Hundreds of thousands of fish discovered dead as authorities investigate mass kill in far west New South Wales #Hundreds #thousands #fish #discovered #dead #authorities #investigate #mass #kill #west #South #Wales #englishheadline


Hundreds of thousands of dead fish have been discovered in outback New South Wales in an apparent fish kill caused by unprecedented flooding and hot weather. 

The mass mortality of wild fish occurred on the Darling River at Menindee, near Broken Hill, the same area that has been the site of several other fish kills in recent years.

The Department of Primary Industries said Bony Bream make up most of the species of fish found dead on Friday, but smaller numbers of Murray Cod, Golden Perch, Silver Perth and Carp have also been detected. 

“This event is ongoing as a heatwave across western NSW continues to put further stress on a system that has experienced extreme conditions from wide-scale flooding,” the department said.

Bream species typically “boom” in population during flooding and then die off or “bust” when water flows return to normal, the department said.

Hot weather can be an additional environmental stressor as an increase in temperature depletes oxygen levels.

“These fish deaths are related to low oxygen levels in the water (hypoxia) as flood waters recede,” a DPI spokesperson said.

“Significant volumes of fish including Carp and Bony Herring, nutrients and organic matter from the flood plain are being concentrated back into the river channel.

“The current hot weather in the region is also exacerbating hypoxia, as warmer water holds less oxygen than cold water, and fish have higher oxygen needs at warmer temperatures.”

In 2019, millions of fish were found dead over a 40-kilometre stretch in the same area following a period of severe drought.

An expert panel of scientists later deemed the ongoing drought in combined with the mismanagement of the Murray-Darling river system led to the mass fish deaths.

The DPI defines a fish kill as a sudden mass mortality of wild fish.

“Fish kills can occur at any time although data indicates fish kills are more likely to occur in summer or following sudden changes in temperature,” the department said on its website.

English Headline

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