南海区金线鱼刺网网目选择性

Mesh selectivity of Nemipterus virgatus gillnet in South China Sea

为科学制订南中国海区金线鱼(Nemipterus virgatus)刺网最小网目尺寸标准,2008年5月在南海北部进行了5种网目(40mm、45mm、50mm、55mm、60mm)刺网联合捕鱼实验,渔获种类合计达72种,其中5种网目刺网均有捕获的仅13种。根据刺网渔获的种类、数量和生物量,利用研究生物群落的多样性指数、相似性指数和ABC曲线方法,研究了金线鱼刺网的种间选择性,探讨了不同网目刺网作业对渔业资源的影响。结果表明,不同网目实验刺网的渔获组成存在明显差异,随着网目尺寸的缩小,渔获种类和数量呈上升趋势,渔获平均体质量则呈下降趋势。多齿蛇鲻(Saurida tumbil)、长尾大眼鲷(Priacanthus tayenus)、金线鱼、带鱼(Trichiurus haumela)和花斑蛇鲻(Saurida undosquamis)为主要渔获种类,其渔获生物量分别占总渔获量的21.35%、15.76%、14.78%、8.43%、7.20%,40mm和45mm刺网中多齿蛇鲻和花斑蛇鲻的渔获比例较高,50mm、55mm和60mm刺网中长尾大眼鲷、金线鱼和带鱼的渔获比例较高。根据ABC曲线计算的40mm、45mm、50mm、55mm和60mm5种网目刺网W统计值分别为-0.023、-0.012、0.039、0.083和0.073。40mm和45mm刺网对渔获生物群落的干扰较大。南海区金线鱼刺网最小网目尺寸标准的制订应综合考虑金线鱼、带鱼、长尾大眼鲷这3种主捕经济种类的尺寸选择性和最小可捕标准,同时注意网线粗度对捕捞能力的影响。

In order to establish the minimum mesh size standards of Nemipterusvirgatus gillnet in South China Sea,fishing trials for gillnets with five different mesh sizes（40mm,45mm,50mm,55mm and 60mm with twine diameters of 0.25mm,0.25mm,0.30mm,0.30mm and 0.35mm,respectively）were carried out in northern South China Sea in May,2008.The catches were composed of 72 species in all,among which only 13 species appeared in all experimental gillnets.Based on species composition,abundance and biomass of catch,diversity index,similarity index and abundance-biomass compariso（nABC）curve were used in the study of intra-selection of Nemipterus virgatus gillnet and the effect of different mesh size on fishery resources.The results indicate that the catch species composition was different between the experimental gillnets.With mesh sizes reducing,species quantity and abundance of catches increased,while average individual weight decreased.Sauridatumbil,Priacanthus tayenus,Nemipterus virgatus,Trichiurus haumela and Saurida undosquamis were dominant catch species,whose biomass percentages in all catches were 21.35%,15.76%,14.78%,8.43%and 7.20%,respectively.Sauridatumbil and S.undosquamis had higher percentages in 40mm and 45mm gillnets,while Priacanthus tayenus,Nemipterus virgatus and Trichiurus haumela had higher percentages in 50mm,55mm and 60mm gillnets.Biological community stability of catches declined with mesh sizes reducing.Statistical values of W of 40mm,45mm,50mmmm,55 and 60mm gillnets were-0.023,-0.012,0.039,0.083 and 0.073,respectively,which indicated 40mm and 45mm gillnets had serious impact on fisheries resources.N.virgatus,Trichiurus haumela and Priacanthus tayenus are the targeted species in fishery.Minimum mesh size of N.virgatus gillnet should be determined based on size selection and minimum fishing standard of the three species.The effect of twine diameters on fishing power of gillnets should also be taken into account.