Walleye Vision

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.