This statement provides an overview on carp in the Murray-Darling Basin, current efforts to manage the species and the role of Commonwealth environmental water.
- Carp are an abundant invasive fish species that has been contributing to environmental degradation across the Murray-Darling Basin since the 1960s.
- The introduction of a biological control mechanism to tackle the pervasive carp problem may be an important tool complement existing natural resource management and environmental watering programs that are helping to build the resilience of native fish populations.
- Water for the environmental aims to re-establish natural variable river flows by reconnecting Basin rivers with floodplains and wetlands and creating conditions to support healthy populations of native fish.
- Carp populations benefit much more from natural flooding events, than small, targeted environmental watering. Monitoring of water for the environment deliveries has found native fish are spawning and recruiting in response to delivery of water for the environment which creates more competition for carp.
What are carp?
Carp are an invasive fish species that are widespread and abundant across the Murray-Darling Basin. They are adaptable and have biological features that allow populations to increase rapidly. Carp now account for up to 90% of fish biomass in some areas of the Basin.
Why are carp an issue in the Murray-Darling Basin?
Carp contribute to environmental degradation in the Basin. Reported impacts include reduced water quality, river bank damage and they may contribute to algae blooms. The increased spread of carp and its impact on freshwater habitat has come at the expense of native fish species and aquatic vegetation.
What is being done to manage carp?
The Australian Government is investigating a long-term biological control plan to reduce the impact of carp on our waterways. More information about the National Carp Control Plan is available here: National Carp Control Plan - DAFF (agriculture.gov.au)
The combination of a biological control mechanism and an improved environmental flow regime could benefit native fish across the Murray-Darling Basin. Delivery of water for the environment continues to be important to increase native fish populations and target any reduction in carp numbers.
A range of activities are being implemented to support carp management. For example, carp exclusions screens installed at many wetlands across the Basin.
How is carp considered in the management of Commonwealth environmental water?
Analysis of historical records show that carp populations benefit much more from natural flooding events, than from smaller volume, asset-targeted environmental watering actions. The Commonwealth Environmental Water Holder's water management planning is a very considered and managed process, involving a comprehensive risk assessment. Every watering event evaluates if the benefits to native species will outweigh the benefits to carp.
If the benefits to carp are found to outweigh the benefits to native species, we do not deliver water.
All environmental watering events aim to benefit native species over carp. Carp can take advantage of environmental flows, but this does not diminish the importance of our efforts to improve the environmental conditions that favour native species, in particular re-establishing flows that provide the breeding conditions and feeding opportunities that native fish rely on. We know that using the right volumes of water at the right time and in the right locations improves environmental conditions for native fish, which unlike carp, have specific seasonal flow requirements for breeding and feeding.
How is Commonwealth environmental water benefiting native fish populations?
Monitoring of Commonwealth environmental water delivery is showing that native fish are recovering in response to the delivery of water for the environment, providing greater competition for carp in our rivers and wetlands.
Water for the environment is also being used to improve the overall resilience of the ecosystems – that is, ensuring the rivers and wetlands are in good condition to promote diverse and healthy native plants, fish, waterbirds and other animals.