Walleye (Sander vitreus, formerly Stizostedion vitreum) is a freshwater perciform fish native to most of Canada and to the Northern United States. It is a North American close relative of the European pikeperch. The walleye is sometimes called the yellow walleye to distinguish it from the blue walleye, which is a subspecies that was once found in the southern Ontario and Quebec regions, but are now presumed extinct. However, recent genetic analysis of a preserved (frozen) 'blue walleye' sample suggests that the blue and yellow walleye were simply phenotypes within the same species and do not merit separate taxonomic classification.