCE AND TECHNOLOGY-TAIWAN 25 3 343 - 351 2017年06月 [査読有り][通常論文]
     
    Acoustic methods can be used to assess seaweed meadows. The accuracy of the methods is a key factor in the estimation of seaweed distribution and conditions. We obtained and verified thickness and spatial distribution values measured using an echo sounder. We determined the thickness of seaweed growing in the coastal waters off Higashidoori-mura, Aomori, Japan on June 5-6, 2013. Acoustic data were collected using an on-board quantitative echosounder at 120 kHz. The thickness was also directly measured at 14 points. The root mean square error (RMSE) of the thickness determined by the acoustic and direct methods was calculated. A survey to determine the spatial distribution was performed in Miyako-shi, Iwate on July 18, 2014. The estimated spatial distribution was determined from the thickness data collected by the acoustic method of varied transect lines by changing transect orientation and intervals. The kelp forest distribution was also observed directly at 106 points. Then, the concordance rates of the visual observations and estimated spatial distribution were obtained. The RMSE of the acoustic and directly measured thickness of the kelp forests (Saccharina japonica), was 0.06 m, similar to the vertical resolution of the echosounder. The concordance rate between the acoustic and directly measured values was 92% when the maximum transect interval was 21 m. Smaller transect intervals yielded higher accuracy. High accuracy for the thickness and acoustically derived spatial distribution were obtained by the acoustic method when suitable thresholds were used, which has important applications for the evaluation of seaweed stands.
  • Tabitha C. Y. Hui, Yuka Morita, Yumi Kobayashi, Yoko Mitani, Kazushi Miyashita
    MARINE ECOLOGY-AN EVOLUTIONARY PERSPECTIVE 38 3 2017年06月 [査読有り][通常論文]
     
    The number of harbour seals in Japan has been rebounding since protection began in the mid-1980s. With the increase in seal numbers, increased conflict with fisheries has occurred through depredation and the belief that seals compete with fisheries for prey. However, competition can only be determined if the prey species and quantities seals consume over time are known. We studied the diet of harbour seals in Erimo, site of the largest population of harbour seals in Japan, from 2011 to 2012 and assessed the degree of prey overlap with local fisheries. We used both hard parts and DNA techniques to identify prey items in seal scats, and compared these results to local fisheries data. A total of 46 prey occurrences was detected by both methods, of which 17 matched between techniques at least to the family level. Hard parts methods identified five incidences of prey undetected by DNA methods in five scats (one incidence per scat). DNA methods identified 24 additional prey occurrences in 13 scats, for which no hard part evidence for that prey had been found. This more than doubled the total number of prey occurrences across the 15 scats compared. Overall, the most frequently occurring harbour seal prey were walleye pollock (Theragra chalcogramma), sculpins and snailfishes. In contrast, the top three groups targeted by fisheries were codfishes, salmon and invertebrates. Many species common in the harbour seal's diet such as snailfishes and blennies were not targeted by fisheries. Fishes such as greenlings, sculpins, rockfishes and Japanese anchovy (Engraulis japonicus) were common in the diet of harbour seals, but made up a very small proportion of fisheries catches in Erimo. The importance of other prey species varied between seasons. Sculpins, greenlings and forage fishes were the top three prey groups for harbour seals in spring by percent modified frequency of occurrence, whereas the most important target groups by percentage mass caught by fisheries were codfishes, cephalopods and other invertebrates. Sculpins and rockfishes remained as important prey items for harbour seals in summer and autumn, in addition to codfishes, snailfishes and blennies. In contrast, the main groups caught by fisheries in summer were other fishes, particularly Japanese amberjack (Seriola quinqueradiata) and various species of sharks and eels, and invertebrates. By autumn, Erimo fisheries had focussed on catching salmon. Salmon were taken by harbour seals as well during this period, but at a relatively lower frequency compared to other prey groups. The results of our study show that although harbour seals consumed several of the prey species targeted by fisheries, the relative importance of these species to seals and fisheries and the seasons in which they were targeted were different.
  • Daisuke Saijo, Yoko Mitani, Takuzo Abe, Hiroko Sasaki, Chandra Goetsch, Daniel P. Costa, Kazushi Miyashita
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 140 163 - 170 2017年06月 [査読有り][通常論文]
     
    The Transition Zone in the eastern North Pacific is important foraging habitat for many marine predators. Further, the mesopelagic depths (200-1000 m) host an abundant prey resource known as the deep scattering layer that supports deep diving predators, such as northern elephant seals, beaked whales, and sperm whales. Female northern elephant seals (Mirounga angustirostris) undertake biannual foraging migrations to this region where they feed on mesopelagic fish and squid; however, in situ measurements of prey distribution and abundance, as well as the subsurface oceanographic features in the mesopelagic Transition Zone are limited. While concurrently tracking female elephant seals during their post-molt migration, we conducted a ship-based oceanographic and hydroacoustic survey and used mesopelagic mid-water trawls to sample the deep scattering layer. We found that the abundance of mesopelagic fish at 400-600 m depth zone was the highest in the 43 degrees N zone, the primary foraging area of female seals. We identified twenty-nine families of fishes from the mid-water trawls, with energy-rich myctophid fishes dominating by species number, individual number, and wet weight. Biomass of mesopelagic fishes is positively correlated to annual net primary productivity; however, at the temporal and spatial scale of our study, we found no relationship between satellite derived surface primary production and prey density. Instead, we found that the subsurface chlorophyll maximum correlated with the primary elephant seal foraging regions, indicating a stronger linkage between mesopelagic ecosystem dynamics and subsurface features rather than the surface features measured with satellites. Our study not only provides insights on prey distribution in a little-studied deep ocean ecosystem, but shows that northern elephant seals are targeting the dense, species-diverse mesopelagic ecosystem at the gyre-gyre boundary that was previously inferred from their diving behavior.
  • Makoto Tomiyasu, Wan-Yu Kao, Koki Abe, Kenji Minami, Taro Hirose, Michio Ogawa, Kazushi Miyashita
    ICES JOURNAL OF MARINE SCIENCE 73 8 2049 - 2057 2016年09月 [査読有り][通常論文]
     
    During movement, the body angles of ribbonfish change, including a unique vertical swimming motion that influences their target strength (TS). In this study, we observed body angle changes in ribbonfish using an acceleration data logger and video recordings. Based on these data, variations in echo intensity in response to body angle changes were revealed using radiograph images of the swim-bladder and the respective TS values. The frequency of a body angle >60 degrees was 57.78% peak at 77 degrees. The swimbladders were found to be slender ellipses inclined 3-4 degrees upward from the body axis. The TS peaked (about -30 dB for the average pre-anal length of 223.9 +/- 21.8 mm) when the body angle was horizontal or inclined 2-3 degrees downward. The TS decreased substantially when the body angle was vertically inclined. From about 10 degrees upward inclination to vertical, the TS fluctuated between -50 and -60 dB. In a comparison of the average TS values among body angle categories, the TS values for body angles grouped as 'vertical' (between 60 degrees and 90 degrees), showing static mode activity patterns in video recordings, were low (-55.7 +/- 3.9 dB, Mean +/- SD), whereas those for the horizontal body angle (between 0 degrees and 30 degrees) category, comprising the active mode, were high (-47.0 +/- 8.7 dB) (P-value < 0.01). In the natural habitat, ribbonfish are known to gather at the sea floor during the daytime. In contrast, at night they disperse and move actively while foraging. Consequently, their echo intensities in natural habitats change substantially in response to their diel changes in behavioural ecology. Additional measurements or theoretical models considering the influence of ribbonfish behaviour should be undertaken as a result of this study.
  • Koki Tsujii, Mayuko Otsuki, Tomonari Akamatsu, Ikuo Matsuo, Kazuo Amakasu, Minoru Kitamura, Takashi Kikuchi, Kazushi Miyashita, Yoko Mitani
    ICES JOURNAL OF MARINE SCIENCE 73 8 2085 - 2092 2016年09月 [査読有り][通常論文]
     
    Fin whales (Balaenoptera physalus) undergo seasonal migration in the Arctic Sea. Because their migration and distribution is likely affected by changes in global climate, we aimed to examine the migration timing of fin whales, and the relationship with prey availability within the oceanographic environment of the Arctic Sea, using passive and active acoustic monitoring methods. Automatic Underwater Sound Monitoring Systems were deployed in the southern Chukchi Sea from July 2012 to 2014 to determine the acoustic presence of fin whales. Furthermore, water temperature and salinity were recorded by a fixed data logger. An Acoustic Zooplankton Fish Profiler was additionally deployed to estimate prey abundance through backscattering strength. Sea ice concentrations were obtained by remote sensing data. Fin whale calls were automatically detected using a custom-made software, and the per cent of half-hours containing calls were counted. Fin whale calls were detected from 4 August to 20 October 2012 (78 d) and 25 July to 1 November 2013 (100 d). The extended period of acoustic presence of fin whales during 2013 when compared with 2012 is likely related to a longer ice-free period during 2013. Furthermore, generalized linear model analyses showed that half-hour periods containing calls increased with a rise in water temperature and zooplankton abundance during the initial call presence period, while they decreased with a decrease in water temperature and salinity during the end of the call presence period. Our results suggest that the rise in water temperature and zooplankton abundance affect the timing of migration of fin whales in away that is consistent with the expansion of their suitable habitats and the extension of their presence in the Arctic Sea.
  • Yuka Iwahara, Amane Fujiwara, Keizo Ito, Kazushi Miyashita, Yoko Mitani
    POLAR SCIENCE 10 2 173 - 176 2016年06月 [査読有り][通常論文]
     
    Gray whales (Eschrichtius robustus) are distributed within the productive neritic and estuarine waters of the North Pacific Ocean, the Bering Sea, and adjacent waters of the Arctic Ocean. They migrate to high-latitude feeding grounds each spring. Their main feeding grounds in the Arctic include the Chirikov Basin, the northeastern Chukchi Sea from Pt. Hope to Cape Lisburne and Pt. Lay to Pt. Barrow, and the northwestern Chukchi Sea along the Chukotka coast. Although sightings are rare in the Canadian Beaufort Sea, we observed three gray whales in two groups in this area in September 2014. A mud plume was observed near one of the whales, suggesting the animal had been feeding. In the Alaskan Beaufort Sea, large-scale monitoring of the distributions of marine mammals has been continuously conducted since 1979; however, there has been less monitoring in the Canadian Beaufort Sea. Therefore, it is necessary to record opportunistic sightings, such as those described here. (C) 2016 Elsevier B.V. and NIPR. All rights reserved.
  • Salaheddine El Ayoubi, Kamal Mamza, Tadanori Fujino, Koki Abe, Kazuo Amakasu, Kazushi Miyashita
    FISHERIES SCIENCE 82 3 417 - 423 2016年05月 [査読有り][通常論文]
     
    The target strength (TS) patterns of Sardina pilchardus and Sardinella aurita at 38 and 120 kHz were estimated by a prolate-spheroid model, using measurements of swimbladder length and width. The ratio of swimbladder length to total length (TL) was similar in both species, however the ratio of swimbladder width to TL was smaller and more variable for S. aurita. Assuming a normal distribution of fish swimming orientation angle (theta (fish)) with mean +/- A standard deviation (SD) of 0 +/- A 10A degrees, the normalized (by TL) average TS (b (20)) was estimated to be -64.0 dB (38 kHz) and -65.2 dB (120 kHz) for S. pilchardus, and -66.2 dB (38 kHz) and -67.2 dB (120 kHz) for S. aurita. Compared with currently applied b (20) values at 38 kHz, our results under four different theta (fish) assumptions (0 +/- A 10A degrees, 0 +/- A 15A degrees, -5 +/- A 10A degrees, and -5 +/- A 15A degrees) were 6-9 dB higher for S. pilchardus and 5-7 dB higher for S. aurita. This suggests four- to eightfold overestimation risk for S. pilchardus and three- to fivefold overestimation risk for S. aurita when using the currently applied b (20) values.
  • Satoshi Yamamoto, Kenji Minami, Keiichi Fukaya, Kohji Takahashi, Hideki Sawada, Hiroaki Murakami, Satsuki Tsuji, Hiroki Hashizume, Shou Kubonaga, Tomoya Horiuchi, Masamichi Hongo, Jo Nishida, Yuta Okugawa, Ayaka Fujiwara, Miho Fukuda, Shunsuke Hidaka, Keita W. Suzuki, Masaki Miya, Hitoshi Araki, Hiroki Yamanaka, Atsushi Maruyama, Kazushi Miyashita, Reiji Masuda, Toshifumi Minamoto, Michio Kondoh
    PLOS ONE 11 4 e0153291  2016年04月 [査読有り][通常論文]
  • Shiori Sonoki, Huamei Shao, Yuka Morita, Kenji Minami, Jun Shoji, Masakazu Hori, Kazushi Miyashita
    PLOS ONE 11 3 2016年03月 [査読有り][通常論文]
     
    Eelgrass beds are an important source of primary production in coastal ecosystems. Understanding seasonal variation in the abundance and distribution of eelgrass is important for conservation, and the objectives of this study were to 1) monitor seasonal variation in eelgrass beds using an acoustic monitoring method (Quantitative echo sounder) and 2) broadly quantify the carbon circulation function. We obtained acoustic data of eelgrass beds in coastal areas north and east of Ikunojima Island. Surveys were conducted nine times over the 3-year period from 2011 to 2013 in order to monitor seasonal variation. Acoustic data were obtained and used to estimate the spatial distribution of eelgrass by geostatistical methods. To determine supporting services, we determined carbon sink and carbon fixation by eelgrass beds using data from the National Research Institute of Fisheries and Environment of Inland Sea (2011). The height and distribution of eelgrass beds were at a maximum in May and at a minimum in November of each year. Distribution trends were different between the north and east areas. Supporting services showed the same patterns throughout the year. The area of distribution was considered to be coincident with the life history of eelgrass. Distribution differed by area and changed yearly due to the effects of bottom characteristics and wind direction. Quantifying the supporting services of eelgrass beds was shown to be useful for managing the conservation of coastal ecosystems.
  • Takahiro Takashima, Nozomi Okada, Hiroki Asami, Noboru Hoshino, Osamu Shida, Kazushi Miyashita
    FISHERIES SCIENCE 82 2 225 - 240 2016年03月 [査読有り][通常論文]
     
