(© Bonnie Schiedel. Originally published in Outdoor Canada, October 2006). 

Biologists are scratching their heads over a strange new colour of walleye 

Some anglers in northwestern Ontario are seeing blue—and it’s not just in the clear sky overhead. Seems walleye in the area are occasionally turning up with a distinctly blue hue, a phenomenon that so far has fisheries biologists baffled.
Blue walleye? No, these aren’t the same fish as the extinct blue walleye, or blue pike, which was overfished in Lakes Erie and Ontario in the 1950s. Rather, they’re regular walleye that, for reasons yet to be fully determined, are blue instead of the familiar greeny-yellow. 
Wayne Schaefer, a University of Wisconsin biology professor, became intrigued when he first started hearing about blue walleye in the lakes around his cottage north of Ear Falls, Ontario. He and his students began doing fieldwork in 2000.
The first time he caught a blue walleye, he put it in a plastic bag; by the time he got back to his Wisconsin lab, the bag was coated with blue goo. “We realized then that the pigment is in the mucus, not the skin or scales, and that was extremely unusual,” says Schaefer. “All other fish, not just walleye, have clear mucus.” 
Schaefer theorized that the blue colouring was caused either by bacteria or minerals, such as copper. Further tests performed at the University of Iowa’s microbiology lab revealed otherwise. “The pigment is a complicated protein that is something brand new in fisheries biology,” he says. “We just haven’t seen it before.”
Since the blue pigment is mainly found on top of the fish, Schaefer speculates it may act as a sort of shield against the sun’s UV rays. Bolstering this theory is the fact that the colour deepens throughout the spring and summer as the days lengthen and the sun’s rays intensify. 
Angler Roger Mayer can attest to the strange coloration, having caught and released a three-pound blue walleye on a small lake near Thunder Bay. “The fish was a lightning blue colour,” he says, “and when I brought it in, it actually stained my white T-shirt.” 
Interested in also catching a blue walleye? Schaefer says the fish are usually found in isolated lakes in the upper ends of river systems. They’ve been caught most often in waters around Ear Falls and Armstrong, although they’ve also been found in the Lake Nipissing area, as well as northern Quebec and northeastern Manitoba. 
If you hook a blue walleye, Schaefer encourages you to post details of your catch on his Web site (www.bluewalleye.com), where you can also learn how to take a slime sample to help further his research. Adds Schaefer: “Right now we’ve got more questions than answers.”