基于裤式拖网法的虾拖网网囊网目选择性试验与分析

为研究虾拖网网囊网目对主要渔获种类的选择性,于2017年9月在南海区采用裤式拖网法进行选择性试验。在SELECT模型框架下,使用极似然估算法,结合单网次和联合网次的数据,同时考虑网次间差异,估算网囊对主要渔获种类的平均选择性。共完成14网次作业,其中对照网囊之间的渔获性能比较试验4次,试验网囊的选择性试验10次。研究表明:对照网囊的位置对其渔获性能无显著影响;试验网囊对刀额新对虾(Metapenaeus ensis)的网次50%选择体长(L 50)为78.84~92.09 mm,平均为82.38 mm,网次选择范围(SR)为5.01~11.32 mm,平均为6.39 mm,网次相对作业强度(p)为0.44~0.71,平均为0.52;试验网囊对黄斑蓝子鱼(Siganus oramin)的网次L 50为59.20~76.80 mm,平均为71.17 mm,网次SR为5.30~16.87 mm,平均为14.20 mm,网次p为0.43~0.71,平均为0.63。试验网囊对刀额新对虾的网次和平均L 50值均大于其首次性成熟体长(80 mm),可见试验网囊对刀额新对虾的资源利用是合理的。本试验的裤式拖网法和数据处理方法可为今后拖网选择性研究提供参考。

Selective Trial and Analysis of Shrimp Beam TrawlCodend Mesh Based on Trouser Trawl Method

To select the codend mesh applicable for the main target species with trouser trawl method,this study was carried out in the South China Sea in Sep.2017.The SELECT model was selected and maximum likelihood method was used.Both haul-level and combined-haul level methods were used to analyze the experimental data by considering the between-haul variation.In total,14 hauls were successfully finished,including 4 to check the fishing performance of both control codends,and 10 to investigate the selective properties of the test codend.The results indicated that there was no significant system variation among the experiments by attaching which side of the control codend.The 50%retention length(L 50)of test codend to Metapenaeus ensis ranged between 78.84 and 92.09 mm,with a mean of 82.38 mm.The selection range(SR)varied between 5.01 and 11.32 mm,with a mean of 6.39 mm.The relative fishing intensity(p)ranged from 0.44 to 0.71 with a mean of 0.52.The L 50 of test codend to Siganus oramin ranged from 59.20 to 76.80 mm with a mean of 71.17 mm.The SR ranged from 5.30 to 16.87 mm with a mean of 14.20 mm.The p ranged from 0.43 to 0.71 with a mean of 0.63.The L 50 of M.ensis from both haul-by-haul estimate and the combined-haul estimate was larger than that of the first maturity length(80 mm).Therefore,the tested codend could harvest M.ensis resource sustainably.Our trouser trawl method and analysis way of data could offer a good example for future selectivity study.