Murray River: Investigators blame fish kill on water quality

The Department of Water and Environmental Regulation have completed an investigation into the deaths of approximately 500 bream and herring in the Murray River last month.

The fish were found in the Murray River between Ravenswood and South Yunderup on June 25.

An autopsy of the dead fish undertaken by fish health experts at the Department of Primary Industries and Regional Development revealed that the fish had suffered stress from exposure to poor water quality.

The department’s Peel region manager Bob Pond said the autopsy results were consistent with testing of water samples taken from the investigation area.

“Evidence suggests a heavy organic load associated with recent rainfall, combined with strong outgoing tides, led to a deterioration in water quality,” he said.

Mr Pond said the investigation process was now complete.

The investigation comes after another mass fish death on the Murray River in the South Yunderup area in May, which confirmed nearly 30,000 fish had died in the catchment as a result of poor water quality.

University of Western Australia aquatic ecology expert Anas Ghadouani urged the public and the government to “ask harder questions” in the wake of May's “catastrophic” fish kill.

“It’s a bit like saying what’s the cause of death? Well, their heart stopped,” he said.

“Different species of fish don’t all hang out in the same place. They are not sensitive to the same level of oxygen. So I don’t buy the one explanation. It is simplistic.

“And why are these systems at this level that a rain could wash things into the river and cause this much damage? This is serious damage and a serious incident; multiple species, large numbers.

“Thirty thousand fish dying is not an ‘incident’. It is not business as usual. It is a reminder that the system is fragile.”

Professor Ghadouani, executive director of the Cooperative Research Centre for Water Sensitive Cities, said he was not criticising the government, but gave the analogy of the need to go to a specialist when a blood test at the GP showed a major abnormality.

“The official line is we are monitoring, we are measuring,” he said.

“Monitoring doesn't cut it. A better understanding of the systems is needed. They are doing it by the book but we need more than a textbook reaction. We need serious attention.”

The department encouraged people to report any fish deaths to the FishWatch 24 hour hotline on 1800 815 507.