Site specific distribution of the mud shore crab Helograpsus haswellianus in temperate wetlands

An important aspect in determining the ecology of a species is an understanding of its abundance and distribution. The population structure and distribution of Helograpsus haswellianus (Brachyura, Grapsidae) were evaluated over 12 months at four intertidal wetland sites that differed in vegetation and inundation. Surface activity of H. haswellianus varied over time with no consistent seasonal pattern. Sex ratios were always significantly skewed towards males, and crabs of both sexes were distributed evenly across habitats at all sites. Recruitment patterns and size frequency distributions varied significantly between sites, independent of habitats. Crabs were smaller in wetter, more sheltered areas, but size ranges overlapped between habitats. The site-specific difference in population structure and distribution of H. haswellianus indicates that the functional role of this burrowing crab may vary across wetlands.