Codend selectivity in the East China Sea of a trawl net with the legal minimum mesh size Codend selectivity in the East China Sea of a trawl net with the legal minimum mesh size

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東シナ海の魚類 20 種とイカ類 2 種に対する最小規制目合(目合内径 54 mm)のコッドエンドを持つトロール網のコッドエンド選択性曲線を,カバーネット装着操業試験の結果から求めた。魚類 18 種(タチウオとハモを除く)の選択性パラメータ(50% 選択体長と選択レンジ)と魚体型の関係から,細長い体型の魚種ほど網目を抜けやすくかつ選択性が鋭くないことを示した。さらに,50% 選択体長と最小成熟体長など再生産パラメータを比較することで,単一目合のコッドエンド選択によって複数種を対象とした資源利用の持続性を検討した。

Selectivity curves were obtained for 22 species from stock assessment research data in the East China Sea between 2001 and 2011, conducted using a cover net attached to the codend of a trawl net (Seikai National Fisheries Research Institute SS-RI type trawl net). The trawl net codend used was made of diamond mesh net with a legal minimum mesh opening size of 54 mm (mesh length of 66 mm). The cover net with a mesh opening of 18 mm (or 10.3 mm depending on the research year) was attached to the codend. For each of the 20 fish species and two squid species, we pooled data of hauls where body size for the whole catch was measured without subsampling to obtain the body size compositions of both of the codend and the cover net. The maximum likelihood method was performed for estimation of parameters in the logistic curve equation representing the codend selection curve. For 18 fish species (excluding Trichiurus japonicus and Muraenesox cinereus), we examined the relationship of the obtained selection parameters [l50, length of 50% retention and SR, selection range (= l75 - l25)] to the fish body shape. We demonstrated that fish species with a smaller ratio of body height/width to body size (i.e. more slender body type) show a tendency of larger values of l50 and SR. Furthermore, by comparing the l50 of each fish species with the reproductive parameters such as minimum maturity length, we examined the sustainability of the resources based on the minimum mesh size regulation.


  • Fisheries science

    Fisheries science 85(1), 19-32, 2019-01



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