Drought helps control carp in regional waterways

November 8, 2007

The on-going drought is having at least one positive spin-off - fewer carp are being distributed through our inland waterways.

Known as the vermin of inland waterways, carp became a major pest in Australia in the 1970’s and now make up 80 to 90% of the fish in inland NSW.

The reduced numbers of carp is great news for native fish, fishers and for the inland waterways of NSW.

DPI researchers at Narrandera, in conjunction with the Invasive Animals Cooperative Research Centre (CRC), are identifying what are believed to be a relatively small number of locations where huge numbers of carp breed.

Their research indicates that carp like to breed in the inland waterways that are most precious to us - our wetlands.

The concentration of carp in these hot-spots is astounding; at one site there are around 30,000 carp larvae per mega litre of water.

Ten hot-spots have been identified, and four of these are internationally recognised wetlands - the Gwydir wetlands, Namoi wetlands, Barmah-Millewa forest and the Macquarie Marshes.

In total, it is estimated there are around 20 major carp breeding hot-spots within the Murray Darling Basin.

Researchers have found that carp like to breed in shallow, swampy areas that are regularly inundated by water - heavy rain and floods enable the carp to disperse into adjoining river channels.

These results support the larval drift theory, indicating the carp’s need for high water flow events to disperse their larvae.

The drought initially hindered this research, because the lack of water flow meant carp movements could not be tracked.

However, researchers were able to access NSW DPI’s records of freshwater fish to map the distribution of baby carp over the last 13 years.

Researchers from NSW DPI and the CRC expect that targeted carp control at these major breeding locations will have a huge impact on massively reducing carp numbers throughout regional waterways.

Source: NSW Department of Primary Industries