Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)


Marine Biology


Robert S. Steneck

Second Committee Member

Joseph T. Kelley

Third Committee Member

Robin Hadlock Seeley


The intertidal Asian shore crab, Hemigrapsus sanguineus, (De Haan, 1835) recently (2001) appeared in very low densities along the southern Maine (USA) coast. Indigenous to Russia and Japan, this species arrived first to southern New Jersey around 1988 and by the early 1990's had rapidly expanded its range south to the Carolinas and north to southern New England (CT, RI, MA). We surveyed over 30 intertidal sites from 2002 to 2005 and found relatively low rates of geographic expansion and virtually no colonization northeast of Penobscot Bay on the central coast of Maine. We hypothesize that further geographic expansion of established populations of H. sanguineus in Maine may be limited by coastal temperatures colder than in its native range. For this we 1) compared published summer and winter SST data for coastal waters in the western North Atlantic and in the native Asian range of H. sanguineus and 2) quantified and compared H. sanguineus abundance in Maine with thermal microenvironments at these sites. We found that in warmer seasons (summer), population densities of Hemigrapsus sanguineus in Maine are greater in warmer localities (southern Maine) than in cooler localities (eastern Maine). We also found that the reproductive cycle corresponds with the short periods when mean daily air and water temperatures exceed 15°C. The slow geographic expansion of H. sanguineus in Maine along with results showing a link between population density, recruitment and temperatures suggests that range expansion has stalled at the terminus of the cold, Eastern Maine Coastal Current. The future distribution of this crab may be limited to the warmer areas of the Maine coast (south and west of Penobscot Bay).