At the time of European settlement, these fish were found in nearly all waterways in the Murray-Darling basin.
Today these fish still exist in these waters. Though they are in limited numbers which hardly amount to the numbers in the past. So much so that these fish are listed as “threatened under the Victorian Threatened Species Legislation and classified as vulnerable by the Victorian Department of Natural Resources for management purposes” and in NSW “Cod are identified as a member of the Endangered Ecological Community in the Natural Drainage System of the Lower Murray River Catchment” .

The Murray Cod is a long-lived species that is territorial and very aggressive, with a life span estimated to be as high as 75-114 years. Murray Cod of 80-90cm have been determined to be between 8 and 22 years of age. A Murray Cod of 125cm, weighing 36kg, was determined to be 34 years of age. The population of mature fish is vulnerable to population decline due to habitat degradation, fishing (commercial, recreational and illegal) and reduced recruitment success.

The larger fish inhabit deep, slow moving water with plenty of structure (snags, rocks etc). The smaller fish tend to inhabit similar water, but can also be found in shallow faster moving water.

The fish are very territorial and will defend their snag at all costs. They like to live in areas with a plentiful supply of shrimp, crayfish, smaller fish, turtles, waterfowl and will eat pretty much anything that moves near them.

Snag piles such as that pictured on the right are almost guaranteed to hold fish. There is plenty of cover, water depth and food stalking (for the cod) areas.

Murray cod reach sexual maturity at 4 to 5 years of age and around 2 to 3 kg in weight. These smaller fish produce only around 10,000 eggs, whereas the larger fish over 20kg can produce up to 90,000 eggs.

Although 90,000 eggs sounds like a large number, when compared with survival rate of the Murray Cod larvae is it quite small. They need a large number of zooplankton (usually caused by a flood) to feed on. Without enough zooplankton (which is sometimes the cause in some lakes, dams and rivers), these Cod will literally starve to death.