|
Water Made for
Walleye
|
Greenback Giants
What colour is your walleye?
If it has been caught in the
Red River, south of Lake Winnipeg,
chances are that it is an iridescent
green - and more than likely,
it is 6, 8 or even 10 kilograms
in weight. In addition to being
enormous, Red River "greenback"
walleye are uniquely brightly-coloured.
All walleye hues are highly
influenced by the water that
they live in. In larger lakes
with moderate clarity, the fish
will tend to be olive green
or yellowish, with brassy flecks.
In dark, bog-fed bays and rivers,
they are almost black with few
distinct bars or mottling. But
no matter what their overall
colour, adult walleye are characterized
by a white underbelly, a silver
or milk-white tip on the lower
lobe of their tail (caudal)
fin, and one large dark blotch
near the base of the last 2
or 3 spines of their posterior
dorsal fin. (These consistent
markings distinguish the walleye
from the look-alike sauger.)
The walleye is also spiny: its
forward dorsal fin is particularly
sharp.
|
|
Large, shallow, windy, murky-what more
could a walleye ask for? The waters of Lake
Winnipeg provide an ideal habitat for one
of North America's most wide-ranging, adaptable
and sought-after sport fish.
Varying widely in size (from as little
as 33 centimetres and 1 kilogram to as many
as 64 centimetres and 10-12 kilograms, depending
on environmental conditions), torpedo-shaped
walleye are the celebrities of the perch
family. Yellow perch, saugers and darters
are their genetic relatives.
From an evolutionary point of view, the
success of the walleye as a top-level aquatic
predator throughout central North America
is due to several factors:
• Acute night vision -The large,
glassy, pearlescent eye of the walleye is
equipped with a "tapetum lucidum,"
a layer of pigment in the retina that gathers
light very efficiently. This feature allows
walleye to feed in dim light and murky conditions.
• Sharp teeth - The canine-like,
curved teeth of the walleye also make it
an effective predator. Baitfish and other
prey caught in the grip of a walleye's mouth
have little chance of escaping.
• A highly-developed lateral line
- The ultra-sensitive nerve endings along
each side of the walleye's body allow it
to detect minute vibrations in the water
and avoid danger and disturbance.
• Opportunistic feeding habits
- Although the walleye is by preference
a piscivorous fish - feeding on smaller
fish, including yellow perch, whitefish
and even other walleye - it will eat whatever
nature provides, including insects, snails,
frogs and small mammals.
• Environmental adaptability
- Ideally, walleye prefer relatively shallow
aquatic habitats that offer intermediate
temperatures, medium to low clarity, light
currents, and clean, hard, gravelly bottoms
for spawning. They rely on rocky shorelines
and reefs to provide crevices to protect
their eggs from predators, and winds and
waves to keep the eggs from silting over.
But the species can adapt to an exceptionally
wide range of environmental conditions,
moving into depths of up to 12 metres to
avoid light penetration, tolerating low
levels of dissolved oxygen, and laying eggs
in slack water. Walleye in northern lakes,
such as Winnipeg, can spawn at temperatures
of 6-8 degrees Celsius, while walleye in
more southern bodies of water spawn at 10-
13 degrees Celsius. After a series of repeated
cold snaps, walleyes may re-absorb their
eggs and not spawn at all.
Northern Longevity:
The walleye of Lake Winnipeg and other northern
lakes and rivers grow more slowly than those
in warmer locations, but live longer and
ultimately reach the same average size.
In the south, walleyes older than 15 years
are rare, while in the north, the fish have
been known to live as long as 26 years.
Smelt Smorgasborg:
Recent catches of Lake Winnipeg walleye
have revealed that the piscivorous predators
are feeding heavily on rainbow smelt, a
non-native baitfish that has made its way
into Lake Winnipeg through the Winnipeg
River system. The walleye appear to be growing
larger and more numerous with the new addition
to their diet, but some biologists are concerned
that the smelt could become a dangerous
source of biomagnified mercury contamination.
|
