Canada>Canada http://damplips.in.net/ damplipss Just how the northern snakehead made its way into the Potomac River has yet to be confirmed. The species, which first appeared in the United States in a Crofton, Md., pond in 2002 is a native of Asia and recognized for the large scales on its head, long dorsal fins and large, protruding mouth chock full of sharp teeth. Fish caught back then topped out at about 12 or 13 pounds.