08-07-2025
NSW authorities investigate mass fish kill event at Lake Cargelligo
The New South Wales fisheries department is investigating a mass fish kill at an inland lake in the west of the state.
Aquatic ecologist Adam Kerezsy started seeing small numbers of dead fish at Lake Cargelligo and nearby Lake Curlew a fortnight ago.
It has since escalated, with thousands of the small silver fish now covering the banks of the lake near the township, about 200 kilometres west of Parkes.
The NSW Department of Primary Industries and Regional Development (DPIRD) said in a statement it was "aware of a fish kill event in Lake Cargelligo which has affected a large number of bony herring".
It said it was taking the matter "extremely seriously" and had launched an investigation into the cause.
It said DPIRD Fisheries would be working with WaterNSW and other agencies to conduct site investigations and sampling.
The event appears to have only affected a single species, the bony bream or bony herring, which is one of the most common natives in the Murray-Darling Basin system.
It is consumed by other species including Murray cod, golden perch and water birds.
Dr Kerezsy, who lives at Lake Cargelligo, said it was unusual for the area, with the last mass bony bream die-off around 2010.
While he was uncertain on the cause, he suspected it could be linked to a recent cold snap or low water levels.
"Maybe when you get a combination of a cold spell and not much water … that might be enough to knock them," he said.
"It might demonstrate something we didn't know about how these animals die off in the winter."
In June, WaterNSW, which manages Lake Cargelligo, announced it was starting more works to improve flood-damaged and old embankments.
Since then, the water authority has dropped the lake's water levels from approximately 57 to 53 per cent capacity, its lowest point since March 2024.
It is set to remain at or below that level for about six months while the infrastructure is repaired.
In a statement, a WaterNSW spokesperson said it was "aware of the fish deaths at Lake Cargelligo and will support DPIRD Fisheries in any investigation undertaken as required".
