Effect of gillnet mesh size on the capture probability and capture patterns in the Asian paddle crab (Charybdis japonica) fishery

In the Asian paddle crab (Charybdis japonica) gillnet fishery in the Yellow Sea, China, the minimum mesh size (MMS) regulation has been of a major importance due to high bycatch rates of undersized crabs. In this study, we evaluated how gillnet mesh size can affect the capture probability of C. japonica and capture patterns in this fishery by comparing the performance of gillnets with four different mesh sizes (60, 70, 80, and 90 mm). Our results showed that changes in gillnet mesh size significantly affect the capture probability of different sizes of crabs. Specifically, increased mesh size decreased the capture probability of undersized crabs and their fraction in the catches decreased from 64 % to 24 % when mesh size was increased from 60 mm to 90 mm. In contrast, gillnets with larger mesh sizes significantly improved the capture probability of legal-sized crabs. Moreover, no significant differences were observed for the species catch composition between gillnets of different mesh sizes. Based on these results, we recommend 90 mm as the MMS in gillnets to improve sustainability in C. japonica fishery.