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.

Color My World

While Ryder focused his attention on how walleyes regulate their daily activity levels and habits according to various light levels, Burkhardt concentrated on the fish’s ability to distinguish between different colors.

He did this by inserting minute probes into the receptor cells in the retina and then recording how the fish reacted when he flashed various lights into their eyes. He selected walleyes because the cone receptor cells in their eyes are much bigger than in humans. In fact, they’re the largest found in any animal, which in itself speaks volumes about the walleye’s magnificent sense of sight.

Burkhardt discovered that walleyes are not color blind like so many other animals who live in black and white worlds. Rather, they have excellent color vision and can discriminate between various shades and hues. Like humans, who can see certain colors better than others—like yellow highway signs—Burkhardt found that walleyes are most sensitive to orange and its spectral derivatives. And, to a much lesser degree, green.

“In reasonably clear water,” Burkhardt explained, “orange is by far the most visible color. In deeper or more turbid water, the most visible color shifts slightly more toward the red end of the spectrum.”

Burkhardt went even farther. He found that visibility depends not only on the wavelength of available light, but also on the amount of light that an object—in this case a walleye’s eyeball—reflects. (Remember that color diminishes, the deeper you go into the water column). What this means, is that all else being equal, a walleye can see an orange-red jig the easiest. Also, it can see a bright orange-red jig better than a dull jig, and presumably, a fluorescent orange-red jig better still.

Finally, Burkhardt found that walleyes have the ability to adjust their eyes to available light, just as we do when we step from a dark room into bright sunlight. More importantly, though, he found that a walleye can turn this adjustment dial way down. If you’re reading this in a well-lit room, the light level is probably about 100 lux. A walleye can see images and details at levels as low as 0.01 lux. That is tens of thousands of times less light, and it accounts for the ease with which a walleye can see at night and under the darkest winter conditions.

Lighting The Way

While Burkhardt showed us what colors walleyes can see best, Dr. **** Ryder demonstrated that the amount of light in a walleye’s watery world is the primary factor that triggers its feeding throughout the seasons. Indeed, when you finish reading Ryder’s massive work, you’re left concluding that light levels control just about everything a walleye does.

Ryder researched the effect of light on walleye activity for more than 15 years. During that time, he spent over 1,000 hours underwater, visually monitoring the fish in six Northwestern Ontario study lakes and four rivers. He wanted to prove his thesis, that the rapid change in light levels at dusk and dawn trigger walleye feeding patterns.

As part of his rigorous scientific protocol, Ryder dove only between 10 a.m. and 1:00 p.m. and only on bright, sunny days. He took surface and subsurface light readings every half hour with an electrophotometer and entered the water only when the readings were within a narrow range. This eliminated the external effects of wind and cloud cover. In order to minimize the impacts of other parameters, Ryder kept meticulous notes on current speed, bottom depth and cover—and, of course, on walleye activity levels.

Knowing that walleyes were present on his study shoals, Ryder then fished the spots where earlier he had dived. He used the same technique, fishing with small minnows 11⁄2 to 3 feet off the bottom, at exactly the same time (30 minutes before sunset until the fish ceased feeding or he could no longer read the level of light on his meter).

Based on his catch-per-unit effort, Ryder showed that walleye feeding peaked 30 minutes before sunset. That’s when he caught 90 percent of his fish. He was careful to note however, that his drop in success after this sunset period was more likely related to his method of fishing than to a decline in feeding. Ryder’s most studied shoal topped out in 23 feet of water, and he acknowledged that the fish likely remained active, but moved into shallower water.

Indeed, Ryder demonstrated that as bright daylight diminishes, it reaches a level that walleyes find optimal. That also means, though, that as the light level continues to drop after sunset and to fall below the walleye’s preferred level, the fish have two options whereby they can prolong and maximize their time, or bask in the glow of ideal light. They can move to shallower water, following their preferred light level, or they can rise vertically and accomplish the same end. In fact, Ryder observed both behaviors. He caught feeding walleyes at night when he moved into water as shallow as three feet.

Most remarkable, though, Ryder discovered no seasonal differences or changes. In other words, he found that walleyes reacted the same way—turning on at dawn and dusk—in winter as in summer. But when he recorded absolute light levels under the ice, he found they were typically only 10 percent of summer levels. So the amount of light clearly wasn’t the trigger. The stimulus for walleyes to become active, regardless of the season, was the rate of change of light intensity.

