Carp Cage Project
Murray LLS is investigating the implementation of carp cages across several rivers in the Murray catchment. The feral fish has exploded in numbers since the floods in 2010-11. Estimates by fish experts indicate that the numbers of Carp have increased by over 40 times in parts of the Murray catchment and there are reliable reports of large numbers of carp, (1600 per day), passing through fishways at Torrumbarry Weir on the Murray, or accumulating at weirs such as Stevens Weir on the Edward River.
Carp degrade aquatic ecosystems, causing a decline in the numbers and diversity of native fish. They are a particularly invasive pest species, fuelled by a constant drive to spread as far and as fast as they can into creeks, billabongs and channels.
Up till now, efforts to trap carp have rarely been successful because of a lack of effective control techniques, but a new "carp cage" has been trialled successfully at Lock 1 on the Lower Murray River at Blanchetown in South Australia, where it has removed 200 tonnes or 80,000 carp since 2008.
The Williams cage, designed by Alan Williams, weir-keeper at Torrumbarry, uses an innovative design to allow native fish to pass through, while using the jumping behaviour of carp to trap them.
Murray LLS has engaged a leading carp scientist, Dr Ivor Stuart, to work with its own carp specialist, Anthony Conallin, to investigate the feasibility of installing carp cages on a number of fishways within the NSW Murray region. The Williams cage, designed by Alan Williams, weir-keeper at Torrumbarry, uses an innovative design to allow native fish to pass through, while using the jumping behaviour of carp to trap them.
Each fishway will be evaluated against environmental, social and economic criteria to ensure that the design, construction, operation, and cost-effectiveness are addressed. "Carp removal from rivers will have obvious benefits to the environment, but could also generate useful products such as garden fertiliser from waste carp" Mr Conallin said. "The feasibility study is looking at fishway sites on the Murray and Edward River, as well as Colligen, Yallakool and Gulpa Creeks to trap carp before they reach the redgum forests and do more damage", he added.