    The sexual maturation process and reproductive biology of female Arabesque greenling Pleurogrammus azonus in the Sea of Japan, off the west coast of Hokkaido, was examined using histological observations of ovaries. Maturation of P. azonus was classified into seven phases based on the presence of nine oocyte stages, post ovulatory follicles, and residual unspawned ova. Although vitellogenesis of P. azonus begins annually in August, hydrated oocytes were present in September and likely occurred several times during the spawning season until November. However, few oocytes at the intermediate stages of development were found during the premature and spawning phases. Based on these observations, the maturation pattern of female P. azonus can be classified as "group-synchronous, spawning several batches in a single spawning season," as in other hexagrammid fish. The probability of maturation of female P. azonus depended on body size rather than age. The estimated length at 50 % maturity was approximately 240 mm in standard length (SL). The mean SL of age-1 females just before the spawning season varied yearly around the 50 % maturity length. Overall, these findings suggest that the growth of female P. azonus before the spawning season at age 1 year can markedly affect spawning biomass.
  • 吉江直樹, 眞野能, 藤井直紀, 宮下和士, 富安信
    沿岸海洋研究 53 2 165 - 167 日本海洋学会沿岸海洋研究部会 2016年 [査読有り][通常論文]
  • バイオロギングによる海洋生物のモニタリング．
    宮下和士
    沿岸海洋研究 53 169 - 172 2016年 [査読有り][通常論文]
  • Wan-yu Kao, Makoto Tomiyasu, Ryuzo Takahashi, Michio Ogawa, Tarou Hirose, Kouhei Kurosaka, Sentarou Tsuru, Yasuhiro Sanada, Kenji Minami, Kazushi Miyashita
    Journal of the marine acoustics society of Japan 42 4 167 - 176 特定非営利活動法人 海洋音響学会 2015年 [査読有り][通常論文]
     
    To ensure sustainable utilization of the hairtail (Trichiurus japonicus) fishery resources in the coastal and offshore waters of Japan, 15 acoustic surveys were conducted from 2007 to 2013 using a 38 kHz split-beam echo sounder. The hairtail was mainly distributed depth between 80 and 280 m in winter (particularly between 80–120 m), 60–280 m in depth (particularly between 120–160 m) in autumn, and 70–260 m in depth (particularly between 70–140 m) in summer. The average area backscattering coefficient (sa) was higher in winter and spring between 2008 and 2009; in the other years it was highest in autumn. The average sa was significantly influenced by depth, temperature, salinity, and turbidity in univariate analyses (p<0.05). However, in linear regression analyses, the average sa significantly increased only with increases in temperature and salinity, whereas the effects of depth and turbidity were not statistically significant.
  • 南憲吏, 安間洋樹, 濱野明, 中村武史, 村瀬昇, 東条斉興, 宮下和士
    海洋音響学会誌 42 1 - 10 2015年 [査読有り][通常論文]
  • Takehisa Yamakita, Hiroyuki Yamamoto, Masahiro Nakaoka, Hiroya Yamano, Katsunori Fujikura, Kiyotaka Hidaka, Yuichi Hirota, Tadafumi Ichikawa, Shigeho Kakehi, Takahiko Kameda, Satoshi Kitajimal, Kazuhiro Kogure, Teruhisa Komatsu, Naoki H. Kumagai, Hiroomi Miyamoto, Kazushi Miyashita, Haruyuki Morimoto, Ryota Nakajima, Shuhei Nishida, Kou Nishiuchi, Shingo Sakamoto, Masayoshi Sano, Kenji Sudo, Hiroya Sugisaki, Kazuaki Tadokoro, Katsuhiko Tanaka, Yoshie Jintsu-Uchifune, Kentaro Watanabe, Hiromi Watanabe, Yumiko Yara, Norishige Yotsukura, Yoshihisa Shirayama
    MARINE POLICY 51 136 - 147 2015年01月 [査読有り][通常論文]
     
    After the adoption of the Aichi Target, data accumulation and evaluation regarding biodiversity have progressed rapidly. The use of ecologically and biologically significant areas (EBSAs) criteria to evaluate important areas enables the identification of effective and prioritized areas for ecosystem management. This includes strategic environmental assessment and discussions aimed at establishing protected marine areas based on scientific data. This paper reviews previous and current ideas as well as the methods used, for the identification of EBSAs. In particular, the following issues are addressed: problems associated with different types of marine ecosystems in the Japanese Archipelago, such as seagrass and seaweed beds, coral reefs, offshore pelagic plankton, and deep-sea benthic ecosystems; and problems associated with the integration of multiple criteria that are not totally exclusive. Several candidate variables accounting for each of the 7 criteria used to identify ecologically important areas are presented. Data availability is the most important criterion that allowed for the comprehensive evaluation of different types of ecosystems in the same localities. In particular, for coastal ecosystems such as seagrass, seaweed beds, and coral reefs, it is possible to carry out broad spatial comparisons using variables representing most of these 7 criteria. Regarding methods for the quantitative evaluation of each criterion and their integration, application of these methods to kelp forest ecosystems in Hokkaido, Northern Japan is presented as a case study. (C) 2014 The Authors. Published by Elsevier Ltd.
  • Hiroshi Yamaguchi, Yoko Goto, Noboru Hoshino, Kazushi Miyashita
    FISHERIES SCIENCE 80 4 665 - 678 2014年07月 [査読有り][通常論文]
     
    We examined growth of northern shrimp Pandalus eous in the Sea of Japan, off western Hokkaido, to improve estimations of catch-at-age for stock assessment. Multiple length frequency analysis based on length frequency data collected by a scientific research vessel was conducted to examine length-at-age in the shrimp population. Multi-normal distributions estimated using maximum likelihood indicated a good fit to length distributions. AIC values and regression analyses revealed annual growth variation and a decreasing trend in the length at several age classes in the shrimp population. We revised the method for estimating catch-at-age from the age-conversion table (ACT), which is a simple method for age determination, to age-length keys (ALK) calculated from the results of multiple length frequency analysis. Abundant year classes caught successively year after year could be more easily identified from the catch-at-age data computed using ALK than by using ACT. Our results suggested not only that the mean size of commercial landings fluctuated based on changes in age composition but also that a decrease in the length-at-age in the population influenced the consistent size decrease of commercial landings.
  • Kenji Minami, Naoki Tojo, Hiroki Yasuma, Yusuke Ito, Takahiro Nobetsu, Shin-ichi Fukui, Kazushi Miyashita
    FISHERIES SCIENCE 80 3 405 - 413 2014年05月 [査読有り][通常論文]
     
    In the Shiretoko Peninsula, a World Natural Heritage site, the sustainable management of kelp forests has drawn public attention because of the economic and ecological importance of kelp. We spatially estimated the distributions of kelp forests in the Shiretoko Peninsula before and after harvest. Field surveys were conducted in coastal waters (23.74 km(2)) at the ends of July and August 2008, immediately before and after harvest. Data on the presence or absence and thickness of the kelp forests were collected via acoustic observation. The data were interpolated using geostatistical methods. Before harvest, the kelp forests were continuously distributed over 5.64 km(2) (thickness 33-132 cm), especially near the north part of the study area. After harvest, they were sparsely distributed over 2.73 km(2) (thickness 35-105 cm). In the southern part of the study area, the influence of harvests was observed as declines in forest area. In addition, relatively thickly forested areas formed the majority of the part most likely to be harvested. Selective harvesting for area and size was confirmed though quantitative mapping of kelp forests. The quantitative mapping of both the distribution and harvest of kelp forests was successful.
  • Kentaro Honda, Haruka Kagiwada, Nobuyuki Takahashi, Kazushi Miyashita
    Ichthyological Research 61 2 142 - 151 2014年04月01日 [査読有り][通常論文]
     
    The behavior of endangered adult Sakhalin taimen Parahucho perryi was tracked during 2008–2010 using acoustic telemetry in the Bekanbeushi River system, which flows through eastern Hokkaido, Japan. Movement distances per unit time of tracked P. perryi were compared between mid- and downstream habitats. Results indicated that movement distances were significantly longer in downstream habitats during all seasons. The movement distances in each stream decreased from spring to autumn. Moreover, tracked P. perryi exhibited crepuscular movement patterns however, patterns were less pronounced in downstream habitats than in up- and midstream habitats. These findings strongly suggested that adult P. perryi exhibit nearly distinctive movement patterns across stream habitats thus, fish may adopt different foraging tactics in each stream habitat. Fish moved more frequently in spring, which included the post-wintering and post-spawning season, most likely to search for food and more desirable habitat for recovery.
  • Osamu Shida, Yukio Mihara, Takashi Mutoh, Kazushi Miyashita
    Fisheries Science 80 2 173 - 179 2014年03月 [査読有り][通常論文]
     
    The southwestern Pacific coast of Hokkaido is the main spawning ground for the Japanese Pacific stock of walleye pollock Theragra chalcogramma. A commercial gillnet fishery targeting spawning adult pollock in this area mainly operates from October to January to coincide with the migration of adult pollock from the feeding ground. Given the results of acoustic surveys, and changes in the proportion of the monthly total catch that was monthly walleye pollock caught by the commercial gillnet fishery, it is thought that the timing of walleye pollock spawning migration to the Donan area varies among years and that the pollock catch of the gillnet fishery clearly reflects changes in pollock abundance in this area. A time series of interannual variability in catch data from 1980 to 2005 suggested that adult pollock migrated and concentrated on their spawning ground later in the 1980s and after 2000 than in the 1990s. Such decadal-scale shifts are presumably caused by climatic changes (e.g., in water temperature) in the Oyashio region. These shifts affect the gillnet fishery through differences in monthly unit prices of pollock and changes in the formation of fishing grounds. These scientific findings can aid the establishment of rules for more efficient walleye pollock resource management under the total allowable catch system.
  • Yohei Kawauchi, Masayuki Chimura, Takashi Mutoh, Masamichi Watanobe, Hokuto Shirakawa, Kazushi Miyashita
    FISHERIES SCIENCE 80 2 139 - 149 2014年03月 [査読有り][通常論文]
     
    We examined factors affecting the vertical distribution of juvenile walleye pollock during "the second critical period" (i.e. the transition period of prey size) in and around Funka Bay, Hokkaido, Japan. During the day, small juveniles (< 30 mm) were distributed mainly in shallow, warm, and low-salinity water within the bay, whereas larger ones (a parts per thousand yen30 mm) occurred in deeper, cold and saline water. During the night, the large juveniles migrated to shallower depths. Outside the bay, small- and large-sized juveniles were distributed in water masses of similar physical properties during the daytime, whereas during the nighttime, most of the juveniles moved to shallower depth, and some juveniles dived to deeper water mass. Dietary analysis revealed that large juveniles fed on large copepods (a parts per thousand yen0.5 mm in body width) more than small juveniles did. The composition of zooplankton in our survey area showed that large-sized copepods often occurred in deeper saline water. From these results, there is a possibility that juvenile pollock inside and outside Funka Bay occupied different water masses preferable for each feeding advantage.
  • 藤田弥生, 大槻真友子, 宮下和士, 三谷曜子, 北夕紀
    東海大学紀要・生物学部 3 3 11 - 17 東海大学生物学部 2014年 [査読無し][通常論文]
  • 石狩川上流におけるサケOncorhynchus ketaの2012年の自然産卵状況．－大規模放流個体群回帰2年目の報告－．
    有賀誠, 山田直佳, 伊藤洋満, 有賀望, 宮下和士
    旭川市博物科学館研究報告 6 21 - 36 2014年 [査読無し][通常論文]
  • 中村 武史, 濱野 明, 安部 幸樹, 安間 洋樹, 宮下 和士
    日本水産學會誌 = Bulletin of the Japanese Society of Scientific Fisheries 79 3 345 - 354 日本水産學會 2013年05月15日 
    計量魚探機によりマアジ幼魚の現存量を推定する上で最適な周波数を検討するため，尾叉長 7.5～12.9 cm のマアジの音響散乱特性を理論と実測から検討した。鰾の計測に基づき推定した理論 TS は実測 TS に近い値を示した。一方，18～200 kHz における最大 TS と平均 TS を尾叉長の二乗で理論的に規準化した規準化最大 TS は−66.2～−68.4 dB，規準化平均 TS は−68.7～−69.9 dB をそれぞれ示した。また，周波数間の TS 差は平均 0 度，標準偏差 15 度の姿勢角範囲内では比較的小さかった。
  • 佐野稔, 前田圭司, 高柳志朗, 和田雅昭, 畑中勝守, 菊池肇, 宮下和士
    北水試研報 84 84 1 - 9 北海道立総合研究機構水産研究本部 2013年 [査読無し][通常論文]
  • 石狩川上流におけるサケOncorhynchus ketaの2011年の自然産卵状況．－大規模放流個体群回帰回帰1年目の報告－．
    有賀誠, 山田直佳, 伊藤洋満, 有賀望, 宮下和士
    旭川市博物科学館研究報告 5 47 - 57 2013年 [査読無し][通常論文]
  • Safruddin, Yohei Kawauchi, Yusuke Ito, Kenji Minami, Kazuhiro Itaya, Keiji Maeda, Ryuichi Matsukura, Koki Abe, Hiroki Yasuma, Kazushi Miyashita
    Journal of the marine acoustics society of Japan 40 329 - 338 2013年 [査読有り][通常論文]
  • Spatial estimation of the kelp forest (Laminaria spp.) distributions in coastal waters of Osatsube Hokkaido, Japan, using acoustic method and geographic information system.
    Huamei Shao, Yusuke Ito, Kenji Minami, Hiroki Yasuma, Kazushi Miyashita
    GIS/Spatial Analyses in Fishery and Aquatic Sciences 5 133 - 150 2013年 [査読有り][通常論文]
  • 松倉隆一, 澤田浩一, 安部幸樹, 南憲史, 永島宏, 米崎史朗, 村瀬弘人, 宮下和士
    日本水産学会誌, 79, 638-648 (2013) 79 4 638 - 648 2013年 [査読有り][通常論文]
     
    The target strength (TS) of juvenile sandeel (3.1-7.7 cm in standard length, SL) was measured for various tilt angles (-30° to 30°) at 120 kHz, and was compared with the theoretical TS calculated using the theoretical sound scattering model. The maximum TS measured at the tilt angle of 0° ranged from -68.8 to -60.8 dB, whereas the range of the theoretical TS was from - 68.7 to - 61.5 dB. The difference of the measured and theoretical values of the maximum TS was -1.6 to 0.9 dB, and the TS patterns showed good agreement, particularly in the range of the main lobes, in the tilt angle (-10° to 10°). The theoretical model was used to calculate the TS under the same conditions where the specimens were collected. The correlation between the SL and the maximum TS is given by the equation: TS=43.1 log SL - 96.1.
  • 理論モデルとTS測定に基づくマアジ幼魚の音響散乱特性．
    中村武史, 濱野 明, 安部幸樹, 安間洋樹, 宮下和士
    日本水産学会誌 79 383 - 393 2013年 [査読有り][通常論文]
  • Tadanori Fujino, Tsuneo Goto, Tsuyoshi Shimura, Hiroki Yasuma, Yongjun Tian, Hideaki Kidokoro, Shinya Masuda, Kazushi Miyashita
    Journal of Marine Science and Technology (Taiwan) 21 1 58 - 62 2013年 [査読有り][通常論文]
     
    Egg abundance of Maurolicus japonicus, a dominant mesopelagic fish in the Japan Sea, was analyzed during 1981-2005 as an index of the spawning-adult abundance. There was a major change in egg abundance around 1988/1989, with negative anomalies occurring during 1981-1988 and positive anomalies occurring from l989. At about the same time (1986/1987), the Tsushima Current shifted from cold to warm conditions. Environmental indices were found to be positively correlated with egg abundance two years later. Our results suggest that the abundance of M. japonicus is affected by climatic regime shifts, and that it could be used as an indicator species.
  • 高嶋孝寛, 星野 昇, 板谷和彦, 前田圭司, 宮下和士
    日本水産学会誌 79 3 383 - 393 2013年 [査読有り][通常論文]
     
