PARENT SESSION
Thursday, August 10, 5:00-6:30 pm
Poster Session 24 - Modeling, statistics, and spatial analysis
Exhibit Hall, Ballroom Level, Cook Convention Center
Spatial organization and local resilience of a mangrove crab population analyzed with an individual based model.
Piou, Cyril*,1, Berger, Uta1, 1 Center for Marine Tropical Ecology, Bremen, Germany
ABSTRACT- Ucides cordatus is a slow-growing, semi-terrestrial crab, feeding on leaf-litter collected on the mud surface of neo-tropical mangrove forests. In North-Brazil, this crab is heavily harvested and its economic and ecological importance has been demonstrated. Field surveys as traditional methods of ecological understanding gave some interesting but incomplete information on its behavior and population dynamics. The characteristic cryptic movement of U. cordatus was the main limitation of these methods. With the help of an individual based model, reproducing the patterns observed during field surveys, and simulating the movement of individual crabs, this study demonstrate first how the competition among individual drive the spatial organization of U. cordatus population at different scales. At small scale (<2m), the intraspecific competition organize the crabs at regular intervals, corresponding to specific use areas around each individual′s burrow. At large scale (>2m), the asymmetrical competition between large and small individuals organize them following habitat quality patterns. Secondly, we analyze the effect of refuge areas (buffers) on the capacity of harvested areas to come back to their initial state of density and spatial organization. The engineering resilience of these harvested areas depends mainly on the density within the buffers, and not as much on the spatial size of these buffers. We conclude that the buffered configuration of U. cordatus population with un-fished rooted areas and fished open areas is a perfect situation for blind over-harvesting by slowly decreasing the overall density if no consideration of spatially structured population is taken in the management recommendations.
Key words: individual based ecology, engineering resilience, geostatistics