In the Northeast region, 35 species of mollusks and 18 species of crustaceans are known to have been introduced into both freshwater and marine ecosystems (Appendix B and C). The former includes 18 bivalves, 15 gastropods, and two nudibranchs; the later includes crayfishes, crabs, and smaller zooplankton such as amphipods, copepods, isopods, and cladocerans. Twenty-six of these 53 species have from other continents. The others are intracontinental transfers. The marine species have been introduced via solid ballast (periwinkles), ballast water (rapa whelk), ship hull fouling (shipworms), intentional release (Asian clam), and aquaculture (oysters).  While the freshwater introductions are the results of migrations through man-made canals, ballast water (Great Lakes), coincidently with packing material, and aquarium releases.