    There is a need to establish a method of determining age and to investigate the relationship between the age and body size of the Northern Hokkaido stock of the Arabesque greenling Pleurogrammus azonus. Therefore, we examined the method of age validation by using otoliths, and estimated the relationship between age and size. A mass-processing method was used to section the otoliths. The annual growth of otoliths was verified using edge-type analysis. The age of individual fish could be accurately validated by counting the number of outer edges of the translucent zones. Because of disagreement between the annual growth of otoliths and the formation of checks, the number of checks was considered unsuitable for age validation of the stock. Logistic growth models, which indicated differential asymptotic length by sex, were estimated as the age-size relationship of the stock. The growth of the Arabesque greenling was rapid up to 2 years of age, then slowed. We conclude that age validation is necessary for the stock because it is impossible to predict the age of the fish on the basis of size after 2 years of age.
  • Kentaro Honda, Haruka Kagiwada, Nobuyuki Takahashi, Kazushi Miyashita
    ECOLOGY OF FRESHWATER FISH 21 4 640 - 657 2012年10月 [査読有り][通常論文]
     
    Behavioural tracking of endangered adult Sakhalin taimen (Parahucho perryi) by acoustic telemetry was conducted in the Bekanbeushi River system that flows through eastern Hokkaido in 20082010. A total of 39 tracked P. perryi showed extensive use of the river system, both upstream and downstream, regardless of the month or year. No tracked adult P. perryi stayed in the ocean for more than 1 day. Some of the fish (20%) dwelled in upstream habitat consistently from spring to autumn, while 40% of individuals showed wide utilisation of the entire upstream and downstream systems. Although 39.4% of tracked fish utilised two or more primary tributaries to the main river, 6.1% used only the main river system. Distinct variability was observed between individuals based on the proportion of time spent in each stream reach (up-, mid-, and downstream). A trend was observed in 2008 and 2010 showing that tracked fish moved to the upper stream reaches when water temperatures downstream increased. This trend was not observed in 2009 when the summer water temperature downstream was more than 2 degrees C below average when compared to 2008 and 2010. Our results suggest that adult P. perryi in the Bekanbeushi River system exhibit high behavioural plasticity, that is, the fish can select habitats based on their own individual requirements. Our results also demonstrate the importance of physical continuity among river reaches both upstream and downstream such that P. perryi does not experience barriers in moving to optimal habitats.
  • Hiroto Murase, Atsushi Kawabata, Hiroshi Kubota, Masayasu Nakagami, Kazuo Amakasu, Koki Abe, Kazushi Miyashita, Yoshioki Oozeki
    FISHERIES SCIENCE 78 4 761 - 773 2012年07月 [査読有り][通常論文]
     
    The distribution pattern and biomass of the Japanese anchovy Engraulis japonicus in the offshore region of the western North Pacific (north of 35A degrees N and west of 170A degrees E) were studied using a quantitative echosounder. This is the first attempt at such a study in this region. Data were collected in summer from 2004 to 2007. The biomass was estimated using data collected at 38 kHz. Species compositions in the backscatterings from pelagic fish were assigned based on the results of trawl hauls taking account of sea surface temperature (SST). Japanese anchovy tended to be high density to the west of 153A degrees E and were distributed in an SST range of 9-24 A degrees C. Although the temporal and spatial coverage of the survey differed each year, at least 1.5-3.4 million tons of Japanese anchovy were present in the survey area between 2004 and 2007. To take account of the spatial coverage of the survey each year, the most reliable biomass estimate for this region in the time period was 3.4 million tons (coefficient of variation 0.22).
  • 石狩川上流におけるサケOncorhynchusketaの自然産卵．－大規模放流個体群回帰前の実態－
    有賀誠, 山田直佳, 伊藤洋満, 有賀望, 宮下和士
    旭川市博物科学館研究報告 4 35 - 46 2012年03月 [査読無し][通常論文]
  • K. Honda, T. Arai, S. Kobayashi, Y. Tsuda, K. Miyashita
    JOURNAL OF FISH BIOLOGY 80 2 408 - 426 2012年02月 [査読有り][通常論文]
     
    Acoustic telemetry and microchemical analysis of otolith strontium-calcium ratios were used to evaluate how exotic brown trout Salmo trutta have responded to Japanese riverine environments of south-western Hokkaido by observing their migratory patterns. The existence of anadromous S. trutta was also verified. Most S. trutta caught in rivers for otolith analysis were freshwater residents (95.6%), whereas those caught in the sea were mainly smolts (91.3%), which had just migrated from rivers during spring. Anadromous S. trutta (n = 6) were captured in rivers and in the sea, confirming the existence of mature pre- and post-spawning fish. According to telemetry results, both mature and immature S. trutta used the river in winter, and their estimated sea-run timings showed individual differences. Through the combination of these two methods, migratory patterns on various spatio-temporal scales were observed. This first documentation of the presence of both male and female anadromous S. trutta in the same region within Japan indicated the risk of further colonization of exotic S. trutta via oceanic migration. (C) 2012 The Authors Journal of Fish Biology (C) 2012 The Fisheries Society of the British Isles Key words: acoustic tracking; alien species; anadromy; life history; migration; otolith chemistry.
  • Osamu Tamaru, Kazushi Miyashita, Nobuo Kimura, Yasuzumi Fujimori, Hideo Takahara, Teisuke Miura
    Bulletin of Fisheries Sciences, Hokkaido University 62 3 75 - 82 北海道大学大学院水産科学研究院 2012年 [査読無し][通常論文]
     
    In recent years in Japan, falling fish prices and rising fuel costs have worsened the economic conditions for many fisheries-dependent households. Many fishermen select the fishing ground in which they anticipate they can maximize their total catch, even when such grounds are far from their home harbor. As a result, fishermen have the potential to select a fishing ground in which they do not maximize their income. Especially the Japanese coastal squid jigging fishermen need to develop energy-saving squid jigging fishery practices, because of the high fuel consumption in comparison to other fisheries. By using the Management Simulation Method, we show that income fluctuations are caused by various factors. We used social factors and fishing ground factors in this simulation. According to the simulation results, small changes in social and fishing ground situations can result in changes in selection of the optimal fishing grounds. We conclude that the selection of fishing grounds by fishermen based only on their own knowledge and/or intuition might not result in choices that maximize their income, and it is necessary to develop objective methods to choose the fishing ground in which they can maximize their income.
  • Ko Fujioka, Alistair J. Hobday, Ryo Kawabe, Kazushi Miyashita, Yoshimi Takao, Osamu Sakai, Tomoyuki Itoh
    FISHERIES OCEANOGRAPHY 21 4 269 - 280 2012年 [査読有り][通常論文]
     
    The arrival of the warm tropical Leeuwin Current (LC) into southern Western Australia (SWA) may influence the movement timing and foraging habitat of juvenile southern bluefin tuna (SBT). Seasonal and interannual changes in the strength of the LC lead to thermal differences and potential changes in food availability between tropical and temperate waters in SWA. This phenomenon could influence the habitat utilization of SBT in these summer grounds. Movement characteristics determined from SBT tagged with acoustic transmitters (N = 244) using cross-shelf lines of automated receivers for three summer-autumn seasons (2004/2005, 2005/2006, 2006/2007) in SWA revealed interannual variability. Each year, the eastward movements of tagged fish increased as temperatures increased, and fish left the region when temperatures exceeded 20.0 degrees C, a temperature indicative of the leading edge of the LC in SWA waters. Interannual fluctuations in the timing of movements were detected. When the LC was narrow and restricted to the shelf edge in 2004/2005, the distribution of SBT in shelf waters did not change before or after LC intrusion. In contrast, long distance eastward movements frequently occurred when the LC intrusion was spread wide over the continental shelf in 2005/2006 and 2006/2007. This suggests that, off SWA, juvenile SBT move quickly out of local foraging habitats defined by cool sub-tropical temperate waters ahead of the tropical LC intrusion, despite these waters not being physiologically limiting. These results suggest that the behavioural response of SBT may be related to changes in prey availability as a result of changes in oceanographic conditions.
  • 音響手法を用いたコンブ場の高さ計測
    南憲吏, 安間洋樹, 東条斉興, 伊藤祐介, 福井信一, 野別貴博, 宮下和士
    数理水産科学 9 62 - 74 2012年 [査読有り][通常論文]
  • 南憲吏, 濱野明, 東条斉興, 中村武史, 安間洋樹, 宮下和士
    日本水産学会誌 78 2 171 - 179 2012年 [査読有り][通常論文]
     
    Sargassum beds play important ecological roles as nursery grounds, feeding grounds and hiding grounds for coastal fauna in Kuruminose, Yamaguchi, Japan (12 km 2). In this study, we tried to estimate the spatial distribution of a Sargassum bed using an acoustic method. For this purpose, binarization and geostatistical methods were used. The binarization provided the optimum thresholds to separate the bottom and head of the Sargassum bed. The bottom threshold and the head threshold were -22.4 dB, and -56.4 dB, respectively. The horizontal distribution was interpolated every 1 m 2 using kriging. The area of the Sargassum bed was estimated to be 1.94 km2, with thickness of 0.50 to 2.24 m. The Sargassum bed in the south-southeast of Kuruminose was thicker and larger than that near Kuruminose, suggesting that the south-southeast Sargassum bed is important for the coastal ecosystem in Kuruminose. The estimated thickness and distribution corresponded with those by direct observation by diving and underwater TV camera, suggesting that acoustic measurement is adequate for estimating the spatial distribution of Sargassum beds.
  • Minoru Sano, Keiji Maeda, Siro Takayanagi, Masaaki Wada, Katsumori Hatanaka, Shinichi Motomae, Hajime Kikuchi, Kazushi Miyashita
    NIPPON SUISAN GAKKAISHI 77 6 999 - 1007 2011年11月 [査読有り][通常論文]
     
    The populations of sea cucumber Apostichopus armata in four coastal areas of northern Hokkaido, Japan were estimated based on data collected between June and September 2008 using two methods: the initial population was calculated from CPUE (catch per dredge-net) against cumulative catch (DeLury method), and from the catch against dredged area (swept-area method). The estimation obtained using the DeLury method did not reflect the actual population size in the two areas as the data requirements were insufficient: the slope of linear regression of CPUE on cumulative catch was gentle or the coefficient of determination was low. The estimates using the swept-area method seemed to be lower than the actual population size for all the areas because the catch efficiency was assumed as 1; however, sampling errors were low, as the estimates were based on a large number of sampling data collected directly from a wide area. We conclude that the swept-area method provides a more accurate assessment of sea cucumber stock in the coastal areas of northern Hokkaido than the DeLury method.
  • Hiroto Murase, Atsushi Kawabata, Hiroshi Kubota, Masayasu Nakagami, Kazuo Amakasu, Koki Abe, Kazushi Miyashita, Yoshioki Oozeki
    JOURNAL OF MARINE SCIENCE AND TECHNOLOGY-TAIWAN 19 3 267 - 272 2011年06月 [査読有り][通常論文]
     
    Effect of the depth-dependent target strength (TS) on biomass estimation of Japanese ahcovy was examined by using following four TS models: (1) TS = 20logL(1)-71.9, (2) TS = 20logL(1)-72.5, (3) TS = 20logL(1)-(20/3)log(l+z/10)-67.6 and (4) TS = 20logL(1)-(2013)log(l+z/10)-64.7, where L, and z represent total length (cm) and depth (m), respectively. (1) and (2) have been used in conventional fisheries resources surveys; (3) and (4) take account of depth-dependent TS. Because (1)-(3) were based on in-situ measurement, pitch angles of individuals used in the models were not known. Pitch angle is assumed 00 (+/- 10 degrees std) in (4). Biomass estimated by (3) was 82% and 73% of (1) and (2), respectively. Biomass estimated by (3) was 195% of (4). The results indicated that the effect of the pitch angle on the biomass estimation could be large even if the effect of the depth-dependent TS was taken account. Mean distribution depth can be used as a value for z.
  • Naoki Tojo, Kenji Minami, Ryuichi Matsukura, Yohei Kawauchi, Tetsuichiro Funamoto, Masayuki Chimura, Akira Nishimura, Kazushi Miyashita
    JOURNAL OF MARINE SCIENCE AND TECHNOLOGY-TAIWAN 19 3 294 - 301 2011年06月 [査読有り][通常論文]
     
    This study focused on euphausiid distribution and biomass estimation over the coastal shelf of the Pacific coast of Hokkaido Japan in early summer 2008. Acoustic data were obtained in both day (6:00-18:00) and night (18:00-6:00) using a quantitative echosounder (EK60, Simrad) with two frequencies (120 and 38 kHz). Echoes of euphausiids were specified based on the Delta MVBS, calculated with seasonal theoretical target strength of Euphausia pacifica. The best-fit kriging models were used to quantitatively interpolate euphausiid distribution. The detected euphausiid biomass reached 38,278 t (> 15 gWWm(-2)), suggesting abundant prey for large fishes over study area. On the other hand, the distribution was spatially heterogeneous in produced GIS map, suggesting the spatially limited available prey. Observed day-night difference of estimated biomass was caused by spatial variability of diel movement of euphausiids. Acoustic dead zones and behavioral change in euphausiids may strongly influence biomass estimation in night in coastal shelf environment.
  • Yohei Kawauchi, Osamu Shida, Hiroya Okumura, Naoki Tojo, Hiroki Yasuma, Kazushi Miyashita
    JOURNAL OF MARINE SCIENCE AND TECHNOLOGY-TAIWAN 19 3 279 - 286 2011年06月 [査読有り][通常論文]
     
    We examined the vertical distributions of walleye pollock Theragra chaleogramma juveniles for two size groups (smaller and larger than 30 mm) during the period of transition for feeding (PTF) and after this period in Funka Bay, Hokkaido, Japan. Samplings were conducted in May and June in 2006 and 2007, and water temperature and salinity were measured. The correlation between juvenile sizes and distributed depth was observed using net sampling. From this result, size groups were divided by depth. In addition, the distribution and abundance of juveniles were examined using acoustic data. In the PTF (May), juvenile size increased with increasing depth, and after the PTF (June), most juveniles descended. In the PTF, juveniles smaller than 30 mm in TL dominated above 43 m depth in 2006, while juveniles larger than 30 mm in TL dominated below 18 m depth in 2007. After the PTF, juvenile sizes were larger in 2006 than in 2007. The relationships between juvenile distributions and water masses in the PTF were analyzed, and it was found that surface water of coastal Oyashio water (S-CO) dominated in the layers where small juveniles were distributed, and that Oyashio water (OW) dominated in the layers where large juveniles were distributed.
  • Yusuke Ito, Hiroki Yasuma, Reiji Masuda, Kenji Minami, Ryuichi Matsukura, Saho Morioka, Kazushi Miyashita
    FISHERIES SCIENCE 77 2 161 - 167 2011年03月 [査読有り][通常論文]
     
