Mary River cod

Mary River cod (Maccullochella mariensis) are a Maccullochella cod found in the coastal Mary River system of southern Queensland, Australia. Mary River cod are significant because they are the most northerly of the four Maccullochella cods found or once found in coastal river systems of eastern Australia.

Description

A large fish, reliably recorded to at least 27 kilograms in the early years of European settlement. Very similar in appearance to Murray cod and eastern freshwater cod; a striking looking, deep-bodied fish with dark green or black mottling. Curiously, Mary River cod have a slightly shorter, thicker caudal peduncle (tail wrist) than the other cod species.

Conservation

Mary River Cod are subject to the usual story of woe. Incredibly abundant at the time of first European settlement, they were grossly overfished with nets, lines and explosives by the early European settlers and, as with other Maccullochella cods, were even used as pig feed. This overfishing, combined with the massive siltation of their habitats by land-clearing, destruction of riparian vegetation and cattle trampling river banks, and dams and weirs blocking migration, rapidly caught up with this large, slow-growing, long-lived Maccullochella cod species, as it has with all its close relatives.

Classification

Taxonomically, Mary River cod were once designated as "Maccullochella peelii mariensis", which denoted that they were a sub-species of the Murray cod, Maccullochella peelii. This was done on the basis of studies of muscle proteins and enzymes.

As of 2010, after studies of mitochondrial and nuclear DNA, Mary River cod have been raised to full species status (Maccullochella mariensis) (Nock et al., 2010). This research reveals the Mary River cod's closest relative is the eastern freshwater cod (Maccullochella ikei) of the Clarence River system.

References

• Nock C.J., Elphinstone M.S., Rowland S.J. and Baverstock, P.R. (2010). Phylogenetics and revised taxonomy of the Australianfreshwater cod genus, Maccullochella (Percichthyidae). Marine and Freshwater Research 61: 980–991.

• Rowland, S.J. (1993). Maccullochella ikei, an endangered species of freshwater cod (Pisces: Percichthyidae) from the Clarence River System, NSW, and M.peelii mariensis, a new subspecies from the Mary River System, QLD. Records of the Australian Museum 45: 121-145.

• Simpson, R.R. and Mapleston, R.J. (2002). Movements and Habitat Use by the Endangered Australian Freshwater Mary River cod, Maccullochella peelii mariensis. Environmental Biology of Fishes 65: 401–410.