The Williams’ Carp Cage was developed through a cooperative project between the Arthur Rylah Institute, Department of Sustainability and Environment and the Goulburn Murray weirkeepers, through funding and support from the former Murray-Darling Basin Commission. This innovative technology was first trialled at Torrumbarry weir in 2003, and Carp cages have now been established in a variety of sites along rivers and wetlands in the MDB and other sites.
The device exploits the unique jumping ability of Carp, enabling them to be captured in cages as they move through fishways. Diagrams of how the cages operate have been developed. Fish move through a funnel into a holding area, where carp then jump over a baffle into a confined area from which they are collected. The operation of the cage also enables automatic release of native fish underneath the cage so they can continue their movement upstream.
Diagram of a carp cage in operation. (from Stuart et al, 2006)
A) shows the operating position to catch and separate jumping carp (black fish symbols) and non-jumping Australian native fish (grey fish symbols)
B) shows the raised position, where
1 is the false lifting floor
2 the cone trap
3 native fish exit gate
4 the non-return slide.
Carp cages definitely capture the public’s imagination, and many field days and events have enabled demonstration of their operation. Where possible, presentations would include video footage of a carp cage in operation, which was a highly effective educational tool. For those not able to see the cage in situ however, it is often hard for people to envisage exactly how the device operates. In 2007, the NFS funded the development of a portable Carp cage model that could be used as an educational tool.
The prototype was created in Victoria and the response was clear and immediate. People are automatically drawn to it …. “What is that?” Upon explanation, the response was . “Ah ha! Now I understand.” Audiences were attracted to the simple elegance of the Carp cage. Model Carp cages were subsequently developed for use in each jurisdiction. Each model sat protected within a Perspex tank which could be partially filled with water to depict the fishway ‘cell’ in which a carp cage would sit in a river. The tank also provided secure storage and transport for the model.
Model Carp cages also provided an additional benefit of acting as a conversation starter on a display stall. Such a tool helps to easily engage with both young and older audiences who are very attracted to the simple concept and how it actually works.