The Richmond River cod was a form of Maccullochella

Maccullochella

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

cod, now believed to have been eastern freshwater cod

Eastern freshwater cod

Eastern freshwater cod, Maccullochella ikei, also known as eastern cod, are a large and striking predatory freshwater fish of the Maccullochella genus and the Percichthyidae family, that occur in the coastal Clarence River system of north-eastern New South Wales...

, Maccullochella ikei, that occurred naturally in the Richmond River

Richmond River

The Richmond River is a river in the north-eastern corner of New South Wales, Australia. It runs for approximately 170 km from the foothills of the Border Ranges past the towns of Kyogle, Casino, Coraki, Woodburn, where it turns northward and empties into the Pacific Ocean at Ballina. It has a...

 system, an east coast river system in north-east New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

Eastern freshwater cod in turn are a species of Maccullochella cod found in east coast drainages and originating from Murray cod

Murray Cod

The Murray cod is a large Australian predatory freshwater fish of the Maccullochella genus and the Percichthyidae family. Although the species is a called cod in the vernacular, it is not related to the northern hemisphere marine cod species...

, Maccullochella peelii, that crossed the Great Dividing Range

Great Dividing Range

The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...

 and entered east coast drainages from a river capture

River capture

Stream capture, river capture, or stream piracy is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighbouring stream...

 event between 0.62 and 1.62 million years ago (mean estimate 1.1 million years ago).

Richmond River cod are extinct, from overfishing

Overfishing

Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....

, habitat destruction

Habitat destruction

Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...

 including gross siltation, and whole-of-catchment scale bushfires and fish kill

Fish kill

The term fish kill, known also as fish die-off and as fish mortality, is a localized die-off of fish populations which may also be associated with more generalised mortality of aquatic life...

s in the 1930s.

The Richmond River system has now been restocked with small numbers of eastern freshwater cod from the Clarence River

Clarence River (New South Wales)

The Clarence River is situated in northeastern New South Wales, Australia. The river originates on the watershed that marks the Queensland border. After flowing south and northeast for 394 km it then empties into the Pacific Ocean at Iluka/Yamba. On its journey it passes through the towns of...

system, but these appear to have been insufficient to re-establish populations; there is no evidence of these stocked fish reproducing as yet.