‘Drought, poor management’ caused mass fish kill

Drought and poor management was responsible for mass fish kills on the Darling River, a report by an expert panel has found.

Dead fish in the Menindee weir pool in January. Picture: AAP

Drought and poor management, not climate change, were responsible for mass fish kills on the Darling River in December and January, a Labor-commissioned report by an expert panel has found.

Millions of fish, including ­decades-old Murray cod, were killed when a “perfect storm” of factors combined to devastate the river system in the far west of NSW.

The Academy of Science panel, which included former climate commissioner Tim Flannery, said while climate change linked to increasing emissions had contributed to hotter conditions, it was unlikely the observed reductions in flows were attributable to a steep change in climate.

Climate change impacts could be an issue in future, the panel found, but different models gave conflicting results for what could be expected in the northern catchment. “We cannot tell with the variability in natural rainfall patterns exactly when the climate change impacts will be expressed,” the report said.

It made eight recommen­dations to improve river flows and community consultation.

Federal Agriculture Minister David Littleproud said many findings and recommendations in the Labor-commissioned report were political, not scientific.

“It’s a shame the Australian Academy of Science seems to have done the Labor Party’s bidding and opened itself up to claims that he who pays the piper calls the tune,” Mr Littleproud said.

The federal government has commissioned a report from Melbourne University’s Robert Vertessy, which is due next month.

The academy report said the fish kill was significant but not unprecedented, with historical data indicating large fish kills had occurred in the hundreds of thousands and millions on the Darling and Murray rivers previously.

They have also occurred on Menindee Lakes and the Lower Darling.

On December 15, tens of thousands of dead fish were reported along a 30km stretch of the Darling River near the NSW town of Menindee.

A larger fish kill event involving hundreds of thousands of fish was reported on January 6 on the same stretch of river.

A third event followed on January 28, killing millions of fish.

“The immediate cause of the fish deaths was stratification and then mixing of a large volume of oxygen-depleted bottom water with the smaller oxygenated surface layer,” the Academy of Science report said.

The Australian Conservation Foundation welcomed the report’s findings and called on the federal government to immediately reverse a decision to cut the environmental water recovery target for the northern basin by 70 gigalitres.