More than 100,000 native fish have died at Lake Menindee in western NSW following last week’s record heatwave. This marks the first significant fish kill at the lake since 2023. Luke Driscoll, head of the Barkandji Native Title Group, stated that at least 100,000 bony bream have washed ashore, and he suspects many more have sunk to the lake’s bottom.
Residents nearby, especially in Sunset Strip, are dealing with an unpleasant smell. Even those located three kilometers away from the lake report a strong odor. Lake Menindee is part of a system of nine lakes southeast of Broken Hill.
This incident mirrors the mass fish kills that occurred in 2019 and 2023. Extreme weather conditions—like shallow waters heating up—caused tens of millions of fish to perish back then. Disturbingly, last week, Barkandji rangers found hundreds of dead fish downstream in the Darling-Baaka River; most were introduced carp. Fortunately, by the weekend, the situation seemed to stabilize.
The drastic temperature changes during the heatwave added to the stress on local fish. For example, in Broken Hill, the temperature dropped from 40°C to 22°C within an hour. Timing is crucial; rapid changes can be deadly for fish like bony bream, making them unable to handle such shocks.
Professor Fran Sheldon from Griffith University explains that the main cause of these mass deaths is low oxygen levels in the water. While good water flow has allowed fish populations to grow, drying rivers mean they’re forced into smaller, less hospitable areas. This concentration not only leads to overcrowding but also worsens oxygen depletion.
Moreover, blue-green algae blooms can further diminish oxygen levels at night, stressing fish even more. Recent satellite imagery and water tests confirmed the presence of these harmful blooms in Lake Menindee.
Driscoll highlights the ongoing struggle with the health of the river and lakes, stating they have been “sick” for quite some time. He added, “Seeing the fish die—especially species like the bony bream that hold cultural significance—hurts the community.”
Mass fish deaths can occur in various environments, not just lakes and rivers. For instance, over four million salmon died in Tasmania in 2025 due to heatwave conditions. Similarly, thousands of fish in Western Australia washed up after a marine heatwave.
While some fish populations may recover, many are still vulnerable to ongoing climate challenges. Driscoll and his team are now working closely with local agencies for cleanup efforts, aiming to restore the health of Lake Menindee for the local community.
For more detailed insights on environmental issues, you can keep track of developments through the NSW Environment Protection Authority.
