Menindee residents have taken to social media to share footage of thousands of dead fish floating in the Menindee Weir pool, located on the Darling River.

Fish kills are defined as a sudden mass mortality of wild fish. According to the NSW Department of Primary Industries 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.

A spokesperson for the NSW Department of Primary Industries told ACM that millions of fish, predominantly Bony Herring (Bony Bream) have been affected, as well as smaller numbers of other large-bodied species such as Murray Cod, Golden Perch, Silver Perch and Carp.

"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 spokesperson said.

"NSW DPI understands that fish death events are distressing to the local community, particularly on the Lower Darling-Baaka."

The spokesperson advised that Bony Herring species boom and bust over time, meaning it 'booms' in population numbers during flood times and can then experience significant mortalities or 'busts' when flows return to more normal levels. This may have contributed to the fish kill.

Menindee, a town of about 500 people, is located an hour's drive from Broken Hill. It has been the site of several mass fish killings in recent years.

This is the second major fish kill in recent weeks at Menindee. In late February tens of thousands of dead fish were reported in the Darling-Baaka River from Menindee Main Weir to Menindee Town.

The cause was attributed to low dissolved oxygen levels as flood waters receded.

Also in late February, tens of thousands of dead fish, largely Bony Herring with some Carp, Murray Cod and Golden Perch were found in the Darling-Baaka River from Bindara Station near Menindee downstream towards Pooncarie.

At the time the cause was attributed to large floodwater draining back into the river with high nutrient loads and hot weather. The combination of these factors contributed to Dissolved Oxygen, or the amount of oxygen available to living aquatic organisms, depleting and resulting in fish deaths.

IN OTHER NEWS:

Famous as the last stop for ill-fated explorers Burke and Wills, the tiny town of Menindee is the oldest European settlement in western NSW.

The Murray Darling Basin Authority decided to drain the Menindee Lakes in 2014 and 2017 to meet water demands downstream.

Multiple agencies across NSW and Commonwealth are continuing to work together on the response to the fish kill today.

Community members are encouraged to report any fish deaths or observations through the Fishers Watch phoneline on 1800 043 536.