Optimised wetland carp separation cage evaluation

Project Leader: Dr Ben Smith, SA Research and Development Institute

Aim: To evaluate the use of a carp separation cage in a field situation: Lake Bonney.

Project:  4.f.17

Project summary

This project follows on from the earlier work done in project 4.F.12 that developed an optimised wetland carp separation cage and lifting infrastructure set-up, designed by SA Research and Development Institute’s Aquatic Sciences team and approved by professional engineers to be safe, effective, easy to operate by just one person, vandal-resistant and transferable to other wetland sites across the Basin.

This project will provide quantitative data on the ‘performance’ of the cage and the movements of carp in response to spring filling events of drying wetlands, which might become ‘the norm’ if the prolonged water shortages and drought conditions persist.

Lake Bonney in South Australia is a 1700 ha shallow freshwater lake fed from the Murray River through the Chambers Creek Wetlands. Lake Bonney was disconnected from the Murray River in mid-2007 (to reduce the amount of water lost to evaporation), resulting in water quality deterioration and fish kills.

The lake received a partial refill allocation of 10 GL, which reduced salinities and prevented further fish kills. This filling event created a large aggregation of resident carp at the inflow point, comprised of large numbers of adult carp vigorously attempting to migrate from the lake, the majority of which were harvested. In 2008-09 the SA MDB NRM Board invested in the installation of two box culverts, the design, construction and installation of an optimised wetland carp separation cage, and the establishment of routine reporting requirements to ensure that carp are harvested when delivery of a second environmental water allocation
(26 GL) occurs towards the end of 2009.

In preparation for the installation of the cage and the subsequent carp removal trial, a number of carp in the lake were captured, tagged and released back into the system. This will enable a quantitative estimate to be made of the lake population by monitoring of the proportion of tagged fish in the trap.

Key deliverables

  • IA CRC occasional report entitled ‘Carp removal by an optimised wetland carp separation cage and associated lifting system: an experimental trial at Lake Bonney (Barmera), South Australia’, which will summarise the process involved including costs of installation and operation and the benefits in terms of quantified proportions of total lake population removed.

Project team

Qifeng Ye, Leigh Thwaites, David Fleer.

Project partners

IA CRC, Murray-Darling Basin Authority, SA Research and Development Institute

Further information

For further information, contact us.