Development of Low Drag Trawls for Energy Efficient Fishing

Abstract

Trawl drag is an important factor determining the energy efficiency and profitability of trawling. Drag experienced during trawling depends on the design, rigging, accessories of the net, hydrographic and dragging conditions and has a direct bearing on fuel consumption. Fuel cost can alone constitute up to 75% of the operational expenditure of a trawler. Stronger materials will permit the use of thinner twines to reduce twine surface area and hence drag. Empirical estimations of drag of different commercial trawl nets in Kerala showed it to range from 1.37 to 48.94 kN. Comparative fishing trials were carried out with 24 m trawls made of HDPE twine and ultra-high molecular weight polyethylene (UHMWPE). Study revealed that average fuel consumption of HDPE trawls was 31.86±1.25 l-h whereas it was 25.31±1.38 l-h for UHMWPE trawl. CPUE were 8.1 kg h-1 and 7.9 kg h-1 for UHMWPE trawl and HDPE trawl respectively. Results shows that material substitution, coupled with improvement in trawl design, appropriate gear accessories and towing speed can help significantly in reducing the drag and concurrent reduction in fuel use.