NSW opposition leader Michael Daley wants the Berejiklian government to establish a special commission of inquiry after up to a million fish died in the river at Menindee.

Mr Daley on Thursday vowed to establish an inquiry into the "catastrophe" if Labor wins power at March's general election.

University of Queensland economist John Quiggin blames the NSW and federal governments for "throwing out the window" policies which protected the river.

"This happened because we are mismanaging the system," he told AAP on Thursday.

Prof Quiggin wants an independent scientific body to publicly document what is happening in the basin to ensure the Water Act 2007 is being adhered to.

Some residents, including Rob McBride, are blaming the fish deaths on the amount of water allocated to irrigators and mismanagement.

Premier Gladys Berejiklian on Thursday assured residents the government was working to find "solutions".

"We're working through it as fast as we can to see what solutions we can contribute towards," she told reporters in Sydney.

NSW Primary Industries Minister Niall Blair on Thursday told AAP there had been two more fish kills in the state's north at Lake Keepit, where up to 1000 fish died, and at Lake Cathie, where hundreds were found dead.

Mr Blair - who has been savaged by some Menindee locals for partly blaming the drought - in a statement said fish kills are not a new phenomenon and happened in the region between 2002 and 2004 during the millennium drought.

He's requested an urgent report into the mass fish deaths.

Ex-Greens and now independent MP Jeremy Buckingham also visited Menindee and in a video uploaded to his Facebook page is seen retching while holding a dead fish.

Mr Buckingham then buckles over and walks away from the camera because of the "massive stink".

"I felt so sick that I panicked and jumped in the river to escape it - as bad as it is!" he said in a Facebook post.

The peak body for the cotton growing industry, whose members have properties upstream of the river, on Thursday said it was tired of being the "whipping boy" for problems caused by the drought.

Cotton Australia general manager Michael Murray said a move by the Murray-Darling Basin Authority to release water from Menindee Lakes, which is part of the river, was in hindsight a "poor decision" but highlights the difficulties of managing the system.

The MDBA says it draws water from the lakes first because they are less efficient than others and have higher evaporation rates.

A South Australian royal commission held in 2018 investigated allegations of water theft from the Murray-Darling Basin by rogue irrigators with its report expected on February 1.

Australian Associated Press