In 2002, an expert panel advised the then Murray Darling Basin Commission that recovery of native fish populations required integrated action to mitigate the impact of several factors that had led to a major decline in native fish. These included:
- allocation of environmental flows
- habitat restoration
- abatement of cold water pollution
- provision of fishways
- establishment of aquatic reserves
- carp management
- management of other introduced fish species that are threatening native fish communities.
The panel stressed that management of Carp (Cyprinus carpio) alone would not lead to significant recovery of native fish populations, and that the eradication of Carp was not possible using currently available techniques and strategies. It was decided that reducing the damage Carp caused and managing them within the Basin’s river systems was a more realistic focus for ongoing research and practice.
This approach triggered the development of user-friendly, step-by-step guides that outline a structured but flexible methodology to assist with the development of Carp management plans. The overall aim of these plans is to reduce the impact of Carp on key environmental values in each area. The methodology focuses on identifying and prioritising management units across the region (these will vary depending on how the organisations in each region define the ‘unit’), and ranking the units for conservation, water quality status and the threat of carp.
Through the Native Fish Strategy, the Murray-Darling Basin Commission supported several demonstration reaches to develop plans using the new methodology. Several of the demonstration reach plans identified Carp as a threat and, by using the new methodology, developed actions to reduce carp and recover native fish populations.
The strength of developing a Carp plan is that the management of this problem species is set within a broader framework of river rehabilitation. This requires a clear definition of the problem and the outcomes to be achieved. In general these outcomes are the recovery of native fish populations and restoration of their essential habitat. Other key steps are identifying feasible management units; encouraging the engagement of the community; and including rigorous monitoring and evaluation.
The currently available methods for managing carp all have limitations and in each case their success depends on a range of factors including the biology of the species, location, costs of control, resources available, potential impacts on non-target species, and the objectives of the management program. For most of the plans typical actions include:
- Installing Carp harvest systems (eg separation cages) and Carp screens at key sites
- Restoring passage for native fishes
- Improving instream habitat (eg resnagging)
- Stabilising banks to control erosion hotspots
- Managing other pests (fish, terrestrial animals and plants)
- Removing woody weeds
- Restoring connections with other parts of the system and more natural flows
- Improving riparian health (including fencing to keep stock out)
- Improving water quality
- Using Carp separation cages, carp ‘musters’, trapping, netting to reduce numbers
Regional Carp Plans have been developed for the Lachlan River (near Forbes); Logan Albert (SE Qld); Barmah-Millewa (Murray R); Rocklands and the Glenelg River (Vic); Dewfish Reach (Condamine River); Macintyre – Border rivers (SW Qld); Tahbilk (Goulburn R)Victoria; Katarapko (Murray R, SA); and the Upper Murrumbidgee (NSW/ACT).
Implementation of the Regional Carp Plans has been mixed, and largely depends on the ongoing motivation and commitment of the local groups involved. Plans that have been developed as part of a Native Fish Strategy Demonstration Reach have usually had more uptake and longevity. This is probably due to the involvement of Native Fish Coordinators and being part of a wider program of activity.
Key messages/Implications for native fish
Eradication of widely established species of pest fish such as Carp, is not possible using currently available techniques and strategies. Consequently the focus on managing pest fish, is on reducing the damage that they cause to an acceptable level, rather than trying to eradicate the species.
A recurring theme for regional plans is the need to for them to use an adaptive approach to management so that new information on the effectiveness of activities management can be incorporated over time. Adaptive approaches support experimentation, monitoring and evaluation as ways to regularly improve and update management activities.
The experience gained through this work shows that plans need to be based on a catchment or sub-catchment approach where the desired outcomes from pest fish management are clearly defined and relate to the desired environmental and production outcomes for the area.
Plans need to be locally developed, owned and implemented by those that have the greatest stake in the results. A whole-of-system approach is required so that the plan for managing pest fish is integrated into broader strategies for managing other threats to native fish. Managers then need to determine where to put their limited resources in order to get the best return.
Effective management of Carp damage is possible provided the available techniques are applied strategically, usually in combination and taking into account the range of other factors that influence the health of the river system. Integrated programs that employ a number of methods offer the most promise for effective long term control.
Braysher, M. Stuart, I. and Higham, J. (2008). Dalby Demonstration reach carp management plan, A sub-component of the Condamine River Rescue program
Braysher, M. Stuart, I. and Higham, J. (2008). Tahbilk Lagoon carp management plan, A sub-component of the Tahbilk Native Fish Demonstration Site
Ayers, R. and Clunie, P. (2010). Management of freshwater fish incursions: a review. Arthus Rylah Institute for Environmental Research. Department of Sustainability and Environment, Heidelberg, Victoria
Braysher,M. and Barrett, J. (2000). Ranking Areas for Action: A Guide for Carp Management Groups. Murray-Darling Basin Commission, Canberra.
Brasher, M. and Saunders, G. (2003). ALIENPLAN- a guide to setting priorities and developing a management plan for alien animals. Bureau of Rural Sciences and the Natural Heritage Trust, Canberra.