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. After the fish reach approximately 2 inches in length, they begin to add small fishes, minnows, yellow perch, suckers, and bluegill to their diet. 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.
Gizzard shad are the most important forage source in the flood control reservoirs and the Great Border Rivers. Crayfish, frogs, snails, and insect larvae are also utilized at times. The walleye is relatively easy to propagate and rear in hatcheries. Nearly l25 million walleye fry are produced each year in Iowa for stocking larger lakes and reservoirs throughout the state. A smaller number are also raised to fingerling size in shallow nursery lakes and in concrete raceways prior to planting.