中立ブイ装着まぐろ延縄漁具の水中形状に及ぼす流れの影響  [in Japanese] Effect of Water Flow on Shape of Tuna Longline with Midwater Float System Evaluated in Flume Tank Experiment and Numerical Simulation  [in Japanese]

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Abstract

近年まぐろ延縄漁業による海亀類の混獲問題が国際的に注目され、まぐろ資源の地域漁業管理機関や国連食糧農業機関(FAO)の場で対策が講じられるようになっている。著者らは、海亀混獲回避およびマグロ類の効率的漁獲を目的として、まぐろ延縄漁具に中立ブイと長い浮縄を取り付けた中立ブイシステムを開発した。本研究では、回流水槽においてShiodeらが提案した中立ブイを装着したまぐろ延縄漁具を用いた模型実験を行い、一様流中での漁具の水中形状を計測し、ふかれによる漁具の水深変化を評価することを試みる。さらに、その結果と比較しながら、Wanらの有限要素法に基づき、水槽実験と同じ条件で数値シミュレーションを行い、中立ブイ装着漁具のふかれを再現できるかどうかを確認する。そして、この数値シミュレーションによって中立ブイの装着が延縄漁具のふかれに及ぼす影響を評価することができるか検討する。

Midwater float for pelagic longline consists of plural additional small fioat, which keeps the depth of each hook to the same layer, and this study presents three-dimensional shape of longline with the midwater float in uniform stream, by model experiment in a flume tank and by numerical simulation based on finite element method Each part of longline was shoaled by the current, and then the depth of the hooks became shallower with the faster water current. In particular, the principal factor affecting the hooks shoaling was the spread of horizontal spacing between the two successive buoys by the faster current. When the longline was cast with a given angle to the stream, the longline gear had threedimensional structure, and then the hooks were set at much shallower depth. The numerical calculation simulated well the shoaling of the longline in the flume tank. The comparison of the numerical simulation in longline shoaling between the midwater fioat setting and the conventional setting suggested that the depth of longline with the midwater float was susceptible to the current. The possible reason was that the in-water weight of the longline gear was lightened by the midwater float, comparison to the conventional setting. For setting the hooks at the target depth in water current by using midwater fioat, the simulation of longline shoaling was useful to determine the specification of the midwater float system, e. g. the number and buoyancy of the midwater float, and fioat line length.

Journal

  • Journal of Fisheries Engineering

    Journal of Fisheries Engineering 44(3), 185-195, 2008

    The Japanese Society of Fisheries Engineering

References:  36

Cited by:  2

  • Studies on bycatch reduction of sea turtles in tuna longline fisheries  [in Japanese]

    SHIODE DAISUKE

    NIPPON SUISAN GAKKAISHI 76(4), 605-608, 2010-07-15

    J-STAGE  References (35)

  • Effect of water flow on 3-dimensional underwater shape of pelagic longline with midwater float  [in Japanese]

    SHIGA MICHIRU , SHIODE DAISUKE , MIYAMOTO YOSHINORI , UCHIDA KEIICHI , HU FUXIANG , TOKAI TADASHI , MICHIRU SHIGA , DAISUKE SHIODE , YOSHINORI MIYAMOTO , KEIICHI UCHIDA , FUXIANG HU , TADASHI TOKAI , 東京海洋大学海洋生物資源学科 , 東京海洋大学海洋生物資源学科 , 東京海洋大学海洋環境学科 , 東京海洋大学海洋環境学科 , 東京海洋大学海洋生物資源学科 , 東京海洋大学海洋生物資源学科 , Department of Marine Biosciences Faculty of Marine Scineces Tokyo University of Marine Science and Technology , Department of Marine Biosciences Faculty of Marine Scineces Tokyo University of Marine Science and Technology , Department of Ocean Sciences Faculty of Marine Science Tokyo University of Marine Science and Technology , Department of Ocean Sciences Faculty of Marine Science Tokyo University of Marine Science and Technology , Department of Marine Biosciences Faculty of Marine Scineces Tokyo University of Marine Science and Technology , Department of Marine Biosciences Faculty of Marine Scineces Tokyo University of Marine Science and Technology

    NIPPON SUISAN GAKKAISHI 75(2), 179-190, 2009-03-15

    J-STAGE  JASI  References (17) Cited by (1)

Codes

  • NII Article ID (NAID)
    110006647830
  • NII NACSIS-CAT ID (NCID)
    AN10278554
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    0916-7617
  • NDL Article ID
    9414169
  • NDL Source Classification
    ZR26(科学技術--農林水産--水産)
  • NDL Call No.
    Z18-1327
  • Data Source
    CJP  CJPref  NDL  NII-ELS  J-STAGE  JASI 
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