The largest and best known of Australia's
fresh water fishes, the Murray cod was once found in nearly all parts of
the Murray Darling River system, which drains a vast inland basin of more
than 1,000,000 km: (386 102 square miles) in New south Wales. Victoria
and Queensland and finally enters the sea at lake Alexandrina, in South
Australia. Reputed to attain lengths of 1.5m (4.9ft) and weights up to
90kg (1981b) the Murray cod is one of Australia's finest table fish and
when taken on sporting tackle is a worthy opponent for any angler. The
average size taken is 2-3kg hut specimens weighing 30kg (661b) are
not uncommon Although it has been reduced in numbers over much of its original
range, the Murray cod has been introduced into the
Richmond and Clarence rivers of New South Wales and Queenslands Dawson
and Mary Rivers. Dams stocking cod are Burrinjuck Dam at the junction of
the Murrumbidgee and the Coodradigbee rivers (near the southern tablelands
town of Yass). and Burrendong Dam which holds the waters
of the Macquarie and Cudgegon rivers near Wellington in the central west
of New South ales. Murray cod are also present in certain dams of the Sydney
water catchment area, and one or two have even been caught in the
cold waters of Lake Eucumbene.
Murray cod belong
to the family); Serranidae, amongst which are also included several
of Australia's best fresh water angling species, notably Australian
bass, estuary): perch, Macquarie perch and the golden perch or yellow belly.
A close relative of the Murray cod. the
trout cod (.Maccullochella macquariensis ), now bears
the scientific name that was used originally to describe the Murray cod.
This change in species names was the result of research conducted at the
Australian National University, Canberra, which indicated that the Murray
cod and trout cod are two distinct species, differing in their head profile,
jaw length, coloration, size and distribution. Because it was found that
the museum specimen that was the basis of the original (1829) description
and classification of Murray cod was in fact a trout cod, it was given
the old name for Murray cod and the Murray cod re-named M.peeli.
A specialized freshwater predator
The majority of members of the family Serranidae are marine species,
and Australian serranids inhabiting freshwater still bear a strong resemblance
to their saltwater relatives, this is apparent when the Murray cod is compared
with fish such as the marine groper and rock cod. Some serranids, such
as the Australian bass, enter brackish or saltwater in order to spawn.
The Murray cod, however, remains in freshwater throughout its life cycle,
having adjusted its reproductive behaviour to cope with the vagaries of
climate and rainfall which cause many streams and rivers to fluctuate between
big freshes or floods and long dry periods, when once broad rivers are
reduced to strings of isolated water holes. Unhappily, with the advent
of large scale water conservation and irrigation programmes, the very adaptations
that once served to ensure the survival of native freshwater species are
now responsible for the decline or disappearance of native fish from much
of the Murray Darling system.
The impact of environmental change
Research has been conducted
at the Narrandera Inland Fisheries Research Station since 1960 in response
to the decline in stocks of native fish and has confirmed that the stimulus
for spawning in warm water species is an increase in water temperature
in conjunction with a rise in water level, conditions which were once obtained
during the regular spring or summer flooding of the western rivers. It
was found that although golden and silver perch require a combination of
extensive flooding and a rise in water temperature to 240C (75"F) before
they produce their planktonic (free floating) eggs, the trigger for spawning
in the Murray cod is an increase in water temperature to 20"C (68"F). A
fresh, or flood, does not appear to be a necessary prerequisite for spawning;
how-ever, a rise in water level at or after spawning time ensures that
additional food and space are available for the young fish, which are then
able to move downstream to restock other tributaries and streams. Thus,
in areas where regular natural spawning still takes place, which is usually
in the more arid inland parts given over chiefly to grazing, the best fishing
for Murray cod is in the years following extensive summer flooding. On
the other hand, reproduction is jeopardized or forestalled in
those areas where flood mitigation schemes reduce the extent
and duration of flooding, or where the discharge of very cold water from
the bottom of large dams reduces the temperature of the water by as much
as 6"C for considerable distances downstream.
