"Mature fish that survived decades of droughts could not survive the Liberal-Nationals’ water policy," Mr Daley said in a statement. "The [Coalition parties] have been repeatedly warned by far-west residents, community groups, scientists and Labor that their water policies would cause devastation on the Darling River." Taxpayers have stumped up more than $13 billion to restore the health of the basin. The latest fish die off, along with other signs of wildlife and human populations hard hit by drought and heat, add to the likelihood that water will feature prominently in the looming federal and NSW state elections. Loading The immediate cause of the calamity was a change in temperatures that killed much of the blue-green algal bloom on that part of the river. The dying algae worsened low levels of dissolved oxygen in the water, pushing many fish beyond their tolerance levels. “The scale of this disaster is extraordinary and unprecedented," Mr Daley said. "We cannot be indifferent to the ecological impact and the effect on local residents who live along the river."

Labor wants an inquiry to determine why the Liberals and Nationals sought "changes to water rules that reduced river flows and allowed the over-extraction of water by lobbyist irrigators who were National Party donors", while ignoring warnings from the Wentworth Group of Scientists and local communities." NSW Labor confirmed on Thursday that it would seek to overturn the plan - supported by all basin state governments and the Morrison government - to effectively decommission the Menindee Lakes System. Hundreds of bony bream and other dead fish in the Darling River at Menindee. Credit:Nick Moir Such a move - part of the Sustainable Diversion Limits projects - would "further reduce water flows in the lower Darling River and destroy fish breeding grounds in the Darling River", Labor said, adding it had "committed to abandon this plan to prevent further ecological destruction". Mr Blair dismissed Mr Daley's comments saying that he had used his first comments about the drought to "re-write history by ignoring the fact that similar environmental catastrophes happened under their watch when last in government".

“In fact, numerous fish kills occurred in the lower Darling and Menindee Lakes in the period 2002 - 2004 during the Millennium drought," he said, citing Lake Pamamaroo which dried out in December 2002, three separate fish kill events in August 2003 on the Darling including at Menindee and one upstream of Pooncarie in February 2004 involving hundreds of Murray Cod. Earlier on Thursday, Mr Blair told the Herald that he had asked his departments to conduct an urgent study into the fish deaths and the subsequent clean-up. He added the SDL project at Menindee, which aims to save 105 gigalitres a water a year, must proceed. "They don't understand what it would mean [to cancel it]," Blair says, of the NSW Labor stance. "You would blow up the [Murray-Darling Basin] Plan." Jeremy Buckingham, the former Greens and now independent NSW MP, supported the NSW Labor move but said "it is needed at a federal level". “This mass fish kill be a wake-up call for Australia that we need to get out of a broken loop on water policy and that fundamentally adequate water must be prioritised for the environment before being allocated to large-scale irrigation," Mr Buckingham said as he left for Broken Hill after visiting the dead fish zones on Wednesday.

'Poor decision' Michael Murray, general manager of Cotton Australia, sought to counter criticism of irrigators and his industry for the plight at Menindee, say the state’s cotton output would halve this year. “On the Barwon-Darling, the impact on cotton production is even more devastating with zero hectares of cotton being grown in Bourke this season, down from 4,000 hectares the year before,” Mr Murray said in a statement . “Further upstream at Dirranbandi (home of Cubbie Cotton), just 300 hectares of cotton has been planted, which is 1 per cent of what can be planted in a very good season.”. Mr Murray said the decision 18 months ago to drain 2,000 gigalitres of water from the Menindee Lakes was in hindsight “probably a poor decision”.