Lake Erie and Ontario have a blue phase walleye. I caught a blue walleye/blue pike last year or the year before about 16'' out deep. I had a real big thread on it in the fishing forum.
Of course no camera and let it go. It was identical to the blue pike buggy eyes and everything, but in the heat of the moment you have seconds to decide weather or not the fish lives.
When I called a biologist the ONLY real 100percent way to tell the difference is DNA testing. They take measurements and then they send the fish to be examined.
As for the great lakes being huge that water has been gill netted, trolled, fished...exc Blue Pike are more famous to the Lake Erie Region from the central to eastern basin..If you can find an old timer they will tell you there are 2 different species. I believe a commercial fisherman caught a few in the 1980's but they were all female and no males. There is a blue phase walleye, they are pretty cool looking. I think if they were out there they would of found it, maybe I found it and it is still swimming, but biologists say the only way they can tell is with the fishes DNA and compair it to older frozen specimens.
Over fishing and pollution are the big causes to the death of the blues. Weren't some parts of the great lakes considered biologically dead? due to the dilute and disperse method of dumping pcp ddt and everything else. I think they became all one sex and couldn't reproduce, but nobody can be 100 percent sure.
I don't think their dna got mixed in..the walleye spawn in the shallows blue pike spawn in the deep, they were two different species that lived in different areas and ate different foods.