The occupation of artificial burrows by Helice tridens (De Haan) and the length of its stay

The mud-crab Helice tridens (De Haan) influences the cycling of matter in salt-marsh ecosystems through its burrowing activity. If the crabs occupy and stay in their burrows for a short time, their burrowing activity will be great, since they will continuously construct new burrows. Therefore, investigation of the relation between the crabs and their burrows is considered to be important. In the present study, the relation between pipes as a form of artificial burrow and their occupation by the crab was analyzed. A close relationship was recognized between the diameter of the pipe opening and the carapace width of the crab which occupied the pipe, while pipes with a length shorter than the depth of the crab burrows were hardly occupied. These results indicate that the diameter and length of an artificial burrow affects the likelihood of its occupation by this species of crab. The length of the crab's stay in this type of artificial burrow was generally 1 day. This result may be related to the field observation that newly made burrows frequently collapse due to water current occurring through tidal action after the crabs have left.