The involvement of citizens in  research projects is an activity that enhances understanding and appreciation of science.  A Citizen Science project stimulates and inspires public participation in the conservation of nature through direct contact with nature and original scientific research. The project will offer opportunities for participants to explore, conduct research, and acquire practical knowledge about ecosystems, the insertion of humans into natural systems, and the recovery of natural ecosystems.  In this Citizen Science project, we want to promote the conservation of natural resources by monitoring the population of the land crab Cardisoma guanhumi.  In Puerto Rico, Cardisoma guanhumi is a very popular food item and as such its population is declining.  To study the population dynamics, we selected eight locations for monthly monitoring of the crab. Volunteers from the Citizens Science Project participate in the monthly censuses.  Volunteers familiarize with the scientific method, data gathering and natural history of Cardisoma guanhumi.  To estimate abundance and survival, we are doing a mark recapture study.  Measurements of crabs carapace width and length as well as weight and sexing of animals are necessary to determine population structure, and sex ratio. 

Results/Conclusions Preliminary results of this ongoing study showed that abundance of land crabs is highest during August with 120 estimated individuals.  Population structure shows that the most abundant crab size, based on carapace width is between 70 - 80 mm.  Sex ratio is almost 1:1.  A total of 287 volunteers had participated in the monthly censuses (13 months).  Volunteers have participated in capturing, measuring, tagging, weighting and sexing land crabs.  Preliminary results of the volunteer evaluation of the experience, demonstrate that volunteers were satisfied with the experience and expressed gaining new knowledge about the land crab and the scientific method.  The final results of this project will be useful to develop a management plan for the sustainable use as well as for the conservation of critical habitat for this species.