Walleye Vision

No other fish comes by its name more honestly than the walleye. Those big, white, distinguishing globes are to the walleye what the thick heads, soft skin, and waving whiskers are to the catfish—magnificent physical adaptations that allow these fish to take advantage of unique niches and opportunities in their watery environments.

Indeed, when you begin to understand just how important eyesight and vision are to a walleye, you’re well on your way to understanding almost everything you need to know about the species. You’ll know when and where it eats, sleeps, and spawns; why it preys so efficiently and effectively on perch; and how it can see your tiny jig when you bounce it up and down in 25 feet of water under three feet of ice and snow on a late, gray winter afternoon

As we dig deeper into the mystery of the giant eye of a walleye, we find that the key is the presence of tapitum lucidum. These are the millions of reflective, glitterlike particles that coat the retina—the screen upon which the eye focuses visual images. And it’s because of this condition that scientists refer to the walleye as being negatively phototactic. Unlike humans, who are positively phototactic (can see much better during the day), walleyes (seeing much better at night) are crepuscular or nocturnal feeders, becoming aggressive when the sun goes down.

The tapitum lucidum is like a mirror ball of the disco era. It traps the tiniest fractions of light, bounces them around the dance floor, and lets the walleye see at levels impossible in most other animals. In fact, a walleye can gather so much light in its eyes, that it routinely seeks out and prefers shadowy conditions, generally avoiding bright environments.

Dr. Peter Colby, recently retired percid specialist with the Ontario Ministry of Natural Resources, noted in his extraordinary Synopsis of Biological Data on Walleye, prepared for the Food and Agricultural Organization of the United Nations, that researchers have studied the effect of light on walleyes held in aquariums.

They kept the fish under constant light intensity, then gradually reduced the amount of oxygen in the water while increasing the amount of carbon dioxide. It was not until oxygen reached suffocating levels of 1.5 to 1.00 part per million, and carbon dioxide levels soared to 5 to 6 parts per million, “that the walleye began to overcome their negative phototactic tendencies and left their shelters to move to the surface.” In other experiments, walleyes developed cataracts when forced to endure continuous bright light.

Not a surprise to keen anglers, the walleye’s close relative, the sauger, is the only other freshwater fish with such light sensitive peepers. Indeed, a sauger can see even better than a walleye in dim light, which accounts for its presence in slightly deeper water and in the most algae stained and turbid portions of lakes and rivers, when the two fish share an aquatic environment.

But while the walleye has been studied intensively for the past four decades, much of what we know today about its vision and light-sensitive habits comes from the independent pioneering efforts of two researchers, Dr. Dwight Burkhardt of the University of Minnesota and Dr. **** Ryder of the Ontario Ministry of Natural Resources. In-Fisherman magazine was the first publication, in the 1980s, to chronicle and translate the highly technical findings of these scientists into the language of everyday walleye anglers. Over the past twenty years, anglers and scientists alike have built upon Burkhardt’s and Ryder’s work, but the house stands solid because of the foundations these men laid.