1Department of Fisheries Science and Technology, National Fisheries University, Shimonoseki, Yamaguchi 759-6595, 2Faculty of Marine Sciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
SURF-BRDs which is composed of a pair of rectangular net panels (front panel (FP) with square mesh of 80 mm mesh size, rear panel (RP) with diamond mesh of 27.5 mm mesh size) and two fish vents, was developed for small-scale shrimp beam trawling to separate species and size of fish by the probability of marine organisms encountering the two panels and the mesh selectivity. In this study, the BRD-mounting arrangement and net plan were both improved to maintain the heights of BRD and net mouth for the purpose of more effective separation. As a result of a fishing experiment with the improved BRD trawl, the height of the improved BRD was about 1.7 m, which is much higher than the 0.4 m height of the prototype SURF-BRD. Therefore, the probability of encountering Lizardfish Saurida spp. and Cinnamon flounder Pseudorhombus cinnamoneus became higher, achieving more effective size separation of these species by mesh selectivity of the FR. While small crabs were eliminated through the vent after passing through the FP, most small shrimps, which were the main target species, were caught in the codend.