NSW Department of Planning, Industry and Environment report to the Commonwealth Environmental Water Office
About the document
The ~500-km long stretch of the Lower Darling-Baaka River supports a valuable native fish community. Prior to 2000 there were near-permanent flows to the Lower Darling-Baaka River, however in 2015-2016 and 2018-2020 there were prolonged cease-to-flow events. Major fish deaths occurred in 2018-20 at Menindee and along the river.
From September 2020 through to January 2021, water for the environment was delivered to the Lower Darling-Baaka River for the first time since the fish deaths. The fish response to the flow was monitored by a consortium team of fisheries scientists to understand the impact of the fish deaths on the native fish population, provide advice to adaptively manage the flows in real time, understand the response of native fish populations to the flow and to inform future environmental releases.
The environmental flow supported a strong Murray cod breeding event by increasing the river flow through the breeding season to maximise nesting sites under snags, rocks, and undercut banks. The environmental flow also inundated beaches and benches to increase food (plankton) for tiny Murray cod larvae, and supported migrations of juvenile golden perch from the Menindee Lakes into the Lower Darling- Baaka. These juveniles were spawned in the northern Murray-Darling Basin in early 2020 and were detected in the Menindee Lakes ‘nursery’ habitat in large numbers. The environmental releases supported young fish dispersing into the Lower Darling-Baaka River, providing a valuable opportunity to boost the Lower Darling-Baaka population and potentially broader southern Murray-Darling populations.
These results of the monitoring project, along with analyses of Murray cod genetics, are detailed in the monitoring report.