Spawning
Murray cod usually
spawn at four years of age, when they measure about 55 cm (22 in) and weigh
2.3-2.7kg (5-61b) Spawning normally occurs in September or October, but
may be delayed until December or January. During this time gravid females
have a rounded abdomen and the vent is noticeably swollen. About 20 000
eggs are produced at first spawning; large females may have 200 000 eggs.
The eggs are adhesive, becoming attached to hollow logs or beneath other
hard surfaces, and hatching within one or two weeks.
Murray cod are suitable for stocking farm ponds and dams that
exceed 0.ha (0.5 acre) in area. However, growth is slow and reproduction
is likely to be poor in the absence of the conditions that prompt
spawning in the wild. In consequence, it is usually necessary
to restock every three or four years to ensure a continuing supply of fish.
The predatory and territorial nature of Murray cod sets a limit to the
carrying capacity of the dam. The recommended stocking density is 200 Murray
cod per hectare(80 per acre). Other native or introduced species of sport
fish should not be stocked in the same dam since they will probably be
eaten. Murray Cod fry may be procured from the Inland Fisheries and Research
Station at Narrandera, during January and February, and from a commercial
hatchery at Wagga Wagga.
The most notable Murray cod water Darling and its Queensland and New
Wales tributaries, notably the Paroo, Warrego, Culgoa, Began, Namoi, Macquarie
and Gwydir rivers. Bases for anglers along the Darling River are Brewarrina,
Bourke, Louth and Wilcannia. The Lachlan River is fished between Euabalong
and Hillston and the Murrumbidgee near Flay.
Feeding habits
Murray cod are
omnivorous feeders, preying mainly on other fish, crayfish,and freshwater
mussels, but supplementing this diet with water fowl, frogs, water rats,
grubs and worms as available. They are most active in the summer, especially
at night. During the day they tend to shelter near submerged logs and tree
roots, where they often take up a position on the downstream side of the
obstruction and wait for back eddies to bring food to them. Deep holes
in the lee of natural obstructions to the water flow, near weed beds and
spots where the course of the river is narrowed are all likely locations
for Murray cod.
Lures
The best prospect for
an angler seeking Murray cod lies in waters that run clear when not in
a flooded state. Lure fishing is a particularly de-lightful way to try
clean cod water. In such a habitat the fish take on a rich green, mottled
ap-pearance on the back and upper surfaces which blends into a lighter
creamy underside. Murray cod tend to turn after flashing at a lure and
hook themselves as the line tightens. Sometimes, however, they will ease
up to an artificial and suck it in, only to reject it an instant later.
Lur-es are suited to fishing the large inland dams, where a policy of working
around the backwater areas during the warmer months is a good recipe for
success. While artificial lakes are not their natural environment, Murray
cod do well in those at lower altitudes, and become particularly active
during the period between October and May. 'Trolling behind a boat is another
technique: large lures pulled around areas holding dead trees have taken
many a dam dwelling Murray cod.
Casting techniques carl work anywhere in a dam. In the inlets
and backwaters the water takes on much of its former complexion, making
it easier for the angler to 'read'. Casting techniques suit these locations,
since the depths and cover are
more readily distinguished, in contrast to the back-up waters where
there is so much to throw at that it is hard to decide where to cast next.
Set lines
Unfortunately, many
of the good Murray cod waters that remain never clear sufficiently to guarantee
the use of lures. The alternative adopted by fishermen working these western
rivers is the use of set lines, which are usually put out at night. Baits
of live fish, crayfish and wood grubs are used in conjunction with line
that may he of a breaking strain anywhere between 6.8kg (151b) and 36kg
(801b) and hooks from 4/0 extra strong size to 8/0 or 10/0. Four of these
lines are allowed in most areas (be sure to check with the local authority),
but this form of angling has done little to enhance the sporting reputations
of either the practitioners or the quarry, which puts up !;little fight
after spending half the night exhausting itself against the unyielding
restraint of a heavy line.
class Osteichthyes
order Perciformes Serranidae
family Serranidae
species Maccullochella peeli
| Boat fishing for Murray cod can be particularly successful. It allows the angler to cast near submerged logs, tree roots and weed beds, all of which are likely locations for cod. |
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