Walleye
The walleye (Sander vitreus) is a species of freshwater percid fish native to the St. Lawrence-Great Lakes, Arctic, and Mississippi River basins, ranging from Quebec and the Northwest Territories southward to Alabama and widely distributed across rivers, lakes, and reservoirs in North America.[1] This predatory fish, characterized by its reflective eyes adapted for low-light vision, inhabits both clear and turbid waters, from shallow to deep environments, and prefers cool to moderate temperatures.[2] Adults typically reach lengths of up to 91 cm and weights exceeding 10 kg, feeding primarily on fish, aquatic insects, and crustaceans as they mature from a diet of zooplankton in early life stages.[1][3] Walleye reproduce by spawning in spring within streams or shallow shoreline areas, with eggs hatching after about one month, supporting self-sustaining populations in suitable habitats despite introductions beyond native ranges.[4] Classified as Least Concern by conservation assessments due to robust management and wide distribution, the species sustains significant recreational fisheries, with anglers targeting it for its fighting qualities, and commercial harvests valuing its mild-flavored, firm white flesh.[5][6]Taxonomy and Etymology
Taxonomic Classification
The walleye (Sander vitreus) belongs to the domain Eukarya, kingdom Animalia, phylum Chordata, subphylum Vertebrata, class Actinopterygii, order Perciformes, family Percidae, subfamily Luciopercinae, genus Sander, and species S. vitreus (Mitchill, 1818).[7][8] Historically classified as Stizostedion vitreum since the early 19th century, the walleye's genus was revised to Sander in the late 20th century following molecular phylogenetic studies that demonstrated its monophyly with other Sander species, including the European zander (S. lucioperca).[9][10] This reclassification aligned North American percids with Old World relatives based on shared morphological traits and genetic evidence from mitochondrial DNA sequencing.[8] Within Sander, the walleye and sauger (S. canadensis) form a North American sister clade, with molecular data estimating their divergence at approximately 2.75–3.12 million years before present, reflecting Pleistocene isolation events.[8][10] Genetic analyses confirm walleye endemism to North America, distinguishing it from Eurasian congeners through fixed nucleotide differences and lack of hybridization outside introduced ranges.[10] A proposed subspecies, S. v. glaucum (blue pike), described from Great Lakes populations in 1926, represented a distinct morph with bluish coloration but is now extinct and considered invalid as a subspecies due to insufficient genetic differentiation from nominal S. vitreus.[8]