1987 Fiscal Year Final Research Report Summary
Practical Experiment on the Selectivity and Operating Efficiency of the Bottom Trawl Net
| Project/Area Number |
61560218
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General fisheries
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| Research Institution | Kagoshima University |
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Principal Investigator |
HIGO Nobio Faculty of Fisheries, Kagoshima University (Professor), 水産学部, 教授 (10041691)
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| Co-Investigator(Kenkyū-buntansha) |
KAKIMOTO Makoto Faculty of Fisheries, Kagoshima University (Assistant), 水産学部, 助手 (40117487)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Bottom trawl net / Fish behavior / Hanging chain / Mesh size / Net resistance / Net shape / 底びき網の漁具性能 |
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| Research Abstract |
Net shape and net resistance were investigated in standard and large mesh size off-bottom trawl nets. Data from model and full scale nets were used for computer analysis of hanging chain shape.
1. A hanging chain link diameter of 16 mm was found to be the best. Distance from sea bottom to fishing line affect the catch size and species composition.
2. The off-bottom and the on-bottom net almost always had the same shape. The off-bottom trawl net resistance showed a 10 - 15 % decrease, enabling greater fishing efficiency.
3. At high speeds, the shape of the large mesh size and standard net are almost the same. However the resistance was much lower for the large mesh size net.
4. Underwater video was used to determine when the net mouth was well spread, and much sand smog was produced. Computer analyzed hanging chain shape and distance from sea bottom to fishing line showed a high degree of correlation with the full scale net.
5. The off-bottom net caught mainly large fish species, while benthic matter did not enter the net.
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