Use of chemicals as poisons
for pest fish control
Introduction:
Chemicals can be used to eradicate small, isolated
populations of pest fish quickly (spot removal) and
with a moderate cost, provided that the benefits
clearly outweigh any harm to native species and the
environment1. There have been a number of attempts to
control pest fish in Australia and almost half of these have
included the use of chemicals (fish poisons are known as
‘piscicides’). Examples are the successful eradication of
carp from Tasmania in the 1970s and from the Cooper
Creek drainage in South Australia2.
Presently available piscicide options:
There is no piscicide available that is specific to particular
fish species, and in fact, no chemicals are fully registered
as piscicides in Australia. Rotenone is the only chemical
currently legal to use in Australia to control any pest fish.
Rotenone is a naturally occurring chemical, obtained
from the roots of several tropical and subtropical plant
species. It is widely used as an insecticide and pesticide.
Historically, the states and territories have applied for
a ‘minor use’ permit to be able to use chemicals such
as rotenone for a specified time and under permit
conditions. The current permit for the use of rotenone is
APVMA Permit 13011 (Oct 2011-Oct 2020). This permit is
held by New South Wales Fisheries and allows the use of
rotenone by employees of state and territory government
departments responsible for pest fish eradication and
persons under their direct supervision. It can be used in
all jurisdictions except Victoria.
Currently available
methods of chemical control
for pest fish can be used to
eradicate small, isolated
populations quickly
There are other conditions applied by the APVMA for the
permitted use of rotenone to kill pest fish, such that
there:
A successful rotenone application removed over 13,000 kg of
carp in the Laguna de Zóñar, south of Córdoba, in Spain. Image:
from VESO (Norway) publication. Available at: www.veso.no
•is a high probability of successfully eradicating the
pest fish, with a low chance of immigration or recolonisation
•has been a review of environmental factors that
identified benefits outweigh impacts on native species
•is no risk to the health of humans, stock or domestic animals through direct contact or contaminated
drinking water
•is generally strong public and political support for
the operation.
Issues to consider when using rotenone:
Other legal approvals and permits are also required for the
use of rotenone (eg Environmental Protection Authority
authorisation and Bureau of Animal Welfare animal
ethics approval). Rotenone may also only be applied to
a water body by certified agricultural chemical users
(eg ChemCert accredited users). These requirements
may slow response times to critical situations so much
that potentially controllable situations may become
lost causes. So, it is advisable to be as well prepared
as possible in anticipation of chemical control activities.
A risk assessment or feasibility study may assist in
determining whether a rotenone operation should
proceed3.
Considerations may include:
•an accurate estimate of water volume to be treated
•calculations of desired concentration of toxicant,
preferably backed by onsite bioassays to account for
variability in product performance under different
water conditions
Advantages and limitations of rotenone for spot removal of pest fish populations.
Advantages
Limitations
• potential to kill pest fish quickly
• removes all fish with 1–2 applications
• readily available
• not persistent in the environment; breaks down quickly
into harmless byproducts
• can be neutralised by strong oxidants (eg potassium
permanganate)
• very low mammalian toxicity, so relatively safe to use
• non-target species can be revived if quickly collected
• various application methods (eg tank/hose, backpack
sprayer, helicopter)
• available in powdered or liquid formulations
• USA rotenone user’s manual available
• registered for use in Australia
• application is human resource intensive (ie planning,
application and removal/disposal of large quantities of
dead fish)
• will kill all fish, not just pest fish
• moderate cost
• APVMA permit needed
• difficult to apply in large water bodies and flowing water
— more suited to closed systems, such as ponds, small
lakes, wetlands
• may result in temporary loss of public water supply and
recreational activities
• causes temporary impacts on aquatic habitats and nontarget species (eg amphibians, macroinvertebrates)
• application is weather dependent
• difficult to apply in complex habitats
•detoxification and cleanup needs (including the removal/disposal of large quantities of dead fish)
•drawdown of the water body if possible to reduce
the quantity of toxicant needed
•notification of all relevant government agencies
(state and local) and obtaining of necessary environmental approvals
•training of staff and occupational health and safety
considerations
•public awareness and notification/consultation.
Other possible options as fish toxins:
A number of other chemicals have been used in certain
situations to control pest fish in Australia and overseas4.
The most promising of these for widespread use would
probably be antimycin, which is used extensively as a
piscicide overseas, but has not been registered for use
in Australia. Antimycin is comparable in many respects
to rotenone with greater toxicity but it is also more
expensive.
Further information:
1. Sanger AC and Koehn JD (1997). Use of chemicals for
carp control. In: J Roberts and R Tilzey (Eds), Controlling Carp: Exploring the Options for Australia. CSIRO
Land and Water, Griffith NSW.
2. Hall DA (1988). The eradication of European carp and
goldfish from the Leigh Creek Retention Dam. Safish
1998:15–16.
3. Risk Assessments as a Tool for Pest Fish Management.
PestSmart Toolkit factsheet, Invasive Animals Cooperative Research Centre, Canberra.
4. Ayres R and Clunie P (2010). Towards a National Emergency Response System for Freshwater Fish Incursions.
PestSmart publication, Invasive Animals Cooperative
Research Centre, Canberra.
5. Allinson G (in prep). A Strategy for Developing Fish Specific Biocides and Delivery Mechanisms. PestSmart publication, Invasive Animals Cooperative Research Centre,
Canberra.
Another option that has been used successfully is lime,
which can be applied to small areas and is especially
useful for treating a defined spawning area such as carp
eggs in shallow marshlands.
Research by the Invasive Animals Cooperative
Research Centre (IA CRC):
Chemical poison options to control or eradicate pest
fish were compared as part of a project looking at rapid
response planning for pest fish control4. Another IA CRC
project5 reviews current regulatory requirements for
the registration of chemicals for pest fish control, and
a range of strategies for using chemicals in pest fish
management programs in a cost-effective manner.
Pest Fish Factsheet
Rotenone treatment of the lake Ratherheath Tarn in the Lake
District, England. Image: Gareth Davies, Environment Agency,
UK
feral.org.au
March 2012
PFFS1