A Theoretical Approach to Determine the Total Resistance on Different Trawl Gears Used in Turkey

Abstract

The study aims to theoretically determine the total resistance forces acting on bottom trawls used in the commercial trawl fishery around the Turkish Peninsula. For this purpose, a total of 14 (2 for Black Sea, 2 for Sea of Marmara, 6 for Aegean Sea and 4 Mediterranean Sea) trawl gears were examined during the study representing all types of the bottom trawl fishery (e.g., fish targeted, shrimp targeted and mix) in Turkey. The calculation of the hydrodynamic forces of the gears was based on the determination of each gear component; net, floaters, sweep, door, warp and the friction force caused by footrope, sweep and door. The total resistance of trawl gears was calculated according to different towing speeds and warp lengths. Average resistance values of the examined nets with a 500 m warp length indicated that the frictional force of the trawl door composed more than 41.3% of the total resistance, followed by net (39.4%), both doors (6.3%), footrope friction (6.1%), sweep frictions (3.1%) and the rest belonged to sweeps, warps and floaters (totally 3.8%). It was determined that resistance caused by friction including sweeps, footrope and doors constituted more than 50% of the total resistance. Among the examined gears, the greatest resistance values were determined for the 600 meshes tailored-traditional Mediterranean type trawl gear.