Aerators installed to help limit fish deaths

A method used in the wake of the 2016 Murray River mass fish deaths is set to be used again in the Darling River to save native fish populations.

Four solar-charged aerator machines will be installed in the Lower Darling region after an estimated one million fish died at Menindee two weeks ago.

NSW Regional Water Minister Niall Blair has admitted the aerators, which will also be installed at Lake Keepit near Tamworth and Lake Burrendong near Dubbo, are a ‘‘Band-Aid solution’’.

‘‘Nothing will stop this fish kill unless we get proper river flows and levels in our dams back to normal,’’ he said.

Charles Sturt University academic Professor Robyn Watts, from the Institute for Land, Water and Society, said comparisons could be drawn between the events of 2016 and the recent mass fish deaths in NSW.

‘‘We can draw on the experience of a hypoxic blackwater event in the Murray River in 2016, where a lot of fish died due to low dissolved oxygen (DO) concentrations following a large flood. While this event was not caused by an algal bloom (it was due to high concentrations of dissolved carbon in the water) the outcome of low DO and subsequent fish deaths was similar to what is currently occurring in the Darling River,’’ Prof Watts said.

Prof Watts said in 2016 local land owners and community members decided to take action and installed aerators to create fish refuges so that small populations of fish and other freshwater animals could survive.

‘‘Water managers were also able to call on water from nearby irrigation canals to provide environmental flows and create small refuges with higher dissolved oxygen. There is evidence that these actions helped a small number of fish and other aquatic organisms to survive. Whilst these local actions did not prevent further fish deaths occurring outside the created refuges, the individual fish that did survive will have contributed to the recovery of the river ecosystem in the years following the event,’’ he said.

‘‘It needs to be understood though, that the lack of water in Menindee Lakes to provide flows will make it more difficult to create small refuges in the case of the Darling River.’’

Despite this, Prof Watts said there was an opportunity for locals along the Darling River to adopt a strategy similar to that undertaken in 2016.

‘‘During previous hypoxic events the community felt powerless and were devastated when they observed fish dying. However, during the 2016 hypoxic event they rallied around and installed these aerators that had the potential to make a small difference.

‘‘Local actions such as these could be initiated in other parts of the Darling River before the algal bloom spreads further and DO concentrations drop too low. It is essential to initiate actions before the algae bloom spreads to these downstream sites or new outbreaks arise elsewhere,’’ Prof Watts said.