Darling River ecology ‘extinct’ and Murray cod ‘in real trouble’, warns expert Dr Stuart Rowland

The Darling River’s aquatic ecology is so degraded it has become extinct and iconic fish species including the Murray cod face an uncertain future, according to one of Australia’s most respected fish scientists.

Dr Stuart Rowland worked for the New South Wales Department of Primary Industries for 33 years until 2011. He is credited with describing the biology of the Murray cod and developed hatchery techniques for a number of native fish species.

He has written a book called The Codfather about his life’s work and the challenges facing the Murray cod.

He said prolonged drought and over-extraction of water for irrigation led to an ecological disaster in the lower Darling around Menindee between 2018 and 2020, which killed huge numbers of fish.

“I would describe it as an extinct system,” Dr Rowland said.

“The system is so changed and it’s so degraded now that the original sort of ecosystem that we knew at the turn of the century, the turn of the 1900s and into the 2000s is just no longer and in my opinion, it’s a system that has just gone extinct.”

Murray cod in danger

Dr Rowland was a member of a NSW Fisheries Scientific Committee that declared the lower Darling an endangered ecological system in 2003 but its recommendations, including limiting water extracted for irrigation further up the system, were not followed.

Instead, he said, “there was a tenfold increase in water extraction”.

“Water extraction is not a problem if the flows are high and the river is in flood, but for low, low rivers, it’s really serious,” he said.

The impacts on the river gained national attention with mass fish kills around the Menindee Lakes two years ago.

“The native fish is where we we see the results of this mismanagement, because they die,” Dr Rowland said.

“They die through poor water quality and lack of connectivity, they stop breeding successfully and so they’re just driven to extinction.”

Dr Rowland said the Darling River snail and the trout cod had already gone extinct and the Murray-Darling river system was “no longer the stronghold of Murray cod”.

“And so this iconic species is just really in trouble in that river,” he said.

Battle to restock

The NSW Government in 2019 committed $10 million as part of its native fish drought response, including the largest effort to date to rescue and relocate more than 5,000 native fish from drying waterways to hatcheries or more secure habitats across the state.

More than 60,000 Murray cod fingerlings were released in the lower Darling between Menindee and Wentworth in December. They were bred from stock rescued from the river in 2019.

A Department spokesman said native fish had suffered from the worst drought on record over three years and had only just begun to recover.

“NSW DPI Fisheries is supporting native fish recovery by ensuring that native fish have the opportunity to move, breed and complete their life cycles,” the spokesman said.

Dr Rowland said restocking was not a panacea and although Murray cod might survive in the system, numbers would never return to what they were just 50 years ago. Crucial breeding opportunities were lost in the fish kill disaster two years ago.

Even if the river flooded again he doubted its aquatic ecosystem could recover.

“You might get more Murray cod and some golden perch and bony bream and other species,” Dr Rowland said.

“They might hang in there and when the big freshes and the floods come, the system will reignite.

“But in my opinion, as a scientist who’s watched it for 50 years, it won’t be the same.”