Walleye

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{{Taxobox | color = pink | name = Walleye | image = walleye painting.jpg | image_width = 310px | regnum = Animalia | phylum = Chordata | classis = Actinopterygii | ordo = Perciformes | familia = Percidae | genus = Sander | species = S. vitreus | binomial = Sander vitreus | binomial_authority = (Mitchill, 1818) }}

This article is about the fish; for the terms related to the eye, see Iris (anatomy) and Strabismus. For the guided missile, see AGM-62 Walleye.

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 blue walleye. In some parts of its range, the fish is known as the yellow pike or pickerel, 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 them 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).

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. 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. 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 absorbing the small amount of yolk, young walleyes begin feeding on invertebrates. After 40 to 60 days, juvenile walleyes become piscivorous. After this time, both juvenile and adult walleyes eat fish almost exclusively, frequently yellow perch or ciscoes, moving onto bars and shoals at night to feed.

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 fishes. Most commercial fisheries for walleye occur in the Canadian waters of the Great Lakes but there are other locations as well. One of the best lakes for catching walleyes is Mille Lacs in central Minnesota.

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 those 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 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.

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