Every few years a Lake Erie fisherman will catch a walleye that just doesn’t look right. Its steely, gray-blue coloring and big eyes are more than just alarming; they’re proof that the blue pike (Sander vitreus glaucus) once existed.
Once just as common in Lake Erie as its larger, gold cousin, the blue pike was declared officially extinct by the United States Fish and Wildlife Service soon after the last known specimen was reported in 1965. At a time when Erie’s polluted tributaries were catching on fire regularly and the only limit to harvesting fish was how big your net was, the sensitive blue pike didn’t stand a chance.
Fisheries biologist Dieter N. Busch mourned the loss of the blue pike in a 1999 interview with the New York Times, revealing that the blue pike held an ecologically important role as one of the few Great Lakes species that lived and spawned in deep water – deeper even than the walleye we know today. Aside from its critical niche in Erie’s fish community, the blue pike would have added an extra $150 million to the lake’s fishing industry had its population survived, Busch suspects.
Dr. Carol Stepien, director of the University of Toledo’s Lake Erie Research Center, has devoted much of her career to uncovering the truth about this little-known fish. Her 2014 study included 52 preserved blue pike from 1923 and 51 preserved Lake Erie walleye from 1923 to 1949. About half of each group was preserved well enough for DNA tests, which were compared to 1,125 genetic samples of contemporary walleye.
Stepien found that, although the blue pike specimens bore features – head shape, eye size, number of fin rays – that were significantly different from those of walleye, blue pike and walleye are genetically indistinguishable from one another. The study concluded that the blue pike was simply a subspecies of walleye and not a unique species itself.
That isn’t to say that the blue pike would have remained a subspecies. Because of walleyes’ tendency to return to their natal ground to spawn, it is unlikely that spawning territories were shared by walleye and blue pike. Pair this with the fact that blue pike allegedly spawned later in the season than walleye, and you have the beginnings of a genetic rift between the two fish. Given enough time, it is possible that the blue pike would have eventually become its own species, genetically distinct from walleye.
So the next time you travel to the shallowest Great Lake, watch out for the big-eyed walleye that carry the long-gone blue pike’s remnant DNA.
[Photo courtesy of NOAA/GLERL]