南海北部竖杆张网网囊网目选择性研究

Cod-end mesh selectivity of stick stow net in north part of the South China sea

使用套网法对南海北部双桩竖杆张网网囊网目的选择性进行分析,根据相对重要性指数(IRI)确定黄斑篮子鱼(Siganus oramin)、周氏新对虾(Metapenaeus joyneri)、小鳞沟鰕虎鱼(Oxyurichthys microlepis)和白姑鱼(Argyrosomus argentatus)4种主要渔获作为张网选择性研究的指标种,使用Logistic曲线作为其选择性曲线模型,求得不同网目尺寸网囊对该4种指标种的体长选择性曲线,并运用极大似然估计法进行曲线参数运算。结果显示,试验网囊网目尺寸为15 mm时,除毛虾(Acetes)外无其他渔获逃逸;试验网囊网目尺寸为25 mm时,4种指标种的50%选择体长(L50)分别为53.17、50.16、61.05、26.37 mm,其选择性范围(SR)分别为13.43、17.50、41.88、12.78 mm;试验网囊网目尺寸为35 mm时,4种指标种的L50分别为80.72、77.12、86.97、68.68 mm,其SR分别为19.48、39.08、28.20、13.17 mm。随着张网网囊网目尺寸的增加,4种指标种的L50随之增加,SR值除小鳞沟鰕虎鱼外也都增加。

The cod-end mesh selectivity of double stake net was studied by using covered net method. Siganus oramin, Metapenaeus joyneri, Oxyurichthys microlepis and Argyrosomus argentatus were the main fishing targets in the area by the index of relative importance （IRI）. Using the catch data of the four fishing targets, different mesh sizes selectivity curves of them were drawn by using Logistic curves as a selectivity model. Parameters of selectivity were estimated according to the maximum likelihood method. The results indicated that when the mesh size was 15 mm, there was no fish escape except Acetes; when the mesh size was 25 mm, the Lso of the four fishing targets was 53.17 mm, 50.16 mm, 61.05 mm and 26.37 mm, the SR of them was 13.43 mm, 17.50 mm, 41.88 mm and 12.78 ram, respectively; when the mesh size was 35 mm, the Ls0 of them was 80.72 mm, 77.12 mm, 86.97 mm and 68.68 mm, the SR of them was 19.48 mm, 39.08 mm, 28.20 mm and 13.17 mm, respectively. When the mesh size of the stake stow net increased, the Ls0 of the four fishing targets would enlarge, and their SR would enlarge expect 0. microlepis.