Carp: a case study
During the nineteenth century, a fish was introduced to some South-Eastern Australian waterways that was to have a disastrous effect on those ecosystems. That fish was the Common Carp (Cyprinus carpio), often referred to as the European Carp.
Pest Animal Control Cooperative Research Centre
Carp is a species that is native to many temperate regions of Asia. The carp is closely related to the Goldfish and is the largest member of the Cyprinidae family.
At least three strains of carp have been introduced to Australia, including an ornamental strain near Sydney (1850–60), a Singaporean strain in the Murrumbidgee (1876), and a hybrid ‘Boolara’ strain in Victoria (1961). All have become major pests in those waterways by their domination of the environment.
Carp are a pest in Australia because they contribute to the degradation of waterways in a number of different ways. Carp increase water turbidity by uprooting aquatic plants, and sifting through sediment during feeding. The greater the water turbidity, the less light can penetrate, which stunts surrounding plant growth. This in turn can lead to the erosion and subsidence of river and lake banks, which further contributes to water turbidity.
Carp also compete with native fish for habitat and food resources.
Traditional methods of control
Carp are extremely adaptable animals and can thrive in environments that would kill other freshwater fish. It is thought it will be impossible to totally eradicate the existing population and so, the most realistic approach is to control carp numbers.
Pest Animal control Cooperative Research Centre
There have been a number of attempts to control the carp population in South-Eastern Australia. Simple measures rely on the cooperation of anglers and hobbyists: if you catch a carp in Victorian waters, it is illegal to throw it back. It is also illegal to keep live carp in Victoria, including Koi carp, which are desired by some people as ornamental fish.
Other current control methods include commercial harvesting and poisoning.
While these options may reduce carp numbers in some areas, other options are being explored for more widespread control.
Biological control – the Daughterless Carp Program
Scientists are investigating this ‘daughterless technology’ which aims to control carp numbers through creating a fish population with many more males than females.
By blocking a specific gene involved in female carp development, only male fish are produced.
The project began in 2003 and is a collaborative project between the Murray-Darling Basin Commission, CSIRO Marine Research and the Pest Animal Control Cooperative Research Centre (PAC CRC).
They have targeted a gene called aromatase which codes for an enzyme that converts testosterone to oestrogens in the developing carp embryo. Without aromatase, the embryo cannot make the hormones required to develop into a normal female fish.
With fewer females in the population, and in conjunction with other management practices, it is hoped that carp numbers in the Murray-Darling Basin will plummet.
This research is in its very early stages and is part of a long-term program, as carp have a very long generation time. A successful Daughterless Carp approach would need to operate over about 40-50 years and be used in conjunction with other short-term control techniques.
View animations of the process: http://www.pestanimal.crc.org.au/research/carpbiotech.htm
Any new technology involves risks that need to be identified and assessed. The researchers are assessing and reviewing the risks from the beginning of the project to identify any risks associated with the technology and to take the steps to ensure they are addressed.
The technology involves manipulating only carp genes and as such is aiming to produce a biocontrol mechanism highly specific to carp, thereby minimising the risk to non-target species. The release of any genetically modified organism into the environment is subject to legislation which considers any economic, social and ethical concerns related to the technology.
All research is being conducted in secure laboratory facilities and has been approved under the strict guidelines of the Office of the Gene Technology Regulator (http://www.ogtr.gov.au).
Read more about carp biology, distribution and the damage they cause at the NSW Department of Primary Industries: http://www.fisheries.nsw.gov.au/thr/species/fn-carp.htm
Get more general information on carp at the National Feral Animal Control Program: http://www.feral.org.au/species/carp.asp
Learn about the carp problem and the Daughterless Carp Program at the Cooperative Research Centre for Pest Animal Control: http://www.pestanimal.crc.org.au/
See how the Murray Darling Basin Commission is involved with the Daughterless Carp Program: http://www.mdbc.gov.au/whatson/news/carpinfo/carpinfo.htm