Carp: Australia's Bane

Dec. 30, 2003 — A delicacy on European and Asian tables, the carp is one of Australia's worst pests and may be heading for eradication down under because of a nearly perfected all-male gene, government scientists in Australia announced Tuesday.

Introduced from central Asia in the 1850s, the carp has thrived in Australia where it has caused an estimated $600 million ($444 million U.S.) in damage per year and devastated native fish populations.

But within the next decade, scientists hope to release a male-only gene that will ultimately lead to the carp's disappearance by preventing it from producing female offspring.

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"We have identified an enzyme in fish that is critical to sex determination and have created a gene that blocks production of that enzyme," Commonwealth Scientific and Industrial Research Organization marine research scientist Ron Thresher told AFP.

The research, undertaken with Australia's Pest Animal Control Cooperative Research Center, seeks to radically reduce carp numbers by producing a new generation of male-only carp.

For the last two years, scientists have been testing the gene on a South American fish known as the gambusia, which is ideal for research because it reaches sexual maturity at an early age.

"When we have adapted the gene we will release the carp equivalent," Thresher said, adding that the gene would be tested on carp within the next four years and released into the wild within seven years.

Carp features prominently in the cuisines of many Asian and eastern European countries but Australians have doggedly refused to acquire a taste for the fish, which they consider to have a "muddy" flavor.

"It's cultural as much as anything else," said Thresher, who has a doctorate in marine biology. "There is a social stigma associated with carp because they are found in muddy conditions."

The southern state of Victoria is home to a small carp export industry, but for the most part the fish is generally considered — along with the rabbit — to be the country's most destructive environmental pest.

An ability to survive warm water and low oxygen levels has helped the fish thrive, especially in Victoria and adjoining South Australia, where it inhabits the Murray-Darling Basin in plague proportions.

Its tendency to dig up aquatic plants has muddied the waterway and wiped out an estimated 90 percent of the native fish population.

The current carp explosion was linked to a hybrid strain accidentally released from dams near Mildura, a town in Victoria close to the South Australian border.

Scientists hope to significantly reduce the carp population in the Murray-Darling by mid-century, to allow native species of Macquarie perch and Australian bass to regenerate.

Thresher said the Murray-Darling Basin was an ideal environment for the carp. "It's a good habitat with still water," he said. "Those conditions are favorable for the carp."