June 6, 2023
Dr Stuart Rowland with a Murray cod (Maccullochella peelii) from the McIntyre River, a tributary of the Murray-Darling River System.
Image credit: Courtesy Dr Stuart Rowland
Who is the man behind The Codfather and why?
The Australian freshwater cod, Maccullochella, is named for the naturalist Allan Riversone McCulloch. Scientists currently recognise four living species:
- Murray cod, Maccullochella peelii (Murray-Darling River System)
- Trout cod, Maccullochella macquariensis (Murray-Darling River System)
- Eastern freshwater cod, Maccullochella ikei (Clarence River System)
- Mary River cod, Maccullochella mariensis (Mary River System)
“The Murray cod is Australia’s most famous and largest freshwater fish, growing to over 100 kilograms,” says fisheries scientist Dr Stuart Rowland. “It is the icon of the Murray-Darling River system.”
Although superficially similar in overall size, form and colouration, these four have evolved in isolation from each other to become separate species. Yet until the mid-1980s, all freshwater cod were classed as either Murray cod or trout cod.
That all changed when Stuart published a paper in 1986 describing the Eastern freshwater cod and naming it Maccullochella ikei, in memory of his late grandfather, Ike.
Then in 1993, Stuart recognised the Mary River cod as a sub-species of the Murray cod and named it Maccullochella peelii mariensis. Following further genetic analysis, in 2010 Stuart and colleagues were able to elevate this fish to species level.
“Freshwater cod play important ecological, cultural, historical and social roles in Australia,” says Stuart, who has been tagged ‘The Codfather’ for his groundbreaking work.
These long-lived giants of our river systems are vulnerable to environmental changes. By the early 1980s, scientists realised that the distribution and abundance of all four species had declined to alarming levels, and they were classified as threatened.
Stuart provides a checklist of factors responsible for their decline: environmental degradation, overfishing, pollution, exotic species and river regulation.
“Poor water quality, over-extraction of water and mismanagement of rivers, pollution and infectious diseases — all continue to threaten Australia’s cod and other freshwater species.”
Conservation programs and fisheries’ regulations have brought them back from the brink, and good natural flows in recent years have helped some local populations recover further.
Yet all except the Murray cod remain classified as endangered or vulnerable. “Massive fish kills in 2019 and 2023 threaten the future of Murray cod and other native fish in the Darling River,” says Stuart. “There is no room for complacency.”
Related: Who is the man in Maccullochella?
Brendan Atkins is author of The Naturalist, the remarkable life of Allan Riverstone McCulloch, published by NewSouth Publishing (in association with the Lord Howe Island Museum), October 2022.