Examining engineering performance of midwater trawl with different horizontal spread ratio, floatage, and weight parameters: A case study of model net for Antarctic krill fisheries

Abstract

It is necessary to investigate the effectiveness of the midwater trawl in reducing fuel consumption and increasing catch performance for the development and improvement of the Antarctic krill fisheries. A 1/35 scale trawl model for Antarctic krill fisheries was designed based on modified Tauti's law and tested in a flume tank, and the effects of flow velocity, horizontal spread ratio, sinking force, and the ratio of buoyancy to fishing line weight on its engineering performance were analyzed in this study. The results indicated that the lower flow velocity and the ratio of buoyancy to fishing line weight conducted to the greater hydrodynamic forces and geometrical performances. The higher horizontal spread ratio and sinking force were found to have exhibited the greater drag force, net mouth opening, wing-end spread, bridle angle, net mouth area, swept area, and volume covered by trawl net. It was revealed that the engineering performance of the midwater trawl (minimal ratio between drag and swept area) was efficient when the horizontal spread ratio was at 0.55 (corresponding to the trawl horizontal opening of 64.65 m in full-scale), the sinking force was at 97.96 g (600 kg of full-scale), and the ratio of buoyancy to fishing line weight was at 4.2 and 2.6 compared to those actually used during Antarctic krill fishing. In addition, the study demonstrated that the modification of the horizontal spread ratio, sinking force, and the ratio of buoyancy to fishing line weight can be one alternative to improve the geometrical shape performance of the midwater trawl net that could improve catchability of the trawl net.

Keywords

• Midwater trawl
• Antarctic krill
• Flume tank
• Energy efficiency
• Mouth opening