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Maccullochella peelii mariensis (Family Percichthyidae)

Mary River Cod

Distribution:

The Mary River Cod once lived in many rivers in south-eastern Queensland. Now they are found only in a few tributaries to the Mary River. Fingerlings bred in a hatchery have also been released in the Mary River, Brisbane River and Burnett River catchments (QLD).

Features:

The Mary River Cod is a large freshwater fish that grows to at least 23 kg. It has a broad and slightly flattened head with a rounded snout. The mouth is large and the tail fin is rounded. It is olive-green to brown on the back, becoming lighter with dark mottling on sides. The belly is cream or yellowish. The fins are green or brown with mottling near the body and with white edges on the dorsal fin, anal fin and tail fin. The pelvic fins have long white filaments. Mary River Cod are difficult to distinguish from other related cod species.

Ecology/Way of Life:

The Mary River Cod lives in deep, shaded pools in rivers and creeks. They prefer pools with abundant shelter including fallen logs and branches, undercut stream banks and overhanging vegetation. Mary River Cod are ambush predators. They eat fishes, crustaceans and sometimes other animals or insects that fall in the water. They reproduce in spring when water temperatures are above 20°C. Pairs will form territories around a hollow log or rocky cave. Females produce many thousands of eggs, which are opaque, about 3 mm diameter and are attached to the substrate of the log or cave. The male guards the eggs for about 10 days until they hatch. The fry are not cared for after they are free swimming. Fry feed upon small crustaceans.

Interaction with Humans/Threats:

This species was once a popular angling fish. They have become very scarce and although some anglers still like to catch them, they are endangered. The major threat to Mary River Cod is the loss of deep pools with lots of snags. This has occurred due to excessive clearing of bushland, particularly along creek banks, which leads to the erosion of creek banks and the filling of waterholes with silt. The construction of weirs and dams has also reduced the number of good waterholes. In some places, introduced fish use breeding spaces, shelter and food that Mary River Cod once used. Mary River Cod are now bred in a fish hatchery so that fingerlings can be put back into dams, rivers and creeks.

Other Comments:

Maccullochella peelii mariensis was named by Rowland in 1993. The name mariensis is derived from the Mary River.

Further Reading:

Allen, G. R., Midgley, S. H. & Allen, M. (2002). Field Guide to the Freshwater Fishes of Australia. Western Australian Museum. Perth. 394pp.

Acknowledgments:

Text: Rob Wager & Peter J. Unmack.

Distribution map: Peter J. Unmack.

Photographer: Gunther Schmida.

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