Efecto de borde sobre la población del cangrejo azul Cardisoma guanhumi (Decapoda: Gecarcinidae) en el manglar de la bahía El Uno, golfo de Urabá (Colombia): una aproximación a su captura artesanal/Edge effect on blue crab population Cardisoma guanhumi (Decapoda: Gecarcinidae) in the mangrove of El Uno Bay, Uraba Gulf (Colombia): an approximation to the folk catchery

The potential impacts of mangrove clearing on communities of benthic macroinvertebrates are uncertain and poorly studied in Colombia, particularly in the Caribbean region. This study investigated the effect of mangrove conversion to pasture on the population of blue crab Cardisoma guanhumi (Decapoda: Gecarcinidae) in the El Uno bay mangrove, Uraba Gulf (Colombia). From March to April 2012, we conducted daily sampling of specimens in three different vegetational covers: mangrove interior, pasture and mangrove-pasture edge (an anthropogenic edge produced by mangrove deforestation). We compared the distribution, abundance, weight and body size of C. guanhumi specimens, and the abundance, diameter, and bioturbation of their burrows. Visits and interviews with folk crab harvesters were conducted during Easter Week. We found a higher number of individuals in the mangrove interior (140), compared with the pasture (105) and the edge (35) sites, with individuals from the mangrove interior exhibiting greater weight and size than those in pasture and edge, with no differences documented between the latter two. We found no differences in the number of burrows or amount of removed sediment (bioturbation) among the different cover types, and there was no significant relationship between burrow diameter and bioturbation. We observed a high pressure on this crab population due to folk harvest during the sampling period. In conclusion, we demonstrated the occurrence of an edge effect on the C. guanhumi population promoted by mangrove conversion to pasture.