In an attempt to establish an efficient and effective method to catch mangrove crabs for sale in distant markets such as Suva, and to develop management strategies that will ensure the continued availability of mangrove crab, we tried, for the first time, to encourage local villagers in Gau Island to catch mangrove crabs with baited trap. We provided the traps and with the cooperation of volunteers from some of the villages, we collected 646 individuals in the study period of about one and half year. Analyzed data indicate that crabs in Gau Island are more abundant and heavier in mangrove areas than those in the river and sandy beach areas although there was no significant difference in mean carapace width. The crabs were harvested fairly intensively with baited traps but there were no decreasing trends in mean carapace width and body weight during the study period in any of the villages where more than 80 crabs were harvested. Comparison of catch according to trap size suggests that larger traps may be more effective to catch larger crabs than smaller traps. These results clearly indicate that a trapping is an efficient and effective method to catch mangrove crabs. If village people get used to keeping the record of carapace width and body weight of their catch, they can notice the changes in resources abundance from decreases in the average size of crabs. Thus, continuous monitoring of the catch could be a good tool for resources management because it is simple and easy for local people to implement and evaluate.