东海区底拖网对小黄鱼的选择性研究

近年来东海由于环境恶化和过度捕捞,小黄鱼资源量发生了严重的衰退。为更有效可持续利用小黄鱼资源,本试验就东海区底拖网菱形目50、55、60、65、70、75和80 mm网囊网目对小黄鱼进行选择性研究,采用套网法对不同尺寸的网目网囊的选择性进行了分析比较。结果表明:(1)当网囊为50和55 mm时产生较高逃逸率,但仍捕获大量当年生经济幼鱼;(2)随着网目由小变大,囊网捕获小黄鱼的平均体长、体重也逐渐变大;(3)拖网时间加长,由于网囊中渔获积累产生的堵塞效应,严重影响非目标鱼类的逃逸率;(4)根据小黄鱼的50%选择体长(L0.5)与不同网目尺寸拟合的直线:L0.5=2.625M-30.7(R2=0.915)。结合现行可捕标准以及渔业生产,建议拖网网目尺寸至少为60 mm。

Selectivity of Parimichthys polyactis of bottom trawl in the East China Sea

A bottom trawl investigation was conducted for selective test of Parimichthys polyactis by using diamond mesh codend 50, 55, 60, 65, 70, 75 and 80mm in the East China Sea in August 2014. By using cover-net method, the catching data were analyzed and selective parameters were estimated by using the logistic equation with the maximum likelihood method. The results show that: (1)when the mesh sizes were 50mm and 55mm, a large number of the commercial juveniles of the same year are caught; (2) According to the Logistic curve, Parimichthys polyactis average body length and weight increased gradually with the mesh size became larger; (3)The longer the trawl towed, the more obvious blocking effect, which contributed to a serious impact on non-target fish escape rate; (4)Based on the relation 50% retention length with mesh sizes of codend, the linear regression equation of the Parimichthys polyactis is L_0.5=2.625M-30.7(R²=0.915). Based on the previous research and the existing catch standard, together with fishery production, the appropriate trawl mesh size is 60mm or bigger.