The western Pacific brachyuran (Hemigrapsus sanguineus: Grapsidae), in its new habitat along the Atlantic coast of the United States: geographic distribution and ecology
The Asian shore crab Hemigrapsus sanguineus (de Haan, 1853), discovered on the coast of New Jersey in 1988, is now known to be distributed in the western Atlantic from Massachusetts (south of Boston) to Oregon Inlet, North Carolina. Living in the mid to upper rocky intertidal zone, it exploits a niche mostly unoccupied by native brachyurans. In the northern part of its range there is some mid-intertidal overlap with the green crab Carcinus maenas. In North Carolina H. sanguineus becomes sympatric in the high intertidal with another grapsid, the wharf crab Armases cinereum. Distributional evidence indicates that H. sanguineus was probably introduced via ballast water at one or more major shipping centres south of Cape Cod (i.e. the New York Bight, Delaware Bay, Chesapeake Bay), perhaps in the early 1980s. Its present latitudinal range in the western Atlantic is only about one-fifth of that in the western Pacific. H. sanguineus is now the most abundant brachyuran at the intertidal monitoring site in southern New Jersey, and apparently in some areas of Long Island Sound to the north. In New Jersey, crabs range in carapace width from 2.3 to 43.9 mm. The breeding season is from late April through September, and recruitment to the intertidal population begins in June and continues through the fall and winter. Some crabs become subtidal, particularly during the winter months, as evidenced by the growth of bryozoans, mussels and barnacles on their carapaces. There is no evidence in this population of parasitism with metacercariae, nemerteans, rhizocephalans or bopyrid and entoniscid isopods.