Walleye (Sander vitreus, formerly Stizostedion vitreum) is a freshwater perciform fish native to most of Canada and to the Northern United States. It is a North American close relative of the European pikeperch. The walleye is sometimes called the yellow walleye to distinguish it from the blue walleye, which is a subspecies that can be found in the southern Ontario and Quebec regions.
In some parts of its range, the walleye is known as the walleyed pike, colored pike, yellow pike or pickerel (esp. in English-speaking Canada), although the fish is not related to other species of pikes which are members of the family Esocidae.
Walleyes show a fair amount of variation across watersheds. In general, fish within a watershed are quite similar and are genetically distinct from those of nearby watersheds. The species has been artificially propagated for over a century and has been planted on top of existing populations or introduced into waters naturally devoid of the species, sometimes reducing the overall genetic distinctiveness of populations.
Walleyes grow to about 80 cm (31 in) in length, and weigh up to about 9 kg (20 lb). The maximum recorded size for the fish is 107 cm (42 in) in length and 11.3 kilograms (25 lb) in weight. The growth rate depends partly on where in their range they occur, with southern populations often growing faster and larger. In general, females grow larger than males. Walleyes may live for decades; the maximum recorded age is 29 years. In heavily fished populations, however, few walleye older than five or six years of age are encountered. In North America, where they are heavily prized, their typical size when caught is on the order of 30 to 50 cm (12 to 20 in), substantially below their potential size.
Because walleyes are popular with anglers, fishing for walleyes is regulated by most natural resource agencies. Management may include the use of quotas and length limits to ensure that populations are not over-exploited. As one example, in the state of Michigan, Wisconsin walleye shorter than 15 in (38 cm) may not be legally kept, except in Lake St. Clair and the St. Clair River where fish as short as 13 in (33 cm) may be taken.
Since walleyes have excellent visual acuity under low illumination levels, they tend to feed more extensively at dawn and dusk, on cloudy or overcast days and under choppy conditions when light penetration into the water column is disrupted. Although anglers interpret this as light avoidance, it is merely an expression of the walleye's competitive advantage over its prey under those conditions. Similarly, in darkly stained or turbid waters, walleye tend to feed throughout the day. In the spring and fall walleye are located near the shallower areas due to the spawning grounds; and they are most often located in shallower areas during higher winds due to the murkier, higher oxygenated water at around six feet deep. On calm spring days the walleye are more often located at the deep side of the shoreline drop-off and around shore slopes around or deeper than ten feet.
"Walleye chop" is a term used by walleye anglers for rough water typically with winds of 10 to 25 km/h (6 to 16 mph), and is one of the indicators for good walleye fishing due to the walleye's increased feeding activity during such conditions. In addition to fishing the "Walleye chop", night fishing with live bait can be very effective.
The current all-tackle world record for a walleye is held by Mabry Harper, who caught a 11.34kg (25 lbs.) walleye in Old Hickory Lake in Tennessee, USA on August 2nd, 1960.