Why is carp a pest

The image above shows the benefits of removing carp from an area. This wetland dried out, carp were prevented from returning using a screen and the system filled again naturally. The improved water clarity is clear to see. Read more about this experiment. Carp have been identified as a priority pest species, both in Australia and internationally. They are capable of tolerating a range of environmental conditions. They have a greater tolerance of low oxygen levels, pollutants and turbidity than most native fish, and are often associated with degraded habitats, including stagnant waters.

Changes to water flows, declining water quality and other changes to river habitats over the past few decades have negatively affected many native fish while favouring carp.

Reproduction : Under suitable conditions, carp are highly prolific. They mature early — as early as 1 year for males and 2 years for females — and the females produce large numbers of sticky eggs up to 1.

Carp migrate to and from breeding grounds during the breeding season, sometimes travelling hundreds of kilometres. Most eggs and larvae die before they reach adulthood, although more may survive if environmental conditions are suitable. Floods seem to provide especially favourable conditions for carp breeding as well as abundant food for juveniles. This may help explain why carp experienced such a population explosion during the large floods of the s.

Feeding : Carp are omnivorous, and their diet varies depending on what is available. They consume a range of small food items such as molluscs, crustaceans, insect larvae and seeds. These food items are sucked up along with mud and water from the bottom and filtered out using the gill rakers. They can also consume plant material and general organic matter, especially when other food sources are not available during winter, for example.

Adult carp have no natural predators. Large predatory native fish, such as Murray cod, golden perch and bass, may consume juvenile carp, although it appears they are not a favoured prey item. The distribution of carp in NSW now includes most of the Murray-Darling Basin as well as many coastal river systems, particularly in the central section of NSW from the Hunter in the north to the Shoalhaven including the Southern Highlands and Tablelands in the south.

Carp have been introduced into Australia both deliberately, in an attempt to imitate the European environment, and accidentally, through the escape of ornamental or aquaculture fish. In Victoria, the stocking of carp began as early as , but early stocking attempts were not successful.

In NSW, the earliest known introductions occurred near Sydney in In the early s, fingerlings were used to establish several wild populations of carp around Sydney, including in Prospect Reservoir where they still persist. Whatever the source s , carp have been established in the Basin since at least the s, although for some time they remained fairly uncommon. In the early s a new strain was imported for aquaculture and reared at a fish farm in Boolarra.

It is thought that the species originally evolved in the east Asian region and spread naturally from there. There are about 20 other species of Cyprinus, mainly around the Yunnan region of southwestern China, with some species restricted to single lakes. The extension of their range across Europe began in the first century AD, helped by the Romans and later by monks who cultured the species in Europe.

Carp were established across Europe by the s and in the United Kingdom by the s. Carp were transferred from China to Japan around years ago where the koi ornamental varieties originated. The first attempts to introduce carp to Australia were made in the late s.

The first of these into Tasmania in was not successful. An introduction to Victoria in succeeded in establishing a population in the Botanic Gardens in Melbourne, which persisted until Carp do not appear to have spread from there.

These introductions reflect the community attitudes at the time, with attempts being made by acclimatisation groups to introduce many European species. For example, brown trout were first successfully introduced to Tasmania from the United Kingdom in and a variety of other new plants and animals were also imported to provide both food and recreation for colonial residents. Around this same period, and again in the early s, carp were introduced to a number of locations around Sydney, including Prospect Reservoir where they established a breeding population.

Carp had become established but not widespread in the Murray—Darling Basin by the s. There were also attempts to introduce carp into Western Australia between and but these introductions did not become established; successful introductions have, however, since been made. In Australia, management authorities are willing to go to extreme measures to stem the invading tide: an eradication program that would introduce a herpes virus deadly to carp but not to other fish is currently being evaluated.

While invasive carp pose threats to native biodiversity in many places, in the highly modified cultural landscape of Europe, low-density carp ponds appear to have become an important element in wildlife conservation strategies. Carp have been cultured on the continent for centuries, and a variety of water birds and amphibians, including many rare species, find refuge at carp-pond complexes Kloskowski Pond culture of carp continues as an industry today, and worldwide aquaculture production of carp exceeds 3 million tons , roughly the combined weight of farmed and wild-caught salmon worldwide.

While the majority of farmed carp are sold as fresh or frozen whole fish, other carp products are marketed as well.