The walleye averages 1 to 2 pounds in most waters, though it occasionally exceeds 10. The torpedo-shaped fish ranges from dark olive brown to yellowish gold, its sides often marked with brassy flecks. The walleye is named for its pearlescent eye, which is caused by the tapetum lucidum, a reflective layer of pigment that helps the fish to see and feed at night or in turbid water. Unlike the sauger, the walleye lacks spots on its dusky dorsal fin, except for a dark splotch at the rear base of the fin, a marking the sauger does not have. The lower tip of the walleye's tail is white, unlike the all-dark lower lobe of the sauger.
The walleye is native to most of Minnesota, flourishing in large, shallow, windswept lakes with gravel shoals, such as Mille Lacs, Leech, Winnibigoshish, Upper and Lower Red Lake, Lake of the Woods and Lake Vermilion. It is also native to many smaller lakes and steams in all of Minnesota's major drainages. Because of its popularity as a game and food fish, the walleye was introduced to many other lakes, where it has become established. The walleye now occupies about 1,700 lakes totaling 2 million acres and 100 warm-water streams totaling 3,000 miles.
The walleye's low-light vision and sensitivity to bright light play a large role in its behavior. They usually feed in shallow water at dawn and dusk. Walleye are fish-eaters, preying heavily on yellow perch, which cannot see as well as the walleye in low light and thus are easy prey at night. With daylight, walleye move into the shadows of cliffs, boulders, logs and even heavy weeds. Lacking this cover, they seek shelter in deeper water. Walleye remain more active throughout the day if turbidity, wave chop or clouds reduce rightness. Walleye may suspend over deep water to feed on open-water species.
Walleye spawn over rock, rubble, gravel and similar substrate in rivers or windswept shallows in water 1 to 6 feet deep, where current clears away fine sediment and will cleanse and aerate eggs. Male walleye move into spawning areas in early spring when the water temperature may be only a few degrees above freezing. The larger females arrive later. Spawning reaches its peak when water temperature ranges from 42 to 50 degrees. A five-pound female deposits more than 100,000 eggs. Neither parent cares for the eggs in any way.
Depending on weather, the success of spawning can vary greatly year to year. Rapidly warming water can cause eggs to hatch prematurely. Prolonged cool weather can delay and impair hatching. A cold snap after the hatch can suppress the production of microcrustaceans that walleye fry eat. Year-class strength can vary 100-fold, depending on the success of the hatch and survival of the fry. One walleye year-class may dominate in a lake, while walleye a year older or a year younger are scarce.
After spawning, walleye move to feeding areas. Walleye are a "cool-water" species, preferring warmer water than do trout and cooler water than do bass and panfish. As the preferred forage fish become larger and more abundant during the summer and walleye need to spend less time hunting food, walleye commonly spend more time in deep, cool water, away from bright light, where they are most comfortable.
Sauger are similar to walleye in appearance and habits, though their distribution is more limited. They live in Lake St. Croix, the Minnesota River and the Mississippi River and the Mississippi River below the Twin Cities. They also are common in Lake of the Woods, Rainy Lake and Lake Kabetogama.
The sauger is smaller and more slender than the walleye, seldom exceeding 3 pounds. Its dorsal fin, unlike the walleye's, is marked by rows of dark spots and lacks the dark blotch at the rear base. The sauger also lacks the white lower tail tip. The sauger sees even better than the walleye in darkness or turbid water, and this determines their distribution.
Though also excellent table fare, the sauger is less popular than the walleye because of its smaller size. The DNR undertakes no direct sauger management other than the evaluation and protection of habitat and the forage base.
Yellow perch are golden or brassy yellow with six to nine dark vertical bars on their sides. They do not have the canine teeth of walleye and sauger.
Perch are found throughout the state, often in such numbers they are stunted for lack of food. Occasionally infected with unappetizing parasites, they are considered pests except in large hard-water walleye lakes, where they may exceed a pound and are excellent table fare. Perch feed on a variety of small fish and invertebrates.
Yellow perch may be single most important prey species in many lakes for largemouth bass, northern pike and particularly walleye. Like the walleye, perch of one year-class may be superabundant while another year-class may be nearly absent. Strong perch year-classes generally coincide with abundant walleye year-classes. Wild fluctuations in perch numbers influence the health and growth rates of walleye. They also affect angling. Fishing may be poor when forage-size perch are abundant, simply because walleye are well fed.