Another mass fish kill is unfolding in the lower Darling River in far western NSW, with thousands of fish floating dead along the banks.
Graeme McCrabb, a resident in the town of Menindee, said on Monday morning that he could see the dead fish - mostly bony herring - stretched out along at least a kilometre.
"It's started again," Mr McCrabb said. "Any fish that's still there is struggling."
"It's a sick spot of the river," he added, saying he could also see other fish, such as carp, trying to find enough oxygen to survive. "They are dying in front of us."
The stretch of the river, known as the Menindee weir pool, was the site of a mass die-off that numbered as many as one million fish earlier this month.
The cull included many giant Murray cod, some decades old, as well as golden and silver perch, the latter of which is endangered.
That fish kill was blamed on low oxygen levels in the near-stagnant waters, with little or no flow coming into the river. The nearby Menindee Lakes were just 3.2 per cent full as of Sunday, according to WaterNSW.
The Menindee region has turned sharply cooler overnight, with temperatures down to about 18 degrees as of 8am on Monday. On Friday, the mercury peaked at a sizzling 48.8 degrees, with the two days following topping 45 degrees.
There was also a couple of millimetres of rain overnight in the region.
In the previous big fish kill, the drop in temperatures caused some of the blue-green algae to die, depleting already low dissolved oxygen levels further.
The overnight rain may also have mixed the stratified layers of water, reducing the ability of remaining fish to find pockets of relatively high oxygenated waters.
It's understood that fisheries experts from the Department of Primary Industries are headed to Menindee to examine the latest fish deaths.
More to come