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引言底层鱼类在底层网板拖网的不同部位的逃逸主要集中在网囊段。研究中发现,除了不同的网身形状外,网囊的逃逸率主要起因在于网囊的结构和网囊不同部位的网目角张开度。此外,当鱼积聚在网囊底部时,鱼体对抗网目的压力和水流扩充而在网囊端部造成阻塞,这就改变了网囊网目的张开形状和网目度的张开度。由于网囊对抗水流使其阻力增加,所以造成网囊的形状和横截面发生变化,从而改变网囊内鱼群的逃逸行为和网目选择性。作者根据渔民使用的六片式底拖网的标准,制作了4种模型网,并在循环水
INTRODUCTION Escapes of the bottom fish in different parts of the bottom trawl are concentrated in the cyst segment. The study found that, in addition to the different shape of the net body, the main reason for the escape rate of the cyst is the structure of the cyst and the cyst angle of the mesh opening in different parts. In addition, as the fish accumulate at the bottom of the cyst, the pressure and water flow of the fish expands against the mesh causing obstruction at the ends of the cyst, which changes the openness and mesh opening of the mesh. As the resistance of the cyst against the water flow increases, the shape and cross section of the cyst are changed, thus changing the escape behavior and net selectivity of the fish in the cyst. Based on the standard of six-piece bottom trawling used by fishermen, the authors produced four model nets,