南海区康氏马鲛流刺网最小网目尺寸的初步研究

为促进南海马鲛刺网渔业的可持续发展和渔业资源的合理利用,于2012年和2015年分别进行了马鲛流刺网渔获组成和选择性试验。运用相对重要性指数(IRI)评价刺网的渔获组成,并在SELECT模型(share each length catch total)的架构下,利用正态分布(Normal)和双峰分布(Bi-normal)概率方程计算刺网对康氏马鲛(Scomberomorus commersoni)的选择性;进一步结合康氏马鲛的最小可捕规格,探讨南海区马鲛流刺网的最小网目尺寸。结果表明,康氏马鲛是南海马鲛流刺网最重要的渔获种类,其2012年和2015年IRI值分别为9 472.00和14 363.02;调查试验共捕获康氏马鲛295尾,其中2012年康氏马鲛的众数叉长组为751~800 mm(占32.52%),2015年康氏马鲛的2个众数叉长组分别为501~550 mm和701~750 mm;正态分布模型估算的选择性众数相对叉长为6.961;双峰分布估算的2个众数相对叉长值分别为4.440和6.728;根据模型残差值的大小,认为双峰分布的拟合效果较好;将康氏马鲛可捕规格定为380 mm的前提下,建议南海马鲛流刺网的最小网目尺寸可暂定为120 mm。

Preliminary study on minimum mesh size of gillnet for Scomberomorus commersoni in the South China Sea

To maintain sustainable development of gillnet fishery for Scomberomorus commersoni and to protect fisheries resources,we conducted the fishery survey and selectivity experiments in 2012 and 2015.The index of relative importance(IRI)was used to evaluate the fished species of the gillnet fisheries.Based on the SELECT(share each length catch total)method,both Normal and Bi-normal models were used to calculate the selectivity of gillnets for S.commersoni.Finally,with consideration of the minimum landing size of S.commersoni,we determined the minimum mesh size of the gillnet for S.commersoni.The results reveal that S.commersoni is the most important catch species for the fishery.Its IRI was 9 472.00 and 14 363.02 in 2012 and 2015,respectively.A total of 295 specimen of S.commersoni were caught.In 2012,the modal fork length groups of S.commersoni were 751～800 mm(accounted for 32.52％).In 2015,the first and second modal fork length groups of S.commersoni were 501～550 mm and 701～750 mm,respectively.The modal relative length of Normal model was 6.961.The first and second modal relative length of Bi-normal model was 4.440 and 6.728,respectively.The result of model deviance indicates that Bi-normal model is the best-fit model.Suppose that the minimum landing size of S.commersoni was 380 mm,the minimum mesh size of the gillnet for S.commersoni would be 120 mm.