Effectiveness of Different Mesh Size to Release Small Blue Swimming Crab on Trap Fishing

Abstract

Blue swimming crab (Portunus pelagicus) is a fishery commodity with important economic value and also become the main commodity for export needs. However, crab production dominantly comes from fishing activities using traps and gillnet. The fisher use traps without escape gaps so that small crabs have no chance of escaping from the traps. One alternative way to improve the crab trap selectivity is the use of larger mesh sizes on the wall of the trap. This study aimed to determine the effective mesh size for escaping small crabs. This study was conducted in Fisheries Laboratory, University of Sultan Ageng Tirtayasa from July to December 2020. We used different mesh sizes on the trap wall including of 2.0; 2.5; and 3 inches. For all experiments, we used 90 crabs with an average carapace width of 72 mm. The results showed that the pattern of crab when escaping through the net at each mesh size was varied. The crab crept up the netting wall before attempting to escape. The fastest time of crab escapes was found on a 3 inch mesh size with an average time of 10 seconds. Moreover, the highest percentage of crabs that can pass was obtained at the 3-inch mesh size with the value 60%. Based on these results, to increase the catch selectivity we recommend a 3-inch mesh to be used in the collapsible trap wall for blue swimming crab fishing.