Virus may control Australia’s ‘river rabbit’

Researchers at CSIRO Livestock Industries’ Australian Animal Health Laboratory (AAHL) in Geelong – with the Department of Primary Industries Victoria – are investigating Koi herpesvirus as a means of controlling the introduced fish.

Project leader Dr Mark Crane says the virus, which first emerged in Israel in 1998*, caused mass mortalities in carp in the US, the UK, Israel, the Netherlands, Japan and Indonesia. So far the virus does not appear to have reached Australia.

Supported with $355,000 from the newly formed Invasive Animals Cooperative Research Centre and the Murray-Darling Basin Commission, the two-year project will investigate the effectiveness of Koi herpesvirus in controlling strains of carp present in Australia and will examine whether the virus will have any impact on certain native fauna.

“All testing will be done within the secure biocontainment facilities at CSIRO AAHL,” Dr Crane says.

Dr Crane says while carp are a valuable resource in Asian countries, in Australia the fish is generally viewed as a major pest.

“Given their reproductive capacity and their hardiness, carp have been termed the ‘rabbit of the river’.”

Carp were introduced into Australia in the early 1900s as a food and sporting fish. During extensive flooding in the 1970s the fish escaped from farm dams and took over the waterways. They can tolerate a wide range of water temperatures, salinity and pH levels. Carp can also survive and breed in polluted, poorly oxygenated water.

“The fish grow to up to 20 kilograms or more in weight and each female can lay up to three million eggs in a single season,” Dr Crane says. “In some areas of south-eastern Australia carp make up more than 85 per cent of the fish in the rivers and creeks.

“The virus works by attacking the carp’s gills as well as other vital organs and eventually killing its host. Koi herpesvirus is attractive as a biological control agent as overseas studies suggest that it has a very limited host range, infecting only carp.

“If the laboratory studies show promise, the next step will be extensive government, public and industry consultation to determine the best course of action to control carp, while protecting and restoring Australia’s valuable waterways,” Dr Crane says.

The virus works by attacking the carp’s gills as well as other vital organs and eventually killing its host.

The project is part of a larger pest fish control program under the Invasive Animals CRC and 50-year Native Fish Strategy at the Murray-Darling Basin Commission. Other technologies being developed in the pest fish program include ‘daughterless’ technology, carp-specific biocides, pheromone and sensory attractants.

“It is anticipated that if these technologies are proven to be effective and safe, they will be applied on-ground in an integrated pest fish control program for the Murray-Darling Basin,” Dr Crane says.

*Earlier outbreaks occurred in UK in 1996 but the first scientific reports appeared following the outbreaks in Israel.