Carp spawning hotspots in the MDB

Project Leader: Dr Dean Gilligan, Industry and Investment NSW

Aim: To identify all carp spawning hotspots within the Murray-Darling Basin (MDB)

Project: 4.f.5

Project summary

This project identified preferred carp recruitment areas across the Murray-Darling Basin (MDB). It builds on previous research which highlighted that 80 per cent of carp recruitment in the NSW section of the Basin is attributed to only 4-5 localities. The sampling was expanded to include the whole of the MDB involving 26 sampling locations in Queensland, 33 in Victoria and 10 in South Australia and the Culgoa, Paroo, Castlereagh, Macquarie, Bogan and Lachlan catchments in NSW.

The project provided data on temporal variability in carp spawning at hotspots, to assess the relationship between spawning and recruitment, to validate larval sampling as a method of detecting recruitment hotspots, and to ensure that the CarpSim model operates at a spatial scale which reflects the carp population structure of the MDB.

Identified hotspots will help define the spatial structure of carp populations of the MDB by specifying the population units (nodes) that contribute most to recruitment within the Basin (source populations). Population sinks can also be identified. Accounting for this spatial variation will create more realistic CarpSim modelling of carp populations and assist in the development of an effective integrated pest management strategy.

Sampling was undertaken at 152 sites in 11 different river systems within the Murray-Darling Basin over three sampling seasons (2005-06, 2006-07 and 2007-08). Four catchments were sampled twice within the three year period in order to provide data on temporal variability. This was a lower number of catchments and sampling occasions than was anticipated (303 sites and 25 catchment areas) as sampling opportunities were substantially limited by drought conditions in many river systems.

NSW electrofishing data confirmed carp recruitment was generally localised to specific regions, with juvenile carp only collected at around five per cent of sites where data were available. Electrofishing data supported the importance of the Namoi Wetlands, Gwydir Wetlands and Barmah-Millewa Forest for carp recruitment within the basin. The electrofishing data identified a further 14 hotspots in catchments that were not sampled using the larval sampling strategy (due to persistent drought conditions). Collectively, it is highly likely that as few as 20-25 carp recruitment hotspot areas exist within the Murray-Darling Basin. However, of these, the density of carp recruits produced is highest at only six to seven sites.

Due to the drought impeding the full completion of the project, a comprehensive set of MDB carp spawning hotspots could not be identified. Gaps include river systems in South Australia. Equipment has been provided to respective State agencies to complete the project and no additional funding has been sought.

The identification of carp recruitment ‘hot-spots’ will assist an Integrated Pest Management strategy by guiding:

  • appropriate spatial parameterisation of the CarpSim model
  • targeted control of adult carp migrating towards spawning areas
  • targeted control of spawning aggregations
  • exclusion of spawning adults from spawning areas
  • control of dispersing juveniles from spawning areas.

Key achievements

  • Five major carp spawning areas were identified within 11 MDB catchments: Namoi wetlands, Gwydir wetlands, Barmah-Millewa Forest, Lower Warrego River and Lower Boomi River.
  • This knowledge enables carp control to be targeted at a finite number of recruitment sources (hotspots) rather than being diluted over tens of thousands of kilometres of river. The information will assist the development of Integrated Carp Management Strategies across the Murray-Darling Basin and provides a cost-effective strategy to detect carp recruitment hotspots in other catchments in Australia and globally.

Project team

Dr Dean Gilligan, Bob Creese, Tim Glasby, Vanessa Carracher, Peter Boyd, Ian Wooden, Simon Hartley, Dean Hartwell, Cameron McGregor, Paul Brown, Qifeng Ye, Michael Hutchinson and Iain Suthers.

Project partners

IA CRC, Industry and Investment NSW, SA Research and Development Institute, Qld Department of Employment, Economic Development and Innovation, Vic Department of Primary Industries, University of NSW, Murray-Darling Basin Authority.

Further information

Gilligan D and Rayner T (2007) The distribution, spread, ecological impacts and potential control of carp in the upper Murray River. NSW Department of Primary Industries Fisheries Research Report No 14, NSW Department of Primary Industries, Cronulla.

Gilligan D (2007) Carp in Australian rivers, in: Lunney D, Eby P, Hutchings P. and Burgin S (eds) Pest or Guest: the zoology of overabundance. Proceedings of the Royal Zoological Society of New South Wales forum held at Taronga zoo, Mosman NSW, 22 October 2005 pp 30-39.