    The swimming angle of larval Japanese anchovy (Engraulis japonicus) was measured in a tank, and target strength (TS) was calculated using a theoretical scattering model. The mean swimming angle was 12.8A degrees (SD +/- 22.1). Increased speeds of flow led to increased mean swimming angles. The mean swimming angle at flow of 5 cm s(-1) was higher than at other speeds. TS values were estimated using a distorted-wave Born approximation model for two cases. Average values were 1-3 cm s(-1) (11.5A degrees A A +/- A 22.1) and 5 cm s(-1) (16.6A degrees A A +/- A 21.7) for cases 1 and 2, respectively. For case 1, TS ranged from -92.0 to -74.7 dB with a mean of -79.4 dB at 120 kHz. For case 2, TS ranged from -92.2 to -75.2 dB with a mean of -79.9 dB. The mean TS in case 2 was lower than that in case 1, with the maximum difference being 1.0 dB at 120 kHz (standard length 22.0 mm). However, there were no significant differences between the regression lines of cases 1 and 2. Thus, changes in flow speed altered the swimming angle of larval Japanese anchovy, but had little influence on TS.
  • 三谷曜子, 岡崎宏美, 関口圭子, 宮下和士
    北海道大学水産科学研究彙報 61 2/3 65 - 74 北海道大学大学院水産科学研究院 2011年 [査読無し][通常論文]
     
    Killer whales Orcinus orca are cosmopolitan in distribution, but study sites are restricted to small geographic areas, primarily shore-based and boat-based studies focusing on nearshore areas. To contribute understanding about the biology of killerwhales in pelagic areas, we created photographic identification catalogue of killer whales sighted during T/S Oshoro-maru cruise to the northern North Pacific, Bering Sea and Chukchi Sea in 2003, 2005-2009. For 6 years, 37 groups were found, containing 182 whales, and 29 individuals were identified from left side photos of dorsal fin. No individual was re-sighted within-year, nor between-year. And no matches were found between killer whales observed in Alaska, Russian far east seas, Kushiro and Shiretoko, Japan. Our result can serve as background information for the future study of pelagic killer whales.
  • 石狩川中流域におけるサケOncorhynchus ketaの自然産卵
    有賀誠, 山田直佳, 有賀望, 津田裕一, 本田健太郎, 宮下和士
    旭川市博物科学館研究報告 3 63 - 73 2011年 [査読無し][通常論文]
  • 佐野稔, 前田圭司, 高柳志朗, 和田雅昭, 畑中勝守, 本前伸一, 菊池肇, 宮下和士
    日本水産学会誌 77 6 999 - 1007 2011年 [査読有り][通常論文]
     
    The populations of sea cucumber Apostichopus armata in four coastal areas of northern Hokkaido, Japan were estimated based on data collected between June and September 2008 using two methods: the initial population was calculated from CPUE (catch per dredge-net) against cumulative catch (DeLury method), and from the catch against dredged area (swept-area method). The estimation obtained using the DeLury method did not reflect the actual population size in the two areas as the data requirements were insuffcient the slope of linear regression of CPUE on cumulative catch was gentle or the coeffcient of determination was low. The estimates using the swept-area method seemed to be lower than the actual population size for all the areas because the catch effciency was assumed as 1 however, sampling errors were low, as the estimates were based on a large number of sampling data collected directly from a wide area. We conclude that the swept-area method provides a more accurate assessment of sea cucumber stock in the coastal areas of northern Hokkaido than the DeLury method.
  • 山口 浩志, 西内 修一, 高柳 志朗, 宮下 和士
    日本水産学会誌 77 5 809 - 821 2011年 [査読有り][通常論文]
     
    aimed to estimate the size selectivity of the shrimp pot for the northern shrimp Pandalus eous by the SELECT analysis method. Comparative fishing experiments were conducted by using shrimp pots of different mesh sizes (bar length: 13.99, 15.30, 16.84, and 19.13 mm) with control pots of 5.33 mm. We obtained size selective curves for non-ovigerous and ovigerous shrimps. The carapace lengths of 50% of the non-ovigerous shrimps caught (L 50) with mesh sizes of 13.99, 15.30, 16.84, and 19.13 mm were 20.10, 22.75, 26.25, and 28.64 mm, respectively. The carapace lengths of ovigerous shrimps caught with a mesh size of 19.13 mm were significantly different from those of shrimps caught with a non-selective mesh size of 5.33 mm. Therefore, mesh size of less than 19.13 mm was nonselective for ovigerous shrimps. The L50 of ovigerous shrimps caught with a mesh size of 19.13 mm was 25.74 mm. The percentage changes in the total catch and income were calculated when mesh sizes of more than 15.30 mm were used: they decreased by 11.8% and 9.5%, respectively, when the mesh size was modified to 16.84 mm, while they decreased by 31.2% and 27.8%, respectively, when the mesh size was modified to 19.13 mm.
  • K. Honda, H. Kagiwada, N. Tojo, K. Miyashita
    JOURNAL OF FISH BIOLOGY 77 7 1526 - 1541 2010年11月 [査読有り][通常論文]
     
    The study identified seasonal habitat use by endangered adult Sakhalin taimen Hucho perryi and the environmental characteristics of their habitat (water depth, amount of riparian forest and sinuosity). Fifteen adult H. perryi with acoustic tags were tracked by towing an acoustic receiver with a canoe in the Bekanbeushi River system in eastern Hokkaido Island, Japan, during each month from late April to late November 2008. Individuals mainly used midstream (shallower than downstream) habitats in all seasons. These locations were generally characterized by relatively dense riparian forests and high sinuosity, indicating the presence of pools. In spring, individuals used habitats with less riparian forest cover compared to mean value of the river channel. From spring to autumn, adult H. perryi selected limnologically complex habitats with meandering channels. From summer to autumn, individuals selected habitats with more riparian forest cover. The inverse relationship between H. perryi detection and riparian forest area in spring was a result of seasonal defoliation in deciduous riparian forests.
  • Kentaro Honda, Takaomi Arai, Nobuyuki Takahashi, Kazushi Miyashita
    ICHTHYOLOGICAL RESEARCH 57 4 416 - 421 2010年11月 [査読有り][通常論文]
     
    Microchemical analysis of the strontium (Sr) and calcium (Ca) ratios of otoliths was conducted to determine the life history and migration of anadromous Sakhalin taimen, Hucho perryi. In 2008 and 2009, 10 specimens were sampled from Lake Akkeshi in eastern Hokkaido, Japan. Our results indicated that some specimens migrated to brackish waters during their early life histories. Because the Sr:Ca ratios of the specimens in this study were all less than those of specimens from Sakhalin Island during a previous study, specimens from Lake Akkeshi may have migrated to brackish water, or may have remained in the ocean for only a short period.
  • Kenji Minami, Hiroki Yasuma, Naoki Tojo, Shin-ichi Fukui, Yusuke Ito, Takahiro Nobetsu, Kazushi Miyashita
    FISHERIES SCIENCE 76 5 729 - 736 2010年09月 [査読有り][通常論文]
     
    Sustainable management of the kelp forests of the Shiretoko Peninsula, a World Natural Heritage site, is necessary due to kelp's ecological and economic importance. The objectives of this study were to estimate the area of kelp forests and to clarify their spatial characteristics in coastal waters of the Shiretoko Peninsula. Data on the presence/absence and thickness of kelp forests were collected via acoustic observation on transects over about 80 km using an echosounder at 200 kHz. Acoustic data were geostatistically interpolated, and the areas covered by kelp forests were estimated. Differences in kelp distribution between the eastern and western sides of the peninsula were compared. The total area of kelp forest was 3.88 km(2) (eastern area: 3.49 km(2); western area: 0.39 km(2)). The range of thickness of the kelp forests was 34-91 cm. Many kelp forests in the eastern area were thick (>78 cm) and distributed continuously, while kelp forests in the western area were sparsely distributed.
  • Ko Fujioka, Ryo Kawabe, Alistair J. Hobday, Yoshimi Takao, Kazushi Miyashita, Osamu Sakai, Tomoyuki Itoh
    FISHERIES SCIENCE 76 3 403 - 410 2010年05月 [査読有り][通常論文]
     
    Acoustic tags were used to examine the spatial and temporal distribution of southern bluefin tuna (SBT) in southern Western Australia, which is in a region where fishery-independent acoustic surveys of the recruitment abundance index of SBT have been historically undertaken. We investigated patterns of SBT distribution within and inshore of the acoustic survey area during three summer seasons. Annual differences in distribution patterns were characterized by two distinctive migration pathways. An inshore-migrating pathway was observed in two seasons (2004/2005 and 2006/2007), with a relatively high proportion of tagged SBT (84.5, 65.0%) migrating inshore of the acoustic survey area. The other pathway was concentrated along the shelf (2005/2006 season), with an estimated 63.3% of tagged SBT moving within the survey area. These variable migration patterns may bias the interannual fluctuations in abundance indices. Current survey methods can be modified to include both inshore and continental shelf areas. This contribution shows that the accuracy of acoustic surveys can be improved by including ecological patterns.
  • Hiroki Yasuma, Kouichi Sawada, Yoshimi Takao, Kazushi Miyashita, Ichiro Aoki
    ICES JOURNAL OF MARINE SCIENCE 67 1 135 - 144 2010年01月 [査読有り][通常論文]
     
    Yasuma, H., Sawada, K., Takao, Y., Miyashita, K., and Aoki, I. 2010. Swimbladder condition and target strength of myctophid fish in the temperate zone of the Northwest Pacific. - ICES Journal of Marine Science, 67: 135-144.
  • Kenji Minami, Akira Hamano, Takeshi Nakamura, Yoshimi Takao, Hiroki Yasuma, Kazushi Miyashita
    Journal of the Marine Acoustics Society of Japan 37 3 147 - 155 The Marine Acoustics Society of Japan 2010年 [査読有り][通常論文]
     
    The size of vesicles and amount of gas they contain is a major factor in the acoustic scattering of Sargassum plants. Here we investigate the morphological character of the vesicles and gas, and their theoretical and experimental target strength (TS) for two Sargassum species, Sargassum macrocarpum and S. siliquastrum. Both species are abundant in the coastal waters of Japan. A total of 593 vesicles were measured using a soft X-ray system, and their gas shapes were applied to two theoretical TS models (non-resonance and resonance). Experimental TS were obtained at 70 and 200 kHz using quantitative echo sounders in a freshwater tank. Gas fields were found in 418 vesicles, and the gas radius and external size of the vesicles were linearly related in both species. The theoretical TS of the non-resonance model was similar to the experimental TS of large vesicles (≥4.1 mm at 70 kHz, ≥2.8 mm at 200 kHz), whereas the theoretical TS of the resonance model was similar to the experimental TS of small vesicles (≤3.1 mm at 70 kHz, ≤1.9 mm at 200 kHz). Finally, we estimated TS-size equations according to the gas-size relationships and compared the results.
  • Kentaro Honda, Alistair J. Hobday, Ryo Kawabe, Naoki Tojo, Ko Fujioka, Yoshimi Takao, Kazushi Miyashita
    FISHERIES OCEANOGRAPHY 19 2 151 - 158 2010年 [査読有り][通常論文]
     
    Juvenile southern bluefin tuna (Thunnus maccoyii, SBT) were monitored in nearshore waters off southwest Australia using acoustic tagging and monitoring over five austral summers (2002/2003-2006/2007) to determine patterns in age-based distribution of SBT. A total of 20-70 receivers were deployed in early December along one to three cross-shelf transects and at three inshore topographic features (lumps) where SBT are known to occur; and a total of 59-84 juvenile SBT (41-90 cm fork length) were tagged and released each year. After several months, receivers were recovered, and data extracted. In 2002/2003 and 2003/2004, 2-yr-old SBT were detected more frequently in nearshore areas than did 1-yr old fish. Similarly in 2004/2005 and 2006/2007, it was the larger 1-yr-old SBT that were detected more frequently at inshore lumps (> 85% of detections) while small 1-yr-old SBT were detected more widely over the study area. In 2005/2006, although large 1-yr-old SBT were still detected more frequently at inshore lumps than small 1-yr old SBT, the percentage of all detections at lumps was lower at 31.5%, indicating wider distribution of both small and large age-1 fish. The observed age-dependent distribution pattern may be enhanced by the distribution of prey, which disperse or concentrate depending on the local oceanography.
  • 安間洋樹, 大島達樹, 本田聡, 宮下和士, 青木一郎
    日本水産学会誌 76 3 362 - 369 2010年 [査読有り][通常論文]
     
    California headlightfish Diaphus theta is the most abundant mesopelagic fish in the subarctic Pacific. Day- and nighttime field acoustic data and biological samples were obtained in January 2000, in the Pacific area off eastern Hokkaido to estimate fish density and total biomass of D. theta. Sound scattering layers composed mainly of immature D. theta (63 mm length on average) were widely distributed around the shelf edge (> 300 m water depth). Relatively dense schools were observed below the depth of 250 m during the daytime, although the schools were scattered widely above 50 m depth during the nighttime. Fish density was estimated to be 17.3 g/m2 on average, which was more than several times higher than that estimated by conventional methods such as net sampling gears. Total biomass in the survey area (2,083 km2) was estimated to be about 35,900 t.
  • Ko Fujioka, Alistair J. Hobday, Ryo Kawabe, Kazushi Miyashita, Kentaro Honda, Tomoyuki Itoh, Yoshimi Takao
    FISHERIES OCEANOGRAPHY 19 3 183 - 195 2010年 [査読有り][通常論文]
     
    The spatial habitat utilization of juvenile southern bluefin tuna in southern Western Australia was investigated using automated acoustic receivers with acoustic transmitters implanted in tagged fish during three austral summers (2004/2005, N = 79 fish, 2005/2006, N = 81, 2006/2007, N = 84). Seventy acoustic receivers were deployed at three cross-shelf lines and three coastal topographic features (lumps) between December and May. We observed markedly different patterns of habitat utilization between the three seasons: (i) aggregation at lumps in 2004/2005 and 2006/2007, and (ii) wide distribution over the continental shelf (i.e., few occurring at lumps) in 2005/2006. Vertical profile by conductivity-temperature-depth casts showed these spatial shifts were caused by interannual changes in the presence of sub-Antarctic water. The sub-Antarctic water was present in the subsurface layer close to the continental slope only during 2005/2006, and the area had higher chlorophyll-a concentrations than the coastal areas, including at the lumps. These environmental characters, related to the nutrient rich sub-Antarctic water, appear to have a strong influence on fish distributions in 2005/2006, and may occur generally during La Nina events. Interannual fluctuations in habitat utilization will influence detection of fish in recruitment monitoring surveys and thus bias the resulting juvenile abundance indices.
  • Spatial analysis of Isada Krill (Euphausia pacifica) distribution in frontal environments in the North Pacific Ocean
    Naoki Tojo, Ryuichi Matsukura, Hiroki Yasuma, Shiroh Yonezaki, Hikaru Watanabe, Shigeyuki Kawahara, Hiroto Murase, Kazushi Miyashita
    GIS/Spatial Analyses in Fishery and Aquatic Sciences 4 115 - 138 2010年 [査読有り][通常論文]
  • Ryuichi Matsukura, Hiroki Yasuma, Hiroto Murase, Shiroh Yonezaki, Tetsuichiro Funamoto, Satoshi Honda, Kazushi Miyashita
    FISHERIES SCIENCE 75 6 1377 - 1387 2009年11月 [査読有り][通常論文]
     
