Scientists Ponder Releasing Virus to Kill Carp
Australian Animal Health Laboratory biocontainment technician, Neil Slater, displays a good sized carp he recently caught.
Credit: Commonwealth Scientific and Industrial Research Organisation (CSIRO)

Australian scientists have a new strategy for dealing with carp that have invaded their waterways: a virus that, if unleashed, could kill the fish.

While carp, also called koi, are considered a valuable resource in many Asian countries, in Australia the fish is generally viewed as a major pest, according to the new project's leader, Mark Crane of the Australian Animal Health Laboratory.

"Given their reproductive capacity and their hardiness, carp have been termed the ‘rabbit of the river,'" Crane said.

Carp were introduced into Australia in the early 1900s as a food and sporting fish. Extensive flooding in the 1970s allowed the fish to escape from farm dams and take over the waterways. The carp are particularly hard to get rid of because they can tolerate a wide range of water conditions and can also survive and breed in polluted, poorly oxygenated water.

"The fish grow to up to 20 kilograms [44 pounds] or more in weight and each female can lay up to three million eggs in a single season," Crane said. "In some areas of southeastern Australia carp make up more than 85 percent of the fish in the rivers and creeks."

The two-year project will investigate the effectiveness of using the Koi herpesvirus as a way to control strains of carp present in Australia and will examine whether the virus will have any impact on certain native fauna.

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

This isn't the first time Australian scientists have thought of using a virus to control a pesky invasive species that threatens to push out native wildlife. In August, researchers at the Pest Animal Control Cooperative Research Center proposed using a highly infectious virus to sterilize female rabbits and keep rabbit populations under control.

For now, these proposals remain in the testing phases. "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," Crane said.