In North America, sturgeon can mean any of 9 native species or subspecies. Six are within the genus Acipenser and three are genus Scaphirhynchus. One species of paddlefish (Polyodon spathula) is native to North America. Habitat degradation and overfishing are considered the greatest threat for all North American sturgeon. Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), shortnose (A. brevirostrum), and Gulf sturgeon (A. oxyrinchus desotoi) are found in rivers, lakes, estuaries, and the coastline of the east coast. All three are protected within U.S. waters under the provisions of the Endangered Species Act. Atlantic and shortnose sturgeon in Canada are listed by the Committee on the Status of Endangered Wildlife in Canada but are not currently afforded protection by the Canada’s Species at Risk Act. Lake sturgeon (A. fulvescens), shovelnose sturgeon (Scaphirhynchus platorynchus), and pallid sturgeon (S. albus) are potamodromous, meaning they remain entirely within freshwater. These species are found in the Mississippi River basin, whereas lake sturgeon are also native to rivers and lakes of the Hudson Bay and Great Lakes basins, including the St. Lawrence River. Pallid and shovelnose sturgeon are found only in U.S. waters and are protected under the U.S. Endangered Species Act. Little is known about the life history of the endangered Alabama sturgeon (S. suttkusi) which is found only in the lower Alabama River. Green sturgeon (A. medirostris) and white sturgeon (A. transmontanus) are native to rivers, estuaries, and the coastline of the west coast. Green sturgeon are protected in the U.S. throughout their range under the Endangered Species Act. Northern populations of white sturgeon are considered to be at greater risk than southern populations. White sturgeon in Canada, with the exception of fish in the lower Fraser River, are listed under Canada’s Species at Risk Act, whereas white sturgeon in the U.S. waters of the Kootenai River are protected under the U.S. Endangered Species Act. Paddlefish are native to the Mississippi River and are considered extirpated in Canada. They are not considered to be at risk in the U.S.