Blue pike are really walleye
In 1983, the U.S. Fish and Wildlife Service declared extinct a once massively abundant species that many biologists now suspect had never actually existed.
Back in 1967, a study published in the prestigious Journal of the Fisheries Research Board of Canada reported that during the 44 year period between 1915 and 1959, the Lake Erie commercial fishery brought in an average of 12.7 million pounds of “blue pike” per year.
That constituted an average of 27% of the total annual catch. However, as a worrisome sign of an unstable population, that catch varied greatly during the period–from 2 to 26 million pounds per year, forming over half of all fish caught in peak years.
And yet by 1959, the take of blue pike had dropped to 79,000 pounds and the last verified specimen was recorded in 1983.
What happened? So abundant that for years, frozen “Lake Erie Blue Pike Fillets” had been a regular feature in grocers’ freezers, it seemed to have suddenly evaporated into thin air.
It’s hypothesized that the damming of rivers and the draining of wetlands along lake shores conspired with pollution and enhanced sediment inputs to negatively impact the cool, clear, deeper habitats they preferred. Overfishing didn’t help matters.
A sad loss with far-reaching implications, certainly. But extinction of the species? Hmm…
In its day, the blue pike had been greatly prized by anglers as well as commercial fisherman. In addition to its abundance, it put up a good fight on the line, was delicious on the plate and, with its steel-grey blue body, was an exceedingly attractive animal.
Interestingly, blue pike are not pike at all, they are–or rather were–a form of walleye (which also goes by pickerel and yellow walleye, among other names, in various parts of the country). Members of the pike family like the muskellunge, northern pike and grass pickerel, are elongated predators with a mouthful of nasty-looking teeth
So are walleyes (a member of the perch family), which may explain the overlap in common names. But while pikes all have a curious duck bill-shaped mouth, walleyes have more of a pointed, Mick Jagger-like profile.
Everyone familiar with them knew from their anatomy and behavior that if blue pikes weren’t a separate species from walleyes, they were at least very closely related. In 1926, Carl Hubbs, one of the nation’s foremost ichthyologists, determined that such differences as there were merited distinguishing it from the walleye as a separate species.
But in 1981, Ohio State University biologist Milton Trautman downgraded it to subspecies status within the walleye species, meaning that he viewed it as a morphologically and geographically distinctive version of walleye that could still breed successfully with other forms of the species.
Still the debate continued. Clearly there’d been a lot of these animals swimming around Lake Erie and the Niagara River who seemed to differ in a generally consistent way from the yellow walleyes occupying the same locales. On the other hand, each group showed a lot of variability in appearance and behavior and they certainly interbred to some extent.
And that all leads right into the thorny question of what do we really mean by the word “species?” The traditional junior high school biology textbook answer–a group of organisms that can interbreed with each other but not with other groups of organisms–falls apart when encountering distinctive groups or organisms that can nonetheless interbreed, at least to some extent.
Anyway, in 2014 Carol Stepien (then at the University of Toledo) and her graduate student Amanda Haponski reported on a genetic study of over a thousand walleye from various parts of their current range together with several dozen formalin-preserved walleyes and blue pikes collected from before the population crash of the late 1950s.
Among other findings, their research revealed that blue pike samples were genetically indistinguishable from walleye samples. Their main conclusion on the topic was stated unambiguously:
“Blue pike does not constitute a separate genetic taxon from walleye and does not merit species or subspecies recognition.” They further noted that color was not a reliable characteristic to go by since it was highly variable among historic and contemporary walleye.
While still the best study on the problem, it did have its flaws. Formalin degrades DNA and not all biologists have been moved to give up the animal’s subspecies status.
Bright turquoise-blue walleyes turn up fairly often, especially in more northern waters. But their coloration is based on a protein (sandercyanin) found in the mucous coating of the skin and, in any case, their color is quite different than blue pike’s dark grey-blue.
It may be worth noting in closing that it made no difference to the blue pike what we humans chose to call it. Species, subspecies, color morph or whatever.
All that mattered was how our activities unintentionally eliminated the conditions they needed to survive.
Ken Baker is a scientist and a retired biology professor. If you have a natural history topic you’d like the author to consider for an upcoming column, email your idea to firstname.lastname@example.org.