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 also called the yellow walleye to distinguish
it from the Blue walleye, which is now extinct in the Great Lakes
and critically endangered elsewhere.
In
some parts of its range, the walleye is also mistakenly known as
the colored pike, yellow pike or pickerel (esp. in English-speaking
Canada), although the fish is related neither to the pikes nor to
the other 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.Contents
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Meaning of the name
The common 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. 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 they can often
be found in deeper water, particularly during the warmest part of
the summer.
Physical
description
Walleyes are largely olive and gold in colour (hence the French
common name: dorégolden). 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 caudal fin which is absent on the sauger. In addition,
the two dorsals and the caudal fin of the sauger are marked with
distinctive rows of black dots which are absent from or indistinct
on the same fins of walleyes.[1]
Length
and Weight
Walleyes
grow to about 75 cm (30 in) in length, and weigh up to about 7 kilograms
(15 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 18-25 inches, substantially below their
potential size.
As
walleye grow longer, they increase in weight. The relationship between
length and weight is not linear. The relationship between total
length (L, in inches) and total weight (W, in pounds) for nearly
all species of fish can be expressed by an equation of the form:
Invariably,
b is close to 3.0 for all species, and c is a constant that varies
among species. For walleye, b = 3.180 and c = 0.000228.[2]
The
relationship described in this section suggests that a 20-inch walleye
will weigh about 3 pounds, while a 25-inch walleye will likely weigh
at least 6 pounds.
Reproduction
In most of the species' range, the majority of male walleyes have
3 testicles and 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 10 °C (43 to 50 °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 crayfish, minnows, leeches, and
earthworms.
As
food
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.
Fishing
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, walleye
of under 15" may not be legally kept, except in Lake St. Clair
and the St. Clair River where fish of 13" may be legally 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.
"Walleye
chop" is a term used by walleye anglers for rough water typically
with winds of 5 to 15 miles per hour (8.0 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.
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