Carp Crusades: Steve Davidson Gives the European Carp a Fair Trial, and Outlines a Potential Genetic Route to Its Long-Term Management

Article excerpt

Abstract: European carp are widespread in the Murray-Darling Basin and occur in all states and the ACT. They are blamed for many aspects of river and wetland degradation, it is unlikely that carp are responsible for declines in native fish or riverbank erosion, but they do cause turbidity, reduce aquatic vegetation and probably increase the occurrence of algal blooms. Successful carp management will require both control techniques and river rehabilitation. A potential long-term control method, daughterless carp technology, entails altering the genetic make-up of carp so that fewer and fewer females are produced from one generation to the next. The technique may be ready in about seven years.

Keywords: European carp, introduced species, feral animals, pest control, environmental degradation, Daughterless Carp Project, genetic manipulation.

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Cast a line into almost any Australian river, stream, lake or billabong and you're more likely to haul in a plump European carp than a native fish.

Admittedly, the European carp is one of the most abundant and widespread large, freshwater fish on Earth, but how has an introduced species become so dominant in Australia? What impact is this rabbit-of-the-river having on the health of our precious waterways? And what is being done about it?

The carp (Cyprinus carpio) actually originates from central Asia, spreading from there to China, Japan, southern Europe, and thereafter to every continent.

Although the carp was introduced to Australia in the 1850s as an ornamental fish, it had little impact until the 1960s when the Boolarra strain was released from a fish farm into the Murray River, near Mildura, Victoria. This invasive strain took a liking to conditions here and the carp population exploded, aided by floods in 1974 and 1975.

Carp are now widespread in the Murray-Darling system and are present in all states and the ACT. They continue to colonise new waterways, often helped by humans, including fishermen using carp as live-bait.

Key to the success of feral carp is their great fecundity (each female carp can lay a million or more eggs a year) and their ecological flexibility (see story opposite).

They are most at home in warm, still waters, such as those of inland southeastern Australia, but can adapt to a broad range of environments, even saline waters. A 1997 survey of rivers in New South Wales recorded carp virtually everywhere except unregulated (free-flowing) coastal rivers and high mountain streams.

Carp now comprise at least 80%, and often more than 90%, of fish biomass in the Murray-Darling Basin. In the lower reaches of the basin's Bogan River, scientists found one carp for every square metre of water. Not surprisingly, carp are generally despised, and they are blamed for many aspects of river and wetland degradation.

Marshalling forces

The scale of the problem is immense. Carp are now a national issue. With the Murray-Darling Basin being the epicentre of the carp invasion, early responses have come from the Murray-Darling Basin Commission (MDBC) and CSIKO, as well as from local government and the Murray Darling Association. In 1996, the association sponsored the formation of the National Carp Task Force, a community forum for addressing carp management and control.

A Carp Control Coordination Group, managed through the MDBC, has developed a National Management Strategy for Carp Control, a strategic research plan and a Guide for Carp Management Groups. It also promotes liaison between the many groups involved in carp control.

The Bureau of Rural Sciences has produced a publication, Managing the Impacts of Carp, that provides the scientific basis of the National Management Strategy. CSIRO is working on control techniques.

Carp crimes

Most people loathe carp. Their abundance and rapid spread causes great concern about their effects on water quality and native fish. …