    The mass density and sound-speed contrasts against surrounding seawater (g and h, respectively) of Neocalanus copepods (N. cristatus and N. plumchrus) were measured in 2006 and 2007 to compute the theoretical target strength (TS). The values of g ranged from 0.997 to 1.009 in N. cristatus and from 0.995 to 1.009 in N. plumchrus. There were no correlations between prosome length (PL) and g. The values of h ranged from 1.006 to 1.021 in N. cristatus and from 1.013 to 1.025 in N. plumchrus and varied with changes in temperature. TS was estimated with the theoretical sound scattering model using the values of g and h based on the temperature, salinity, and depth of the location where the specimens were collected. Regressions of the tilt-averaged TS versus PL were obtained at 38, 120, and 200 kHz. The averaged TS of N. cristatus and N. plumchrus at 120 kHz, which is widely used as a high frequency, ranged from -110.0 to -103.1 dB and from -121.4 to -109.7 dB, respectively. There was a positive correlation between frequency and averaged TS: the higher the frequency, the higher the value of averaged TS. The TS at 120 and 38 kHz varied from 14.8 to 16.4 dB in N. cristatus and from 17.9 to 18.7 dB in N. plumchrus, respectively; that at 200 and 120 kHz varied from 2.9 to 5.5 dB in N. cristatus and from 5.3 to 6.5 dB in N. plumchrus, respectively.
  • Hiroki Yasuma, Ryo Nakagawa, Takashi Yamakawa, Kazushi Miyashita, Ichiro Aoki
    FISHERIES SCIENCE 75 3 545 - 552 2009年05月 [査読有り][通常論文]
     
    Sound-speed and density contrasts (h and g, respectively), important acoustic material properties, of Japanese sandeel Ammodytes personatus were measured to estimate theoretical target strength (TS). The measured sound-speed contrast of adult fish varied between 1.016 and 1.023 (mean 1.020), and showed temperature dependence. The measured density contrast differed significantly between juvenile and adult. The density contrast of juvenile varied between 1.017 and 1.024 (1.021), and that of adult varied between 1.026 and 1.038 (1.032). Using these results, TS at 38 and 120 kHz in the fishing season were estimated by an empirical sound scattering model. TS of an individual fish varied significantly with change of tilt angle. TS of near-dorsal aspect (TS(max)) and tilt-averaged TS (TS(ave)) differed by up to 7 dB. At both frequencies, two different TS(ave)-length relationships (TS(ave) = a log L + b) were obtained for adult and juvenile. The coefficients of log L of adult were close to 20, suggesting that backscattering strength was proportional to square of body length. These values were larger in juvenile (34.0 at 120 kHz, 56.5 at 38 kHz), suggesting that backscattering strength varied drastically with the cube or fifth power of body length.
  • 有賀 誠, 津田 裕一, 藤岡 紘, 本多 健太郎, 光永 靖, 三原 孝二, 宮下 和士
    応用生態工学 12 2 119 - 130 2009年 [査読有り][通常論文]
     
    We tracked eight matured chum salmons (Oncorhynchus keta) using acoustic and radio telemetry to understand their upriver migration around ca. 120 to 180 km site starting from the mouth of the Ishikari River in autumn 2002-2004. This study area was divided into the natural levee area, the gorge area, and the basin area including the past major spawning sites until ca. 1940s. Three tagged fish reached to the basin area, and two fish reached to the natural levee area. The maximum duration of the upstream migration was 17 days, and the maximum migration distance was 56 km. Mean migration speed in the basin area was 6.6 km/day, where the staying behavior was frequently observed, was approximately three times slower than those of the natural levee area (19.5 km/day) and the gorge area (14.8 km/day). The basin area had better conditions of substrates, depth, flow velocity and subsurface flows for O. Keta spawning than the other areas. In addition, groundwater upwelling for egg survival and hatching occurs adequately in the basin area. Their migration patterns reflected geographical differences among three areas. Therefore, the observed slower migration in the basin area was probably due to their pre-spawning behaviors including searching for spawning sites and mates. The faster migration in the natural levee area and gorge areas was due to utilization of these areas as corridors. © 2009, Ecology and Civil Engineering Society. All rights reserved.
  • Alistair J. Hobday, Ryo Kawabe, Yoshimi Takao, Kazushi Miyashita, Tomoyuki Itoh
    TAGGING AND TRACKING OF MARINE ANIMALS WITH ELECTRONIC DEVICES 9 405 - + 2009年 [査読有り][通常論文]
     
    Juvenile southern bluefin tuna (SBT, Thunnus maccoyii), migrate down the coast of Western Australia reaching the southern coast at age-1. In these waters an acoustic survey for SBT schools was initiated to generate a fisheries-independent abundance index. A decline in this abundance index led to an acoustic tagging and monitoring project to determine if a change in migration route or timing could explain the decline. Five years of acoustic monitoring revealed interannual differences in key factors that could impact the abundance index. Acoustic tag data were used to demonstrate that (i) a high proportion of fish (similar to 70%) may be too shallow for detection in the acoustic survey, and that interannual variation in (ii) inshore-offshore fraction (similar to 30-70% each year) and (iii) residence time (12-37 days) will impact calculation of an index. These factors should be included in estimating an abundance index for SBT, together with a correction for (iv) the fraction of juvenile SBT that migrate to southern Western Australia. Collectively, these results illustrate how electronic tagging data can be used to improve understanding of abundance patterns necessary for sustainable management of this exploited species.
  • 本多健太郎, 野田裕二, 津田裕一, 宮下和士
    日本生態学会誌 29 239 - 247 2009年 [査読有り][通常論文]
  • Hiroto Murase, Morio Ichihara, Hikaru Watanabe, Shiroh Yonezaki, Shigeyuki Kawahara, Kazushi Miyashita
    Fisheries Oceanography 386 401  2009年 [査読有り][通常論文]
  • Tadanori Fujino, Kazuhiro Sadayasu, Koki Abe, Hideaki Kidokoro, Hiroki Yasuma, Kazushi Miyashita
    Journal of the Marine Acoustics Society of Japan 36 4 241 - 249 海洋音響学会 2009年 [査読有り][通常論文]
  • Hiroto Murase, Morio Ichihara, Hiroki Yasuma, Hikaru Watanabe, Shiroh Yonezaki, Hiroshi Nagashima, Shigeyuki Kawahara, Kazushi Miyashita
    FISHERIES OCEANOGRAPHY 18 6 386 - 401 2009年 [査読有り][通常論文]
     
    The acoustic characteristics of biological backscattering in the western North Pacific were studied to verify expert knowledge on species composition in the echosigns. The survey was conducted in the Kuroshio-Oyashio inter-frontal zone and the subarctic waters in April 2003. The species composition of backscatterings was identified by using midwater trawl, Isaacs-Kidd midwater trawl and Bongo net. The differences of mean volume backscattering strengths between 120 and 38 kHz (Delta MVBS(120-38)) were calculated for the backscatterings. Six types of backscatterings were classified based on the results of net samples and the Delta MVBS(120-38). The Delta MVBS(120-38) of each group was as follows: copepods 13.7-17.3 dB, krill 11.6-15.3 dB, Japanese anchovy -1.6 to 1.1 dB, a myctophid, Diaphus theta-0.8 dB, sand lance 6.1 dB and larvae and juveniles of pelagic and mesopelagic fish -9.6 to -4.0 dB. The results suggest that biological backscatterings in the Kuroshio-Oyashio inter-frontal zone and subarctic waters of the western North Pacific in spring can be characterized by using Delta MVBS.
  • 本多 健太郎, 野田 裕二, 津田 裕一, 安間 洋樹, 宮下 和士
    日本生態学会誌 59 3 239 - 247 日本生態学会暫定事務局 2009年 [査読有り][通常論文]
     
    現在、絶滅危惧種イトウ(<i>Hucho perryi</i>)の日本における生息分布域は、北海道の一部の河川と湖沼に限られている。本種成魚の生態は、産卵習性に関する知見以外はほとんど知られていない。そこで、本研究では超音波テレメトリー手法を用いてイトウ成魚の季節的な移動パターンを明らかにする野外調査を実施した。北海道東部の別寒辺牛川(べかんべうしがわ)水系において、2007年4月下旬から11月下旬の間、超音波受信機・発信器により5個体のイトウ成魚の行動を追跡した。放流後、5個体すべてからデータが得られ、総受信回数は37,683回であった。上流域で放流した標識個体は、1〜4日かけて平均33.4±12.5km(Mean±SD)を降下した。降下後、調査期間にわたってほとんど移動しない個体と広範囲に移動する個体がみられたが、全体として、春季(5〜6月)は中流域から下流域、夏季(7〜8月)は中上流域から下流域、秋季(9〜11月)は下流域に主に生息する傾向を示した。ロジスティック回帰分析の結果、夏季に下流域に生息する標識魚の上流側への移動は現場の日最高水温の影響を強く受け、春季および秋季における中上流域の日最低水温は標識魚の下流への移動を促すことが明らかとなった。本魚による河川内の季節的回遊行動には、河川の水温レジームが関与することが示唆された。
  • 志田修, 三宅博哉, 金田友紀, 石田良太郎, 宮下和士
    日本水産学会誌 74 2 152 - 160 2008年03月 [査読有り][通常論文]
     
    To understand winter distribution patterns of young walleye pollock Theragra chalcogramma and its determinants, we conducted an echo integration survey on the Pacific coast of eastern Hokkaido (the Doto area) in late February of 1998. Pollock aggregations were mainly located from the shelf edge to the continental slope region (150-400 m) with temperature ranging from 2 to 4°C. In contrast, the fish echoes were not present in the continental shelf region, which was dominated by the low temperature (< 2°C) and low salinity (< 33.0) Coastal Oyashio Water. Walleye pollock showed diel vertical migration patterns, involving staying near the bottom during the day and rising to the mid-water area at night. Our results show the fish's (1) offshore-ward movements and (2) concentrations in deeper water in winter. These observed pollock distribution changes were probably enhanced in marine environmental dynamics, caused by intrusion of the Coastal Oyashio Water into the shelf region. It is suggested that such distribution changes affect young pollock survival and are important for determining year class strength.
  • 永島宏, 村瀬弘人, 米崎史郎, 松倉隆一, 南憲吏, 永木利幸, 川原重幸, 宮下和士
    宮城県水産研究報 8 8 15 - 25 宮城県水産研究開発センター 2008年 [査読無し][通常論文]
     
    春季仙台湾周辺海域に分布する優占種であり、ミンククジラの餌生物として重要であると共に、沿岸漁船漁業の漁獲対象資源であるイカナゴ、ツノナシオキアミについて、計量魚探による音響調査時の魚種確認中層トロール採集で得られたデータを基に、魚群音響エネルギー・形状・分布水深・分布環境に関する計測データから、魚探反応魚種を判別する方法を検討した。その結果、判別対象群の母平均推定量とのマハラノビスの汎距離が最短になる群を判別群とすることで、的中率が96％になる判別方法が得られ、今後の音響調査の効率化と客観性が高められた。
  • 太平洋西部におけるツノナシオキアミ（Euphausia pacifica）の分布特性の定量的空間解析
    東条斉興, 清水大介, 安間洋樹, 川原重幸, 渡辺光, 米崎史郎, 村瀬弘人, 宮下和士
    水産海洋研究 72 165 - 173 2008年 [査読有り][通常論文]
  • 安間 洋樹, 澤田 浩一, 宮下 和士, 青木 一郎
    海洋音響学会誌 35 1 17 - 28 海洋音響学会 2008年 [査読有り][通常論文]
  • Osamu Shida, Tomonori Hamatsu, Akira Nishimura, Akifumi Suzaki, Jun Yamamoto, Kazushi Miyashita, Yasunori Sakurai
    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY 54 23-26 2822 - 2831 2007年 [査読有り][通常論文]
     
    The Japanese Pacific walleye pollock (Theragra chalcogramma) stock is the largest stock of this species in Japanese waters. It is a key component of the Oyashio ecosystem. In southern Hokkaido waters, these fish spawn mainly during January and February near the mouth of Funka Bay (FB), and most eggs and larvae are transported into FB. During midsummer juvenile pollock migrate along the southern coast of Hokkaido to a nursery ground on the continental shelf off eastern Hokkaido (Doto area). However, some eggs and larvae are transported southward to the Tohoku region (TR). Transport depends largely on the Oyashio. which generally flows southward along the eastern coasts of Hokkaido and Tohoku. Thus, this stock has two different recruitment routes: FB-Doto and FB-TR. In the 1980s, when the southward flow of the Oyashio was strong, the number of age-2 pollock estimated from a virtual population analysis (VPA) indicated that recruitment to the entire stock remained at a medium level. In the 1990s, when the Oyashio weakened, strong year-classes occurred in 1991. 1994, and 1995, but not in the latter half of the 1990s. Juvenile catches in the TR by commercial fisheries, which can be taken as indices of recruitment level via FB-TR, were high during the 1980s and decreased in the 1990s. Although there was no significant difference in the average number of recruits between the 1980s and the 1990s as estimated from a VPA, the recruitment patterns differed between the two decades. Here, we propose that recruitment routes of this stock shifted in response to environmental changes. (C) 2007 Elsevier Ltd. All rights reserved.
  • Atsumu Watanabe, Kazushi Miyashita, Ryuich Matsukura, Saho Morioka, Yoshihiro Ikewaki, Keisuke Mori
    GIS/Spatial Analyses in Fishery and Aquatic Sciences 3 347 - 359 2007年 [査読有り][通常論文]
  • H Yasuma, Y Takao, K Sawada, K Miyashita, Aoki, I
    ICES JOURNAL OF MARINE SCIENCE 63 4 683 - 692 2006年05月 [査読有り][通常論文]
     
