Carp herpes virus (CyHV-3) is arguably the most realistic biocontrol agent for the pest species Cyprinus carpio in Australia. However, risks and benefits of use must be carefully evaluated. Low dissolved oxygen and high oxygen concentrations are two potential risks from mass carp mortality. Impacts of carp decay were examined in bucket experiments, 720L ponds, 1000L mesocosms, and in a 2.5ha wetland. Oxygen depletion was strongly accelerated with increased temperature. Mesocosm experiments revealed that high phytoplankton productivity in response to nutrient enrichment can lead to supersaturated oxygen concentrations during the day, but the additional oxygen demand from decaying carp can lead to periods of anoxia. Six tonnes of dead carp were added to a 2.5ha wetland to simulate a mass mortality event. Biological oxygen demand increased to 80 mg/L and periods of anoxia were observed. Results from these trials are being incorporated into a coupled hydrological and biogeochemical model to predict oxygen and biogeochemical response to carp mortality in different aquatic habitats around Australia. Carp density, flow conditions, and temperature are determinant factors in how carp mortality associated with CyHV-3 will affect the River Murray, reservoirs, and wetlands. Key environmental and infrastructure assets may need protection against water quality challenges.