Simple and effective: T90 codends improve size selectivity and catch efficiency compared with diamond-mesh codends for mantis shrimp (Oratosquilla oratoria) in demersal trawl fishery of the South China Sea

Abstract

Size selectivity and catch efficiency of four codends were tested and compared for mantis shrimp (Oratosquilla oratoria) in demersal trawl fisheries of the South China Sea (SCS). These codends were differing in mesh shapes, diamond mesh (T0) and diamond-mesh turned 90° (T90) with mesh sizes of 30 and 35 mm, respectively. The results demonstrated that the T0 codend with a lower mesh size, 30 mm, presented poorer selective properties for the target species, while size selectivity would be significantly improved with the mesh size increasing to 35 mm, or substituting the T0 codend with the T90 codend. For the T90 codend with a larger mesh size, 35 mm, the size selectivity was the highest, whereas the loss of the legal individuals was also significantly considerable. Considering the trade-off between releasing undersized individuals and maintaining the legal ones, the T0 codend with 35-mm mesh size or the T90 codend with 30-mm mesh size might be a better choice to target mantis shrimp in demersal trawl fisheries of the SCS.