Note: There is specific activity based on this topic.

However, a student review sheet is provided as a Current control measures activity (see below). Use it to review a lesson on control measures, as a research activity or as a comprehension activity, depending on the approach taken to this topic.

Permits

The possession of noxious fish is only permitted for display purposes and only if a permit from the Queensland Fisheries Service (QFS) has been obtained. There is no commercial exploitation of noxious fish in Queensland at present.

Current actions

Carp

Carp control is currently not coordinated on a national or even regional scale. Thus far, carp have been the responsibility of state and territory agencies, mainly fisheries departments.
A national task force was formed in 1996 with the aim of eradicating carp from all Australian inland waters. This is to be achieved through a strategic action plan that promotes coordinated research, provides good information, explores commercial opportunities and seeks complementary legislation. Needs a natural resource management strategy.
The importation of live carp is restricted (banned in Queensland).
Currently, QFS alerts the public to the presence of carp, the appropriate legislation and potential impacts of carp by using posters and television advertisements.
Past management actions have been minimal, and legislation is not an adequate response to the management of damage caused by carp. Eradication or control of carp is currently not being attempted. Rather, the priority has been preventing further range expansion.

Tilapia

The import of tilapia was prohibited in 1963.
There is generally no control of existing populations. Spot eradication can be performed in small, contained water bodies (e.g. ponds, dams). It is notable that past eradication attempts using rotenone (in Townsville) have been unsuccessful (O. mossambicus).
Prevention of further spread is a priority. One option to prevent further spread of O. mossambicus into the Mitchell River system and hence the Gulf of Carpentaria drainage is to place a screen on the outfall of Tinaroo Dam.

Gambusia

Encouraging the use of native freshwater fishes to control mosquitoes.

Other exotic pest fish

An education program warning the community of the dangers of dumping ornamental fish in waterways.

Integrated pest management

Combining different pest control strategies is the key to integrated pest management. It can be applied, in theory at least, to any kind of pest — vertebrate, invertebrate, plant, bacteria, fungi or virus.

In part, the development of Integrated Pest Management (IPM) is a response to the failure of many chemical pesticides to provide long-term solutions to pest problems. While some pesticides have dramatic effects when first applied, many pests develop resistance to the chemical over time and often re-emerge to plague an industry. It became a vicious cycle — the farmer increases the rate of pesticide application, producing increasingly resistant ‘super-bugs’ and ‘super-weeds’. If used incorrectly, quantities of poisons may enter the soils and surrounding waterways, with sometimes devastating effects on the environment and human health. The use of an integrated approach to managing pests is more sustainable and, in the long term, can be more cost effective.

Successful IPM usually has several key components.

Knowledge. Understanding the biology and ecology of the pest and the native environment is essential. Information about interactions within ecosystems is also important.
Monitoring. This information is required so that control measures are implemented at the most effective times.
Economic and environmental threshold. This takes into account the revenue losses resulting from pest damage and the costs of treatment to prevent the damage. It also looks at environmental impacts on native ecosystems. Below the economic or environmental threshold, the presence of the pest is tolerated. Only when pest numbers increase above the threshold does action need to be taken.
Adaptability. Agencies must keep informed about what is happening in their regions so that they can adapt their strategies to changing circumstances. Research scientists too, must aim to keep at least one step ahead of the pest, which is also undoubtedly, changing and adapting over time.

Methods for the management of pests

These include:

physical/mechanical control
chemical control
biological control
genetic engineering
environmental management/cultural control.

Physical control

This control method involves the use of human labour in the physical removal/destruction of the pests. This may involve netting or electrofishing. Physical control of pests is suitable for the management of small areas but large-scale infestations are better managed using other methods.

Chemical control

Relying solely on chemicals, such as the fish poison rotenone, as a means of control is not a desirable practice. When the need arises, the use of chemicals should form part of an integrated pest management strategy. The key is to use pesticides in a way that complements rather than hinders other elements in the strategy and which also limits negative environmental effects. It is important to understand the life cycle of a pest so that the chemical control can be applied when the pest is most vulnerable to attack — the aim is to achieve the maximum effect at minimum levels of pesticide 2 so that there is minimal impact on the associated environment. Chemical control should be undertaken using registered products specific to the pest and situation. It is important that chemicals are applied at registered application rates and in the manner specified by the product label.

