The stock level of cone stripe shrimp Pandalus hypsinotus in Funka-Bay of Hokkaido has been estimated to be medium level in recent years; however, because most of the catch is occupied by small individuals, the protection of young shrimp is still an important issue. In this study, we investigated mesh selectivity for several stretched mesh size (32, 35, 39, 43, 46, 52, 65 mm) by water tank experiment. For each experiment, 15 bred shrimps were released into experimental area which installed two netting panels as partitions. The number of shrimps that passed or not passed (retention) the panel during night was recorded, and their carapace length was measured. The retention rate of shrimp in each mesh size decreased as the mesh size expanded: 0.99 (32 mm mesh size) to 0.37 (65 mm mesh size). From the master curve of mesh selectivity, the retention rate of 20 mm carapace length (recruitment size) was estimated as 0.71 at 32 mm mesh size used in the current commercial fishery. The mesh size at which 50% retention length (L50) is 20 mm was estimated to be 35.8 mm.
