1989 Fiscal Year Final Research Report Summary
Studies on fishing mechanism of semi-trammel net
| Project/Area Number |
63560184
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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 | Tokyo University of Fisheries |
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Principal Investigator |
KOIKE A. Tokyo Univ.Fish. Fisheries, Professor, 水産学部, 教授 (60017027)
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| Co-Investigator(Kenkyū-buntansha) |
MACHII T. Tokyo Univ.Fish. Fisheries, Lecturer, 水産学部, 講師 (60181666)
MATUDA K. Tokyo Univ.Fish. Fisheries, Assistant Professor, 水産学部, 助教授 (90026485)
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| Project Period (FY) |
1989 – 1990
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| Keywords | semi-trammel net / trammel net / gillnet / mesh selectivity / fishing efficiency / absolute selectivity / 絶対選択率 / 漁獲機構 |
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| Research Abstract |
Fishing experiments were conducted in Tokyo Bay in October-November, 1988 and 1989 to determine the selectivity and catching efficiency of semi-trammel net to gizzard shad. Results were showed that the selectiveties of the mesh sizes of small-meshed net were calculated and the plotted selectivity curves were showed to the right with optimum lengths of 13.5,18.8 and 25.5 cm for 3.6,5.1 and 6.8cm mesh size, respectively. Variations in vertical slack did not show any substantial change on the shape of the selectivity curves.
Matuda's approximate formula for predicting the floatline height of gillnet was utilized in estimating the floatline height of trammel and semi-trammel net. The estimated values were compared with the actual values obtained from a flume tank experiments. The resulting estimating values were found to be in close agreement with the actual values.
The fishing experiments for semi-trammel net and gillnet were conducted in out door water tank by using experimental fish (rainbow trout), of which the population size and the fork length distribution were known. The effect of light intensity on catch by semi-trammel net was greater than that by gillnet, while the effect of mesh size on catch by gillnet was greater than that by semi- trammel net. On case where the fish caught were suited into the body length distribution, the catching efficiency of gillnet was higher than that of semi- trammel net. This phenomena was in close agreement with the results obtained in the fishing experiments in Tokyo Bay.
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