DataSheet_1_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.pdf

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.

针对南海（SCS）底拖网渔业中的口虾蛄（Oratosquilla oratoria，俗称螳螂虾），本研究测试并对比了4种拖网囊网（codend）的尺寸选择性与捕捞效率。该4种囊网的网目形状分为菱形网目（T0）与旋转90°的菱形网目（T90）两类，网目尺寸分别为30mm与35mm。研究结果显示，网目尺寸为30mm的T0型囊网对目标物种的选择性较差；而当网目尺寸提升至35mm，或是将T0型囊网替换为T90型囊网时，尺寸选择性均会得到显著改善。对于网目尺寸为35mm的T90型囊网，其尺寸选择性最优，但合规个体的流失量也显著偏高。综合考量放流未达标个体与保留合规个体之间的权衡关系，在南海底拖网渔业中以口虾蛄为捕捞目标时，采用35mm网目尺寸的T0型囊网，或是30mm网目尺寸的T90型囊网，均为更优选择。