Inland Waters Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Jonas Ball, Sinclair Knight Merz Pty Limited, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06750 7

Aquatic ecosystems (continued)

Protecting, restoring and managing aquatic ecosystems (continued)

Pest management programs [IW Indicator 6.8]

  • Water hyacinth - Eichhornia crassipes
  • The wetland weed - Mimosa pigra
  • European carp - Cyprinus carpio
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    Australia's aquatic environments have been under increasing pressure from introduced plant and animal species including the loss of native species and changes in ecosystem structure.

    In most states and territories, legislation to protect Australia's aquatic species and environment also contains provisions for the control of noxious or non-indigenous plants and animals. For example, the Queensland Fisheries Act 1994 contains provisions for the management of noxious and non-indigenous fishes in Queensland waters. Noxious fish include European carp (Cyprinus carpio), piranhas (all species of the genera Serrasalmus, Pygopristis, Pygocentrus), tilapia and walking catfish. Heavy fines (up to $150 000) can be imposed on anyone having noxious fish in their possession without a permit or for releasing these fish into the wild. Guilty persons can be charged the costs of eradication.

    In association with legislative measures there are many pest management programs under way. The following examples outline some of the successes to date in reversing the impact of introduced species.

    Water hyacinth - Eichhornia crassipes

    The CSIRO Weed Management Program has been prominent in research on the water hyacinth, one of the world's most serious weeds due to its invasiveness, high growth rate and high biomass.

    Biological agents released since 1975 by the CSIRO are showing promise in controlling water hyacinth. Agents include the weevils Neochetina eichhorniae and N. bruchi, and the moths Niphograpta albiguttalis and Xubida infusella.

    The wetland weed - Mimosa pigra

    Mimosa (Mimosa pigra) is one of Australia's most destructive weeds and is a major threat to biodiversity in northern Australia. It also impacts on the viability of Aboriginal settlements, tourism and pastoral enterprises. Already infesting 80 000 ha of wetlands in the Northern Territory, it has the potential to spread west to Broome in Western Australia and as far south as Ballina in New South Wales.

    In a collaborative project between CSIRO and the Northern Territory Department of Primary Industry and Fisheries (DPIF), 12 species of biological control agents have been released including 10 insects and two pathogenic fungi. These agents collectively damage vegetative and reproductive parts of the plant. Considerable achievements to date include the establishment of the flower-feeder Coelocephalapion pigrae and the stem-borer Neurostrota gunniella over the entire range of mimosa infestation. The distribution and abundance of the stem-boring moth Carmenta mimosa is steadily increasing.

    The current focus of research is assessment of the abundance of biological control agents at over 100 sites. CSIRO is also investigating other potential biological control agents including N. gunniella and other insects. The DPIF and CSIRO have also developed mass rearing methods and procedures for large-scale releases by helicopter of the wet-season fungus Phloeospora mimosae-pigrae.

    A field trial is under way to develop an integrated strategy for mimosa management. This combines physical control, herbicide use, burning, biological control and computer modelling. Computer modelling allows the consequences of different management options to be tested and is an important technological tool for future control of the weed.

    European carp - Cyprinus carpio

    European carp have been present in Australian inland waters for over 100 years, with the first introductions occurring in the 1850s and 1860s in Victoria and New South Wales. The primary impact of carp on aquatic ecosystems is from their feeding habits that disturb the bottom substrate and increase the turbidity of the water, particularly in shallow, warm, slow-flowing waters.

    Carp were first discovered in north-west Tasmania in 1975 and again in 1980, and these populations were eradicated using the fish poison rotenone. In early 1995 the carp were found again and following the discovery of this latest infestation, the Inland Fisheries Service (IFS) has been actively fishing carp populations and ensuring their containment. Carp pose a considerable threat to Tasmania's status as a world class trout fishery so an ongoing program has been developed and funded by the State Government to manage the problem.

    Eradication has been managed through use of radiotracking. Male carp are surgically implanted with transmitters and are located routinely to determine whether the fish are aggregated or spread randomly around a lake. Aggregations, which occur for feeding or spawning, can then be located with radiotracking equipment allowing large numbers of fish to be captured using nets and electrofishing.

    As schooling is required to maximise catches, male fish are released to ensure that population numbers are large enough for schooling to occur. There has been no further evidence of carp spawning in Lake Cresent since 1996/97.

    Another component of Tasmania's Carp Eradication Program is the processing and interpretation of otoliths (ear bones of fish). The deposition of calcium and protein at regular intervals allows the age of fish to be determined and this work has been invaluable in understanding population structure, growth rate and reproductive success. The results are being used to develop management techniques for carp.

    Other states have artificially increased the value of carp to encourage greater exploitation of carp populations, and thus help in the reduction of their numbers. NSW Fisheries has developed a Carp Action Plan that includes mechanisms for assessment and reduction programs. Programs in place include live export, use of carp as liquid fertiliser and use of carp skins in the leather trade (NSW Fisheries 2001).

    Messages about protecting, restoring and managing aquatic ecosystems

    • Since 1996, action plans for the conservation of native frogs and waterbird have been developed and are being implemented.
    • Common responses to restore and protect native fish populations include the construction of fishways and the restocking of native fish. Additional research is required into designing fishways, as many current designs are ineffective. Unless carefully managed, the restocking of native fish can have adverse impacts including loss of genetic diversity, introduction of disease to wild populations and overstocking. A healthy habitat and environment for native fish is essential for the long-term success of fish-stocking programs.
    • Various national, state and local programs to protect and improve riparian zones and habitats have been initiated, and some initial successes have been recorded. However, in comparison to the total areas of degraded riparian zones, overall improvements are minor.
    • Wetlands can be protected through a number of international treaties such as Ramsar, CAMBA and JAMBA. Since 1996 there have been another 13 wetlands listed under the Ramsar Convention. Two states have developed wetland protection policies and many other states and territories are in the progress of developing similar policies.
    • The environmental water requirements of groundwater-dependent ecosystems are poorly understood and are generally not considered when determining the sustainable yield and allocation of an aquifer. More research is needed into groundwater-dependent ecosystems.
    • Environmental water allocations for surface aquatic ecosystems are gradually being developed for all regulated river systems in Australia. However, as of June 2000 only 13% of regulated river systems had operational environmental water allocations. Environmental water allocations must also consider the timing of the delivery of the environmental flows as well as the volume.
    • Most states and territories now have legislative mechanisms for the protection of riparian zones and threatened aquatic species, and the provision of environmental flows. The new Commonwealth environmental legislation Environment Protection and Biodiversity Conservation Act 1999 provides additional protection for threatened aquatic species and Ramsar-listed wetlands from activities on public and private land.
    • Some pest management programs have been very successful; however, these successful programs have focused on pests in specific areas rather than the large-scale eradication of introduced species on a national scale.