1996 Fiscal Year Final Research Report Summary
Research on the process of by-catch of discards in coastal fisheries ; development of environmentally-friendly fishing technology
| Project/Area Number |
06660247
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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, Associate Professor, 水産学部, 助教授 (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) |
1994 – 1996
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| Keywords | prawn (shrimp) / bottom seine net / fishing gear / by-catch / discard / behavior / optomotor response / coastal environment |
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| Research Abstract |
1. Survey of by-catch discards in coastal fisheries : Discards in gochi-ami (non-dragged small boat seine) fishery was surveyed onboard and multi-variable-analyzed. Species compositions were largely different among sub-sectors, or discards occur specifically. Discard ratios also differed among sub-sectors. A large amount of stock-enhanced highly-commercial species were discarded
This was developed in methodological study on large-scale discard estimation. The best factor for discard estimation is a summed discard ratio and a specific discard ratio has no statistical basis because of poor correlation between discards and retentions.
2. Behavior of organisms against fishing gear : Behavior of deep-water prawn against boat seine was observed by infra-red underwater video and unique behavior of prawn to bounce net webbing backwards and pass through a mesh by probability was found. The exclusion process for prawn was modelled and probabilities for prawns for exclusion were simulated.
3. On-boa
… More
rd study on by-catch capture process : Selectivity of boat seine for prawns and by-catch finfishes were studied on the basis of samples captured by an experimental net with pocket and cover nets over the net panels and codend. Prawns are excluded over the gear, while, finfishes, mainly through the codend. Selective characters were quite different between the codend and the net as a whole. Size-selectivty of the gear with different meshes were theoretically calculated and 'mesh-selective size management diagram' was established for recommendation for fishing gear management.
4. Present studies and future prospects : The precise process of exclusion for prawn though a mesh is being analyzed. Together with the field observation of behavior and the above analysis, the process to induce the selectivity is to be modelled. A new series of field experiments to develop selective boat seine is being prepared in order to verify the theoretically evaluated models and to develop practically selective fishing gear. Less
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