Of course, as we know, there are two periods each day of rapid light change: in the morning when it’s increasing and in the evening when it’s decreasing. Ryder found the optimal morning level occurred about 90 minutes before sunrise, and he recorded some excellent catches during this activity spree. Nevertheless, the morning bite when illumination levels were rising paled in comparison to the sunset peak, when surface light levels were decreasing.

Light Lessons

So what does all this mean? We can hear walleye anglers across the continent muttering, “What about all those fish I catch during the day? I never go fishing in the dark, and I have great success. Where do these scientists get off telling me I can’t catch walleyes during the day?”

Well, for starters, no one ever has suggested that walleyes can’t be caught during the day. We’ve all made memorable catches and enjoyed spectacular daytime fishing. But usually, those great bites occurred on overcast days, when the wind was blowing as a storm approached, or when the water was stained or filled with algae. These conditions mitigate against bright light and bring levels down to an intensity that walleyes find ideal.

Need more proof? Remember that Ryder donned his scuba gear only during the brightest days. Then, he watched walleyes lying dormant, resting on the bottom. Often, they had their heads poked under and between rocks. Other times, he spotted them using weeds and boulders for shade. Many times during these midday swims, the only clue he saw that walleyes were present was the white tip on a tail sticking out from cover.

Drop a jig and livebait on the nose of one of those lethargic fish and you may feel your bait sucked in. But miss the walleye’s nose by a foot or two, or run a crankbait over its head, and chances are you won’t get a bite. Now, hit that fish at dawn or dusk, when the rate of light is changing rapidly, and chances are much better that you’ll feel salt and pepper being sprinkled on your Shad Rap before it’s gobbled up.

River rats have long contended that their fish react differently than walleyes in still water. Ryder proved that to be the case. He found that walleyes living in current are more likely active at midday than fish in noncurrent locations. This means rivers are great daytime walleye equalizers. So, too, are riverlike sections in lakes and reservoirs—channels, slots, neck-down areas, constrictions, and bottlenecks where wind-induced currents have a chance to set up.

While Ryder showed us that walleyes are most active at dawn and dusk, it’s important to remember that he carried out his work during the brightest days. He intentionally and specifically ruled out the effect of local weather changes—like an advancing midafternoon storm system or an increase in wind. These conditions could speed up the period of rapid light change to **** the walleye’s feeding trigger earlier.

Ironically, keen walleye anglers have long thought that an approaching storm system, following several days of progressively hotter and more humid conditions, create the spark for an intense flurry of walleye feeding. As Ryder has shown, though, the storm system itself has little to do with the great fishing. Instead, the dark, menacing clouds accompanying its advance intensify the timing of an intense twilight trigger of rapid light change.

To a lesser degree, that’s probably also what happens in naturally turbid, muddy, or algae-stained walleye waters. (Remember, Ryder worked on clear and moderately clear lakes and rivers.) In murkier waters, walleyes are found shallower than normal, and their dawn and dusk feeding clocks likely are set for much earlier in the day.

At the other end of the spectrum are those tough-as-nails clear-water walleye lakes, rivers, reservoirs, pits, and ponds. Make them shallow and devoid of structure and cover, and fish them only during the day, and you’ll leave the water most times wondering if there’s a walleye in the drink. Almost as difficult are the deep transparent lakes and reservoirs where walleyes swim with lake trout, ciscoes, and whitefish. Here they can use deep water to retreat from the light, but daytime fishing still can be dreadful.

When that’s the case, the lessons from Burkhardt and Ryder are conclusive. Slow your presentation. Be absolutely precise. Pick apart every piece of structure and cover you can find. Search for current areas and sections of the lake or river with the dingiest water. Fish on the bottom. And experiment with the colors orange, red, green, and yellow that walleyes find attractive.

Of course, the other key message is that nighttime is the right time. It’s the great equalizer. Nothing—not current, not cloud cover, not water clarity, not structure, nor cover—triggers walleyes more than the magical transition from day to night (and from night to day.)

Of course, the onset of rapid light change varies depending on the depth of the water you’re fishing. Once you find it, though, you should be able to follow it—and the walleyes—ever shallower as evening progresses. These are the kinds of strategies you can put together anywhere on the continent when you understand that the walleye comes by its name so honestly.

* Gord Pyzer, a resource manager in Kenora, Ontario, is a long-time In-Fisherman contributor and a superb walleye angler.