Pillar 3 – On-Ground Interventions: Alien Species Management

Quick tips:

  • An integrated pest management approach must be taken when dealing with alien fishes which includes the development of a management plan.
  • The management plan needs to be developed in consultation with the community and have clearly stated goals.
  • The plan may involve actions to prevent incursions of new species, as well as the control of established species.
  • A range of management actions should be taken to ensure an integrated approach (e.g. community education, removal tools – electrofishing, netting etc., screening, habitat rehabilitation etc.).

Fish assemblages (variety and abundance) in the Murray-Darling Basin are becoming increasingly dominated by alien species –that is species that originate from overseas, but have become established in Australian waters (Harris 1995), or native species that have become established outside their natural range. There are 12 alien fish established in the Basin (see Lintermans 2007) of which Carp (Cyprinus carpio) is the most widespread and abundant. Gambusia (Gambusia holbrooki) is also widespread and has significant impacts on native fishes, particularly small bodied species. Other species such as Tilapia (Oreochromis spp.) are found in catchments close to the Basin and could be introduced in the future.

Alien species have contributed to the decline of native fishes, impacting in many ways including: direct predation, competition and habitat alteration. Alien fish impede the recovery of native fish even when other threats are being addressed. Most alien fish thrive in aquatic habitats disturbed by human activities. They can significantly reduce the impact of habitat management interventions in demonstration reaches.

Most of the work undertaken in demonstration reaches to date has concentrated on Carp management, however, there is a community driven Gambusia removal program in the Upper Murrumbidgee demonstration reach (see Examples 4j). At most of these reaches Carp musters (community run fishing competitions) are the only activity. These musters are a very valuable community engagement, awareness and education tool but do not control Carp numbers. At the Dewfish and Upper Murrumbidgee demonstration reaches a more integrated approach has been taken using the principles outlined below. Although these principles have been chiefly used for Carp, they are equally applicable to the management of other alien fishes.

It is important to take a systematic and strategic approach to managing alien fish in a demonstration reach. This approach begins by establishing the goals of the program and then working out the most cost effective actions to take, given the generally limited resources that are available.  The points below outline a framework for developing an Alien Fish Management Plan for a demonstration reach:

What is the nature of the problem?

The first thing to do is to understand the problem and to set the objectives for a management plan. This should be done in consultation with the community to ensure local ownership.

Are there alien species that may become established in the demonstration reach?
Tilapia are not present in the Basin. but are established in south east catchments in Queensland, very close to the Dewfish demonstration reach on the Condamine. Management actions to prevent an incursion are priorities for this reach and the whole Murray-Darling Basin.

Are there established alien species in the demonstration reach?
Are there established alien fish populations within the reach, what impact are they having on native fishes? Are they widespread within the reach, or are there isolated populations that could be contained?

Setting priorities for management:

Preventing incursions of new species
For prevention, priority actions can include; a targeted education and extension program to prevent human added translocations of alien species into the reach; setting up a surveillance program to detect any incursion as soon as possible; and developing a rapid response strategy with the relevant jurisdictional agency.

Managing established species
Management actions need to focus on reducing the damage caused by alien fish to an acceptable level. The demonstration reach can be broken up into management units which can be ranked based on the perceived threat of the alien species to native fishes. For example, are there floodplain wetland areas were Carp recruitment is occurring? Are Carp threatening spawning sites of native fishes? Are there wetland areas where Gambusia populations could be removed to protect small bodied native fishes?

Management techniques:

There are no “silver bullets” control alien fishes but there are a range of tools available including: capture techniques (electrofishing, nets, traps etc.), Habitat manipulation (draining waterways, draw down of fish breeding areas), Fish exclusion devises (fish screens, Carp cages) etc. Rehabilitation of the habitat and native fish populations will also make the reach more resilient to alien fish disturbance. Invasive species such as Carp, Gambusia and Tilapia appear to thrive in disturbed waterways. Improving the river health in the demonstration reach should remain the overarching management technique. Management actions should be undertaken where environmental conditions maximize the outcomes.


Monitoring of alien fish management interventions should be included in the Monitoring and Evaluation Plan (see Example 4j).

Up to date information about managing carp can be found on the PestSmart website – follow this link.

European carp (Cyprinus carpio). Photo: CSIRO
Gambusia Holbrooki. Photo credit: Gunther Schmida

Example 4j:

Integrated Carp Management Plan – Dewfish Reach – Condamine Alliance
In 2009 an Integrated Carp Management Plan was prepared for Dewfish Reach which recognised the potential for new alien fish to become established (namely Tilapia). The objectives are to:

  • minimise the risk of new alien freshwater fish establishing in the catchment.
  • target reduction of Carp abundance within the reach as measured using standard techniques.
  • limit Carp recruitment within the geographic area of the site, without impacting on native fish recruitment.
  • limit Carp emigration and migration to the site and movement within the site, without impacting on native fish movement.
  • promote community awareness & increase the involvement of community & local management agencies in Carp management & therefore other rehabilitation activities within the site.

The demonstration reach was divided into management units with a number of management actions for each (e.g. install a Williams Carp Separation Cage at Loudoun weir, establish mobile instream carp traps, promote targeted Carp removal, investigate devises to exclude Carp from emergent vegetation, provide adequate disposal facilities for captured Carp. While all the proposed action are yet to be implemented (e.g. Williams Carp Separation Cages cannot be installed under state legislation), the Condamine Alliance has developed and is implementing an Action and Implementation Plan for preventing Tilapia from entering the northern MDB and has been actively removing Carp from key sites along the demonstration reach. Carp numbers have remained low at most sites apart from below Loudoun weir.

