Conservation Status
Vulnerable, Listed under the Victorian Flora & Fauna Guarantee
Act
Habitat
Varies greatly from small clear rocky streams to large, slow-flowing
rivers with lots of deep holes, fallen trees, stumps, clay banks and
overhanging vegetation. Very territorial. Believed to live
for as much as 80 to 100 years.
Distribution
Widespread throughout the Murray-Darling system, although greatly
reduced in abundance throughout its range when compared to the original
population. Murray cod were originally extremely common and supported a
substantial commercial fishery in the nineteenth century and in the
early decades of the twentieth. Prior to European colonisation
aboriginal people were able to exploit the species as a major food
source using relatively simple technologies aided by the fish's great
abundance.
The decline in Murray cod numbers is reportedly due to multiple
causes. The most significant factor that has been identified has
been the regulation of the majority of the rivers in the Murray-Darling
basin. This has resulted in substantial alterations to the natural
flow regimes of virtually all rivers in the system. In addition,
the dams and weirs themselves provide a physical barrier to fish
migration. Loss of river side vegetation, physical damage to stream
banks and beds by large hard hooved animals (especially cattle) and
increased silt inflows due to erosion and road run-offs have led to
major changes in the physio-chemical properties of much of the water in
the system. Also the removal of in stream debris, such as fallen
trees and so on has resulted in a reduction of suitable habitat for
native fish in general and Murray cod in particular. Angling and
commercial fishing have had an effect, but it is insignificant next to
the other factors and is not considered to be of concern, under the
current regulatory regime.
Murray cod have been stocked into many water reservoirs throughout
the Eastern states and are a popular fish for farm dams in warmer areas.
Some re-stocking of river populations has occurred but the most
important tool in restoring cod populations to something like their
former glory is the appropriate management of the river systems.
This is a nettle yet to be fully grasped by government due to the
inherent high costs involved.
History
The Murray cod is Australia's largest and best known freshwater fish.
The stuff of legends, the Murray cod is represented in practically every
pub in South Eastern Australia by photos and mounted examples.
Stories abound of titanic struggles with the almost supernatural fish.
Ply an old codger with a few beers and you are likely to hear how when
he was a boy one of the local water holes was inhabited by some gigantic
cod. The story usually goes along the lines that some farmer lost
a large bait to the fish and kept coming back with heavier and heavier
tackle until eventually he used a whole kangaroo on a meat hook as bait
connected to the steel cable of the winch on his tractor. The fish
in the story then fights the farmer and his tractor to a standstill,
usually resulting in the demise of said tractor. You are then
invited to inspect the wreck of the machine under an old red gum tree
near the pub and shown the stretch of water which was straightened by
the fish in the struggle!
On a more serious note, Murray cod and the closely related trout cod
were formally recognised as separate species in the mid 1970s.
Since that time Murray cod has been subdivided into three further sub
species: Murray cod Maccullochelle peelii peelii, Eastern
Freshwater cod Maccullochella peelii ikai and Mary River cod Maccullochella
peelii mariensis.
 Reproduction
Individuals known to migrate upstream 100 Km or more before breeding
in spring, returning to original location afterwards - even the same
snag in the river at times. Breeding believed to be triggered by
longer daylight hours, increased water temperature and flooding.
Fry feed on zoo-plankton etc. on newly inundated flood plain and are
eventually washed into billabongs and backwaters where they grow rapidly
for 6 to 8 weeks before being recruited into main population by later
flooding. Growth has been estimated in the Murray River as 230,
340, 460, 560, and 640 mm after years one to five respectively.
Will breed in earthen dams in captivity if provided with suitable
spawning sites. 200 litre (44 gal) drums with the ends removed are
suitable structures in a farm dam. Fisheries and commercial
breeders often use more sophisticated devices to facilitate the removal
of eggs, but the general aim is to simulate a large submerged hollow
log. Generally, spawning structures are examined for eggs and when
present they are removed to a hatchery for incubation. If left in
the structure, as would usually be the case in a farm dam, a much lower
survival rate is to be expected, although this is not really a problem
in that case.
Diet
(Top Predator) Murray cod have a varied diet of other fish,
spiny freshwater crayfish,yabbies, shrimp, freshwater mussels, frogs,
water fowl, small mammals, tortoises and other reptiles. Virtually
anything within its realm that moves and is small enough to fit in its
cavernous mouth is considered fair game!
Angling
Generally regarded as Australia's premier freshwater angling species,
the powerful Murray cod can be a difficult customer to deal with.
Most cod specialists use relatively heavy tackle. Line breaking
strains in the 40 to 50 lb or even higher are common amongst those
aiming for the larger fish. The new super braided lines have
proven useful, especially when trolling in heavy cover, which is where
you find the fish.
Cod respond well to large baits and lures. Many cod specialists
fish only large trolled or cast deep diving lures with a wide action at
dead slow speed. Surface lures work well at night and large flies
have been tried with success. Bardi grubs,yabbies, shrimps and
scrub worms all catch cod. Cod have even been caught on such
diverse baits as rabbits and hard boiled eggs! If using fly, you
need heavy gear, as cod can pull like a steam train. Even small
cod will take very large baits and lures, and give you a run for your
money to boot.
Fish close to snags and other structure - if you're not getting
snagged up, you're not fishing in the right place!
Size and bag limits and closed seasons apply in all States where
Murray cod occur, so check your local regulations.
NFA strongly encourages you to practice catch and release when
fishing for Murray cod, especially with large fish which are
important breeding stock for the species and which are less palatable in
any case.
On the table
Murray cod are excellent eating in the smaller legal sizes, up to
around 6-8 Kg. Can be filleted or steaked and are great on the
barbeque. Larger fish can be very oily and are better steaked and
grilled, but are really best still swimming in the river <grin>.
In the aquarium
Smaller examples make excellent and very impressive aquarium
specimens. Juvenile hatchery bred Murray cod are readily available
through the aquarium trade. Murray cod should be kept on their own
as they are very territorial and aggressive to other fish, including
their own species. Best fed on a mixed diet of live yabbies,
shrimp (if available) and fish, although cod are easily trained to
accept dead food. For anglers, a diet of skinned fillets of carp
are an easy to obtain and cheap food. A standard 3 foot aquarium
is satisfactory for a small cod, but make sure the space you use will
accept a much larger tank. Popular tank sizes (in feet) for cod
are 4x2x2 up to 6x2x2 or even 6x3x2, a six foot tank will last a fish
for many years. Cod are very strong fish and the tank should be made
from heavy glass and have a heavy cover as the fish can accidentally
jump out if it makes a strike at an insect on the surface, or even a
bubble!
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