1987 Fiscal Year Final Research Report Summary
Catching Efficiency of Semi Trammel Net
| Project/Area Number |
61560208
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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 Atsushi Faculty of Fisheries,Tokyo University of Fisheries, Professor, 水産学部, 教授 (60017027)
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| Co-Investigator(Kenkyū-buntansha) |
MATUDA Ko Faculty of Fisheries,Tokyo University of Fisheries, Associate Professor, 水産学部, 助教授 (90026485)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Catching Efficiency of Semi trammel Net / Semi trammel net / Trammel net / Slackness / Catch of small mesh netting / Catch of large mesh netting |
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| Research Abstract |
Catching Efficiency of Semi Trammel Net Semi trammel net consists of two pieces nettings such as the small mesh netting and large mesh netting,then handling of this net is easy to compare with trammel net. Semi trammel net, however, has not been used currently in coastal waters of the world. If the catching efficiency of semi trammel net is higher than that of trammel net, it is convenient to replace trammel net with semi trammel net.
For this purpose, the experimental fishing operations concerning to the catching efficiency and the mesh selectivity for semi trammel net, trammel net and bottom gillnet were carried out three different mesh sizes and three different slacknesses (the ratio of the height of inner net to that of outer net) in the Tokyo Port during 1986 to 1987.
The results obtained are summarized as follows:
1.The catch of gizzard shad by semi trammel net was higher than that of trammel net and of bottom gillnet.
2.The catch of gizzard shad changed due to the difference of mesh size of small mesh netting of semi trammel net and inner netting of trammel net, while the slackness of small mesh netting seemed not to be affect the catches in case of semi trammel net, but affected some extent in case of trammel net.
3.The mesh selectivity curves of the above two kinds of net have the same charactoristics as that of bottom gillnet. This means that the smaller size of fish is selected sharply by the size of mesh.
4.To find out the reason of the high catching efficiency of semi trammel net, the change of net shape in water stream was observed in the circular tank, but it could not find out the substantial difference among the semi trammel net, trammel net and bottom gillnet. Then the observation of fish behavior for the above three kinds of net is need in future studies.
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