| Project/Area Number |
09660208
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| Research Category |
Grant-in-Aid for Scientific Research (C).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Kagoshima University |
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Principal Investigator |
MATSUOKA Tatsuro Kagoshima University, Faculty of Fisheries, Professor, 水産学部, 教授 (80244268)
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| Co-Investigator(Kenkyū-buntansha) |
KAWAMURA Gunzo Kagoshima University, Faculty of Fisheries, Professor, 水産学部, 教授 (30041718)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Prawn / bottom seine / selectivity / bycatch / behaviour / simulation / coastal environment |
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| Research Abstract |
Danish seine gear was studied on a combination of a tank experiment and operational survey with a gear newly designed for exclusion of bycatch as;
(1) Observation of behavior of prawns to pass through meshes in a small-tank clarified that probability for prawns to be excluded is ruled by probability to pass through one mesh at once encountering and the probabilistic number of encountering for one prawn. The logistic selectivity of seine nets is induced by repetition of encountering to meshes by organisms. Simulation based on this model well represented the selectivity curve of Danish seine nets obtained from previous trials.
(2) An experimental Danish seine net for exclusion of bycatch finfishes was designed on the basis of the above simulation and its selectivity was examined. Effects of enlargement and opening of meshes was as expected. A mesh size and fish size management diagram to design bycatch-exclusive fishing gears was proposed.
(3) Behavior of finfish to Danish seine was observed underwater by diving. Few finfish were observed in front of the main net and they were conjectured to be excluded more anterierly. Selectivity of Danish seine was hypothesised to be affected by towing ropes, therefore, their motion while being towed was experimented in air. Difference in motion of ropes of a variation in structure under a variation of set condition on ground appeared around anterior positions of the ropes. This indicates that studies on selectivity of seine nets must take stimulation by ropes to organisms into account.
(4) While the above experimental studies, record of discards of bycatch in small coastal Danish seine previously surveyed was analysed and it was clarified that evaluation and estimation of discards based on a newly-introduced concept, i.e. discard per unit effort (DPUE) is most accurate and reliable.
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