Coastal fish eDNA monitoring dataset now supporting Water Sharing Plan evaluations and replacements

The department’s Surface Water Science team has established a coastal fish environmental DNA (eDNA) monitoring program as part of the Environmental Outcomes Monitoring and Research Program (EOMRP). The program targets native fish species, including migratory and flow-dependent taxa, to better understand ecological responses to water management in coastal catchments.

Since 2021, the program has generated a substantial and growing dataset for the NSW coastal catchments, covering over 200 sampling sites in every major coastal river from the Tweed River in the north to the Towamba River in the south. This dataset is already being applied to support water sharing plan (WSP) evaluations and replacements. By linking species detections with flow conditions and water management rules, the program supports the assessment of ecological outcomes, helping us to evaluate whether existing rules are achieving their intended environmental objectives.

As the dataset continues to expand, we expect it to play an increasingly important role in the WSP remake process, environmental water requirement assessments, and in answering research questions such as:

• What flows are required to allow fish to migrate to and from the estuary to complete their lifecycles
• How do habitat quality and river flows affect fish communities throughout a river?
• How will low flows and climate change impact fish communities across the NSW coast?

Some interesting findings from the program so far include:

• Sea mullet migrating 400 km upstream of the tidal limit on the Hunter River and 200 km on the Clarence River
• Detections of endangered species such as Australian grayling, Eastern freshwater cod and Southern purple spotted gudgeon
• Several rivers found to be completely free of invasive fish species. Our data has been shared with NSW Department of Primary Industries and Regional Development Aquatic Biosecurity.