桁拖网渔具刚性栅栏对鱼类的分隔效率研究

东海捕虾桁拖网选择性能不佳,对渔业资源的保护和渔业的合理管理带来了负面的影响.刚性栅栏是实现拖网渔具种类选择性捕捞的主要装置,本文根据在吕四渔场开展刚性栅栏海上生产试验,结合SELECT模型分析不同栅条间距(15、20和25mm)的刚性栅栏对短吻舌鳎、小黄鱼和棘头梅童鱼的分隔效率.结果表明,随着栅条间距的增大,栅栏对鱼类的重量分隔率逐渐减小,分隔栅栏对鱼类的50%选择体长(L50S))逐渐增大;对于短吻舌鳎,个体接触分隔栅栏的概率可使用常数来表示,即接触概率与个体尺寸无关,接触概率在0.2-0.4之间,并随着栅条间距的增大而增大(不显著,P>0.05):对于小黄鱼和棘头梅童鱼,所有进入网囊的个体都将接触刚性栅栏;不同鱼类接触栅栏概率的显著差异说明不同鱼类在网囊中的不同行为习性.

FISH SEPARATING EFFICIENCY OF SORTING GRID RIGGED IN BEAM TRAWLS

Poor selection of the beam trawl fishing in the East China Sea has exerted negative influences on conservation of fish resources and management of fisheries. To solve the issue, sorting grid was developed to separate catch effectively by species retained in non-selective codends in trawl fisheries. In this paper, the separating efficiency of sorting grid of different bar spacings (15, 20, and 25mm) for three-lined tongue sole Cynoglossus abbreviatus, little yellow croaker Pseudosciaena polyactis, and spinyhead croaker Collichthys lucida was analyzed in sea trials carried out in Lvsi Fishing Ground in the SELECT model. The results show that the separating ratio of catch weight of fishes decreases with the increase in bar spacing. The 50% retention length of different grids increases with the bar spacing. For three-lined tongue sole, the probability of contacting grid of shrimps is indicated by a parameter, which means the contact probability is independent of individual size. The maximum likelihood estimates of contact probability for sorting grids of different bar spacings are between 0.2 and 0.4 and increase insignificantly (P>0.05) with the bar spacings. For little yellow croaker and spinyhead croaker, all individuals entering codends would encounter the sorting grids. The difference in contact probability for different fishes indicates distinct swimming behavior patterns in trawl.