The Japanese mantis shrimp (Oratosquilla oratoria) is a commercially important crustacean species distributed around the coastal waters of China, which is harvested with both active and passive fishing gears. Among these, traps are one of the primary passive gears used in the Bohai Sea, which is one of the most important fishing grounds for Japanese mantis shrimp in northern China. However, the use of traps with a small mesh size challenges the sustainability of this fishery. Therefore, this study quantified the size selectivity and harvesting pattern for traps with different mesh sizes for harvesting Japanese mantis shrimp in the Bohai Sea. Results showed that the 50% retention length increased from 6.39 cm to 12.44 cm as mesh sizes increased from 20 (T20) to 60 mm (T60). T20 retained 86.8% and 100% of individuals, respectively, below (np-) and above (np+) the minimum landing size. Increasing mesh sizes decreased both np- and np+. Compared with T20, T30 reduced undersized catch by 67.8% while decreasing legal-sized catch by 8.2%. Increasing mesh sizes beyond T40 provided no significant reduction in np- but caused further reduction in np+. Therefore, the T30 mesh trap was recommended to replace the currently applied T20 in the Bohai Sea.
Xu et al. (Mon,) studied this question.