The story of the Murray Cod mirrors that of most Australian endangered species. Because of its abundance, the cod was commercially fished from the early years of European settlement.
Changes to its natural habitat and competition from introduced fish have also had a big impact on numbers.
In 1883, commercial fisheries sent 147,000kg of cod from the Murray River town of Moama to Melbourne for sale. By the 1920s cod were in short supply and the commercial fishing industry stopped.
The fish was an important source of food to Indigenous people. Its cultural significance differs depending on the Indigenous nation and the area inhabited.
One of the most common stories comes from Ngarrindjeri Country, close to the mouth of the Murray in South Australia. It concerns Ponde or Pondi , a giant ancestral cod. Ngurunderi, a great hunter, chased Ponde. Ponde’s thrashes and gyrations while trying to escape formed the bends and billabongs of the Murray.
Ngurunderi speared the fish at Lake Alexandrina, cut it up and threw some of the parts into the water. These then became other Murray River fish species. One part of Ponde, which was also thrown into the water, remained the Murray Cod.
The Murray Cod is Australia’s largest freshwater fish. The biggest recorded was 1.8m long and weighed 113kg!
The cod’s size depends on its habitat, with those living in smaller waterways reaching at least 60cm and between 3kg to 4kg. In larger waterways they grow to 100 cm or more and weigh up to 20kg.
The cod is one of Australia’s prettiest fish. It’s white underneath and yellowish-green to green on its back. This is overlaid with darker green mottling, which gives the fish leopard-like spots.
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Murray Cod is one of four sub-species in the genus Maccullochella. The others are the Mary River Cod, the Trout Cod and the Eastern Freshwater Cod. None of these are related to the northern hemisphere cod, which is part of the Gadus species.
The Murray Cod inhabits the Murray-Darling basin, which spreads through New South Wales, South Australia and Victoria. Thousands of interconnected creeks and rivers run through the basin. Some of the basin’s major rivers are the Murray, Darling, Warrego, Murrumbidgee, Lachlan, Goulburn, Campaspe, Mitta Mitta and Loddon.
Below the basin is a complex system of aquifers and groundwater. Most of the waterways eventually connect to the Murray River. The cod lives in warm water habitats ranging from clear, rocky streams to slow-flowing turbid rivers and billabongs.
Also known as ‘pigs of the waterways’ Murray Cod are very aggressive and territorial. They’ll also eat almost anything that gets in their way.
Their diet is mostly other fish, including introduced species such as perch, juvenile carp and goldfish. They’ve also been known to eat ducks, cormorants, freshwater turtles, water dragons, snakes, mice, and frogs.
A Murray Cod can live for more than 50 years , which gives it a greater chance of reproducing despite extreme weather events such as droughts.
The cod reaches sexual maturity at between four and six years old. It moves upstream to spawn, often travelling as far as 120km. This usually occurs in late winter or early spring when river levels are high.
Eggs are adhesive and placed on a hard surface such as logs, rocks or clay banks. Once the eggs are laid, the fish will move back downstream, usually to exactly the same place it began. The male guards the eggs, which hatch after 5 to 13 days.
Murray Cod, once listed as ‘Critically Endangered’ on the International Union for Conservation of Nature’s Red List have been downgraded to ‘Of Least Concern’ as numbers increase. They’re still listed as ‘Vulnerable’ under the Environmental Protection of Biodiversity and Conservation Act. According to some estimates, cod numbers have been as low as 10% of those before European settlement.
The cod has moved from being considered as a plentiful source of food to an important but threatened part of the Murray Darling ecosystem.
Our efforts to protect the cod centre on Scottsdale Reserve, just 40km from Canberra. We acquired Scottsdale, on the upper reaches of the Murrumbidgee, in 2006. The Murrumbidgee forms the western and northern boundaries of the property for a distance of about 4.5km.
Bush Heritage is involved in a regional partnership that aims to improve water quality and habitat along a 100km stretch of the river called the Upper Murrumbidgee Demonstration Reach (UMDR). Amongst the projects this group has undertaken, is work focused on European carp control.
Since the carp was introduced about 150 years ago, it’s become a pest. The effects of carp on native fish populations are not well understood. It’s thought, however, that high carp numbers are preventing the recovery of native fish such as the nationally threatened Murray Cod, Macquarie Perch and Trout Cod, as well as locally (ACT) threatened Murray River Crayfish, Silver Perch and Two‑spined Blackfish .
Donate today to help us continue this and other vital conservation work.
* Image reproduced under Creative Commons License.
BLOG 16/06/2015
All fish monitoring stations in a 90km long fish tracking array in the Upper Murrumbidgee River have now been installed thanks to project staff and some pretty dedicated volunteers. This was no mean feat, as deployment of the monitoring stations required 8-hour long paddles into remote sections of the river to ferry in the equipment, including lengths of railway iron that are used to anchor the monitoring stations in the river.
Read MoreBLOG 01/03/2015
Six European carp were electronically tagged by NSW Fisheries staff at Scottsdale Reserve last week to help shed light on when and where carp move along the upper Murrumbidgee River. This information is currently a key knowledge gap in the upper Murrumbidgee catchment and is critical for the better management of this pest fish species in upland river systems.
Read MoreBLOG 16/11/2014
A series of acoustic telemetry receivers have now been deployed in a 20km stretch of the Upper Murrumbidgee River, centered around Bush Heritage Australia's Scottsdale Reserve. This hi tech fish monitoring equipment will be used to track carp and native fish to help threatened fish species management.
Read MoreBLOG 10/08/2014
The upper Murrumbidgee River is home to three nationally listed threatened fish species... highlighted by the recent discovery of a beautiful 93cm Murray cod at Scottsdale Reserve. This fish will be one of the beneficiaries of Scottsdale Reserve's carp trapping program.
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