青岛斋堂岛海域春季双桩竖杆张网网囊网目的选择性

2014年春季,采用平行作业法,以2a=16 mm(a为目脚长度)的菱形目网囊为对照网(CN),选取30 mm菱形目网囊和20 mm、30 mm、40 mm的方形目网囊(分别以30D、20S、30S和40S表示)作为实验网囊,对青岛斋堂岛附近海域的双桩竖杆张网进行了不同网目形状的网囊和不同网目尺寸方形目网囊的选择性比较试验。以多元统计分析方法进行种间选择性分析,以Logistic曲线作为选择性模型、采用极大似然估算法进行种内选择性分析。结果显示,与对照网相比,所有实验网囊均能有效释放玉筋鱼(Ammodytes personatus)、舒氏海龙(Syngnathus schlegeli)等低值渔获以及经济鱼类的幼体。比较不同网目形状网囊的渔获数据发现,方形目网囊较菱形目网囊具有更好的选择性,其中30S网囊对玉筋鱼和舒氏海龙的释放率(以尾数计)分别比30D网囊高4.61%和16.80%,对六丝钝尾虾虎鱼(Amblychaeturichthys hexanema)和日本枪乌贼(Loigo japonica)的50%选择体长(胴长)L50分别比30D网囊大38.47%和61.29%。比较不同网目尺寸方形目网囊的渔获数据发现,当实验网为20S和30S时,六丝钝尾虾虎鱼的L50分别为6.58 cm和7.20 cm,选择范围(SR)分别为3.02 cm和0.87 cm;当实验网为20S、30S和40S时,日本枪乌贼的L50分别为2.88 cm、4.03 cm和10.49 cm,SR分别为0.74 cm、0.52 cm和2.67 cm;不同尺寸的方形目网囊对这2种渔获物的L50随着网目尺寸的增大而增大。根据实验海区各种渔获物的经济价值、低值鱼类和幼鱼的释放比例以及分拣渔获物的劳动力投入等综合分析认为,30 mm方形目网囊在保护渔业资源的同时对渔业生产不会造成显著影响,建议予以推广。

Selectivity of codend mesh sizes in stow netsduring spring on the coast of Zhaitang Island, Qingdao

The selectivities of 30 mm diamond mesh codend (30D) and square meshcodends with mesh sizes of 20 mm (20S), 30 mm (30S), and 40 mm (40S) werestudied using the parallel haul method and a logistic curve on the coast ofZhaitang Island, Qingdao, in spring 2014. Diamond codend of 16 mm (2Multivariatestatistics and the maximum likelihood method indicated that allexperimental codends were effective in releasing of some economic fish species relative to the controlnet. Square mesh codends showed better selectivity than diamond mesh codends.The for 30S were 4.61% and 16.80% higher than those for30D, and the 50% retention body length ( 38.47% and 61.29%Comparison with catch data using squaremesh codends showed that the was 6.58 cm and 7.20cm, and the selection rage (SR) was 3.02 cm and 0.87 cmof was 2.88 cm, 4.03 cm and 10.49 cm,and the SR was 0.74 cm, 0.52 cm and 2.67 cm for the 20S, 30S and 40S,respectively. Thus, t increased with largersquare codend mesh size. A comprehensive analysis of the effects of differentmesh types on the economic value of the catch, the release ratio of low economicvalue captures, and labor input of sorting catches all suggest that the use of30 mm square mesh codend the fishery by reducingunwanted bycatch and therefore should be implemented in the region.