'Disaster': Another mass fish kill under investigation

A DROP in temperatures and some rain is likely behind another mass fish kill reported along the Darling River in far western NSW, the state government says.

Local Graeme McCrabb on Monday morning posted photos on social media of floating dead fish in the weir pool at Menindee.

"It's starting again," he wrote on Facebook.

The NSW Department of Primary Industries has sent officers to investigate the event, which it believes has affected "large numbers of bony bream and smaller numbers of other species".

"It is likely linked to some rain and cooler temperatures in the Menindee area following an extended period of very hot weather," a spokeswoman said in a statement to AAP.

Menindee resident Rob Gregory said there were at least 200-to-300 dead bony bream, as well as some native species.

"There are lots of yabbies crawling up the bank ... they must be suffocating," he told AAP.

"It's a shame."

>>VIDEO: MP throws up while holding dead fish 

Mr Gregory said the latest fish to die would have likely been survivors from previous events.

Up to a million fish died along the Darling River at Menindee earlier in January, while thousands were also found dead almost 900km away along the Macintyre River.

Central Darling Shire general manager Greg Hill, who is in charge of the clean-up, fears the latest mass kill could be as large.

"It's fairly big," Mr Hill told AAP.

The council has hired a clean-up operator which will also record information about the event.

Premier Gladys Berejiklian suggested the mass kill couldn't have been avoided, saying "we cannot control the weather".

"Under the current circumstances, if we could have avoided it we will," she told reporters in Sydney.

"I was advised the sudden drop in temperature makes it conducive, unfortunately, for the fish to be deprived of oxygen."

Federal Labor leader Bill Shorten said the Murray-Darling was "facing the makings of an ecological disaster".

"This is not standard, this is not normal. This is a disaster," he told reporters in Melbourne.

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