    This paper reports theoretical values of target strength (TS) for the lanternfish Stenobrachius leucopsarus, a fish without an airbladder, which dominates the Subarctic marine mesopelagic fish community. Two models for liquid-like slender bodies, the general prolate-spheroid model (PSM) and the deformed-cylinder model (DCM), were used to compute the TS of the fish relative to its orientation. The relative mass density g and the sound speed h in sea-water were measured and used in both models. To confirm the appropriateness of the models, tethered experimental measurements were carried out at 38 kHz for five specimens. The value of g measured by the density-bottle method was very low (1.002-1.009) compared with that of marine fish in general. The value of h measured by the time-average approach was 1.032-1.039 at the water temperature at which S. leucopsarus is found. TS-fluctuation patterns against fish orientation (the TS pattern) estimated from the DCM and PSM were in good agreement in the area of their main lobes. Both models reproduced the main lobes of the measured TS patterns in near-horizontal orientation (<+/- 20 degrees), and they were considered to be effective in measuring the TS of S. leucopsarus in a horizontal (swimming) position. After these comparative experiments, we computed the TS of 57 fish (27.8-106.9 mm) at 38, 70,120, and 200 kHz, using the DCM. A plot of body length (in log scale) against TS showed a non-linear relationship at all frequencies. S. leucopsarus had a very low TS (<-85 dB, TScm), suggesting that acoustic assessment would be highly sensitive, especially when the proportion of small fish is high (e.g. L/lambda < 2), and an appropriate frequency should be considered that takes into account both the length composition and the depth of occurrence. (c) 2006 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All fights reserved.
  • 鈴木勝也, 高木力, 宮下和士
    数理水産科学 4 23 - 28 数理水産科学研究会 2006年 [査読有り][通常論文]
  • S Torisawa, K Miyashita, R Kawabe, Y Fujimori, T Oshima, S Honda, K Sato
    FISHERIES RESEARCH 77 1 4 - 9 2006年01月 [査読有り][通常論文]
     
    Although visual information can help to monitor fish behavior in situ, quantitative analysis from images is difficult. There is little quantitative information from images on fish behavior in situ. In this study, we used digital still-picture loggers (DSLs) to monitor the bearing and tilt angles of walleye pollock, Theragra chalcogramma, in a trawl in situ. We attached two DSLs to a trawl net and recorded still pictures of fish near the mouth of the trawl. Eleven pictures of walleye pollock were obtained during 79 trawl surveys. From the still images, we calculated the bearing and tilt angles of the fish using the ratio of body length and body height. We confirmed the accuracy of the calculated angles by comparing the computed angles using image-processing software. The calculated angles agreed with the angles computed using the software. Therefore, our simple method can be used to monitor fish bearing and tilt angles in situ. Based on our results, bearing angles of walleye pollock were not shown in the same direction to a trawl. Furthermore, the fish tilt angles differed significantly between adults and juveniles. (C) 2005 Elsevier B.V. All rights reserved.
  • 藤野忠敬, 宮下和士, 青木一郎, 増田紳哉, 氏良介, 志村健
    日本水産学会誌 71 6 947 - 956 2005年11月 [査読有り][通常論文]
     
    We examined threshold-setting methods to identify Maurolicus japonicus SL (Scattering Layer) in the Sea of Japan. Acoustic survey data were collected in several months (May, June, Aug., Sep., and Oct.) from 2000 to 2003 around the Oki Islands, southwest of the Sea of Japan. The results showed the following threshold-setting method to be appropriate: to set the value as the lower limit SV threshold obtained by subtracting 10 dB from the averaged maximum SV of the water column. The depth range extracted by this method matched the existence of M. japonicus confirmed by the bottom and midwater trawl sampling. This method corresponds to the change of packing density by seeking the threshold baseline from the M. japonicus SL.
  • T Fujino, K Miyashita, Aoki, I, S Masuda, R Uji, T Shimura
    NIPPON SUISAN GAKKAISHI 71 6 947 - 956 2005年11月 [査読有り][通常論文]
     
    We examined threshold-setting methods to identify Maurolicus japonicus SL (Scattering Layer) in the Sea of Japan. Acoustic survey data were collected in several months (May, June, Aug., Sep., and Oct.) from 2000 to 2003 around the Oki Islands, southwest of the Sea of Japan. The results showed the following threshold-setting method to be appropriate: to set the value as the lower limit S-v threshold obtained by subtracting 10 dB from the averaged maximum S-v of the water column. The depth range extracted by this method matched the existence of M. japonicus confirmed by the bottom and midwater trawl sampling. This method corresponds to the change of packing density by seeking the threshold baseline from the M japonicus SL.
  • Y Fujimori, K Chiba, T Oshima, K Miyashita, S Honda
    FISHERIES SCIENCE 71 4 738 - 747 2005年08月 [査読有り][通常論文]
     
    Variations in trawl dimension, bottom contact, and catch with differing warp lengths during walleye pollock surveys conducted by the Fisheries Research Agency were examined. The ratio of warp length to fishing depth (scope ratio) was set at 2.5, 3.0 and 3.5 at depths of 110 m. At a 2.5 scope ratio, the net mouth shape and footgear contact fluctuated, as the trawl door did not contact the bottom. Footgear contact was complete when the scope ratio was 3.0 or more. Walleye pollock, sculpins and flatfishes were the main catch in all tows, and the catch increased with scope ratio. There was no difference in the length frequency of walleye pollock (n = 300) captured at 2.5 and 3.0 scope ratio. However, the length frequency at 3.5 was significantly different from that of other scope ratios. These results suggest that at a scope ratio of 3.0 or more, the trawl door will not leave the bottom at any depths. To compliment echo surveys for walleye pollock, a 3.0 scope ratio would be optimal, since the catch data for a 3.5 scope ratio was dissimilar from that of scope ratios.
  • 魚群行動における視覚と側線感覚機能の数理モデルによる評価
    鈴木勝也, 高木力, 鳥澤眞介, 福田漠生, 村田修, 山本眞司, 宮下和士
    数理水産科学 3 37 - 42 2005年 [査読有り][通常論文]
  • K Miyashita, K Tetsumura, S Honda, T Oshima, R Kawabe, K Sasaki
    FISHERIES OCEANOGRAPHY 13 Suppl. 1 99 - 110 2004年12月 [査読有り][通常論文]
     
    In this study, we tried to accurately discriminate between zooplankton and walleye pollock using a quantitative echosounder at two frequencies (38 and 120 kHz). To estimate the abundance of walleye pollock and zooplankton (mainly Euphausia pacifica), an acoustic and trawling survey with bongo net sampling and CTD (X-CTD) was conducted during June 2001 off the Pacific coast of eastern Hokkaido, Japan. Neocalanus copepods and E. pacifica were predominant in almost all the net samples. One Size class of Neocalanus copepods (mean TL +/- SD = 2.0 +/- 1.1 mm, N = 1 044 080) and two size classes of E. pacifica (mean TL +/- SD = 6.1 +/- 2.2 mm, N = 13,099; mean TL +/- SD = 15.4 +/- 3.6 mm, N = 7628) were collected. The distribution patterns of these two classes and of walleye pollock were identified using the volume back scattering strength (Sv) difference method. On the continental shelf, the walleye pollock schools (small walleye pollock: mainly age 1 and 2) overlapped with almost all zooplankton layers during both day (near the sea bottom and mid-water) and night (mid-water and sea surface). Near and offshore of the continental shelf break, during day, the walleye pollock schools (large walleye pollock: mainly older than age 3) overlapped with almost all zooplankton layers near the sea bottom, but during night, the large walleye pollock schools (which were mainly distributed near the sea bottom) showed little overlap with most zooplankton layers (which were mainly distributed between mid-water and sea surface). This result suggests differences in feeding strategies between small and large walleye.
  • D Kang, K Sadayasu, S Mukai, K Iida, D Hwang, K Sawada, K Miyashita
    FISHERIES SCIENCE 70 5 819 - 828 2004年10月 [査読有り][通常論文]
     
    Black porgy are hatched and released in marine ranching areas in Japan, Korea and Taiwan to maintain fisheries resources in coastal areas. If acoustic methods are used for field surveys, target strength (TS) information on the species is needed to convert acoustic data to biomass density. Target strength of black porgy (Acanthopagrus schlegeli) 15.5 - 32.9 cm fork length (nine individuals) was measured at 38 and 120 kHz (split beam) by ex situ measurements (cage and fishhook methods) of living fish, a tethered method with shock-frozen fish, and an acoustic scattering model, the Kirchhoff ray mode (KRM) model based on fish morphology. The ex situ TS-to-fork length (FL, cm) relationships were TS38kHz = 20log(10)FL - 64.6 (r = 0.77) and TS120kHz, = 20log10FL - 65.2 (r = 0.70). The values for the KRM model were TS38kHz = 20log(10)FL - 64.8 (r = 0.88) and TS120kHz = 20log(10)FL - 65.4 (r = 0.80). The agreement between the ex situ measurements and the KRM model for the mean TS was very good. In contrast, the results for the tethered method (TS38kHz, = 20log10FL - 69.3 [r = 0.42]) differed markedly from the other two methods, perhaps because of the effects of the shock-freezing procedure in air. The results of the ex situ measurements and scattering model provide basic information for studying TS and conducting acoustic surveys of black porgy, even though the tethered method must be modified.
  • R Kawabe, Y Naito, K Sato, K Miyashita, N Yamashita
    ICES JOURNAL OF MARINE SCIENCE 61 7 1080 - 1087 2004年10月 [査読有り][通常論文]
     
    It is well known that flatfish species such as plaice can utilize the selective tidal stream to conduct vertical movements. However, detailed description of actual swimming behaviour is lacking, principally as a result of the difficulties encountered in monitoring the behaviour of flatfish in the open sea. The present study describes the use of a newly developed data-logger in obtaining simultaneous recordings of the swimming speed, depth, tailbeat, and body angle of free-ranging Japanese flounder (Paralichthys olivaceus) in the open sea. Our data indicate that Japanese flounders adopt a tailbeat-and-glide behaviour. They are found to glide downward without tailbeats for propulsion, and only during the ascent phase are tailbeats conducted. Flounders move horizontally at speeds of 0.59-1.23 km d(-1) and at a maximum speed of 0.70-0.82 km h(-1) in the open sea. Modal flounder swimming speeds are 30-40cms(-1) (0.57-0.76 and 0.58-0.77BLs(-1)), i.e. sometimes lower than the threshold of the speed sensor. In most cases, however, tailbeat oscillations occur at frequencies of 1.2-1.4 Hz. Moreover, flounders travel at a significantly steeper angle during the ascent phase than during the descent phase. In both cases it is believed that flounder optimize the energetic costs of migration, as has been shown for tuna, sharks, and seals. (C) 2004 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.
  • 異なる光環境下における魚群の行動特性について
    鈴木勝也, 髙木 力, 鳥澤眞介, 宮下和士
    数理水産科学 2 37 - 42 2004年 [査読無し][通常論文]
  • 鈴木 勝也, 高木 力, 宮下 和士
    日本水産工学会学術講演会講演論文集 16 195 - 196 2004年 [査読無し][通常論文]
  • Kazushi Miyashita
    ICES Journal of Marine Science 60 3 532 - 537 2003年06月 [査読有り][通常論文]
     
    Diurnal changes in the acoustic-frequency characteristics of "shirasu", a post-larval stage of Japanese anchovy (Engraulis japonicus), were analysed based on theoretical scattering models. Since post-larval swimbladders contain gas at night but not during the day, the distorted-wave Born approximation (DWBA), based on the deformed-cylinder model, which assumes there is no gas in the swimbladder, was applied to daytime observations, and the fish-bladder resonance model, which assumes there is gas in the swimbladder, to those taken at night. The two sets of acoustic frequencies employed were 50 and 200 kHz, which are those used for shirasu commercial fishing, and 38 and 120kHz, which are usually employed for acoustic surveys using a quantitative echosounder. During the daytime, differences in shirasu target strengths between the two frequencies were large, especially between 38 and 120 kHz, but at night there was little difference with frequency, suggesting that acoustic surveys for identifying and estimating the abundance of shirasu should be done during daytime, when differences occur between frequencies and the shirasu form dense schools. (C) 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.
  • H Yasuma, K Sawada, T Olishima, K Miyashita, Aoki, I
    ICES JOURNAL OF MARINE SCIENCE 60 3 584 - 591 2003年06月 [査読有り][通常論文]
     
    This article reports theoretical values of target strength (TS) for mesopelagic lanternfishes based on morphological measurements of their swimbladders. Three species of lanternfishes, Diaphus theta (26.9-77.4 mm standard length (SL)), Symbolophorus californiensis (85.0-108.4 mm SL), and Notoscopelus japonicus (126.0-133.2 mm SL), were examined. After external morphological measurement of the fish body, a specialized "soft X-ray" imaging system was used to map the swimbladders and obtain their morphological parameters. The swimbladder was inflated in D. theta, uninflated in S. californiensis, and was absent in N. japonicus. For D. theta, the swimbladder length does not increase in proportion to the body length, suggesting that the contribution of the swimbladder to acoustic reflection is reduced with growth in this fish. Based on the morphological measurements, the theoretical TS of the fish at 3 8 kHz was calculated using the approximate deformed-cylinder model (DCM) and the general prolate-spheroid model (PSM). For all three species, the calculations showed about 3 dB difference between the TS indicated by the DCM and PSM. Given that the description of body shape is poor in PSM, the DCM results were adopted for fish without a swimbladder or an empty one. The intercept b(20) in the standard formula TS = 20 log SL + b(20) was -85.7 dB (DCM) for S. californiensis and -86.7 dB (DCM) for N. japonicus. On the other hand, the PSM model was adopted for D. theta since its swimbladder has too small an aspect ratio to apply the DCM. For D. theta, the relationship between SL and TS is best expressed by TS = 11.8 log SL - 63.5, which implies that its scattering cross-section is not proportional to the square of the body length. (C) 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd. All rights reserved.
  • 閉鎖空間内における魚群行動の確率モデル
    鈴木勝也, 髙木力, 守冨裕, 鳥澤眞介, 宮下和士
    数理水産科学 1 15 - 20 2003年 [査読無し][通常論文]
  • Hiroki Yasuma, Tatsuki Ohshima, Kouichi Sawada, Kazushi Miyashita, Ichiro Aoki
    ICES Journal of Marine Science 60 585 - 592 2003年 [査読有り][通常論文]
  • J Yamamoto, S Masuda, K Miyashita, R Uji, Y Sakurai
    BULLETIN OF MARINE SCIENCE 71 2 987 - 992 2002年09月 [査読有り][通常論文]
     
    The MOCNESS (Multiple Opening Closing Net and Environmental Sampling System) was used to investigate the distribution of the early life stages of the Japanese common squid Todarodes pacificus in the southwest Sea of Japan near the Oki Islands, a suspected spawning ground of this species. The largest catches of hatchling-sized paralarvae occurred at the surface layer (0-25 in), and paralarval mantle lengths increased with increasing sampling depth, suggesting that T pacificus paralarvae gradually descend in the water column life cycle as they grow. There was no clear difference in the horizontal distribution among the different size groups.
  • M Kang, M Furusawa, K Miyashita
    ICES JOURNAL OF MARINE SCIENCE 59 4 794 - 804 2002年08月 [査読有り][通常論文]
     
