Australian aquatic ecologists say the National Carp Control Plan (NCCP) falls short on safety and efficacy while calling for more research and funding before the deadline at the end of the year.

Key points: A National Carp Control Plan is investigating what impact there would be if a species-specific herpes virus is released in Australian waterways

A National Carp Control Plan is investigating what impact there would be if a species-specific herpes virus is released in Australian waterways Carp is considered a pest in Australia

Carp is considered a pest in Australia The scientific community has many concerns about using the virus to target carp

Researchers were investigating whether a species-specific herpes virus, Cyprinid herpesvirus-3, could reduce numbers of European carp in the Australian waterways where the pest was detrimental to the native environment.

At the end of last year researchers were given a 12-month extension to analyse some of the research gaps identified.

They were expected to have a final plan by the end of 2019 to inform a Federal Government decision on whether the virus should be released.

Impact on other wildlife

CSIRO scientist Dr Heather McGinness is concerned about the impact of the carp herpes virus on waterbirds which eat the fish as a major part of their diet. ( Supplied: Heather McGinness )

CSIRO senior scientist, Heather McGinness, said a mass cull of carp could have devastating effects on native waterbirds if the virus was released at the wrong time or place.

She has reviewed a number of cases of mass fish kills, mostly in marine systems, and the impact on the surrounding ecology.

"When there is a big loss and a sudden loss of a certain fish species, waterbird populations can have big population crashes and failed breeding events," Dr McGinness said.

"Carp, we think in some areas of the Murray Darling Basin, are now about 80 or 90 per cent of the biomass of fish that are in our system and that's a huge percentage.

"It's highly likely that our waterbirds and other animals that consume fish have had to switch their diet and eat carp because their native fish diet has basically disappeared."

Dr McGinness said if the virus was released during the breeding event of a particular bird species, it would result in a large number of chick deaths.

Dead fish raises water quality concerns

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 26 seconds 1 m 26 s Carp herpes virus is extremely effective — but that could also be a problem

Dr McGinness was not confident the "depth and extent" of the research of the NCCP was where it needed to be.

"We do need more investigation into potential impacts on things other than fish and water quality … that includes fish consumers and things that live in the water that will be affected by this mass fish death."

A decline in water quality resulting from tonnes of dead fish in the river has been previously raised with the NCCP.

But Dr McGinness said that animals other than fish could be impacted.

"If you get a massive water quality decline that will effect things like crustaceans, mussels and other invertebrates and those are also food sources for waterbirds."

European carp were first released in Australia in the 1800s and have since dominated the country's river systems. ( ABC Rural: Cheryl Yow )

La Trobe University's fish ecologist, Alison King, said if thousands of carp were removed from the system at one time, other animals would need an alternative food source.

"Maybe we need to think about ways we could test some of this," Dr King said.

"We don't have to be in a rush, we could actually stage this out."

The NCCP aimed for 70 per cent reduction of carp numbers but Dr King said there was a potential for the carp not infected by the virus to breed, re-establishing the species' population.

"We appear to be seeing that the virus may only be effective in certain temperatures ranges.

"So that suggests we're going to have some fish that won't be affected by this virus."

Issues being addressed: NCCP

Plans to release a herpes carp virus have been put on hold. ( Cameron Atkins: ABC News )

NCCP coordinator Jamie Allnut said there was an ongoing comprehensive research program with 19 projects.

"We've built into that research program [the] flexibility to adjust the research as required to ensure we develop a report that goes to government that deals with all of the key questions associated with the virus release."

However Mr Allnut said it was not possible to do trials in the Australian environment because government approvals would be required.

"There are other questions that are raised in the science and literature and we're looking at all of those issues."

"We're also doing a thorough peer review process of our science."

Charles Sturt University's Institute for Land, Water and Society Keller Kopf, said it was problematic for tests to be done in laboratory conditions when variables like temperature could widely differ in the natural environment.

"There haven't been any studies conducted to actually look at how the virus effect any species in wild environments," Dr Kopf said.

"Given that rivers and wetlands out in nature are quite different to experimental lab conditions we expect the virus to work differently both in terms of effecting carp but also ecosystems."

Impact on breeding

European carp make up about 80 to 90 per cent of biomass in the Murray Darling Basin so scientists believe some animals may rely on them for food. ( ABC: Tom Lowrey )

Dr Kopf was also concerned about the lack of certainty around the potential for future generations of carp to become resistant to the herpes virus as they bred with other species.

"That's just one of the forms of resistance we expect to happen," he said.

"Goldfish show a degree of immunity to the virus and we know that in Australian waterways carp and goldfish hybridise.

"That's going to be a key mechanism by which resistance conferring genes that allow fish to survive exposure to the virus will continue on populations and allow recovery."

How widely and often carp and goldfish breed was not known, however the NCCP was analysing resistance of the virus in their research.

Unwise to continue: Scientist

Carp are a freshwater fish native to Asia. Now the most abundant large fresh water fish in some areas — Australia considers them a pest. ( LANDLINE: Kerry Staight )

Dr Kopf said the percentage of carp likely to be killed by the virus would not meet NCCP targets.

He said the virus was used in at least 33 countries including in the United States, in Europe and Japan to remove carp and to date there was little evidence to suggest it would effectively kill carp in Australian conditions long-term.

When researchers were given a 12-month extension to further investigate the virus, no additional funding was given and Dr Kopf said it was putting the scientist under pressure.

"There's just so many gaps … there's a number of questions that need to be answered before we can reliably predict whether this virus is going to have any effect at all on both carp and native species," he said.