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瀬戸内海における小型底びき網漁業の資源管理
https://fra.repo.nii.ac.jp/records/2003219
https://fra.repo.nii.ac.jp/records/20032192732da3b-bd17-4322-ac82-4b0bbcfa49c2
| Item type | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-04-25 | |||||
| タイトル | ||||||
| タイトル | 瀬戸内海における小型底びき網漁業の資源管理 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | Fisheries Management of a Small Shrimp Trawl in the Seto Inland Sea - Discarded Fishes and Mesh Size Regulation | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| キーワード | ||||||
| 言語 | en | |||||
| 主題Scheme | Other | |||||
| 主題 | fisheries management; shrimp trawl; discarded fish; mesh selectivity; mesh size regulation | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| その他（別言語等）のタイトル | ||||||
| その他のタイトル | 投棄魚問題と網目規制 | |||||
| 言語 | ja | |||||
| 著者 |
東海, 正
× 東海, 正 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Small trawl fisheries exploit many small shrimps and depend greatly on them in the Seto Inland Sea. Southern rough shrimp Trachypenaeus curvirostris is the most important target species of small shrimps besides kuruma prawn Penaeuse japonicus. At the same time, the main species of fishes concerned are two juvenile flounders Pleuronichthys cornutus and Limanda yokohamae. The shrimp beam trawl net has small-mesh codends, about 16.5-25.1 mm in stretched measure in the Seto Inland Sea, since its main target species are shrimps. Consequently, two juvenile flounders are caught in the shrimp beam trawl fishery and most of them are usually discarded at sea, because they are considerably smaller than commercial size, about 100 mm in body length. Discards of juvenile flounders occur more abundantly from spring to summer when they are widely distributed in the trawl fishing ground. The annual amounts of the two juvenile flounders discarded at sea were estimated at approximately 200,000 in number (1.12 ton in weight) and 42,000 in number (0.17 ton in weight) per a boat in the Suo-Nada, respectively. The number of the small trawl fishing boats in the Suo-Nada is approximately 550 boats. There is concern that the catching and discarding of these juveniles may possibly have an adverse effect on flounders stocks. Since the fishing grounds and seasons of the small trawl fishery overlap the distributions of juvenile flounders, it is difficult to establish closed seasons and areas. Accordingly, the mesh size regulation was examined and this paper presents an appropriate mesh size for the present shrimp fishery. The mesh selectivity of trawlnets has been usually determined by the trouser trawl, the covered-net or the comparative fishing method. However, the methods can not give the mesh selectivity for a specified mesh size without any fishing experiment with that mesh size. This paper also presents new methods of determining the mesh selectivity curve for an arbitrary mesh size of codend from a fishing experiment with several mesh sizes. A covered-net fishing experiment was carried out of a shrimp beam trawl with codends of six mesh-sizes in the Suo-Nada, on July 7-9, 1984. The mesh selectivity curves of the shrimp beam trawl were determined for two shrimps, southern rough shrimp and mantis shrimp Oratosquilla oratoria. The master curves were obtained from this method and can give the mesh selectivity curves of a specified mesh size for the two shrimps. In the same fishing experiment, the mesh selectivity curves for the two flounders were also determined. In estimating appropriate mesh sizes in a fishery, the objective for fishery management was proposed, that the amount of a few target species discarded is made as small as possible without a remarkable decrease in the landing of the target species. The culling selectivity was defined as the ratio of landing number to catch number(=landing no. + discard no.) at each length class. And the total selectivity was defined as multiplying mesh selectivity and culling one together. Moreover, this objective can be attained by adopting a mesh size whose mesh selectivity curve is the most similar to the patterns of total selectivities for the target species. The culling selectivity and the total selectivity for southern rough shrimp were estimated as a function of body length. For example, the total selectivity for southern rough shrimp begins to increase from the length class of 40-45 mm and steeply increases with length, and then reaches 1 at the length class of 80-85 mm. Thus the mesh used at present(25.1 mm) is too small for southern rough shrimp. Since southern rough shrimp is the smallest target species, the appropriate mesh size was determined at 32.5 mm mesh size as an appropriate mesh size. The amount of the target species discarded at sea were predicted, using the fishery model. The adoption of 32.5 mm mesh size will make southern rough shrimp discards almost nothing, while the amount of landing shows an increase of 16% without an immediate decline, as compared with the one of the present fishery. It was often stated that it is difficult to convince fisherman of the need for restrictive measures, because an excessive increase in mesh size brings an immediate loss before long-term benefits. The mesh size regulation for the objective of reducing the amount of discards at sea increases the total landing without an immediate loss. This mesh size regulation is probably acceptable for the small trawl fishermen. | |||||
| 言語 | en | |||||
| bibliographic_information |
ja : 南西海区水産研究所研究報告 en : Bulletin of Nansei National Fisheries Research Instituite 巻 26, p. 31-106, ページ数 76, 発行日 1993-03 |
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| 出版者 | ||||||
| 出版者 | 南西海区水産研究所 | |||||
| 言語 | ja | |||||
| 出版者 | ||||||
| 出版者 | Nansei National Fisheries Research Instituite | |||||
| 言語 | en | |||||
| item_10002_source_id_9 | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 0388-841X | |||||
| item_10002_source_id_11 | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00181988 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | nnf_k_26_31 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010501877 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本農学文献記事索引(agriknowledge) | |||||
