Behavior of the Japanese rock crab ‘Ishigani’Charybdis japonica towards two collapsible baited pots: Evaluation of capture effectiveness

抄録

An underwater camera was used to record the behavior of the crab, Charybdis japonica, towards two baited pots. These were commercial collapsible pots commonly used by Japanese fishermen to catch crabs. One was box shaped with two slit entrances at the ends, while the other was dome shaped and had two open funnel entrances. The pots were placed on the bottom of a pond that was connected to Kagoshima Bay, southern Japan. Underwater video recordings were used to study the different behaviors of the crabs towards the two types of pot. Crabs approached the pot mostly by crawling up current (75%) following the bait odor trail. They made several attempts to enter the pot until they reached the entrance or otherwise they gave up. While the dome-shaped pot allowed the crabs to enter it easily by crawling sideways, the box-shaped pot's tight slit entrances and netting material prevented the crabs from getting in due to entanglement of their spines on the netting. Ingress could only be achieved after several trials and mostly by crawling backwards into the pots. The dome-shaped pot was more efficient (100%) than the box- shaped pot (31%) in catching crabs that came in contact with it.