Community Control of Gambusia in the Upper Murrumbidgee
Gambusia occur in a number of habitats in the Upper Murrumbidgee including ponds and small farm dams. The primary vector for their introduction to these habitats appears to be humans. The Upper Murrumbidgee Waterwatch (UMWW) together with ACT Conservation Planning and Research (CPR) began a program in 2011 to engage the local community in removing Gambusia from urban dams and ponds. The aims are to achieve cost-effective removal of Gambusia and to educate the community about the negative consequences of spreading this species.
Key points are:

  • The UMWW has used its networks to identify bodies of water that have community interest in Gambusia control.
  • These water bodies have been assessed to determine their level of infestation (dip netting and visual observations), connectivity to other waterways, locality in the catchment, size and access etc. UMWW and CPR then prioritised the ponds for control.
  • Removal is undertaken in winter months when fish numbers are low and the fish congregate in warmer areas.
  • The UMWW is running concurrent community education and engagement program.
  • If the project is successful and Gambusia free sites are achieved, they will be considered for introductions of small bodied native fish.
  • Fish are euthanized by UMWW of CPR persons under ethics approval through the ACT government. The fish are not euthanized in the presence of children.

Upper Murrumbidgee Demonstration Reach – Carp Reduction Plan
Carp are well established in the Murrumbidgee demonstration reach and the surrounding areas. A Carp Reduction Plan, which sits under the Implementation Plan for the demonstration reach, lists three overarching issues to be implemented:

  • Promoting community engagement (e.g. “Carp out/Carp Muster” events).
  • Addressing priority knowledge gaps (e.g. lack of detailed knowledge of Carp distribution, local habitat preferences, population dynamics etc.).
  • Examine operating policy or regulatory ‘levers” to assist Carp control (e.g. e.g. coarse fishing events, keeping of Koi Carp etc.)

The plan identifies three management units, two of which cover the demonstration reach, with the third extending the area to the Molonglo River and Lake Burley Griffin. The management plan highlights that managing Carp cannot only be confined to the demonstration reach area. Individual actions include installing screening off takes, surveillance and rapid response in Carp free zones etc. A rigorous monitoring program is also used. It is emphasised that Carp control is part of a suite of management interventions to rehabilitate the demonstration reach for native fishes.

The demonstration reach is undertaking a cooperative research project with a mix of government and non-government organisations to:

  • Track Carp using radio telemetry to establish movement biology and microhabitat preferences.
  • Trial trapping measures suitable to the Upper Murrumbidgee.
  • Determine the population structure of Carp caught in the trapping trials.
  • Examine ecosystem/native fish response to long term Carp removal.
  • Collate community reports on Carp spawning and aggregation sites in the whole of the Upper Murrumbidgee catchment via an online portal supported by the Invasive Animals CRC’s Feral Scan platform.
  • Gather information on angling catches by working with recreational fishers.
  • Undertake a regional Carp out event targeting riverine Carp in the Upper Murrumbidgee.

Braysher, M. and Barrett, J. 2000. Ranking Areas for Action: A Guide for Carp Management Groups. Murray-Darling Basin Commission, Canberra.

Braysher, M. and Saunders, G. 2003. PESTPLAN – a guide to setting priorities and developing a management plan for pest animals. Bureau of Rural Sciences and the Natural Heritage Trust, Canberra.

Braysher, M., Stuart, I. and Higham, J. 2009. Dewfish Demonstration Reach Carp Management Plan. A sub-component of the Condamine River Rescue Program. Condamine Alliance, Queensland.

Butcher, A. and Norris, A. 2010. Integrated Carp Removal in the Dewfish Demonstration Reach: A Report to the Condamine Alliance. June 2010. Department of Employment, Economic Development and Innovation, Brisbane, Queensland.

Condamine Alliance 2012. Keep tilapia out: an action plan to exclude tilapia from the Northern Murray-Darling Basin 2012-2022. Condamine Alliance, Queensland

Condamine Alliance 2012. Keep tilapia out: an implementation plan to exclude tilapia from the Northern Murray-Darling Basin 2010-2014.Condamine Alliance, Queensland.

Invasive Animals Cooperative Research Centre 2012. The importance of Public Consultation for Pest Fish Management. PestSmart Toolkit Fact Sheet, Invasive Animals Cooperative Research Centre, Canberra.

Lintermans, M. 2007. Fishes of the Murray-Darling Basin:An introductory guide. MDBC Publication No. 10/07, Murray-Darling Basin Commission, Canberra.

Norris, A., Chilcott, K. and Hutchison, M. 2013. The Role of Fishing Competitions in Pest Fish Management. PestSmart Toolkit Publication. Invasive Animals Cooperative Research Centre, Canberra.

Harris, J.H. 1995. The use of fish in ecological assessments. Australian Journal of Ecology, 20, 65-80.

Smith, B., Thwaites, L. and Conallin, A. 2009Guidelines to inform the selection and implementation of carp management options at wetland inlets: a test case for South Australia. Report to the Invasive Animals Cooperative Research Centre by South Australia research and Development Institute, Invasive Animals CRC, Canberra.

Stuart, I., Higham,J., Lintermans, M., Braysher, M. and Phillips, B. 2010. Carp reduction plan for the Upper Murrumbidgee Demonstration Reach and surrounding region. Department of Territory and Municipal Services, Canberra.