Walleye Vision

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.