The lower Darling River remains in a critical condition and without significant inflows, more fish deaths can be expected, according to a preliminary report commissioned by the Federal Government released on Thursday.

Key points: The Vertessy report, ordered by the Government, found that "exceptional climatic conditions, unparalleled in the observed climate record" contributed to the mass fill kill

It made 20 provisional recommendations including calls to improve water monitoring in tributaries and greater transparency around floodplain harvesting

A final report by Professor Vertessy's panel is expected by the end of next month

Chaired by Melbourne University Professor Rob Vertessy, the report found that "exceptional climatic conditions, unparalleled in the observed climate record" contributed to the fish deaths.

The report was ordered by the Government following mass fish kills near Menindee, NSW, in December and January.

It follows a separate report by the Australian Academy of Science, requested by Labor, which found irrigators pumping too much water upstream, drought, and low flows into and from Menindee Lakes had contributed to the deaths of millions of fish.

The Vertessy report has made 20 provisional recommendations including calls to improve water monitoring in tributaries that feed the Barwon-Darling River and greater transparency around floodplain harvesting in NSW and Queensland.

It also called for real time monitoring of diversions across the Barwon-Darling.

The report found sudden reductions in the air temperature and low oxygen levels in the water were the primary cause of the fish deaths.

"Recent extreme weather events in the northern Basin have been amplified by climate change," the report found.

"Future changes in the global climate system are likely to have a profound impact on the hydrology and ecology of the Murray-Darling Basin and exacerbate the risk of fish deaths."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 43 seconds 43 s Mass killing of fish in Darling River, near Broken Hill

Water Minister David Littleproud responded to the interim report by committing to urgent works in the river, including the establishment of fish ladders and a warning system to predict when more fish deaths might occur.

The Government also announced $3 million for fish research and separate funding for communities that installed aerators to pump oxygen into the water and create fish refuges.

"I welcome the findings of the independent panel and will begin work in response immediately, including on allowing fish to move more freely around the river system," Mr Littleproud said.

A final report by Professor Vertessy's panel is expected by the end of next month.