Interim Independent Assessment of Fish Deaths release

21 February 2019

Agriculture and Water Resources Minister David Littleproud has released the Independent Assessment of Fish Deaths interim report.

“I’m pleased to hear Professor Vertessy say he thinks the Murray Darling Basin Plan is the right way to improve the ecology and environment in the Basin,” Minister Littleproud said.

“I also welcome the independent panel’s finding that the hot weather caused algal blooms and different temperatures between the top and bottom of the river, and that when that water mixed again due to cold weather, the oxygen came out of the water and ‘this was the primary cause of the fish deaths’.

“The panel was chosen independently by Prof. Vertessy and had access to all state and federal water managers. He’s extremely pleased with the team he was able to assemble.”

Work which will begin immediately following the release of the Interim Report:

  • Working with NSW to allow better fish movement through the system by installing fishways, fish ladders and removing obstacles between Menindee and the Murray, after the report found allowing fish to move between both systems will help recovery. These include:
    • Construction of a fishway at the Menindee Main Weir;
    • Removal of the Old Menindee Town Weir to allow fish to pass through;
    • Upgrading two existing fishways and creating a new fishway on the Lower Darling below Menindee Lake; and
    • Construction of a fishway around the inlet regulator between Frenchman’s Creek and Lake Victoria which is a major barrier to fish passage along the Murray River.
    • Creating an early warning system—an MDBA risk assessment matching where fish deaths have previously occurred with current factors such as water quality, weather and flow.
  • Funding the local community for aerators that the report found created refuge zones for fish.
  • Extending the Native Fish Demonstration Reach program to the Lower Darling; directly involving local and Indigenous communities and fisherman in habitat restoration and re-stocking.
  • Committing an extra $3 million into fish research and basin research.

“I welcome the findings of the independent panel and will begin work in response immediately, including on allowing fish to move more freely around the river system,” Minister Littleproud said.

“I know this is an issue Minister Blair is passionate about too—we need fish to be able to move around the river system. Fishways to allow fish to get around dam walls can really help here.

“Removing obstacles and creating fishways allows fish to go where conditions are better for them. As a recreational fisherman, I think this is fantastic. Fish are an important part of the food chain, providing food for birdlife and other animals.

“An alert system to trigger responses to reduce fish deaths before they happen is a great idea. I’m pleased our management of the system is improving through this process.

“The Coalition will provide $3 million to establish a Basin-Level monitoring and evaluation research program that will help to monitor the health of native fish stocks and the system as a whole.”

The interim report is published on the MDBA website.

Provisional findings:

Page 43:

“The fish deaths in the lower Darling were preceded and affected by exceptional climatic conditions, unparalleled in the observed climate record.”

“Runoff responses to rainfall in the northern Basin appear to have been more severely reduced during recent drought when compared to previous droughts, compounding the impacts on long-term water availability.”

“2017-18 flows on the Darling River at Bourke and Wilcannia were the lowest observed at those points over the last 20 years.”

Page 44:

“Hot conditions resulted in significant algal blooms in Lake Pamamaroo, the weir pools of the Menindee Main Weir and Weir 32.

“Continued hot conditions, combined with low flow, caused the weir pools to stratify. High fish numbers and algal biomass became concentrated in the epilimnion (surface water) and hypoxic or anoxic conditions developed in the hypolimnion (bottom waters).”

“Sudden reductions in air temperature and increased wind associated with storms caused water in the weir pools to suddenly de-stratify, resulting in low oxygen water throughout the water column and no escape for the fish. This was the primary cause of the fish deaths.”

Provisional recommendations:

Page 45:

Rec 1: “Undertake a risk assessment to identify parts of the Basin most at risk of fish death events. This should inform the development of early warning signals and crisis intervention plans.”

Rec 2: “Address gaps in water quality monitoring (dissolved oxygen, temperature, algae) at high risk sites across the Basin.”

Rec 4: “Support emerging initiatives within the Basin to remove barriers to fish movement, especially in locations with high stratification potential and locations that act as refuges during low flow events.”

Rec 5: Continue short-term efforts to prevent further fish deaths, through use of aerators and other technologies as well as fish translocations, noting these are short-term emergency measures and may not prevent additional fish death events if adverse conditions arise again.

Rec 9: “Progress implementation of the northern Basin Toolkit Measures, prioritising those that would support native fish population’s recovery (eg fish passage).

Rec 16: “Introduce real-time monitoring of diversions in the Barwon-Darling, to ensure protection of managed connectivity events.” (IE, protect environmental flows from harvest.)​