Background

An integrated pest management system should include a range of physical, chemical and biological options.  Chemical options for fish (piscicides) are commonly used for control or eradication of new and localised pest species incursions or for the restoration of small to medium sized water bodies in North America. They are an essential component of any rapid response plan for incursions of new pest populations.

Roteneone, a non-specific piscicide, is the most commonly used - primarily because it is considered to be the most environmental friendly of available fish poisons (Ling, 2003).

In Australia, Rotenone is presently the only option available to chemically control invasive species in Australian fresh-water environments (Sanger and Koehn, 1997), though Antimycin has also been identified as having potential (Sanger and Koehn, 1997).  Rotenone has been used to successfully eliminate carp from Tasmania in the 1970s (Sanger and Koehn, 1997) and for the local eradication of trout from streams in south-eastern Australia (Lintermans and Raadik, 2003).  Rotenone has also been used in New Zealand to eradicate Koi carp and Gambusia from farm dams (Chadderton et al., 2003). 

Dawson (2003) determined that rotenone and antimycin appeared to be the only piscicides available in the United States that could be applied in the short term to control or eradicate invasive fish species without considerable additional expense. 

While rRotenone is considered a useful tool (Rowe, 2003), its use may be restricted by regulatory limitations associated with deployment in natural freshwater environments (Sanger and Kohen, 1997). It is actually registered as a pesticide for treatment in banana crops.  There is a need consolidate all regulations and protocols pertaining to the use of piscicides in Australia, as different state and territories have different rules (Roberts and Tilzey, 1997) which have the potential to slow down response times.

There is also an international need to develop better chemical tools that minimise non target impacts and selectively target specific pest fish species.

Dawson (2003) reviewed over 45 chemicals that could be used to control invasive fish in the US and identified seven biocides as being worthy of further evaluation for use as specific piscicides. This review was conducted for the American south-west and its applicability to other jurisdictions for (eg. Australia and New Zealand) needs to be assessed.

In order to effectively assess new candidates, we would need to:

1. Identify interspecific differences in the biochemistry of different species relating to their strategies for self-sustenance.
2. Identify interspecific differences in how successful different species are at tolerating potential poisons.
3. Make science based evaluations of newly discovered chemicals (particularly those that inhibit electron transport systems / oxidative phosphorylation).
4. Develop specific combinations of currently registered piscicides what would allow some selective toxicity between target and non-target fishes.

Gingerich (2003) concluded that at present too little biochemical and pharamacokinetic information exists to produce selective biocides and suggests that scientific direction be directed to existing compounds.

However the biology, physiology and metabolism of invasive fish also needs to be nvestigated with the aim of identifing potential traits that are unique to them, which could be exploited chemcially.

For example, it has been hypothesised that as New Zealand and Australia have no native fish that are exclusive detrivores or herbivores, the digestive processes of carp may provide a species-specific vulnerability that could be exploited chemically.

What are we doing? 

The piscicide project aims to:

• maximise availability of existing tools for application in Australia and New Zealand
• identify compounds that warrant further toxicological investigation for carp and/of other pest fish
• build upon existing data to identify a suite of biocide delivery options that would improve biocide selectivity to invasive species
• identify physiological traits unique to invasive fish species that could be exploited through chemical inhibition to reduce fitness or induce mortality
• identify, for further evaluation, a suite of candidate chemicals with models of action that can exploit these physiological traits.

To do this we have firstly completed a comprehensive literature review of:

• the legal and legistalative requirements and toxicological (testing) requirements for the registration of existing biocides for application in Australia and New Zealand freshwater environments
• potential piscidies and exisiting delivery options
• international drug literature (focusing especially that from Europe) to identify novel compounds that have show lethal effects on carp in laboratory trials.

From this review we are:

• summarising the legislative and regulatory framework for the registration of chemicals as 'piscicides for use in Australia and New Zealand', and which identify the scientific data and administrative processes required to enable the registration of known non-specific piscicides  in Australian and New Zealand freshwater environments - underway and ongoing.
  
• Summarising the range of candidate compounds that are known to be lethal to selected invasive fish of concern in Australia and New Zealand, eg. carp and tilapia, and which identify a suite of biocides for further evaluation and sets out the scientific data required to undertake such an evaluation.
• Summarising and identifying any pharmacological products, and/or compounds that are known to be lethal to and or disrupt these pathways in invasive freshwater species in Australia/ New Zealand. As part of this process, the reviews will assess the unique traits, physiological or metabolic pathways of target organisms, and/or compounds that could be used to selectively target and control invasive freshwater fish species in Australia. This may include detailed discussion of:
• • biochemical or physiological traits that are unique to invasive freshwater species and which may be vulnerable to disruption. These may include mode of feeding, diet, unique enzymatic or metabolic pathways.
  • Biological differences between invasive species and native and valued introduced fish species in Australasia that may make carp vulnerable to specialised toxin delivery systems. 
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This project is not expected to be completed before at least the end of 2008.