Doubts cast on carp virus plan, delayed until at least 2021

The Lower Murray will be spared from tens of thousands of tonnes of dead fish for a while longer.

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A year ago, the towns along the Lower Murray might have expected to be up to their gills in dead carp by now.

But a controversial plan to release a carp-killing virus into the River Murray has now been delayed until at least mid-2021.

What’s more, recent research has raised serious doubts about whether it will ever happen at all.

Carp plan will be delayed until mid-2021

The last progress report from the National Carp Control Plan, published in December, said the plan was “being finalised” and would be delivered to the federal government within weeks.

But FRDC managing director Patrick Hone told a parliamentary committee last month that the plan would not be finalised until the middle of next year.

It was to have been a summary of more than three years’ work by scientists around the nation, an answer to one of the great environmental challenges of our time.

Specifically, scientists at the Fisheries Research and Development Corporation were asked to assess whether a virus – cyprinid herpesvirus 3 – could be used to bring the pest fish under control.

Releasing it would cause tens of thousands of tonnes of dead fish to wash up along the banks of the River Murray and Lower Lakes within days.

In the longer term, it would theoretically improve water quality and restore the Murray-Darling Basin’s ecosystem to a healthier state.

A version of the plan had been finished in January, Dr Hone said, but the FRDC had decided to go back and do extra research into the risks associated with it.

Specifically, they wanted to double-check that native fish could not be infected, and confirm the time of year that would be best for releasing the virus.

“It’s not just about the science; it’s also about the perception of the science,” he said.

“We as scientists are pretty black and white sometimes, but we understand that people want additional information.

“So we’ve gone out and we’re doing that.”

The extra research had then been slowed by COVID-19, he said.

Risks would outweigh benefits, researchers find

Meanwhile, on the other side of the world, researchers at the Universities of Exeter and East Anglia have found carp would quickly become immune to the virus even if it were released.

Researcher Jackie Lighten said carp needed to be controlled around the world, as they muscled other species out of river ecosystems by uprooting vegetation and stirring up sediment.

But modelling similar to that used to predict the spread of COVID-19 had shown that releasing a carp virus would would only cause an ecological catastrophe, he said.

“Viral biocontrol ... is unlikely to reduce carp numbers in the long term,” he said.

“Our modelling shows that even under the most optimal conditions for biocontrol, populations quickly recover.

“Releasing (the herpesvirus) carries significant risks to human and ecosystem health which likely outweigh the benefits.”

Lead author Katie Mintram said the world was watching with concern as Australia decided how to proceed.

“There needs to be an extremely high level of diligence and scientific rigour in applying a biocontrol method because it will set the standard for global biocontrol in the future,” she said.

She doubted that the public would be enthusiastic about releasing a virus in light of COVID-19, which had shown that “viruses are difficult to predict and almost impossible to manage”.

Instead, the researchers suggested reducing the amount of water extracted from the Murray-Darling Basin for “thirsty” crops such as cotton.

Meningie carp fishers have suggested commercial fishing as part of the solution, too.

Where are we now, then?

When the National Carp Control Plan is completed, it will be up to federal, state and territory ministers to decide whether to go ahead with it.

Parliamentary approval would also be required.

A spokesman said the state government was waiting on more detailed information before deciding whether to endorse the release of the carp virus, or any other control method.

Murray Bridge News is seeking comment from federal Agriculture, Drought and Emergency Management Minister David Littleproud.

At any rate, it looks like it will be another six months before the tourism and fishing industries, and those of us living along the river, get much more certainty about the future.

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