Review of the management of feral animals and their impact on ...

In South Australia, between 30 <strong>and</strong> 120 small populations <strong>of</strong> carp have been
successfully eradicated, but <strong>the</strong>se mostly have occurred outside <strong>the</strong> Rangel<strong>and</strong>s (Hall
1988). A high priority has been given to <strong>the</strong> eradication <strong>of</strong> carp when <strong>the</strong>y are
detected in new areas, such as <strong>the</strong> Cooper Basin in <strong>the</strong> north <strong>of</strong> <strong>the</strong> State. Wetl<strong>and</strong>
<strong>management</strong> frequently includes measures to control carp <strong>and</strong> is <strong>of</strong>ten undertaken by
non-government agencies such as community groups.
General control techniques
Carp are presently controlled mainly with chemical agents, commercial harvesting,
recreational fishing, electro fishing, nets <strong>and</strong> traps <strong>and</strong> exclusion devices. Whilst
<strong>the</strong>ses options may reduce carp numbers, <strong>and</strong> may even eradicate <strong>the</strong>m from isolated
areas, o<strong>the</strong>r options are needed <strong>and</strong> being explored for more widespread control.
Environmental rehabilitation
Environmental rehabilitation is being seen as one way <strong>of</strong> improving habitat quality to
favour native fish. By potentially increasing native fish numbers, particularly large
predators, predation pressure on carp will be increased.
Biocontrol
The use <strong>of</strong> viral agents for biocontrol has also been considered, however a suitable,
species-specific lethal virus has yet to be identified for carp. If such a virus were
found, it would have to undergo intense scrutiny <strong>and</strong> overcome potential public outcry
before being released. Biocontrol has one major advantage in that it can be <strong>the</strong> most
cost-effective <strong>management</strong> technique if successful. A self-disseminating biocontrol
agent can require only minimal ongoing investment once successfully established in
<strong>the</strong> carp population. A classic example <strong>of</strong> this is <strong>the</strong> myxoma virus in rabbits,
discussed elsewhere in this report. One potential virus that has recently been
discovered is <strong>the</strong> Koi Herpes Virus. This virus has decimated both wild <strong>and</strong> cultured
stock <strong>of</strong> carp in areas ranging from <strong>the</strong> middle-east to Europe. The new Invasive
Animals CRC plans to conduct trials into <strong>the</strong> suitability <strong>of</strong> this virus as a biocontrol
agent.
Genetic manipulation
Ano<strong>the</strong>r potential approach to carp control is <strong>the</strong> use <strong>of</strong> genetic manipulation. Genetic
technology <strong>of</strong>fers potential opportunities to succeed where traditional approaches
have failed. One potential genetic technique is <strong>the</strong> ‘daughterless technology’.
Daughterless technology works by altering population sex ratio towards males whilst
maintaining <strong>the</strong> fitness <strong>of</strong> individuals. The technology is hereditary <strong>and</strong> passed on to
<strong>the</strong> male only <strong>of</strong>fspring, thus disseminating through <strong>the</strong> carp population. As <strong>the</strong> trait
spreads through <strong>the</strong> population, fewer breeding females exist <strong>and</strong> population
recruitment declines. The population <strong>the</strong>n steadily declines before eventually
crashing. The research is currently being undertaken by <strong>the</strong> Pest Animal Control
Cooperative Research Centre in conjunction with CSIRO <strong>and</strong> is funded by <strong>the</strong>
Murray-Darling Basin Commission as part <strong>of</strong> <strong>the</strong>ir 50 year Native Fish Strategy.
Long-term support for this type <strong>of</strong> project is essential as it may take 30-50 years or
more for <strong>the</strong> technique to work, once a viable genetic construct is released into <strong>the</strong>
environment.
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