T90 Codends Improve the Size Selectivity and Catch Efficiency of Shrimp Trawl Fisheries for Southern Velvet Shrimp (Metapenaeopsis palmensis) in the South China Sea

Abstract

In order to obtain gear-based management instruments of shrimp trawl fishery for southern velvet shrimp in the South China Sea (SCS), the size selectivity and catch efficiency of four codends were tested and compared. These codends included two mesh sizes, 30 and 35 mm, and two mesh shapes, T0 (diamond-mesh) and T90 (diamond-mesh turned by 90°), respectively. Our results demonstrated that increasing the mesh-sizes of the T0 codends or/and applying the T90 codends would statistically and significantly improve the size selectivity and catch efficiency. Comparing the size selectivity and catch efficiency of four codends tested, and accounting for the results of the previous study, we conclude that the T0 codend with a mesh size of 35 mm (T0_35) or T90 codend with a mesh size of 30 mm (T90_30) would be potential choices for mitigating the bycatch issue of undersized individuals for southern velvet shrimp (Metapenaeopsis palmensis) in the SCS. We recommend that they are applied as the compulsory gears in the fishery management regulation. Our study will be beneficial for the decision-making regarding gear-based management for sustainable fishing in the specific shrimp trawl fishery of the SCS.