The National Carp Control Plan (NCCP), operating within the Fisheries Research and Development Corporation (FRDC), is developing a plan for potential release of the virus known as Cyprinid herpesvirus 3 (CyHV-3) to control invasive common carp, Cyprinus carpio, in Australian freshwater environments.
If the carp virus is approved for release, major carp mortality events are likely. It is necessary to better understand the potential ecological consequences of such events, and hence to inform clean-up strategies for carp biomass post-release. One potential risk is hypoxia or anoxia in the river system associated with microbial degradation of carp carcasses in accumulation hotspots. As carp inhabit a range of habitat types, including reservoirs, lakes, river and wetlands it is necessary to understand the oxygen dynamics in each of these habitats so that the risk can be adequately managed.
The aim of this project is to predict the impact of mass carp mortality on the dissolved oxygen concentration of wetlands, rivers and floodplain habitats. This requires assessment of how the key processes that affect oxygen in these different environments respond to changes in hydrologic flushing, temperature and other environmental attributes, and consideration of the likelihood of carp accumulation.
This modelling will be used to inform the cost-benefit analysis of the carp control program of FRDC, aid assessment of what ecological and infrastructure assets are at greatest risk, and determine whether flow can be used as a strategy to re-aerate water in the event of hypoxia.
This investigation was undertaken by the University of Adelaide and the University of Western Australia as a part of the research priorities for the National Carp Control Plan. While proposed biological control agents to reduce carp numbers may have positive impacts to aquatic ecosystems, it is possible that wide-spread carp mortality may present considerable risks to the quality of water in Australian wetlands and waterways that need to be managed. Specifically, large-scale carp mortality in aquatic systems will lead to the generation of:
- High oxygen demand
- A pulse of fish-derived nutrients
There is a concern that these impacts will generate water quality risks for humans and ecosystems associated with persistent low oxygen (hypoxia and anoxia), excessive levels of ammonia, and the build-up of cyanobacteria blooms, including the associated challenges of cyano-toxin release, and further deoxygenation during bloom collapse. This study modelled risks to water quality that could arise from carp inputs to a representative set of Australian waterways using data from field and laboratoty trials.