Murray cod recruit in April 2017. Photo: NSW DPI Fisheries and Qld DAF
Macrophyte beds in the Dumaresq River. Photo: CEWO
Monitoring, Evaluation and Research
Monitoring and evaluating the use of water for the environment is helping to build knowledge about the best way to improve the health of the rivers and wetlands of the Basin, based on what works and what doesn’t work.
The Commonwealth Environmental Water Office (CEWO) works with Basin states, the Murray-Darling Basin Authority, scientists and the local community to build this knowledge. There are a number of programs currently underway in the Border Rivers.
To build on the body of ecological knowledge of the Border Rivers, and inform future adaptive management, the Commonwealth Environmental Water Office funded two projects involving NSW and Queensland state agencies. The first project assessed native fish populations and responsiveness to environmental flows in the Macintyre, Severn and Dumaresq Rivers from 2015 to the end of 2018. The second project involved mapping key fish habitat along the Dumaresq River and is now complete.
Some recent examples of learnings include:
- Murray cod are found throughout the upper Border Rivers. There was evidence of many young fish (recruits) in the Dumaresq and Macintyre rivers, possibly due to natural flows.
- Freshwater catfish are also found throughout the Border Rivers, and small-bodied fish (purple-spotted gudgeon and olive perchlet) were found in the Dumaresq and Macintyre rivers. These populations may be particularly important for re-colonising other rivers when there is flow connection.
- No young Murray cod were found in the Severn (NSW) River, with the last possible recruitment estimated to have occurred in 2013 (same season as NSW stimulus flow provided a priming pulse to the system in late winter).
- The Severn River has a distinctive fish community including silver perch but shows a lack of recruitment for all species and an absence of small-bodied fish.
- There was very limited evidence of golden perch in the Border Rivers (one stocked individual detected) and no recruitment. There may be silver perch spawning in the Severn but there is little evidence of recruitment (silver perch not recorded in either the Dumaresq or the Macintyre).
- Low flow events in the Dumaresq, including water for the environment released in late 2017 inundated a large proportion of key habitat features in the system and contributed to improving overall fish condition in the Dumaresq and Macintyre rivers in early 2018. Similarly, the release of water for the environment in the Severn in late winter 2017 to prime the system and support movement, habitat inundation, productivity, and recruitment helped lead to an improvement in overall fish condition in late 2017 and early 2018.
- The release of water for the environment in the Severn and Dumaresq rivers during late winter/early spring in 2017 also contributed to specific responses from target species, including:
- Increased numbers of Murray cod young-of-year in both the Macintyre and Dumaresq systems.
- Increased freshwater catfish nests and recruits in both the Dumaresq and Severn rivers, with larval trapping in the Severn River confirming successful breeding with freshwater catfish larvae caught.
- The abundance of unspecked hardyhead and Murray-Darling rainbowfish increased in seasons following the release of water for the environment.
- The release of water for the environment during the sampling period also benefited carp gudgeon, and although populations for this species were highly variable, improved spawning and recruitment responses were observed following flow events.
- There was also an absence of carp recruits over the 4 years of monitoring; suggesting conditions were not suitable for the breeding and/or recruitment of this species during the sampling period.
- Important fish habitat, like the location of undercut banks (Murray cod nesting sites) and woody snags, occur throughout the Dumaresq River and have been mapped. Also we have a better understanding of how much water is needed to inundate macrophyte beds so smaller fish can lay eggs.
The Dumaresq aquatic habitat mapping report and Fish and Flows Intervention Monitoring in the Border Rivers are both available on our webpage.
The outcomes from these monitoring activities are used to inform portfolio management planning and adaptive management decision-making.
Monitoring information is also provided by state governments.