The NSW Government today released its interim report on the fish kill which occurred on December 15, 2018 and a further larger kill on January 6, 2019 in the Menindee town weir pool section of the Lower Darling River near the Menindee Lakes.
Deputy Premier and Minister for Regional NSW, John Barilaro said the fish kill was unprecedented and a major ecological disaster.
“We know there is anger and frustration following this incident but we are working hard to support Far West communities with practical measures.
“We’ve brought in six aerators which may provide small areas of fish refuge in the hope we can mitigate any further devastation to the ecosystem but we accept that this is not a silver bullet.
“The interim report today shows that drought has played a significant role and without rain the outlook for our communities, not just in Menindee, but right across NSW is dire. That’s why we’ve already committed more than $1 billion in drought funding, and stand ready to do more.”
Mr Barilaro announced that NSW Cross Border Commissioner, James McTavish, would be immediately appointed as Regional Town Water Supply Co-ordinator, to oversee the work already done to ensure water supply and quality in towns and communities all over NSW.
“This could include the provision of funding for water carting to towns at risk of low water supply, or the provision of bottled or chilled water to schools or health care facilities in these communities”, Mr Barilaro said.
Minister for Primary Industries, Niall Blair said the interim report allows the Government to look at the best available science to protect and recover native fish populations when conditions eventually improve.
“We understand how devastating this event has been on the community of Menindee and Broken Hill and we are doing everything we can to assist now and prepare for potential further kills this month.
“DPI scientists consulted with Murray-Darling Basin experts in biochemistry and algal ecology and found that both fish kills were likely to have been caused by several related and compounding factors resulting in low dissolved oxygen levels in the river.
“Our scientists have concluded that hundreds of thousands of fish were affected including Bony Herring, thousands of Golden Perch and Silver Perch, dozens of Murray Cod and a small number of Carp.”
The report identified a number of factors that contributed to the fish kills including: ● High temperatures and low or no flow conditions led to thermal stratification. A warmer surface layer of water sat above a cooler deeper layer of water with very low dissolved oxygen. The warmer upper layers were conducive to blue green algal blooms.
- Rainfall on 15 December 2018 and an associated drop in temperature appears to have mixed water layers and potentially disrupted surface algal blooms, which contributed to very low oxygen throughout the water column.
- Substantial drops in daily temperatures from 46 degrees to 28 degrees on 4 and 5 January 2019 and associated cold fronts passing through the region caused layers of water with different dissolved oxygen levels to mix, reducing the overall dissolved oxygen available.
- High algal content in stock and domestic flow releases drawn from Lake Pamamaroo, which increased oxygen demand and consumption, further reduced dissolved oxygen available to fish.
Investigations also found numerous fish deaths occurred in the Lower Darling River and Menindee Lakes between 2002 and 2004 during the millennium drought.
Mr Blair said the Government is on high alert for future potential fish kills right across NSW.
“We know that if weather conditions don’t improve this summer, limited flows, algal blooms and thermal stratification will continue to persist in the Lower Darling,” Mr Blair said.
“Our scientists from DPI have collected otoliths (ear bones) from the Murray Cod, Golden Perch and Silver Perch to improve their knowledge of the species and their future management. Preliminary analysis of the otoliths has shown that the four largest Murray Cod collected, the biggest of which was 127cm, ranged from 17 to 25 years old.
“Further work will be done on the otoliths in the near future to determine where these fish were spawned and how long they have been residents of the Lower Darling, providing important information on the recovery potential for the system.
“Today, I have also written to the Premier on the back of this report and requested approval for the Natural Resources Commission to bring forward their scheduled review of the Barwon-Darling Water Sharing Plan, to commence immediately.
“I want to work with other States and Federal agencies to deliver improved management for protecting and enhancing our native fish populations in the Murray Darling Basin including better water quality and fish monitoring, increased restocking and improving fish passages to allow fish to move, feed and breed.”
