NSW mass fish deaths a 'man-made disaster'

The deaths of up to a million fish in far western NSW is being described by residents as a "man-made disaster" that could end in millions more dying.

NSW Primary Industries Minister Niall Blair says the mass deaths in the Darling River system at Menindee are devastating and on Wednesday asked for an urgent report from the Department of Industries and WaterNSW which will be made public.

He's argued the deaths could be due to ongoing drought conditions followed by a recent big drop in temperature.

Water was also released from the Menindee Lakes to South Australia under the Murray-Darling Basin Authority's approval and because of the drought there was no water to replenish the system, Mr Blair says.

The minister on Wednesday inspected the river and was confronted by more than 100 angry residents demanding answers.

Rob McBride, a grazier who lives about 40 kilometres south of Menindee on the Lower Darling, insists the deaths have nothing to do with the drought and 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.

"The blue-green algae will take over each stretch of the 600km river and it will kill billions of fish. It's a collapsing 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 the 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 mass deaths as "tragic" and 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.

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.