• Carp are an invasive species, causing mass damage to the ecosystem. (AAP)Source: AAP
International researchers and local experts describe the federal government's plan to release Kopi Herpesvirus into the Murray-Darling Basin as "madness", saying the science is still out on its safety and effectiveness.
Rae Johnston

20 Oct 2020 - 11:54 AM  UPDATED 20 Oct 2020 - 11:54 AM

Researchers say plans to release a virus to reduce numbers of invasive Common Carp in Australian waterways should be abandoned. 

The plan includes the release of Koi Herpesvirus (KHV) into the continent's largest freshwater supply, the Murray-Darling, to kill non-native carp.

The $15 million National Carp Control Plan (NCCP) was first proposed in 2016 and delivered to the federal government in January 2020. 

A new study by scientists in the UK showed how carp evolve resistance to the virus and has dubbed the plan "madness".

The carp problem

Carp are an abundant invasive fish species, causing damage by uprooting vegetation and increasing sediment in the water and this has a major impact on native species in the ecosystem. 

The Murray-Darling has experienced issues with the pest species since the 1960s.

Kamilaroi man and hydrogeologist Bradley Moggridge told NITV the carp "just dominate."

"It's a national issue that we need to fix because it's a pest species, it's been introduced. It's excelled - it loves low flows, murky waters. It outcompetes natives in some places," said Mr Moggridge.

"They can wreak havoc and be a huge part of the biomass in any of our rivers."

The virus problem

Koi Herpesvirus was first used in European fish farming in the late 1990s and has killed millions of carp globally. The NCCP says releasing Koi Herpesvirus could help manage carp numbers in the Murray-Darling Basin.

"The introduction of a biological control mechanism to tackle the pervasive carp problem will be an important complement to existing natural resource management and environmental watering programmes that are helping to build the resilience of native fish populations," the plan reads. 

There is no argument that carp control is needed – but the study, and other experts, say releasing KHV is not the way to go. 

"Viral biocontrol is highly questionable and, as our study shows, it is unlikely to reduce carp numbers in the long term," said Dr Jackie Lighten, of the University of Exeter.

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

"Releasing KHV carries significant risks to human and ecosystem health, which likely outweigh the benefits, and we have previously urged further detailed research to avoid an unnecessary ecological catastrophe.

"Based on our findings, we believe the plan to control Australia's carp with KHV is dead in the water."

Mr Moggridge agrees, telling NITV "the science is still out" on the impacts of KHV.

"If the [Koi Herpesvirus] is introduced, you've got to make sure that it doesn't get into native fish. That it doesn't get into other species that eat the native fish - the birds and the predators. And then it doesn't get into humans when we eat the native fish."

"Because the virus is so clever, they've been around forever, they adapt and evolve so quickly. I think that's the challenge with science - is it going to be enough to knock [the carp]out, and keep them knocked out?"

Mr Moggridge sat on the Native Fish Recovery Strategy Technical Committee. He then assisted with consulting around the Koi Herpesvirus process. 

"There were a lot of concerns around transparency and what's happening, and it's gone all quiet. Barnaby Joyce pushed it hard when he was water minister, but the science wasn't ready."

Two years ago, Mr Moggridge attended a meeting of the Australian Freshwater Farm Society, which is linked to the Australian Society of Limnology (rivers). 

"There was a massive session on the carp," said Mr Moggridge. "There were papers for the [Koi Herpesvirus], and there were papers against it."

"There's still a lot of science to be done, and I think that's a little bit off. Barnaby was pushing hard to get it out there, but it could have been detrimental to the whole Murray Darling system, the whole ecology could have collapsed."

Dr Lighten said if the current global Covid-19 pandemic has reminded of anything, it's that viruses are hard to predict and manage.

"It is madness that the release of a high pathogenic virus is being considered as one of the first steps to restore a damaged and fragile ecosystem."

Missing research

Dr Lighten said the NCCP was leaving out important areas of research from its work, like the creation of a computer simulation, a model, to work out if the virus would kill the fish with resistance to KHP. Genetic resistance to KHP exists in carp all around the world. 

Dr Katie Mintram from the University of Exeter said this modelling is "essential for risk assessment."

"We built a simulation model which allowed us to examine realistic interactions among carp, virus and disease resistance, to estimate how long it would take carp populations to recover - even if 95 percent of them were wiped out.

The modelling showed populations of carp infected with KHP recovered quickly, because they breed so quickly. Even in tests with carp that have no resistance to KHP, they evolved resistance. 

The researchers said it was "worrying" that the NCCP "chose to ignore" this vital method of research. 

Improving the health of the waterways

Dr Lighten said the researchers recommend the Australian Government "takes bold steps to significantly improve the health of its waterways, rather than releasing a potentially catastrophic virus into its ecosystems."

"Freshwater is in desperate shortage in large parts of Australia, so the first step must be to reduce the amount of water extracted for thirsty crops such as cotton. This would help to restore habitat for native species, thereby reducing habitat for carp.

"Proper governance is what's needed, rather than giving an unhealthy and fragile ecosystem a foreign virus, which could significantly tip the balance out of favour for native species."

Dr Lighten said "very little progress" has been made in reducing the volume of water taken from the Murray-Darling Basin, and that this step should be "primary in restoring river health over releasing a pathogen that could have significant ecological repercussions."

Mr Moggrodge said reducing the amount of water taken from the rivers "will never happen" under the current state and Federal Government.

"You've got the fox in charge of the chicken coop. They'll never impact their constituents. I think it'd be a brave government to start taking water off people to increase the environmental flow."

A missed opportunity and business opportunities

Mr Moggridge says different methods to control the carp have been tried over the years - from genetic engineeringg, to carp traps placed in the weirs of the Murray-Darling Basin.

"But a lot of the times you couldn't keep up with the numbers that were going into these traps," said Mr Moggridge. "When we were in a massive drought, they did take a hit in a lot of the rivers; the numbers were hammered. I think the time would have been to do something then."

"There were opportunities to create industries, out of it, like fertilizer. In desperate times they did make a carp cookbook."

Globally, Common Carp are up there with the world' most farmed fish. They are used for food, pets and fishing. 

"There used to be aquaculture projects that you used to produce fish for the restaurant. And now, that sort of industry is long gone. I suppose if the mobs can keep water in the river to catch fish, can that opportunity turn into a commercial operation yeah give them, give them a leg-up."

The aftermath

If a virus is released that kills of huge amounts of carp, what then? How do you clean it up? 

"They will rot and stink out every river in the whole basin, so you've got this huge amount of rotting dead biomass carp stinking," said Mr Moggridge. "There are opportunities there for Aboriginal people to get involved to be part of the cleanup. But then what, do they go into landfill?"

For Mr Moggridge, and other experts, this plan poses more challenges than solutions. 

The National Carp Control Plan did not respond to NITV's request for comment. 


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