Thousands of dead fish discovered at Menindee Lakes

Thousands of fish – mostly carp – have washed up dead in the water system. (ABC Broken Hill: Bill Ormonde)

Thousands of dead fish have been discovered at the Menindee Lakes in the New South Wales Far West.

With the major "fish kills" of 2019 still fresh in mind, locals and officials are on edge.

The Department of Primary Industries (DPI) and Fisheries have been quick to smother any talk of another such event, which was caused by poor river health, among other factors.

A DPI spokesperson said there was a simple explanation for the latest incident.

"These deaths are likely related to trauma from fish passing through inlet/outlet regulators, or aggregating directly downstream of structures (like a weir) and becoming injured in the highly turbulent water," they said.

A number of residents contacted by the ABC declined to comment but agreed with the DPI's assessment of the situation.

The fish that have washed up dead are nearly all carp. (ABC Broken Hill: Bill Ormonde)

Not blackwater

In the past month or so concerns have been raised about toxic blackwater and low oxygen levels in the river system.

These issues can occur when floodwater stagnates and deoxygenates, suffocating fish.

There has been only one recent reported sighting of a small fish kill – potentially caused by blackwater – in Tilpa, 152 kilometres upriver of Menindee, more than a month ago.

Although blackwater has been spotted in the area around Menindee, it is not believed to have caused deaths of the mostly juvenile fish.

Despite repeated requests, the DPI declined to tell the ABC if and where it tested for oxygen levels in the river.

If there is a silver lining, it is that many in the community are happy to see a few less environmentally destructive carp in the river system.

The DPI spokesperson encouraged community members to "report any fish deaths or observations through the Fishers Watch hotline on 1800 043 536".