桁杆虾拖网选择性装置的试验分析

设计并研制了一种内、外圆环形刚性框架和柔性六角形网片组合而成的桁杆虾拖网选择性装置。所研制选择性装置在东海区近海桁杆虾拖网中,采用对比试验法开展了海上选择性试验,并针对试验期间主要渔获品种哈氏仿对虾,以Logistic曲线为选择性模型,对六角形网目水平缩结长度分别为D1=31.00 mm,D2=27.50 mm,D3=21.25 mm三种规格选择性装置的选择性效果进行分析。结果表明,3种规格选择性装置均具有选择性效果,其中安装六角形网目水平缩结长度为31.00 mm和27.50 mm的选择性装置的目标网囊内哈氏仿对虾的优势体长均为75~95 mm,相应非目标网囊内哈氏仿对虾的优势体长分别为25~45 mm和35~55 mm,具有较显著的差异性;而安装六角形网目水平缩结长度为21.25 mm的选择性装置的目标网囊内哈氏仿对虾的优势体长35~55 mm,相应非目标网囊内哈氏仿对虾的优势体长同为25~45 mm。六角形网目水平缩结长度31.00 mm的选择性装置对哈氏仿对虾的50%选择体长L50最大,为48.89 mm,而选择性范围SR最小,为16.75 mm,在试验规格范围内的选择性效果最显著。

Experimental analysis on the performance of a selectivity device in shrimp beam trawl

A new kind of a selectivity device which was constructed with rigid metal cirque and hexagon mesh net inside was designed.Fishing experiments were carried out in East China Sea to study the performance of the selectivity device.Based on the main catch species,Parapenaeopsis hardwickii,Logistic curve was used as a select model to analyze the performance of three selectivity devices which were different in horizontal hanging length,D1=31.00 mm/D2=27.50 mm/D3=21.25 mm,of the hexagon mesh.Experiments indicated that all three selectivity devices showed selectivity results.Selectivity devices with horizontal hanging length 31.00 mm and 27.50 mm of the hexagon mesh had obvious difference in the dominant body length of Parapenaeopsis hardwickii caught by target and non-target codends.For selectivity device with D1=31.00 mm and D2=27.50 mm,the dominant body length of Parapenaeopsis hardwickii caught by the target codend was the same,75-95 mm,but 25-45 mm and 35-55 mm for non-target codends respectively.For selectivity device with D3=21.25 mm,the dominant body length of Parapenaeopsis hardwickii caught by the target codend was 35-55 mm,and 25-45 mm for non-target codends.Comparatively,selectivity device with D1=31.00 mm,showed better selectivity result for Parapenaeopsis hardwicki,that the maximum 50% selectivity body length(L50) was 48.89 mm,while the selection range(SR) was 16.75 mm.