Biological control

The Commonwealth Scientific and Industrial Research Organisation (CSIRO), Department of Natural Resources and other agencies undertake predator and pathogen research for the control of significant pests in Queensland. This process requires an intensive search for predators and pathogens from the native country where the pest originates. Strict measures are in place to ensure these agents do not affect native plants and animals or crops and livestock. The process is long and time-consuming, but the benefits can be substantial.

There are three general approaches to biological pest control. The first of these is the importation of a biological agent. For example, the Mexican prickly pear once covered 250 000 square kilometres, mostly in Queensland, greatly reducing the land’s carrying capacity for sheep and cattle. It was brought under control very effectively by the introduction of the Argentinean moth, Cactoblastus cactorum, the larvae of which eats the leaves of the offending plant.

But there are dangers with this approach. When the cane toad (Bufo marinus) was introduced into north Queensland to reduce populations of the cane beetle, Bufo failed to have any impact on the beetle. Not only that, it has become a major pest itself, spreading through much of northern Australia and threatening the survival of several native animals species. Nowadays biologists are required to carry out extensive research before a control organism is released because it is important to find out whether it will attack species other than the pest species.

The second approach to biological control is augmentation, which is the manipulation of existing natural enemies to increase their effectiveness. This can be achieved by mass production and periodic release of natural enemies of the pest, and by genetic enhancement of the enemies to increase their effectiveness at control. Also the release of genetically altered sterile pests (e.g. male fruit fly and screw worm fly) can be used to disrupt the breeding of some pest organisms. It is not presently known if any native fish are effective predators of tilapia and carp. It is thought that barramundi and mangrove jack in stocked impoundments may impact on tilapia numbers, and there is some conjecture that Australian bass may prey on carp. However, it appears that neither carp nor tilapia is a favoured prey species and introduction of predators can lead to increased predation pressure on native fish.

The third approach is conservation. This involves identifying and modifying factors that may limit the effectiveness of the natural enemy. In some situations, this may include reducing the application of pesticides, since such pesticides may kill predators at the same time as killing the pests.

Environmental management

Environmental management involves changing the environmental conditions in an area in which a pest plant or animal has invaded such that pest populations are reduced. Environmental management may also include the revegetation of areas using a combination of native grasses, trees and shrubs. Revegetation of native species creates competition for pest plant species and provides a habitat for native animals, which prey upon other pest plants and animals. Pest fish seem to have a competitive advantage over native fish in disturbed environments, so habitat rehabilitation may reduce their impact.

Genetic modification

Genetic modification of pest fish is a possible method of control. The idea is to engineer a disadvantageous trait in a pest and then release modified individuals into the outside world. The sterile insect release method is an example of this approach. The genetic engineering of organisms is controversial. Some people argue that toxins produced as a result of gene transfer may have harmful effects on beneficial organisms or on human health, while others suggest that the transferred gene might ‘escape’ into wild, related species of the organism, with possible ecological implications.

Integrated pest management is aimed not so much at trying to eradicate pests totally, as this is almost always impossible, but more at keeping pests under control so that the extent of their damage is kept within acceptable boundaries.

Student activity

IPM stands for ___________________ ________________ ________________________.
List 3 of the potential shortcomings of chemical pesticides:
What is a ‘super bug’? ______________________________________________________

_________________________________________________________________________
Complete the sentences using the methods of pest management listed below.
- environmental management
- genetic engineering
- physical control
- chemical control
- biological control
a. ___________________ _____________________ requires research into the predators and pathogens from the native country where the pest originates.

b. ______________________ ______________________ (e.g. electrofishing) is not well suited to large-scale infestations.

c. Rotenone is sometimes used in _________________ ____________________.

d. Introducing a disadvantageous trait into a species is an example of _____________________ ___________________________.

e. Revegetation is one way of implementing _________________________________.

5. Circle true or false. Rewrite the false statements to make them correct.

Integrated pest management is aimed at totally eradicating the pest species. T/F
Cane beetles were introduced for the biological control of prickly pear. T/F
The aim of chemical control is to achieve the maximum effect at minimum levels of pesticide so that there is minimal impact on the environment. T/F
Native fish seem to be better competitors than pest fish in disturbed environments, so habitat rehabilitation usually increases their numbers. T/F
It is not presently known if any native fish are effective predators of tilapia and carp. T/F

6. Review the resources in the module and summarise some examples of ways in which fish pest fish are being managed in Australia.

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