中立ブイを装着した浮延縄漁具の3次元形状に及ぼす海中流れの影響  [in Japanese] Effect of water flow on 3-dimensional underwater shape of pelagic longline with midwater float  [in Japanese]

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Abstract

流れによる浮延縄漁具の 3 次元形状変化を,海亀混獲回避と漁獲効率向上を目的とする中立ブイを装着した場合について調べた。超音波 3 次元水中測位システムと水深計,GPS ブイを用いて漁具各部の 3 次元位置を計測すると同時に,海中の流れを ADCP で計測した。漁具全体の移動方向は流れの抵抗を大きく受ける幹縄の敷設水深の流向と一致した。枝縄のふかれ方向はその敷設水深の流向と一致した。流れが漁具の設置方向に平行な場合,幹縄の弛みは下流側に寄せられた。特に上層と下層で流れの向きが異なる場合,幹縄の形状変化は 3 次元的であった。<br>

  A midwater float system for pelagic longlines was developed to reduce sea turtle incidental catch and to improve tuna catch efficiency. This paper presents changes in the three-dimensional shape of the pelagic longline with midwater float by water flow. The 3-dimensional underwater shape of the pelagic longline with a mainline of 180 m length in one basket was measured, using an ultrasonic positioning system and GPS buoy, and simultaneously the water currents at 11 depth levels (from 10 m to 60 m at 5-m intervals) were measured by an acoustic Doppler current profiler. The whole longline gear drifted in the direction of the current at the same depth where the mainline was located, because the mainline was most influenced by the drag of the water flow. Similarly, the hook of the branch line was shoaled in the current direction. Due to the current component parallel to the mainline, the mainline was skewed downstream, and the slack of the downstream part in the mainline became large while the upstream part of the mainline was shoaled. Especially, when a large difference was found in the current direction and velocity between the vertical depths, complicated 3-dimensional deformation occurred on the mainline.<br>

Journal

  • NIPPON SUISAN GAKKAISHI

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

    The Japanese Society of Fisheries Science

References:  17

Cited by:  1

Codes

  • NII Article ID (NAID)
    110007131483
  • NII NACSIS-CAT ID (NCID)
    AN00193422
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    00215392
  • NDL Article ID
    10221866
  • NDL Source Classification
    ZR26(科学技術--農林水産--水産)
  • NDL Call No.
    Z18-345
  • Data Source
    CJP  CJPref  NDL  NII-ELS  J-STAGE  JASI 
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