Carp

Scientific Name: Cyprinus carpio
Other Names: European carp
Size: Can grow up to 120cm in length
Weight: In Australia, most commonly found at 4-5kg, can reach up to 10kg

General Description

Carp were introduced into Australia over 100 years ago. They are a pest fish species which cause major damage to the quality of inland waterways as well as native fish populations.

Currently making up 80 per cent of the fish biomass in many Australian waterways, carp are considered to be the worst freshwater pest in south-eastern Australia. They are present in every state or territory in the country – excluding the Northern Territory. Carp are extremely prevalent in the Murray-Darling Basin and are a dominate species with the carp populations exceeding 350 kilograms per hectare in some areas.

Some of the main environmental, social and economic impacts of carp include:

Water quality
Carp are bottoms feeders and stir up mud and sediments as they feed which has a negative effect on water clarity by making it muddy. This impacts the amount of sunlight which the aquatic vegetation is exposed to and sediment then covers the vegetation and native fish eggs which can impact food sources and reproduction of native fish. Carp also increase the nutrient levels in the water which may also cause outbreaks of toxic blue-green algae blooms in the waterways. They may reduce habitat and food for native fish, waterbirds and invertebrates.
Native fish populations
Female carp can produce up to one-million eggs per year, they grow quickly, mature early and can tolerate extreme conditions including temperature changes and water quality. Carp can out-compete native freshwater fish species which has an adverse effect on native fish populations.
Fishing opportunities
Recreational fishers often see carp as getting in the way of the natives they really want to catch while out for a fish.
Irrigation
Carp, especially juveniles, can block irrigation pumps and other farming equipment which cause loss of time and maintenance costs for agriculture businesses and farmers.

Behaviour

Carp are omnivorous feeders. They feed on molluscs, crustaceans, insect larvae, seeds, detritus generally by sucking and straining mud from the bottom to filter out food items. This increases water turbidity and has a negative impact on our waterways.

Where to Find

Carp are found right across Australia, and are present in every state or territory – expect the Northern Territory. They’re widespread in south-eastern Victoria, waters of the Murray-Darling system and are found in other systems and waters in western and south-western Victoria.

Fishing Rules

There are no size limits or bag limits for European carp. Due to their status as a noxious species in Victoria under the Fisheries Act 1995, carp must not be returned to the water alive.

Carp must be killed immediately. Fishers are reminded not to leave the dead fish on shore at the fishing location. The Victorian Fisheries Authority recommend returning dead carp to the water and cutting the carcass so that it sinks. For further information, visit the Victorian Fisheries Authority’s recreational fishing guide for carp.

Threats and Management Issues

National Carp Control Plan (NCCP)

In 2016, the Australian Government began investigating the use of carp virus to control carp numbers in Australia. The work was led by the Fisheries Research and Development Corporation (FRDC) and included contributions from eleven research institutions, over 40 research scientists as well as policy and expert scientific workgroups.

The National Carp Control Plan (NCCP) aimed to explore the possible release of the carp virus, Cyprinid herpesvirus 3 (CyHV-3 or carp herpesvirus) to drastically reduce the number of carp in our waterways. Researchers have tested the effects of the carp herpesvirus on 13 native fish species, chickens, mice, frogs and turtles and found that it does not cause harm for these other species. The virus is highly contagious and is mostly transferred through carp-to-carp contact. The virus can also be spread via water when a carp swims within the same waterbody as an infected carp and can be active in the water for up to three days. The ideal temperatures for the virus to show signs of disease in the fish are between 18 and 28 degrees- celsius.

Findings of the NCCP

The NCCP was publicly released in November 2022 with a number of findings including:

If successful, the carp virus could reduce carp populations by approximately 40–60%.
Integrated approaches may help to further reduce the impact of carp.
Releasing the virus would most likely, cause an initial major outbreak followed by ongoing seasonal outbreaks that suppress the carp population.

According to the Department of Agriculture, Fisheries and Forestry, the NCCP report confirmed that the carp virus has credible potential as a biocontrol agent. It also identified several areas requiring further research, including:

more testing to ensure other species are not susceptible to the carp virus.
further understanding of disease transmission and ongoing effect of the virus in natural settings.
cost and benefits analysis of using the carp virus as a form of biocontrol to manage carp.

View the National Carp Control Plan here.

Projects and Campaigns

The NCCP are conducting a CARPMAP survey where the Australian public record where they have seen carp aggregating in high numbers to plan future carp control programs.

Other Information

Below is an interview from the National Carp Control Plan’s Riverside Stories with former VRFish Executive Officer, Michael Burgess. Where he talks about the high level of community interest in controlling carp to support native fish recovery across the state.