Controlling carp – pest species of the Australian waterways

Carp (Cyprinus carpio) is native to Eastern Europe and central Asia and has been bred as an ornamental and aquaculture species for many years. Translocations have now resulted in carp invading waterways in other parts of Europe, Asia, North, Central and South America, Australia and Oceania (Koehn 2004).

Carp were first introduced into Australia in the mid 1880s, and the population remained contained until the introduction of the ‘Boolara’ strain to the Gippsland in Victoria in the 1960s. This strain was translocated to farm dams and rapidly spread throughout south-east Australia, particularly the Murray-Darling system. Harris and Gehrke (1997) reported that they can achieve a biomass of 3,144kg/ha and densities up to 1,000 fish/ha. They destroy aquatic plants, increase turbidity and reduce photosynthetic production and visibility for visually feeding native fish. CSIRO scientists claim that carp now comprise up to 90% of the fish biomass in the Murray-Darling Basin.

CSIRO and the Australian Animal Health Laboratory have been investigating the potential use of the cyprinid herpesvirus 3 (CyHV-3) as a biological control agent for carp in Australia (McColl and Crane 2013). A literature review by McColl (2013) on CyHV-3 as a biological control agent suggests that it can be associated with up to 100% mortality in both common carp (Cyprinus carpio carpio) and koi carp (Cyprinus carpio koi). CyHV-3 affects fish of any age and is now considered to represent a significant threat to the carp industry, and carp aquaculture, but also has the potential to be a useful biological control agent. The outcome of the infection is very temperature sensitive, with the maximum water temperature tolerated by the virus being about 28oC. The virus can persist in water for at least three days, but not seven days (McColl 2013).

The potential for using CyHV-3 for controlling carp has been getting increasing media attention including ABC news, The Australian, Sydney Morning Herald, The Guardian and The Conservation just to name a few.

When tested in ‘field trials’ there was no evidence that Murray cod, golden perch, silver perch, galaxiid fish and rainbow trout are susceptible and no evidence of any cross-reactive cyprinid herpesviruses that might compromise the efficacy of CyHV-3 were it to be released into the Murray–Darling River system (McColl and Crane 2013).

CSIRO indicated that CyHV-3 mainly damages the kidneys, skin and gills of koi carp and common carp. Damage to the gills affects the carp’s ability to breathe and this is the cause of death. The virus is transmitted by direct contact among fish and from infected water. The CSIRO blog site answers many common questions about the virus if you want further information. Norm Halliwell sort information from the NSW Department of Primary Industries on potential issues to do with the release of the virus in Australian waterways and received a very informative response (Halliwell 2016), and Sue Neales from the Australian reported the carp herpes virus is ready for release.

So is the virus safe for use? CyHV-3 has had a significant negative impact of carp aquaculture worldwide but there is no evidence of it spreading to humans.

Terrestrial Ecosystems believes this to be a very useful initiative, as carp have significantly damaged our waterways and had a devastating effect on native fish.

References

Harris, J. H., and P. C. Gehrke. 1997. Fish and Rivers in Stress – The NSW Rivers Survey. Canberra.

Koehn, J. D. 2004. Carp (Cyprinus carpio) as a powerful invader in Australian waterways. Freshwater Biology 49:882-894.

McColl, K. A. 2013. Review of the literature on cyprinid herpesvirus 3 (CyHV-3) and its disease. Canberra.

McColl, K. A., and M. S. J. Crane. 2013. Cyprinid herpesvirus 3 (CyHV-3): its potential as a biological control agent for carp in Australia. Canberra.

Photo credit: Top – Carp caught in a prototype trap on the upper Murrumbidgee river (picture by James Bennett and sourced via ABC website; A koi carp caught in a local wetland during a a fauna management program in Perth