On Lake Nipissing, walleye begin spawning at about age four for males and age six for females. A female lays between 16,000 and 143,000 eggs each year.
Spawning begins in the spring soon after the ice breaks up, usually mid to late April, when the water temperature is 6 – 9 degrees Celsius.
Walleye prefer to spawn in white-water rocky areas below falls or dams. They prefer the running waters of the rivers entering the lake. Major spawning runs include Wasi Falls, Sturgeon and South rivers. They also spawn on shallow coarse gravel shoals in the lake, such as those around Iron Island. There is no shortage of walleye spawning habitat on Lake Nipissing.
Males move tot he spawning ground first. Spawning takes place at night, in groups of one larger female and one or two smaller males or two females and up to six males. Males are not territorial and no nest is built. Before spawning, there is a courtship that involves pursuit, pushing, circular swimming, and fin raising. Finally, the spawning group rushes upward into shallow water, stops, the females roll on their sides and eggs and sperm are released. Most individual females deposit most of their eggs in one night of spawning.
After the eggs are released, they fall and stick in crevices between the rocks and rubble. The eggs usually hatch within twenty days. After they lose their yolk sacs, the young walleye swim into the midwater area where they spread out into the main lake. There they feed on tiny animals known as plankton. Later in the summer, these young of the year walleye change their diet and eat other fish. During this time, young of the year yellow perch is a very important food source. Walleye can reach up to 20 years of age or more in the north, but only live to age 10-12 in the south.
Adult walleye eat mainly fish. Yellow perch, cisco, emerald shiners and other minnows are their main diet. But in late June, they switch their diet almost exclusively to shadflies.
Anglers and other fish such as Northern pike are likely the most important walleye predator. Musky also prey on walleye.
Walleye compete for food with northern pike, smallmouth bass, adult perch and lake whitefish.