    Acoustic species identification is very important for fisheries' operations and surveys. One of the most promising methods for identification is to utilize the difference of mean volume backscattering strengths (DeltaMVBS) among frequencies. Improvement of this technique is the aim of this study. The DeltaMVBS must be obtained for a common observation range among frequencies so that the difference can be attributed solely to frequency characteristics of the sound scattering of targets organisms. We derived the common observation range of at least up to 150 m for our quantitative echosounder operating at 38 and 120 kHz with the same beam widths of 8.5degrees. We related DeltaMVBS data obtained off northeastern Japan to specific marine organisms combined with the swimming depth and water temperature information. The echoes with small DeltaMVBS ( - 1 dB<DeltaMVBS<4 dB) were attributed to the walleye pollock (Theragra chalcogramma) and the echoes with large DeltaMVBS (> 10 dB) to krill (Euphausia pacifica). The changing pattern of DeltaMVBS suggested complicated behaviour between species such as predator and prey interaction. In order to obtain reliable and detailed information the integration cell should be small and the DeltaMVBS should be displayed as an echogram in an absolute colour scale. (C) 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea.
  • Yoo-Won Lee, Kazushi Miyashita, Tsutomu Nishida, Sei-ichiro Harada, Tohru Mukai, Kohji Iida
    Journal of Fisheries Science and Technology 5 3 206 - 211 2002年 [査読有り][通常論文]
  • 宮下 和士
    日本水産学会誌 68 4 564 - 568 2002年 [査読有り][通常論文]
     
    The diurnal changes in the acoustic frequency characteristics of Japanese anchovy (Engraulis japonicus) larvae were analyzed based on theoretical scattering models. Larval swim bladders contain gas at night, but not during the day, so the straight cylinder model (no gas in a swim bladder) was used for daytime observations, and the fish bladder resonance model (full gas in a swim bladder) was used for night observations. The sets of acoustic frequencies used were 50 kHz and 200 kHz, which are those used for shirasu commercial fishing, and 38 kHz and 120 kHz, which are those commonly used for acoustic surveys using a quantitative echo sounder system. During daytime, differences in the target strength (TS) of the anchovy larvae between the two frequencies were large (especially between 38 kHz and 120 kHz), but at night, there were few differences between frequencies. These results suggest that acoustic surveys for identifying and estimating the abundance of Japanese anchovy larvae should be performed during the day rather than at night, since this is when differences occur between frequencies and when larvae form dense schools.
  • Identifying fish species around the Oki island using echogram analysis
    Tadanori Fujino, Ryousuke Uji, Kazushi Miyashita, Koutarou Tetsumura, Shinya Masuda, Jun Yamamoto
    Proceedings of the ACOUSTGEAR2000 1 89 - 97 2001年 [査読有り][通常論文]
  • Verification of diurnal change of target strength of walleye pollock. - An effect of resolution volume -
    Koki Abe, Satoshi Honda, Tatsuki Oshima, Kazushi Miyashita, Kohji Iida, Tohru Mukai
    Proceedings of the ACOUSTGEAR2000 1 48 - 54 2001年 [査読有り][通常論文]
  • Acoustical measurement of the horizontal distribution of isada krill (Euphausia pacifica Hanssen) off the Sanriku coast
    Kazushi Miyashita, Koutarou Tetsumura, Kouji Kooka, Hiroki Yasuma
    Proceedings of the ACOUSTGEAR2000 1 190 - 193 2001年 [査読有り][通常論文]
  • Koutarou Tetsumura, Kazushi Miyashita
    Proceedings of the ACOUSTGEAR2000 1 74 - 79 2001年 [査読有り][通常論文]
  • In situ TS measurements of live southern bluefin tuna (Thunnus maccoyii) in cages
    Kazushi Miyashita, Tsutomu Nishida, Sei-ichiro Harada
    Proceedings of the ACOUSTGEAR2000 1 45 - 47 2001年 [査読有り][通常論文]
  • Acoustical survey for estimation of tuna abundance using the Omni scan sonar
    Tsutomu Nishida, Kazushi Miyashita
    Proceedings of the ACOUSTGEAR2000 1 98 - 107 2001年 [査読有り][通常論文]
  • Accurate frequency difference of volume backscattering strength for fish species information
    Myoung-Hee Kang, Masahiko Furusawa, Kazushi Miyashita
    Proceedings of the ACOUSTGEAR2000 1 65 - 73 2001年 [査読有り][通常論文]
  • Observation of juvenile southern bluefin tuna (Thunnus maccoyii C.) school in response to the approaching vessel using a scanning sonar
    Yoo-Won Lee, Kazushi Miyashita, Tsutomu Nishida, Sei-ichiro Harada, Tohru Mukai, Kohji Iida
    Proceedings of the ACOUSTGEAR2000 1 108 - 112 2001年 [査読有り][通常論文]
  • Spatial dynamics of southern bluefin tuna (Thunnus maccoyii) recruitment
    Tsutomu Nishida, Vincent Lyne, Kazushi Miyashita, Kiyoshi Itho
    GIS/Spatial Analyses in Fishery and Aquatic Sciences 1 86 - 103 2001年 [査読有り][通常論文]
  • Aoki, I, K Miyashita
    FISHERIES RESEARCH 49 2 155 - 164 2000年12月 [査読有り][通常論文]
     
    A sampling survey for Japanese anchovy Engraulis japonicus larvae and juveniles was carried out using two types of sampling gear for capturing a wide size range of fish in the Kuroshio Extension and Kuroshio-Oyashio transition regions in August 1996. Anchovy larvae were found widely far offshore. Total lengths (TLs) of the fish ranged mostly from 6 to 40 mm, which corresponded to 5-50 days after their hatching in July. The number of anchovy collected varied with sampling sites, but it was not clear what factors accounted for the variation. While the mean lengths of larvae taken in the Kuroshio Extension area tended to be smaller offshore, those in the transition area significantly increased in size as the distance offshore increased, perhaps because larger larvae migrated northward into the transition region. The mean growth rate of otolith-aged larvae was 0.63 mm per day, which was similar to those previously reported in the coastal waters. The daily mortality coefficient, which was estimated based on age-frequency distribution converted from length-frequency distribution, ranged from 0.362 to 0.136 per day. The mortality rates decreased with growth, being lowest for larger larvae offshore. (C) 2000 Elsevier Science B.V. All rights reserved.
  • K Miyashita, Aoki, I
    MARINE ECOLOGY PROGRESS SERIES 180 105 - 109 1999年 [査読有り][通常論文]
     
    Two methods for acoustic estimation of zooplankton abundance using the difference in volume back-scattering strength (SV) at 2 frequencies between 38 and 200 kHz were examined in a situation where the biological composition was simple. Method 1 used the SV difference, and Method 2 used both SV difference and body length data from net samples. The high-pass sphere model and straight cylinder model were applied depending on dominant target species: when they were relatively small, such as copepods, the high-pass sphere model was used, and when adult krill were dominant the straight cylinder model was used to take the swimming angle of the adult krill into consideration. Acoustic estimates were compared with net samples. Using the high-pass sphere model, Method 1 provided plausible estimates of zooplankton size and biomass, and Method 2 provided better biomass estimates. Furthermore, it was shown that by using the straight cylinder model and swimming angle distribution, Method 1 can be applied to obtain estimations. of the krill's size and biomass.
  • 「実験イケス内のミナミマグロThunnus maccoyii幼魚のターゲットストレングスの直接測定」
    宮下和士, 西田勤
    水産海洋研究 63 8 - 13 1999年 [査読有り][通常論文]
  • Kazushi Miyashita, Ichiro Aoki, Tadashi Asami, Hideki Mori, Kenji Taki
    Journal of the Korean Society of Fisheries Resoureces 1 128 - 135 1998年 [査読有り][通常論文]
  • K Miyashita, Aoki, I, K Seno, K Taki, T Ogishima
    FISHERIES OCEANOGRAPHY 6 4 266 - 271 1997年12月 [査読有り][通常論文]
     
    In this study, the feasibility of identification and abundance estimation of isada krill, Euphausia pacifica, was examined using a two-frequency (38 and 120 kHz) method. The acoustic survey and midwater trawling were conducted off the Sanriku coast, northern part of Honshu, Japan. In one pattern, the SV difference between the two frequencies was large, and in the other, the SV difference was small. These results were interpreted by scattering models, and showed that discrimination between isada krill and walleye pollock was possible.
  • 「４周波計量魚群探知機を用いた動物プランクトのサイズ別密度推定の試み」
    宮下和士, 青木一郎, 稲垣正
    水産海洋研究 61 61 - 66 1997年 [査読有り][通常論文]
  • K Miyashita, Aoki, I, T Inagaki
    ICES JOURNAL OF MARINE SCIENCE 53 2 303 - 308 1996年04月 [査読有り][通常論文]
     
    The swimming angle of isada krill (Euphausia pacifica Hansen) was measured in a tank and the target strength (TS) values were calculated using a theoretical scattering model. The average swimming angle was 30.4 degrees (s.d.=19.9 degrees), which was about 15 degrees less than that reported for Antarctic krill (Euphausia superba). Parameters for the swimming angle distribution were substituted into the straight cylinder model and the corresponding TS values were determined. The mean TS values of 16.4 mm isada krill for hovering animals were lower than the maximum TS; differences were 7.8-5.0 dB, 14.8-8.6 dB, and 18.1-10.8 dB at 50, 120, and 200 kHz, respectively. These differences will lead to a 1/6-1/3, 1/30-1/7, and 1/65-1/12 proportional difference, respectively, in estimating abundances compared to estimates based on the maximum TS. Measurements carried out al higher frequencies are more influenced by swimming angle than those at lower frequencies. However, the TS is less at lower Frequencies and it is more difficult to filter out noise. Thus, medium frequencies are suggested as the best for krill surveys. Additionally, when conducting resource surveys by echosounding, it is necessary to assign the appropriate swimming angles for different targets. Swimming angles need to be investigated further under a variety of conditions.
  • K Miyashita, Aoki, I, T Inagaki
    FISHERIES SCIENCE 62 2 327 - 328 1996年04月 [査読有り][通常論文]
  • 制御法を用いたツノナシオキアミEuphausia pacificaのターゲットストレングスの測定
    宮下和士, 青木一郎, 飯田浩二, 向井徹, 黄斗湊
    水産海洋研究 60 215 - 220 1996年 [査読有り][通常論文]
  • 宮下 和士, 青木 一郎, 稲垣 正
    日本水産学会誌 62 1 68 - 72 1996年 [査読有り][通常論文]
     
    We examined two methods for acoustical estimation of zooplankton abundance using the high-pass sphere model and two frequencies. Frequencies were 50 kHz and 200 kHz. In Method 1, the body length of the zooplankton, which is necessary to estimate the biomass density, was derived theoretically from the difference of volume back-scattering strength (SV) at two frequencies. In method 2, this information was obtained by actual net sampling. Method 1 was useful to estimate size and biomass approximately in the survey area. Method 2 was useful to estimate biomass closely when biological compositions were simple. Both methods can be applied to acoustic observations of macro zooplankton by common echo sounders mounted on research vessels.
  • K Miyashita, Aoki, I, T Inagaki
    NIPPON SUISAN GAKKAISHI 62 1 68 - 72 1996年01月 [査読有り][通常論文]
     
    We examined two methods for acoustical estimation of zooplankton abundance using the high-pass sphere model and two frequencies. Frequencies were 50 kHz and 200 kHz. In Method 1, the body length of the zooplankton, which is necessary to estimate the biomass density, was derived theoretically from the difference of volume back-scattering strength (SV) at two frequencies. In method 2, this information was obtained by actual net sampling. Method 1 was useful to estimate size and biomass approximately in the survey area. Method 2 was useful to estimate bio-mass closely when biological compositions were simple. Both methods can be applied to acoustic observations of macro zooplankton by common echo sounders mounted on research vessels.
  • 音響推定におけるツノナシオキアミの遊泳姿勢に関する研究
    宮下和士, 青木一郎, 稲垣正
    水産海洋研究 59 235 - 240 1995年 [査読有り][通常論文]

MISC

書籍等出版物

  • Fish Population Dynamics, Monitoring, and Management
    宮下 和士 (担当:共著範囲:Acoustic survey)
    Springer 2018年
  • スマート農業
    宮下和士 (担当:分担執筆範囲:音響計測などの多次元計測とその応用による水産業のスマート化)
    農林統計出版 2014年
  • 水辺と人の環境学（上）
    宮下和士 (担当:分担執筆範囲:ブラウントラウト・ニジマス．)
    朝倉書店 2013年
  • フィールド科学への招待
    宮下和士 (担当:分担執筆範囲:海洋生物資源を可視化する)
    三共出版 2006年

所属学協会

  • 音響水産資源調査研究会   北海道総合ICT水産業フォーラム   サケ学研究会   バイオロギング研究会   Asian Society of Fisheries Acoustics（アジア水産音響学会）   北太平洋科学機構（PICES)   日本海洋学会   水産海洋学会   日本水産学会   海洋音響学会   

共同研究・競争的資金等の研究課題

  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 南 憲吏, 宮下 和士
     
    藍藻類が異常繁殖した状態であるアオコは、ダム湖の水質悪化の原因となる。本研究は、アオコの分布を空間的かつ定量的に評価することを目指した、音響計測手法を用いたアオコの分布推定手法の開発を目的とする。本年度は、2020年度に取得した音響反射強度および藍藻類の細胞数に関する情報の解析を進めた。これにより、藍藻類の細胞数と音響反射強度の間に関係性が示され、藍藻類以外の植物プランクトンや動物プランクトンと音響反射強度の間には関係性がみられないことが明らかとなった。このことから、音響反射強度を定量的に計測可能な計量魚群探知機によるアオコの分布推定が有効であることが示された。また、本年度も昨年度に引き続き、アオコの音響反射強度および細胞数に関する調査の実施を予定していた。調査は、福島県田村郡三春町の三春ダムにおいてアオコが一年のうちで最も多くなる夏季（8月）に実施する計画で進めた。本計画では、中程度のアオコが発生している地点において周波数38kHzおよび120kHzの計量魚群探知機を用いた音響計測、バンドン式採水器（植物プランクトン用サンプル採集）とシンドラープランクトントラップ（動物プランクトン用サンプル採集）によるサンプリングをおこない、2020年度と同様に藍藻類の細胞数と音響反射強度に関係性があるかについて明らかにする予定であった。しかし、新型コロナウイルス感染症の拡大時期と重なり、調査の中止を余儀なくされ、2022年度の調査に持ち越すこととなった。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2014年04月 -2017年03月 
    代表者 : 宮下 和士, 藤原 孝洋, 本多 健太郎
     
    電磁誘導方式のパッシブタイプと，電波を用いたアクティブタイプのモニタリングシステムを構築した．パッシブRFIDは，作動距離が10cm程度と短いために制約が多いが，アクティブRFIDは水中での電波が減衰するも，実験から淡水であれば深度60cm程度までは利用できる．この電波をデコードする装置を開発し，アクティブRFIDを実用するための知見を得た．また，条件の異なるモニタリングの場合，システムを拡張するアーキテクチャとして，ミドルウェアによるデバイスの統合を実装した．さらに，広域モニタリングと多数の対象物を想定したデータ収集に関して，モニタリングのための圧縮センシングの検証を行った．
  • 海洋生態系の動態解析に関する研究
    研究期間 : 2002年 -2017年
  • 海洋生物資源の空間的可視化技術の高度化に関する研究
    研究期間 : 1998年 -2017年
  • 海洋生物資源の持続的利用に関する研究
    研究期間 : 1998年 -2017年
  • 海洋生物の行動計測に関する研究
    研究期間 : 1997年 -2017年
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2013年04月 -2016年03月 
    代表者 : 佐野 稔, 板谷 和彦, 内田 康人, 輿水 健一, 宮下 和士, 坂東 忠男
     
