The Murray Cod population declined substantially in the last 50 years. Although good local populations still exist the decline on a national scale resulted in listing the Murray Cod as vulnerable and Critically Endangered. Estimates indicate the remaining Murray cod is only 10% of the total cod population before European settlements
Smaller Murray Cod averages from about 60 centimetres in length in smaller habitats to an average of 130 centimetres in length in larger habitats
They can weigh anything from about 4 kilograms to about 45 kilograms in their natural habitat, but there are exceptions. The largest Murray Cod on record weighed a whopping 113 kilograms with a length of 183 centimetres. They are a long lived species and can live up to and beyond 50 years
The Murray Cod, also called the “King of the waterway” is prevalent in the Murray-Darling Basin in Australia which spreads through New South Wales, South Australia and Victoria
This freshwater predator has a large mouth, a cream to white belly and can easily be identified by the light to dark green colouring with a mottled dark green pattern on the body and head. This colouring allows the cod to blend with their surroundings. The Murray Cod has a powerful rounded tail; this helps them to strike prey with force and precision. The single dorsal fin is spiny and smaller in the front and longer and softer on the back of the body. They have small eyes at the top of their head and this helps them to see and attack prey from beneath.
The Murray Cod behaviour consists of:
- The Murray Cod is a very aggressive fish and very territorial and are often called the “pigs of the waterway”
- They are willing to strike and are extremely hard fighting and this makes them a very popular fresh water sport fish
- The Murray Cod reach sexual maturity at about 4 – 6 years and they migrate upstream in late winter to early spring to spawn.
- They can travel up to 120 kilometres to spawn in water of about 20˚C.
- The male guards the eggs during incubation. The eggs will hatch anytime between 5 – 13 days. The male will guard the newly hatched larvae until they are about a week old.
- The fish will migrate back downstream and return to the exact same spot they inhabited before migration to spawn.
As an apex predator the Murray cod eat anything smaller than itself and everything in their way. They lay and wait under in-stream cover rocks, stumps, fallen trees or undercut banks to strike at their prey. They mostly eat other fish, even smaller Murray Cod, but they have also been known to eat duck, freshwater turtles, snakes, mice and frogs. If the prey fits in their mouth, they will eat it.
The Murray Cod are found in warm slow flowing freshwater rivers, clear rocky streams and creeks. They can adapt to different environments, but will find and live in the best habitats closest to their needs. They rely on snags, holes, rocks and overhanging vegetation for food, shelter and to spawn. Snags provide a surface for eggs to be laid and also give them refuge from predators and fast flowing water.
Their habitat is severely altered by human activities. Habitat loss due to de-snagging, barriers to movement, changes to water flows, water temperature and water pollution, loss to irrigation systems, the introduction of alien fish species and recreational and illegal fishing, especially in breeding season, are just some of the threats the Murray Cod faces.
Initiatives are in place to improve the water quality and habitat of the Murray Cod and all can assist by re-snagging rivers, reinstating water flows and vegetation and by minimising carp as an alien fish species. Catch and release practices when fishing and fishing restrictions during breeding season can minimise the threat to the Murray Cod and help them to survive and thrive as a species.