Publication (Media): Ridding rivers of the roach - study looks at water levels and carp breeding

Publication Type:	Media Release
Publication Name:	Ridding rivers of the roach - study looks at water levels and carp breeding

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Gawne, B. and Markwort, K (1998) Ridding rivers of the roach - study looks at water levels and carp breeding - Jul 29 1998, CRCFE, Canberra - Media Release.

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July 29

CRCFE

Ridding rivers of the roach - study looks at water levels and carp breeding

A two-year project being conducted in the Murray, Darling and Murrumbidgee rivers of NSW will investigate the role of river flow in the success of carp breeding and juvenile survival.

The project will also provide valuable information about the biology of carp that will assist in developing control methods for this pest species.

The Department of Land and Water Conservation's Water Management Fund is supporting this project which is being conducted by the Cooperative Research Centre for Freshwater Ecology (CRCFE) and the University of Adelaide.

Dr Ben Gawne from the CRCFE and the Murray-Darling Freshwater Research Centre's Lower Basin Laboratory said most of the current available information on carp biology came from studies conducted in Europe.

"We need to confirm whether this information relates to Australian conditions before we embark on a control program," Dr Gawne said.

The study will involve determining the age structure of carp populations from the River Murray near Renmark (SA) and Tocumwal (NSW), the Darling River near Menindee (NSW) and the Murrumbidgee River about Maude weir (NSW).

Techniques have been developed whereby the age of carp can be determined by looking at ring structure of the fish's otoliths or ear bones, a bit like ageing a tree according to the number of growth rings. Studies to date suggest that carp in the Murray-Darling Basin live between 15 and 20 years.

The carp population age structure will be compared to environmental variables such as water levels, discharge, rainfall and temperature at each river site. This comparison will help us determine the conditions that either promote or inhibit successful carp reproduction.

Field as well as laboratory studies will be used to determine the preferred carp spawning sites, the development times and factors in the survival of eggs. They will also find out whether the eggs or carp larvae are vulnerable to drying or exposure due to varying water levels.

Dr Gawne said the researchers would also develop a model of carp recruitment so that the study could be applied to other river catchments.

"A recent study conducted by NSW Fisheries and the CRCFE has shown that in some river reaches there is one carp to every square metre of river which truly makes this prolific invading species the 'rabbits of the river'", he said.

"It is reassuring to know that the battle to rid our rivers of this river roach has won the support of the NSW Government and especially the community."

It is likely that successful carp control will depend on a range of complementary strategies, one of which may well be manipulating water levels to limit the success of carp breeding.

Media contact: Dr Ben Gawne: 017 844 507
Karen Markwort: 06 201 5369

The Murray-Darling Freshwater Research Centre's (MDFRC) Lower Basin Laboratory in Mildura is a joint initiative between the community and the Cooperative Research for Freshwater Ecology (CRCFE) which was established in 1993 under the Federal Government's Cooperative Research Centres Program.

The CRCFE is a collaborative venture comprised of industry, government and research agencies as well as universities. Its aim is to provide ecological understanding to improve inland waters by collaborative research, education and resource management.

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