    ミズダコが季節的に浅所と深所を行き来する要因を初めて明らかにした。本研究では、宗谷海峡において水温を連続的に記録する標識を用いた標識放流調査、水温別の飼育によるミズダコの成長の観察、漁獲されたミズダコの胃内容物観察、ソナーやカメラを用いた固着生物の調査を行った。その結果、ミズダコは夏季に水温が15℃以上になると移動し始め、生理的な限界の水温21℃以上の海域を避けて深所へ移動する。そして、秋季に浅所の水温が19℃未満に下がると、餌条件の良い浅所へ餌を食べに移動して、春季まで留まることが明らかになった。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2011年04月 -2014年03月 
    代表者 : 宮下 和士, 藤森 康澄, 木村 暢夫
     
    藻場には構成種の違いにより、アマモ場、ガラモ場、クロメ場といった数種の藻場がある。本研究では藻場に関する音響反射強度（SA）と波形の特徴（ウェーブレット係数）を調べることにより、音響学的手法を用いた藻場の種類判別方法について検討を行った。その結果、藻場の種類判別は、第一段階でSA値（ガラモ場-33.3~-57.0 dB 、アマモ場-39.2~-66.1 dB、クロメ場-59.8~-74.3 dB）による判別、第二段階でウェーブレット係数（Lv4）による判別(アマモ場12000～39000、クロメ場3000～12000)を行うことで可能であると考えられた。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2010年 -2012年 
    代表者 : 宮下 和士, 三谷 曜子, 綿貫 豊, 米崎 史郎, 服部 薫
     
    北方海洋生態系を広く回遊し,摂餌を行っている海鳥や海棲哺乳類などの高次捕食者をモデルとして,様々な計測機器や分析によりモニタリングを行った.各種において回遊や摂餌生態は個体・地域によって様々であり,このような違いが繁殖成功や生残を左右する可能性が考えられた.また,高次捕食者の生態を通じて,海洋生態系の変動を捉えることができた.今後もモニタングを続けていくことで,我々の目には見えにくい海の中での生態系変動を把握することができるようになるだろう.
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2009年 -2012年 
    代表者 : 仲岡 雅裕, 田中 法生, 堀 正和, 四ッ倉 典滋, 宮下 和士, 磯田 豊, 野田 隆史, 灘岡 和夫, 山本 智子, 浜口 昌巳
     
    本研究は、日本の温帯と冷温帯の沿岸生物群集を対象に、生産者と消費者の広域分散過程、および温度変化に伴う生産者と消費者の相互作用の変異を調べることにより、地球規模での環境変動に伴う沿岸生物群集の変化を理解し、沿岸資源生物および沿岸生態系の保全・管理に資することを目的とする。広域野外調査、リモートセンシング・GISを用いた長期変動解析、メタ群集決定構造の数理的解析、集団遺伝解析、野外操作実験を組み合わせたアプローチにより、沿岸生物群集の構成には、水温等の広域スケールの変動要因と、競争・捕食等の局所スケールの変動要因が複雑に関与していることが判明した。今後の気候変動に伴い、沿岸生物群集の動態は、植物-動物間相互作用の変化を通じて不安定化する可能性が高いことが予測された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2006年 -2009年 
    代表者 : 齊藤 誠一, 帰山 雅秀, 桜井 泰憲, 松田 裕之, 綿貫 豊, 宮下 和士, 河野 時廣, 工藤 秀明, 平譯 享, 塩本 明弘, 山本 潤
     
    知床世界自然遺産海域の海洋環境と海洋生物のモニタリング手法の開発とフィールド調査を実施した。その結果、知床半島の南北沿岸における基礎生産システムの違いが明らかになった。さらに、知床世界遺産地域に遡上するサケ属魚類の遡上産卵動態とヒグマの行動パターンとの関係を明らかにするとともに,カラフトマスによる海起源物質の陸域生態系への輸送の動態とメカニズムを明らかにした。順応的管理をベースとした資源管理技術による生態系管理方法を検討した結果、知床の沿岸漁業については、漁獲量と漁獲高を用いて、魚種別評価を行う方法を提案できた。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2006年 -2007年 
    代表者 : 宮下 和士, 帰山 雅秀, 田中 秀二
     
    本研究では,イトウの生息範囲を正確にとらえ,そのデータを活用した生態学的なアプローチにより,本種の行動メカニズムを明らかにし,将来的な保護や周辺環境の保全に寄与する情報を得ることを目的とし,バイオテレメトリー手法を用いてイトウの正確な位置・時間とその移動の情報を収集・蓄積した。 調査は,厚岸郡厚岸町の別寒辺牛川水系において,2006年4月下旬から同年12月上旬,2007年4月下旬から同年11月下旬の期間に行った。イトウは2006年に2個体、2007年に5個体捕獲し,超音波発信器を装着した。超音波受信機を河川内の定点(間隔約2km〜5km)に設置し,並行してカヌーの舷側に取り付け,GPSで位置情報を取得しながら河川内を移動した。 受信機データから放流した全個体の受信が確認でき,受信回数は2006年に130回,2007年に37,683回であった。産卵後の降下行動の平均時間は44.1±29.1時間(Mean±S.D.),平均距離は33.4±12.5km,平均速度は0.46±0.21BL/sであった。 受信機の結果から季節別の分布は,春季(5,6月);中流域から河口域,夏季(7,8月);中上流域から中流域,秋季(9,10,11月);下流域から河口域,であった。また,下流域の水温が急激に上昇した際た,中流域まで遡上した個体も見られ,その移動距離は最大約13kmに及んだ。さらに,季節間だけではなく昼,夜間においても行動の傾向が異なっており,春季では夜間の1時間あたりの受信数が昼間の受信数の約2倍あり,夏季では日出,日入時刻の受信数が多かった。 以上より,産卵直後の降下行動においては,イトウは好条件の生息場所の確保を目的に降下していると推察された。季節移動には,水温と餌環境が影響していることが推察される。また,比較的短期での行動は,昼夜,潮汐,降雨などの影響を受けていることも考えられた。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2004年 -2006年 
    代表者 : 宮下 和士, 綿貫 豊, 高尾 芳三, 河邊 玲, HOBDAY Alistair
     
    当該研究期間において、主に2項目について成果を挙げることが出来た。以下に成果の概要をそれぞれ記す。 1. 海洋環境が分布特性に及ぼす影響 ルーウィンカレントの勢力が強かった年(2004年度)は、温かい水(約19.5℃)が調査海域を満たした。この年、ミナミマグロ幼魚は海山周辺海域に集中して(全出現数の92%)分布した。一方、ルーウィンカレントの勢力が弱かった年(2005年度)は、他海域からの冷水の浸入が考えられ、陸棚上に暖水塊・冷水塊が多数存在した。また、本種幼魚は海山周辺に集中せず、水塊縁辺部に出現する傾向が見られた。以上の結果および過去の知見より、本種幼魚の分布は、海洋環境に左右されやすい餌生物(Sardinops sagaxやScomber australasicusなど)の分布に大きく影響されている可能性が示唆された。 2. サイズ別分布特性 全ての年において、大型個体ほど沿岸の受信機に出現する傾向が見られた。また、2歳魚と1歳魚が同海域に同時に分布しだ場合(2002、2003年度)は2歳魚が、2歳魚が分布しなかった年(2004、2005年度)では1歳魚の中でも大型の個体(尾叉長>50cm)がより沿岸域に出現した。特に2005年度では大型1歳魚が沿岸域の海山周辺海域に集中して分布した(大型1歳魚の全出現数の97%、小型50%)。以上の結果より、本種幼魚は、餌生物(Spratelloides robustusやEngraulis australisなど)が多く分布する沿岸域の海山周辺海域のニッチを巡り、サイズ依存の個体間競合を展開していると判断された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2004年 -2005年 
    代表者 : 宮下 和士, 綿貫 豊, 河邊 玲
     
    ターゲットストレングス(TS)は、計量魚群探知機やソナーでスケトウダラの資源量を見積もる際の最重要パラメータである。TSは、スケトウダラの遊泳姿勢角度により大きく変動するためその資源量推定を左右する。しかし、これまで技術的な困難さからスケトウダラの遊泳姿勢角度の計測はない。そこで本研究では、本種の現存量推定精度向上に資するために、加速度データロガーを用いて遊泳姿勢角度を直接計測した。実験は2005年3月16-27に実験水槽内でおこなった。スケトウダラ6個体(平均体長:45.3cm)の腹腔内にデータロガーを装着し約3日間にわたり遊泳姿勢を測定した。結果、遊泳中の個体ごとの平均遊泳姿勢は-6.2度から3.75度(-が長軸方向下向き、+が長軸方向上向き)であり、ほぼ水平を示した。最大遊泳姿勢角度は-75.4度から-66.9度であった。また、夜間に比べて昼間にやや上向き角(平均角度差:7.2度)であった。以上の結果より、閉鎖空間である水槽で得られたものであるが、本手法を用いた遊泳姿勢角計測の有効性が示された。今後、回収方法を考案し、フィールドでの実証実験を重ねることにより、本種の自然状態での遊泳姿勢角推定が可能となることが予想される。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2003年 -2005年 
    代表者 : 飯田 浩二, 芳村 康男, 向井 徹, 宮下 和士, KANG Don-Hyug, TANG Young, KANG Don?Hyug
     
    魚群探知機と比べて探査範囲が格段に広いスキャニングソナーを用いて,魚群の形状,体積,密度等の定量解析が可能な次世代型計量ソナーとその応用手法の開発を目的とし,以下の研究を行った。 1.実船による魚群データの取得とデータ解析 試作した計量ソナーをノルウェーのトロール・巻網漁船に装備し,ニシンやタラのソナーデータと漁獲データを比較した。また国内の巻網漁船に仮装備し,サバ,イカ,ブリのソナーデータと漁獲データを比較した。大型魚群が3千メートル手前から探知され,推定した魚群面積や体積と漁獲データに比例関係が認められた。 2.魚の横方向ターゲットストレングス(TS)の測定 ソナー周波数を含む7周波数の魚群探知機を用いてカタクチイワシ活魚の3次元TSを測定した。TSの姿勢変化に対する変動は高周波ほど大きく,ソナー周波数(24kHz)では小さかった。また,真横からのTSは背方向TSに近く,指向性パターンは8の字形を示した。 3.魚の占有体積(TV)の推定 魚群体積から魚群量を推定するためには1匹の魚のTVが必要となるが,自然状態でのTVの直接測定は困難である。そこで,計量魚群探知機で捉えた魚群の体積後方散乱強度(SV)を魚のTSで割って魚群密度を推定し,魚のTVを考察した。スケトウダラ稚魚のTVは体長の2.6乗に比例すること,昼夜間でTVが8倍変化することが示された。 4.魚群の3次元表示の検討 ノルウェーで得られた航走時の垂直ビームデータを用いて,魚群の3次元形状を再現することができた。また水平ビームデータを用いて,広域の3次元魚群形状を表示すると共に,魚群の移動を解析することができた。 5.研究成果の発表 国内外で開催された水産関連および音響関連の国際学会において,講演および論文発表した。平成18年度の日本水産学会では「計量ソナーの現状と展望」をテーマにしたシンポジウムを開催し,国内の研究者ほか,ノルウェー,オーストラリアからの招へいを実現した。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2002年 -2003年 
    代表者 : 青木 一郎, 宮下 和士
     
    1.14魚種を対象に、軟X線法を用いて鰾内の気泡の有無、及び形状を観察した。これらの鰾形態には発育段階による変化が見られた。また、多くの魚種では、鰾が体長と比例して成長しないことが示され、さらにいくつかの魚種では、ある発育段階を境に鰾が退行していくことがわかった。 2 密度比はアラハダカを除く5魚種では1.003〜1.020の範囲内にあり、特に、セッキハダカ属の2種では密度比が低く(1.004)、海水と非常に近い値を示した。音速比には顕著な温度特性が見られた。各魚種の生息水温を考慮すると、音速比はコヒレハダカで1.032〜1.039、オオクチイワシでは1.024〜1.036であり、一方、アラハダカの音速比は1.012〜1.024で、他の2魚種に比べて低い値となった。 3.有鰾魚において鰾形状を気体反射モデルに適用した場合、全ての個体でPSMとDCMによる推定値には2〜5dB程度の差が生じていた。測定値はPSMの結果と比較的よく一致していた。一方、無鰾魚では、測定した体長範囲ではPSMとDCMのTSパターンはピーク値の付近で比較的よく一致した。 4.ハダカイワシ類の鰾は非常に小さいため、38〜200kHzの範囲内では姿勢によるTSの変化は殆ど見られなかった。この周波数範囲内では、全ての個体で基準化TS(TScm)が-70dB以下を示し、かなり低いことがわかった。また、魚体と鰾が比例的に成長しないことから、有鰾のハダカイワシ類ではTSを体長の2乗で一般化できないことがわかった。 5.2002年冬季、ベーリング海南部海域におけるコヒレハダカの音響調査の結果、調査海域における推定バイオマスは280万t、魚群密度は50〜100g/m^2と見積もられた。2000年冬季、道東海域におけるトドハダカの音響調査では、推定された平均魚群密度は約35g/m^2で、道東陸棚斜面におけるバイオマス約7.5万tと推定された。
  • 日本学術振興会：科学研究費助成事業
    研究期間 : 2000年 -2001年 
    代表者 : 宮下 和士
     
    本申請研究の目的は、道東・三陸沿岸域において濃密に分布するオキアミ類に対し、その3次元分布構造の解明と資源量推定法の開発を行うことである。申請年度内において、以下の研究事項に従事し、結果を得た。 海洋水産資源開発センターによるスケトウダラ・オキアミ資源調査(北海道太平洋沿岸域、2001年6月10〜7月30日、2002年1月6日〜2月4日)において、2周波(38kHz、120kHz)計量魚探による音響情報、CTD、X-CTDによる海洋環境情報、ボンゴネットによる生物採集情報を収集した。 次に、調査で得られた音響情報および生物情報より、音響周波数特性を利用したオキアミ類のサイズ別判別を試みた。生物情報より本調査海域におけるオキアミ類の体長を等価球半径で標準化した結果、そのサイズは、小(0.027mm≦等価球半径≦0.075mm)、中(1.72mm≦等価球半径≦2.47mm)、大(3.47mm≦等価球半径≦3.76mm)3階級に分別された。得られたサイズ階級情報より、音響周波数特性を利用したオキアミサイズ判別を行った結果、それぞれのサイズ階級におけるオキアミの定量的な音響情報の抽出が可能となった。また、抽出したオキアミの音響情報と、水深情報、水温情報等をGIS技術を用いて重ね合わせることにも成功した。 今後はこれらの結果をもとに、3次元表現、4次元表現の技術の高度化を目指すと同時に、スケトウダラ等のオキアミを餌としている生物の情報とのリンクを図る予定である。
  • Quantitative Spatial Visualization of Aquatic Living Resources
    研究期間 : 1998年
  • スマート水産業に関する研究

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