Spatial and temporal variation in relative numbers of grapsid crabs (Decapoda: Grapsidae) in northern Australian mangrove forests

Crabs belonging to the family Grapsidae are possibly one of the most important components of the fauna of mangrove forests globally, in part because of their influence in nutrient cycling by feeding on litterfall. This study investigated spatial and temporal patterns in relative numbers of 11 grapsid species in northern Australian mangrove forests. The results indicated that Perisesarma spp., Neosarmatium meinerti and an undescribed species of Episesarma were most abundant, followed by Clistocoeloma merguiensis, Ilyograpsus paludicola, Sesarmoides borneensis, Metopograpsus frontalis and Sarmatium spp. Mangrove assemblage was the most important spatial factor affecting the distribution and abundance of these species. Perisesarma sp. was most abundant in midand low-intertidal assemblages, whereas N. meinerti and Episesarma sp. were largely limited to high intertidal assemblages. In many cases, crab species occurrence and abundance were specific to certain assemblages, areas, aspects, and times during the two-year study period, which probably reflects the specificity of species to particular environmental conditions.