文章摘要
帆张网网囊网目尺寸对带鱼的选择性
Selectivity of different mesh size codends of canvas spreader stow net for Trichiurus lepturus
投稿时间:2020-07-01  修订日期:2020-11-12
DOI:
中文关键词: 帆张网  带鱼  网目尺寸  选择性  东海区
英文关键词: canvas spreader stow net  Trichiurus lepturus  mesh size  selectivity  the East China Sea
基金项目:国家重点研发计划,浙江省重点研发计划项目
作者单位邮编
徐国强 上海海洋大学 201306
朱文斌 浙江省海洋水产研究所 316021
许柳雄 上海海洋大学 201306
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中文摘要:
      为探索帆张网不同网目尺寸网囊对带鱼(Trichiurus lepturus)的选择性,作者于2018年10月在大沙渔场用传统选择性试验方法(套网法)对5种不同网目尺寸(35mm、45mm、55mm、60mm、65mm)网囊进行了选择性对比试验,应用Logistic选择性模型对带鱼选择性曲线进行拟合,采用极大似然法估算模型参数。结果表明:(1)试验期间测量带鱼4265尾,肛长范围76~305mm,平均肛长167±43mm;(2)网目尺寸为35mm时,带鱼基本无逃逸行为;网目尺寸为65mm时,套网和囊网中的带鱼肛长分布基本一致;随着网目尺寸的增加(45~60mm),网囊中带鱼优势肛长总体上大于套网;(3)网囊网目尺寸为45mm、55mm和60mm时,带鱼L50分别为171.839mm、180.562mm和215.905mm,SR分别为60.402mm、104.861mm和157.292mm,L50呈现逐渐增大的趋势;(4)带鱼网囊网目尺寸(m)与50%选择体长(L50)的关系为:L50=2.643m+48.491 (R2=0.748);(5)以带鱼最小可捕肛长205mm(浙江省地方标准)计算,即当带鱼50%选择肛长为205mm时,帆张网对带鱼的网囊最小网目尺寸应为59.2mm。综合以往研究结果,帆张网最小网目尺寸应为57.47mm。综上分析可知,同时结合目前渔业资源状况,为保护当前带鱼幼鱼资源,目前实施的最小网目尺寸55mm是较为适宜的,能满足保护幼鱼资源的目的。
英文摘要:
      In order to explore the selectivity of different mesh size codends for Trichiurus lepturus, the traditional selective method (covered net method) was adopted, and a selection experiments were carried out with 5 different mesh size(35mm、45mm、55mm、60mm、65mm) codend nets on canvas spreader stow net. The Logistic selection model was used to fit the selectivity curve of Trichiurus lepturus and the model parameters were estimated by the maximum likelihood method. The results showed that: (1) 4265 tail of Trichiurus lepturus were measured during the experiment, the anal length ranged from 76~305mm with an average anal length of 167±43mm; (2) When the mesh size was 35mm, there was basically no escape behavior of Trichiurus lepturus. While the mesh size was 65mm, the distribution of anal length of Trichiurus lepturus in covered and codend net was basically the same. With the increase of mesh size, the dominant body length of Trichiurus lepturus in the codend nets was larger than that of the covered nets; (3) When the mesh size for Trichiurus lepturus was 45mm、55mm and 60mm,its L50 was 171.839mm、180.562mm and 215.905mm, its SR was 60.402mm、104.861mm and 157.292mm, respectively, L50 showed a gradual increase trend; (4) The relationship between the codend nets mesh size of Trichiurus lepturus and L50: L50=2.643m+48.491 (R2=0.748); (5) When the anal length of Trichiurus lepturus is 205mm, the minimum mesh size of canvas spreader stow net should be 59.2mm.Based on previous research results, the minimum mesh size of canvas spreader stow net should be set as 57.47mm. Based on the above analysis, it can be seen that: the current minimum mesh size of 55mm is more appropriate to protect the juvenile Trichiurus lepturus resources, which can meet the purpose of protecting the juvenile Trichiurus lepturus resources. There was still a large difference in the minimum mesh size of two kinds of fish. The optimal mesh size of the canvas spreader stow net is determined by the minimum mesh size of Trichiurus lepturus (57.47mm) or Larimichthys polyactis (65.63mm), which is a scientific problem worth further study. From the composition of the catch, Larimichthys polyactis is the main target catch of the canvas spreader stow net, followed by Trichiurus lepturus. If the mesh size is determined according to the catch amount, it will inevitably cause a large number of other catches to escape. Therefore, it is appropriate to determine the minimum mesh size of the canvas spreader stow net by the minimum mesh size of Trichiurus lepturus.
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