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What is a Murray Cod?

The Murray Cod is an iconic freshwater fish native to Australia, revered for its size and significance in river ecosystems. Known for its striking green pattern, it's a symbol of ecological health and a prized catch among anglers. As we explore the challenges this majestic species faces, consider the impact of environmental stewardship on their survival. What role might we play in their future?
K. K. Lowen
K. K. Lowen

Murray cod is a freshwater fish that is native to Australia. The predatory, long-lived fish is known for its impressive size. A favorite of both commercial and recreational fishermen, Murray cod populations have continued to dwindle.

Contrary to its name, the Murray cod is not related to the cod species. It is a member of the Percichthyidae family of fish, and is more closely related to perch. Similarities also exist between Murray cods and groupers, enormous game fish found throughout the world’s warm seas.

Murray cod live in the Murray-Darling river system, the largest such system in Australia.
Murray cod live in the Murray-Darling river system, the largest such system in Australia.

Murray cod received its name from the Murray River in Australia. These fish have a wide range of habitats, as the Murray-Darling river system is the largest in Australia. Although they are found throughout the river system, the fish prefer to live in the lowlands.

The fish has a distinct appearance, with a long body and round mid-section. Brown or black speckles may be present, though shades of green are the animal’s predominant colors. Small needle-like teeth line its mouth, and its jaws may align or create an underbite. The dorsal fin is spiny, whereas all of its other fins are soft and round.

Murray cod fish may eat mice.
Murray cod fish may eat mice.

This fish is easily recognizable by its size. The Murray cod is the largest freshwater fish in Australia, and one of the largest exclusively freshwater fishes in the world. An adult is generally between 32 and 39 inches (80 to 100 centimeters) in length, but fishermen have found much larger specimens.

A predatory fish, the Murray cod eats mostly other fish. Although much of its diet consists of fish such as smelt, catfish, and perch, Murray cods will eat anything small enough to consume. Crustaceans, including crayfish and shrimp, are also targets. Ducks, mice, frogs, and snakes are potential prey as well.

As the Murray cod’s life can span many decades, the fish do not reach sexual maturity until they are four to six years old. Females lay about 10,000 eggs when they first reach sexual maturity, but large females lay more eggs, usually between 80,000 and 90,000. After laying the eggs, females leave while males stay behind to guard the eggs until they hatch.

The long-term survival of the species may be in jeopardy because of recreational and commercial over-fishing. Humans also have damaged the animal’s habitat through pollution, dams, and irrigation ditches that changed the natural water-flow patterns in the Murray-Darling river system. The Australian government has been raising Murray cod in hatcheries and releasing them into the wild as a conservation effort.

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    • Murray cod live in the Murray-Darling river system, the largest such system in Australia.
      By: Tupungato
      Murray cod live in the Murray-Darling river system, the largest such system in Australia.
    • Murray cod fish may eat mice.
      By: Anatolii
      Murray cod fish may eat mice.