Walleye, Canadian IQF
Walleye is a freshwater fish native to most of Canada and to the northern United States.
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 name, "walleye" comes from the fact that their eyes, like those of cats, reflect light. This "eyeshine" 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.
The fish's eyes also allow them to see well in turbid waters which gives them an advantage over their prey. This excellent vision also allows the fish to populate the deeper regions in a lake and they can often be found in deeper water, particularly during the warmest part of the summer.
Walleyes are largely olive and gold in colour. 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.
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 5 or 6 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.
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.
The walleye is considered to be a quite palatable freshwater fish, and, consequently, is fished recreationally and commercially for food. 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.