Angry residents in far western NSW are calling the death of up to a million fish a "man-made disaster" but the state government insists the drought is partly to blame.
NSW Primary Industries Minister Niall Blair admits the mass fish death in the Darling River system at Menindee is devastating, and on Wednesday he asked for an urgent report from the Department of Primary Industries and WaterNSW.
The minister has been savaged by some locals who claim water levels are low because of the amounts diverted to irrigators.
But Mr Blair insists no one is getting water because of the prolonged drought.
"In the past six months there's been 30 gigalitres in the system - on an average year there is 4000 gigalitres," he told AAP on Wednesday.
"You cannot dismiss the fact there is a drought and a lack of water."
Water has been released from the Menindee Lakes to South Australia under the Murray-Darling Basin Authority's approval and because of the drought there's been nothing to replenish the system, Mr Blair says.
The NSW government is in talks with the Commonwealth about operating rules and water-sharing arrangements, he added.
The minister on Wednesday inspected the river and was confronted by more than 100 angry residents demanding answers.
Rob McBride, a grazier who lives south of Menindee on the Lower Darling, insists the deaths are the result of a "man-made engineered disaster".
"It has everything to do with the total mismanagement and corruption of the water system," Mr McBride told AAP on Wednesday.
"They (irrigators) are using our water from a fragile ecosystem."
The Menindee Lakes, which are about four times the size of Sydney Harbour, were drained twice in four years and are sitting at between 2.6 per cent and four per cent capacity, he said.
Mr McBride features in a viral Facebook video where he's standing in the Darling River alongside Dick Arnold holding dead fish.
The duo blame state and federal governments for the "environmental disaster" affecting the golden perch, Murray cod and bony herring.
"You have to be bloody disgusted in yourselves," Mr Arnold said in the video posted on Tuesday.
Mr McBride's daughter, Kate, says the deaths are due to the diversion of water from the river for irrigation and the draining of Menindee Lakes.
"These huge Murray cods are about 80 years old, they've survived the drought and extreme weather but the one thing they can't survive is this draining," she told AAP on Wednesday.
The Murray-Darling Basin Authority has described the deaths as a terrible reminder of the impact drought has on the environment.
The latest kill follows an incident in December resulting in more than 10,000 fish mortalities along a 40km stretch of the Darling River.
The DPI said ongoing dry conditions and a recent big temperature drop could have caused the deaths.
A South Australian royal commission was held in 2018 to investigate allegations of widespread water theft from the Murray-Darling
Basin by rogue irrigators with its report expected on February 1.