Yellow perch, sauger, and smallmouth bass are the walleye s main competitors for food. Immediately after the yolk sac is absorbed, the fry begins to feed. At first only the tiniest planktonic organisms can be utilized, but as the fish increase in size, cladocerans and immature aquatic insects are consumed. Small fry are sometimes observed in schools on the spawning grounds but soon disperse. Adult walleye consume large quantities of fish, sometimes feeding upon them almost entirely.
Yellow perch make up a substantial part of the walleye diet in the natural lakes.
The next time you catch a walleye, or for that matter its first cousin a sauger, take a moment to carefully examine its eyes. Not only are these features the origin of its common name and a prominent part of their appearance, but their unique physiology permits this fish to adapt into an ecological niche that is occupied by few other species. Walleye are perfectly adapted for capturing prey in very low light, or even in total darkness. At the same time in most clear waters that they occupy, they forage most effectively at dawn and dusk when the prey fishes have limited vision but remain active. For this reason, walleye are termed low light condition feeders, and fishing success is traditionally best during these periods.