Effect analysis of gear structure and sinker on the performance of Antarctic krill beam trawl

Beam trawl is an important part of Antarctic krll (Euphausia superba) continuous fishing system. In order to further understanding the gear performance under different conditions, a series of model test were designed to study the effect of gear structure and sinker on gear performance. The gear structures include 3 kinds of belly width and 2 types of knitting for each belly width, represented by A, B, C, AA, BB and CC respectively. Modified Tauti’s law was used to designed beam trawl models. The full scale was 20, mesh size or twine diameter scale was 10. Based on the energy efficiency coefficient, vertical opening and resistance, the performance of different gear structure were compared. The result showed that: the performance of different gear structure was in the order of BB>CC>C>A>B> AA, but the difference was not obvious (P>0.05). Less total line area of net can effectively improve the vertical opening of the beam trawl and reduce the energy efficiency coefficient, especially under the high trawling speed. Sinker weight was significantly correlate with gear resistance and vertical opening, and not significantly correlate with energy efficiency coefficient. In order to keep good performance in vertical opening of test nets, heavier sinker were needed under higher trawling speed. According to the model test, sinker weight should not be less than 3.05 t at the trawling speed of 1.5 m/s for test nets; a power function was observed between net resistance and trawling speed, and the index ranged from 1.49 to 1.64. These conclusions can be used as reference for the performance optimization of E. superba beam trawl and promote the development of E. superba fishery.