Adjusting Trap Mesh Size and Entrance Color to Increase Capture Efficiency of Blue Swimming Crabs

ABSTRACT Coastal fishing for blue swimming crab ( Portunus pelagicus ) is economically important in Indonesia. Baited traps to capture crabs are increasing in use due to their low operational costs and high catch quality. However, the transition to using baited traps has been hindered by their low capture efficiency that leads many fishers to continue using gillnets that cause greater environmental impacts than traps. To catalyze a transition to trap fishing, improvements in the efficiency of traps are needed. Five different trap designs were tested in the laboratory to quantify the effects of trap entrance color and cover mesh size on blue swimming crab capture efficiency and size selectivity. Three trap designs were also tested in field trials in Banten Bay, Indonesia, and were compared to commercial trap designs with a dark‐green entrance color and 25‐mm cover mesh size. Entrance color affected fishing efficiency, and cover mesh size affected size selectivity. In laboratory and field trials, traps with yellow entrances attracted more crabs than traps with dark‐green or red entrances. In laboratory trials, cover mesh size affected escapement rates of undersized crabs, with larger mesh sizes (75 mm) allowing smaller crabs (carapace width < 100 mm) to escape. Our findings suggest that catch rates of blue swimming crabs in traps can be significantly increased by using yellow entrances, and catches of undersized swimming crabs can be reduced by using > 75 mm mesh sizes. This would improve the economic performance and sustainability of trap fishing.