CANBERRA, July 3 (Xinhua) -- An audacious plan to use a targeted herpes virus to rid Australia's waterways of the invasive European Carp species of fish could indirectly put native fish at risk, an ecological expert from the University of Canberra said.
According to Professor Ross Thompson from the University of Canberra's Institute of Applied Ecology, the mass killing of European Carp - an invasive species which destroys the habitats of native fish - could create a blackwater event, which is when waterways are starved of vital oxygen, killing native species.
The 15-million-Australian dollar (11.5-million-U.S. dollar) plan was given the go-ahead in recent months, and will involve the release of the virus, which will spread among carp - and only carp - through contact.
Carp currently make up around 85 percent of the total biomass of Australia's rivers and lakes, meaning the sudden death of the majority could throw the local ecosystem out of balance.
Thompson told Xinhua on Monday that while it may seem logical that quickly killing the invasive species would leave more oxygen in the water for native fish, the process of decomposition consumes more oxygen and releases carbon in deadly amounts.
"In the long term, (quickly killing the carp would work). The issue is the carp carcasses, which decompose - a process which consumes oxygen. In warm conditions, this happens quickly and can de-oxygenate the river," he said.
Thompson said the plan to release the species-targeting herpes virus needed to be carefully planned, adding that simply releasing the strain en masse to kill the fish could do more harm than good in the short term.
He said the best way to manage the massive carp cull would be to release the strain slowly and only among small stretches of rivers at a time.
"A strategic release moving upstream and in the cooler months would reduce the risk of a blackwater event," Thompson said.
Thompson added that a quick carp cull may not have the intended effect of handing the waterways back to native fish, explaining that some other introduced species breed much faster than the natives, meaning they could "take the place" of carp in the near future.
He said while it was "hard to predict" which species could take over as the dominant river fish, there was a growing threat from common goldfish which have been released by pet owners who could no longer care for them.
"Other possible beneficiaries are European redfin perch, oriental weather loach, tench, roach and new invaders such as tilapia," Thompson told Xinhua.
"We don't have a clear idea of the longer-term outcome of those changes, but it is unlikely to be worse than having carp in the system."
The herpes strain is expected to be released into Australian waterways sometime in 2019.
