Development of water-mass cluster analysis software to analyze the water-mass variations off the coast of Tohoku Japan: A case study for future application to analyze fisheries catch variation

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  • TANAKA Takahiro
    Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • IMAMURA Yutaka
    Fisheries Research Institute, Aomori Prefectural Industrial Technology Research Center
  • KODAMA Takuya
    Iwate Fisheries Technology Center
  • OIKAWA Toshiyuki
    Iwate Fisheries Technology Center
  • YAGURA Asagi
    Miyagi Prefecture Fisheries Technology Institute
  • SAEKI Mitsuhiro
    Miyagi Prefecture Fisheries Technology Institute
  • MAKABE Kouhei
    Fukushima Prefectural Fisheries and Marine Science Research Centre
  • SUZUKI Yuuya
    Ibaraki Prefectural Fisheries Research Institute
  • OHATA Satoshi
    Chiba Prefectural Fisheries Research Center
  • KANEKO Hitoshi
    Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • OKAZAKI Yuji
    Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • KURODA Hiroshi
    Hokkaido National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • WAGAWA Taku
    Japan Sea National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • HASEGAWA Daisuke
    Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • KAKEHI Shigeho
    Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency
  • OKUNISHI Takeshi
    Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency

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Other Title
  • 水塊クラスター解析ソフトの開発と東北近海域の水塊変動解析への適用―漁況変動解析への応用に向けた事例解析―
  • スイカイ クラスター カイセキ ソフト ノ カイハツ ト トウホク キン カイイキ ノ スイカイ ヘンドウ カイセキ エ ノ テキヨウ : ギョキョウ ヘンドウ カイセキ エ ノ オウヨウ ニ ムケタ ジレイ カイセキ

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Abstract

<p>Hydrographic data off the Pacific coast of Tohoku and off the Boso Peninsula were analyzed using newly developed software that conducts a statistical cluster analysis to reveal the spatial distribution and temporal variation of occurrence frequency of water-masses in surface and subsurface layers. The interannual variation of water-mass occurrence frequency off the coast of Tohoku in summer was most associated with the interannual meridional shift of the Oyashio first branch, and the cold, fresh (warm, saline) clusters were more frequently observed when the Oyashio first branch shifted southward (northward). This tendency was also detected at a 10-m depth, where the previous water-mass classification method was difficult to apply. At a 100-m depth, multiple clusters were classified as Tsugaru Warm Current water, but those that could not be formed by isopycnal mixing between Kuroshio and Oyashio waters were limitedly distributed along the coast of Tohoku. It was suggested these clusters originated from the Tsugaru Strait. Off the coast of the Boso Peninsula in spring, the occurrence frequency of cold water-mass tended to increase when the Kuroshio axis departed from the coast. To relate the water-mass variations to fisheries catch variations, the number of clusters may need to be determined by considering the physiological characteristics of each fish species, such as optimum temperature range. By expanding the analysis to different regions and fish species and accumulating knowledge, the software is expected to provide a useful tool for extracting characteristic water-mass variations and clarifying the relationship between water-mass and fisheries catch variations.</p>

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