The Mary River cod (''Maccullochella mariensis'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

temperate perch The members of the family Percichthyidae are known as the temperate perches. They belong to the order Perciformes, the perch-like fishes. The name Percichthyidae derives from the Latin ''perca'' for perch and Ancient Greek ἰχθύς, ''ichthy ...

native to the coastal Mary River system of southern

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. Mary River cod are one of Australia's most endangered freshwater fishes and are notable for being the most northerly of the four ''

Maccullochella ''Maccullochella'' is a genus of large Australian predatory freshwater fish within the family Percichthyidae. The genus ''Maccullochella'' was named after an early Australian fish researcher with the surname ''McCulloch''. The ''Maccullochella'' ...

'' cods found or once found in coastal river systems of eastern Australia.

Description

The Mary River cod is a large fish recorded up to almost 40 kg and 120 cm in the early years of European settlement, but now are mostly less than 5 kg and 70 cm. Very similar in appearance to Murray cod and

eastern freshwater cod The eastern freshwater cod (''Maccullochella ikei''), also known as the eastern cod or Clarence River cod, is a large predatory freshwater fish of the genus ''Maccullochella'' and the family Percichthyidae, that occur in the coastal Clarence Rive ...

, they are a striking looking, golden-yellow to dark green or brown, deep-bodied fish with dark green to black mottling. Curiously, Mary River cod have a slightly shorter, thicker caudal peduncle (tail wrist) than the other cod species.

Conservation

The Mary River Cod is listed as

Endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

under the

Environment Protection and Biodiversity Conservation Act 1999 The ''Environment Protection and Biodiversity Conservation Act 1999'' (Cth) is an Act of the Parliament of Australia that provides a framework for protection of the Australian environment, including its biodiversity and its natural and cultu ...

and is estimated to only occur in less than 30% of its historic range. Incredibly abundant at the time of first European settlement, Mary River Cod were grossly

overfished Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the ...

with nets, lines and

explosives An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...

by the early European settlers and, as with other ''Maccullochella'' cods, were even used as pig feed. This

overfishing Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

, combined with the massive

siltation Siltation, is water pollution caused by particulate terrestrial clastic material, with a particle size dominated by silt or clay. It refers both to the increased concentration of suspended sediments and to the increased accumulation (temporary or ...

of their habitats by

land clearing Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...

, destruction of riparian vegetation and cattle trampling river banks, and

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, a ...

s 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. Outside of a few stocked Queensland impoundments- upstream of the walls of Cressbrook, Hinze, Maroon, Moogerah, North Pine, Somerset and Wivenhoe Dams and lakes Dyer (Bill Gunn dam) and Clarendon- the fish is a no take species and any caught should be carefully released. A strict bag limit of one fish with a minimum size of 50 cm applies to the stocked impoundments.

Classification

Taxonomically, Mary River cod were originally described as a subspecies of the Murray cod, ''Maccullochella peelii'' based on 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.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. This research reveals the Mary River cod's closest relative is the eastern freshwater cod (''Maccullochella ikei'') of the Clarence River system.

References

* 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, A.J. (2002). Movements and Habitat Use by the Endangered Australian Freshwater Mary River cod, ''Maccullochella peelii mariensis''. ''Environmental Biology of Fishes'' 65: 401–410. {{Taxonbar, from=Q6780612

Mary River cod The Mary River cod (''Maccullochella mariensis'') is a species of temperate perch native to the coastal Mary River (Queensland), Mary River system of southern Queensland, Australia. Mary River cod are one of Australia's most endangered freshwa ...

Mary River (Queensland) Freshwater fish of Queensland