The Walleye (Sander vitreus vitreus, formerly Stizostedion vitreum 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 also called the yellow walleye to distinguish it from the extinct blue walleye.
In some parts of its range, the walleye is also known as the yellow pike or pickerel (esp. in English-speaking Canada), although the use of these names should be discouraged since the fish is related neither to the pikes nor to the pickerels, both of which are members of the family Esocidae.
Genetically, 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.
The common name, "walleye", comes from the fact that their eyes, not unlike those of cats, reflect light. This is the result of a light-gathering layer in the eyes called the tapetum lucidum which allows the fish to see well in low-light conditions. In fact, many anglers look for walleyes at night since this is when most major feeding patterns occur. Their eyes also allow them to see well in turbid waters (stained or rough, breaking waters) which gives them an advantage over their prey. Thus, walleye anglers will commonly look for days and locations where there is a good "walleye chop" (i.e. rough water). This excellent vision also allows the fish to populate the deeper regions in a lake and can often be found in deeper water.
Walleyes grow to about 75 cm (30 in) in length, and weigh up to about 7 kg (15 lb). The maximum recorded size for the fish is 107 cm (42 in) in length and 11.3 kg (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 5 or 6 years of age are encountered.
Walleyes are largely olive and gold in colour (hence the French common name: doré -- golden). The dorsal side of a walleye is olive, grading into a golden hue on the flanks. The olive/gold pattern is broken up by five darker saddles that extend to the upper sides. The colour shades to white on the belly. The mouth of a walleye is large and is armed with many sharp teeth. The first dorsal and anal fins are spinous as is the operculum. Walleyes are distinguished from their close cousin the sauger by the white colouration on the lower lobe of the tail.
The walleye is a relatively r-selected species. They require fairly clean waters and are found most often in deep mesotrophic lakes and moderate- to low-gradient rivers. The walleye is considered a "cool water" species.
In most of the species' range, the majority of male walleyes mature at age 3 or 4. Females normally mature about a year later. Adults migrate to tributary streams in late winter or early spring to lay eggs over gravel and rock, although there are open water reef or shoal spawning strains as well. Some populations are known to spawn on sand or on vegetation. Spawning occurs at water temperatures of 6 to 10º C (43 to 50º F). A large female can lay up to 500,000 eggs and no care is given by the parents to the eggs or fry. The eggs are slightly adhesive and fall into spaces between rocks. The incubation period for the embryos is temperature-dependent but generally lasts from 12 to 30 days. After hatching, the free-swimming embryo spends about a week absorbing the relatively small amount of yolk. Once the yolk has been fully absorbed, the young walleye begins to feed on invertebrates such as fly larvæ and zooplankton. After 40 to 60 days, juvenile walleyes become piscivorous. Thenceforth, both juvenile and adult walleyes eat fish almost exclusively, frequently yellow perch or ciscoes, moving onto bars and shoals at night to feed. Walleye also feed heavily on rusty crawdads, fathead minnows, leeches, and earthworms.
The walleye is often considered to have the best tasting flesh of any freshwater fish, and, consequently, is fished recreationally and commercially. Because of its nocturnal feeding habits, it is most easily caught at night using live minnows or lures that mimic small fish. Most commercial fisheries for walleye are situated in the Canadian waters of the Great Lakes, but there are other locations as well.
The walleye is a light-avoiding fish, caught most often under low light conditions. Fishing is generally best on cloudy or overcast days, or on days when waves keep light from penetrating too deeply into the water.
In springtime walleye will take almost any bait or lure, but may be more challenging to catch through the summer months. Fall often brings another peak of walleye feeding activity.
Casting or trolling with spinners or minnow-imitating plugs is a good bet. Special worm harness rigs of spinners and beads are often trolled. Jigs, either traditional bucktails, or tipped with any of the modern plastics, a piece of worm or minnow are walleye angling favorites.
Excellent live bait includes minnows, earthworms and crayfish.
Live baits are often still-fished, drifted or trolled on slip-sinker or "bottom-bouncing" rigs. Walleye are readily caught through the ice, usually on jigs, jigging spoons or minnows.
The walleye is the state fish of Minnesota. Its popularity with Minnesota residents means that the residents of that state consume more of the fish than in any other jurisdiction. In 2004, it was revealed that some restaurants in the Minneapolis-St. Paul region had been substituting the less expensive, imported zander for the walleye indicated on the menu. Zander (pikeperch) is a closely-related species and is almost impossible to tell apart by taste, so the television station that did the exposé had to send samples of food for DNA testing. Though sold as "walleye", several samples were found to be zander, which is considered an illegal practice by the U.S. Food and Drug Administration.
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.
"Walleye chop" is a term used by walleye anglers for rough water typical with winds of 5 to 15 mph (7 to 24 km/h), and is one of the indicators for good walleye fishing due to the walleye's increased feeding activity during such conditions. The eyes of a walleye allow it to see much better than their prey in breaking waters.