Reading the river: the smart way to help protect Gulf wildlife
When monsoonal floodwaters swept across Queensland's Gulf-Savannah region in the 2022–23 wet season, the damage wasn't confined to areas in the floods’ path.
Beneath the surface of some of the state's most remote river systems, the ecological balance was also at risk.
Scientists needed a smart way to find out what was happening beneath the waterline.
With the answer hidden in the water, Queensland’s Department of Environment, Tourism, Science and Innovation (DETSI) and Department of Local Government, Water and Volunteers partnered with James Cook University’s marine science research group TropWATER to launch an environmental DNA, or eDNA, survey of three Gulf waterways.
eDNA works by collecting water samples and analysing trace genetic material such as scales, mucus, and excretions that animals leave as they move through their environment.
This non-invasive, relatively affordable technique avoids the need to physically capture or disturb wildlife and is ideal for vast, hard-to-access river systems like those in the Gulf of Carpentaria.
The project focused on three species of fish, for two very different reasons.
Ensuring the protection of the species is vital for both the Largetooth sawfish, one of the world's most critically endangered fish, and the Northern snake-necked turtle which holds deep cultural significance for Aboriginal and Torres Strait Islander communities across the Gulf.
Mozambique tilapia was targeted as it’s an invasive freshwater fish that has already spread across much of Queensland's east coast, outcompeting native species and disrupting ecosystems.
Major flooding events can act as a highway for invasive species and the 2022–23 event raised concern that tilapia may have used the floodwaters to push further into the Southern Gulf.
Researchers selected eight sampling sites across the Leichhardt, Flinders, and Norman rivers systems.
Samples were collected across two rounds, initially in October 2024 during the dry season, and again in May 2025 following the wet season, to capture any seasonal variation in species movement and distribution.
Significant results included the detection of Largetooth sawfish in the Leichhardt River during the May 2025 sampling round and Northern snake-necked turtles in the Norman River during the October 2024 sampling.
Importantly, Mozambique tilapia weren’t detected at any of the eight sites, suggesting the flooding didn’t result in them spreading into new territory across the Southern Gulf.
Beyond the individual findings, the project created a baseline dataset for these species which can be used to track changes in distribution over time and monitor the ecological impacts of future weather events.
eDNA sampling offers a scalable, evidence-based way to identify critical habitat, flag pest invasions early, and inform where resources should be focused.
The project was supported through the jointly funded Commonwealth–State Disaster Recovery Funding Arrangements (DRFA) Environmental Recovery Program established following the Northern and Central Queensland Monsoon and Flooding, 20 December 2022 - 30 April 2023 event and administered by DETSI.
