Blue walleye


The blue walleye, also called the blue pike, was a unique color morph of walleye which was endemic to the Great Lakes of North America. Morphometric studies led biologists to classify the blue walleye as a separate species 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, rendering the taxon 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, blue walleye/blue pike, and modern walleye found no evidence for concluding that blue walleye/blue pike was a subspecies of walleye. This rendered the taxon invalid.
Occasionally, grey-blue or steel-blue walleye are caught in Lake Erie, Lake Ontario, and the Ohio River drainage. Dark blue yellow perch are also sometimes caught in the same areas.
A turquoise-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.