Mass Fish Kill at Inland Lake Sparks Investigation in New South Wales

The fisheries department in New South Wales is examining a significant fish die-off at an inland lake in the states western region.

Aquatic ecologist Adam Kerezsy first observed a few dead fish at Lake Cargelligo and nearby Lake Curlew two weeks ago. Since then, the situation has worsened, with thousands of small silver fish now washing up along the shores of the lake near the township, approximately 200 kilometers west of Parkes.

The event appears to have affected only one species, the bony bream or bony herring, which is among the most common native fish in the Murray-Darling Basin system. This species plays a vital role in the ecosystem, serving as prey for larger fish like Murray cod and golden perch, as well as water birds.

While Kerezsy is uncertain about the exact cause, he suspects it could be linked to recent weather conditions, such as a cold snap or low water levels. In June, WaterNSW, which manages Lake Cargelligo, announced plans to undertake additional work to repair flood-damaged and aging embankments. Since then, the water authority has lowered the lake’s water levels from about 57 percent to 53 percent capacity, its lowest point since March 2024. The lake is expected to remain at or below this level for approximately six months while infrastructure repairs are carried out.

A WaterNSW spokesperson stated they are aware of the fish deaths at Lake Cargelligo and will support the Department of Primary Industries Fisheries in any investigation. The event has so far affected only the bony bream species, which is a common native in the region.