The blue walleye (''Sander vitreus'' var. ''glaucus''), also called the blue pike, was a unique

color morph In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative ''phenotypes'', in the population of a species. To be classified as such, morphs must occupy the same habitat at the s ...

(formerly considered a subspecies) of

walleye The walleye (''Sander vitreus'', synonym ''Stizostedion vitreum''), also called the yellow pike or yellow pickerel, is a freshwater perciform fish native to most of Canada and to the Northern United States. It is a North American close relat ...

which was

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

to the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lak ...

of North America.

Morphometric Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

studies led biologists to classify the blue walleye as a separate

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in 1926, although it was later downgraded to a subspecies. Listed as an endangered species by the United States in 1967, it was declared extinct in 1983. Genetic analyses conducted in the 21st century show that the blue walleye was not genetically different from the yellow walleye (''Sander vitreus''), rendering the

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

invalid.

Species controversy

The blue walleye was long considered to be different from the yellow walleye. Based on morphological study, Carl Leavitt Hubbs declared the blue walleye to be a separate species in 1926. The species was later downgraded to a subspecies. The blue walleye was a commercially valuable fish in the Great Lakes. Populations appeared to collapse quickly in the 1950s. Between 1950 and 1957, catches in the U.S. and Canada fluctuated between and a year. In 1959, however, just were caught, and in 1964 only . The United States declared blue walleye an endangered species in 1967, and extinct in 1983. A 2014 genetic study of 1,181 preserved "historic" walleye (70 to 90 years old), blue walleye/blue pike, and modern walleye found no evidence for concluding that blue walleye/blue pike were genetically distinct from other walleye. This rendered the taxon invalid. Occasionally, grey-blue or steel-blue walleye are caught in

Lake Erie Lake Erie ( "eerie") is the fourth largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also h ...

Lake Ontario Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border ...

, and the Ohio River drainage. Dark blue

yellow perch The yellow perch (''Perca flavescens''), commonly referred to as perch, striped perch, American perch, American river perch or preacher is a freshwater perciform fish native to much of North America. The yellow perch was described in 1814 by Sam ...

are also sometimes caught in the same areas. A

turquoise Turquoise is an opaque, blue-to-green mineral that is a hydrated phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone and ornamental stone for thousands of year ...

-colored walleye exists in some waters of the Canadian Shield. A mucosal pigment, named "sandercyanin", was hypothesized to be the source of the color, but this has not been confirmed. This fish was also thought to be a separate subspecies of walleye, but genetic testing showed there is no difference between the turquoise walleye and yellow walleye.

Description

''Sander vitreus'' "glaucus" also known as the "blue pike" is endemic to Lakes Erie and Ontario and co-occurred with ''Sander vitreus vitreus''. It is compared to the walleye in many aspects however, the "blue pike" inhabits the deeper and cooler areas of Lake Erie but was also seen in shallow and warmer areas alongside the walleye. In comparison to the walleye the "blue pike" has a steel blue color, larger eyes placed bit higher than the walleyes eye placement, and the eye distance is smaller as well.

Species controversy

Description

References

Further reading