Sander vitreus glaucus

Blue Walleye (Blue Pike)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Percidae
Genus:	Sander
Species:	S. vitreus
Subspecies:	S. v. glaucus
Trinomial name
Sander vitreus glaucus (Hubbs, 1926)

The blue walleye (Sander vitreus glaucus), also called the blue pike, is a subspecies of the walleye that has been critically endangered in the Great Lakes since the 1980s. Until the middle of the 20th century, it was a commercially valuable fish, with about a half million tonnes being landed from about 1880 to the late 1950s, when the populations collapsed.

The fish was endemic to lakes Erie and Ontario of the Great Lakes region of North America, including the interconnecting Niagara River, but most especially to Lake Erie, where it sometimes represented more than 50% of the commercial catch. The subspecies was apparently extirpated in the Great Lakes by about 1983 through a combination of anthropogenic eutrophication, overfishing and competition with the introduced rainbow smelt, Osmerus mordax. The subspecies is now considered extinct.

There are occasional reports of blue walleye being caught from waters in the Great Lakes Basin, because many yellow walleye populations also contain a bluish colour variant. The actual blue walleye, however, was said to be distinguishable from the yellow walleye by various meristics and morphometrics which the blue colour variant of the yellow walleye seems not to share. Reportedly, though, some of the meristic and morphometric differences may simply have been artifacts of the different growth rates of yellow and blue walleyes. The clearest evidence, however, indicates that the blue walleye, whatever its taxonomic status, has been lost. Nonetheless, an investigation of genetic material from preserved blue walleye specimens is currently underway in several research facilities in an effort to decipher the true status of the populations.

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Wikipedia