四片式高口双拖网

本文反映黄海区群众渔业双拖网改进研究取得的一项新成果,报导了设计的依据、改进的特点、网模水池试验及海上实测的验证数据。经三年捕捞试验,取得了比原型网增产40％以上的显著效果。

ON HIGH OPENING TWO-BOAT TRAWL WITH FOUR PANELS

This paper deal with study on improvement of two-boat trawl net of185 Hp trawler used widely in collective off-shore fishery in order to adapt the com-position change of fish resources and increase exploitative capacity of fast migra-ting and locating water layer inhabiting fish in the Yellow sea. The feature of this new designed net is that the height of net opening is increa-sed obviously and drag is still unchanged almost keeping trawling speed from 2.5to 3 knots comparing to old one. Authors adopt some measures to meet needs descri-bed above belly 4 penels, net mouth circumference is increased 10% with mesh sizeincreased 12%, side penels netting have the same length with lower belly, but topbelly is 32% wider than lower belly, wing is short, and lower wing netting stretchlength is 19% of net mouth circumference. According to result of model test in water tank when L/S is 0.35, relationsbetween net dray R, net opening H and trawling speed V are as follows: R=1.677V~(1.533) H=15.304V~(-1.005)when trawling speed is 3 knots drag is the same with old one,net opening is increa-sed 23.4%, net shape is more smooth. Comparing to old one when 4 two-boat trawlers of 185 Hp test fishing havebeen carried out at sea for 3years. The result revealed that both catch yield and pro-fit are increased obviously, mean catch and profit increased 46.3% and 46.5% res-pectively. Not only the size of caught fish is larger but also young fish undercaughtable size of 110 mm is decreased 26%.