MultiSEPT – Initial model scale tests of traditional and alternative trawl ground gears

Abstract

This report describes initial model scale experiments with lighter ground gear in bottom trawls in the MultiSEPT project. This includes tests with traditional rockhopper gear, skirt, modified skirts, modified plate gears and a new bottom gear made with semi-circular profiles. In some cases the different types of gear are combined, i.e. with one type of gear in the side sections and another type in the center section. Tension in lower sweeps, headline, fishing line and gear chain was measured, including measurements of the maximum tension as the gear encountered a bottom obstacle. The results indicated that the towing resistance for a scaled (1:4) bottom trawl in the flume tank (i.e. with low bottom friction and excluding doors and warps) was reduced by approximately 15 % by replacing the rockhopper with a skirt, and that an elastic skirt can be advantageous with regard to passing bottom obstacles compared to a traditional skirt. The proposed semi-circular spreading gear also showed promising features.