The gulf sturgeon, Acipenser oxyrinchus esotoi is a subspecies of sturgeon that lives in the Gulf of Mexico and some rivers draining into it. The gulf sturgeon was first recognized as a separate subspecies in 1955. The nominate subspecies is the Atlantic sturgeon, Acipenser oxyrhynchus oxyrinchus. The gulf sturgeon is listed as threatened under the United States Endangered Species Act, having been listed in 1991. Critical habitat, reflecting the current range of the subspecies, has been designated (see map). The historical range is thought to have been from the Suwanee River on the western coast of Florida (which contains the most viable sub-population and supplied the only historically sustained commercial fishery) to the Mississippi River, and marine waters of the central and eastern portions of the Gulf of Mexico. Three sturgeon species in genus Scaphirhynchus share river territory with the gulf sturgeon; none of these are anadromous.