http://weblogs.nal.usda.gov/invasivespecies/archives/2007/06/chinese_mitten_2.shtml
http://www.anstaskforce.gov/spoc/mitten_crab.php
The Chinese mitten crab is native to Southeast Asia from southern China to the Korean Peninsula was and was first reported in San Francisco Estuary in 1992 . This species is established in only in California, although it has been reported in the Detroit River, Mississippi River, Great Lakes, and Columbia River near Portland, Oregon. Its presence in North America is of particular concern since its prior introduction to and spread throughout Europe had significant adverse impacts. The probable means of introduction was by transport of larvae and small crabs in ship ballast water, adult crabs clinging to ship hulls and barges (very unlikely means of introduction into California), or by deliberate release to establish a fishery or local food resource.
