The state government is keeping a close eye on a fish kill event occurring over the NSW border in the Darling River near Menindee where large numbers of Bony Herring are being affected.

A fish kill is a sudden and unexpected mass mortality of fish or other aquatic organisms usually caused by low dissolved oxygen levels (hypoxia) in the water. Native fish, such as Murray Cod and Golden Perch, may also be affected.

Minister for Climate, Environment and Water Susan Close says that to date, no fish kills due to low oxygenated water, commonly referred to as ‘blackwater’, have occurred in South Australia.

“Whilst it is unlikely that this event will result in fish kills occurring in South Australia, they are common throughout the Murray Darling Basin and are often associated with hypoxia.

“Both DEW and PIRSA are keeping a close eye what is happening upstream to ensure South Australia is prepared in the event of any blackwater events in our state.

“We will continue to keep river communities informed of any updates to ensure they are prepared for any potential blackwater events.”

The NSW event is likely caused by low dissolved oxygen levels in the water in areas where flood waters are receding. 

High air temperatures increase the risk of further reductions in dissolved oxygen and the potential for further fish kill events.

The state government expects that the lower dissolved oxygen water from the Darling River will start to reach SA in the coming week. 

It says this water from the Darling River will have been mixed with the higher oxygen water from the River Murray, such that the water quality outcomes are not expected to be as severe in SA.

The Department of Primary Industries and Regions (PIRSA) monitors the dissolved oxygen levels of the River Murray using the Department for Environment and Water data loggers located along the river. 

PIRSA is the lead agency for the coordination of any large-scale fish kill clean-ups, if they occur in South Australia due to flooding.

The Department of Environment and Water, SA Water and the Murray Darling Basin Authority are assessing if there is opportunity to use river infrastructure such as Lake Victoria to provide some mitigation, should this be required. 

Clare Scriven is the Minister for Primary Industries and Regional Development. 

She says that there is currently no blackwater present in the South Australian section of the River Murray.

“Clean-up operations mitigate the risk of adverse socio-economic, human health and environmental impacts. 

“The need for clean-up works is assessed on a case-by-case basis and will consider factors such as the numbers of dead fish, and proximity to towns and tourist attractions.

“PIRSA has an Operational Response Plan in place and coordinates clean-up operations and the disposal of fish carcasses for large-scale fish kill incidents and continue to monitor the potential to impacts to SA on a regular basis.”

 PIRSA encourages members of the public to contact FISHWATCH on 1800 065 522 if they notice anything unusual along the river