Comparative fishing trials for invasive swimming crabs Charybdis japonica and Portunus pelagicus using collapsible pots

Comparative fishing trials on the crab Charybdis japonica were undertaken in a pond, using three types of collapsible pot. One was box-shaped (2.3 cm mesh size) with two slit entrances at the ends, while the others were dome-shaped and had two open funnel entrances but different mesh sizes (2.3 and 6 cm). Trials (100 pot hauls/pot type) were done using a 1-day soaking time and mackerel as bait. The 2.3 cm mesh dome-shaped pot caught most crabs followed by the box-shaped pot, while the 6 cm mesh dome-shaped pot caught the least. The catch of non-target species and small crabs was much lower in the latter because of the larger meshes and open entrances, which allowed for escapement. The 6 cm mesh dome-shaped pot was more efficient for harvesting larger crabs only, while the 2.3 cm mesh dome-shaped pot was better for eradication purposes since it removed more crabs of all sizes.