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The Management of Invasive Species in
Marine & Coastal Environments
Module 5
Incursion Management
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Module 5 Objectives
• Describe the strategies available for
managing marine and coastal
invasive species, once they have
become established
• Highlight the differences between the
various incursion management
strategies
• Introduce the techniques used in
incursion management
• Describe the decision-making process
for selecting the appropriate strategy
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Strategies
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•
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Eradication
Control
Impact mitigation
Do nothing
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Order of
preference
1
Management
option
Eradication
2
Control
3
Impact
mitigation
4
Do nothing
Goals
To ensure that no individuals of the targeted IAS
population exist at the end of the programme.
Although individuals will still be present, they will be at
lower densities and/or in fewer, contained areas than
before control was initiated.
To reduce the severity of impacts an invasive species is
causing, rather than managing the population itself.
This is a worst-case scenario, although there are many
examples. Doing nothing is the only option when an
invasion is so out of control that any attempts to do
anything would be prohibitively expensive and futile.
The expenditure is not considered worthwhile, and
money and resources would be better allocated to
dealing with more tractable IAS.
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Containment
Don’t wait until it is too late –
immediate action can save
large amounts of time and
money.
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Darwin Marina / Black striped mussel
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Developing the Strategy
Three categories:
• Mechanical/physical e.g. removals by hand (divers),
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mechanical harvesting or the creation of physical barriers
Chemical - e.g. chemical dosing, toxic baits, application
of an inorganic or organic herbicide, larvicide or other
pesticide
Biological – e.g. a target-specific pathogen, parasite,
predator, biopesticide, genetic manipulation, reproduction
manipulation or habitat modification (e.g. salinity change
by salt dosing or freshwater inundation).
Use all sources of information about
the IAS (national, regional and
international) to help decide how
best to manage it
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Approaches to Control
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Mechanical Control
• Labour-intensive and often expensive -
•
•
especially where there are dense
infestations or when an IAS is wide-spread
and occurs in remote or inaccessible areas.
Advantage of being target specific and that
non-target and environmental impacts are
usually minor.
Often the best choice when infestations are
small and easily accessible, because
individual IAS may be specifically targeted.
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Chemical Control
Involves:
• Application of chemicals (agents) directly to
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•
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water column, sediments or target species
Killing or Sterilising target species
Range of options available for various
applications
Legal and safety/health constraints
Limited applicability
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Biological Control
Involves:
• Control/eradication of target species by
•
•
another organism
– insect, bacteria, virus
– biological product (hormone)
– genetic or sterility manipulations
Host-specific pathogen, parasite or
predator
Negligible side effects on native species
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Biological Control
Disadvantages:
• The time and expense required to identify, screen and test
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•
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candidate control agents;
The time required for the released agent to multiply and cause the
required effect
Uncertainty about the level of control the agent will ultimately
bring to bear on the targeted population;
The potential for the agent to exert an unexpected effect on
native species or communities;
The population regulation mechanism underlying the principle of
biological control, which does not anticipate eradication but
reduces the invading population density and fitness, with the
prey/host or predator/parasite relationship achieving a dynamic
balance.
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Biological Control
1. Self sustaining methods:
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Classical biological control: the introduction of a
natural enemy from the original range of the IAS
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Habitat management: enhancing the
populations of native predators and parasitoids
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Adding to the IAS’ enemies (reared or cultured
and released in large numbers) when an
outbreak of the IAS has happened
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Biological Control
2. Non-self sustaining methods:
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Inducing host resistance against the IAS
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Biological chemicals. These are chemicals that
are naturally produced by living species, and
effective against certain introduced species
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The use of pathogens, parasites or predators
that will not be able to reproduce or survive in
the environment
-
Mass release of sterile males
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Caution:
• It is critical that national legislation provides for tight controls and
legal requirements, including risk analysis as an integral part of
decision making on whether introduction of a classical biological
control agent should be authorised.
 Such risk analysis should include all risks, including those for
native biological diversity (including endemic species) in the area
where the agent would be released.
 A control agent approved for one country should hence not
automatically be approved for another country.
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Assessing the Feasibility of
Available Options
Need to analyse the following:
• Background information relating to the species in
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question. This should include biological, ecological
and biogeographic information, as well as the
previous invasion history of the species.
Extent of the invasion, including size/density of the
population, and geographic area covered.
Available methods for the management option being
evaluated.
Case studies of other attempts at managing invasions
with similar characteristics or conditions.
Resources available, including man power, equipment
and budget
Cost-benefit and risk analysis.
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Eradication
Objectives :
• To restore the managed area to the condition it was
in before the introduction of the alien species.
• To accomplish the above by removing all evidence of
the introduced species.
• To maintain the managed area free of the introduced
species following the eradication programme.
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Control
Control involves reducing the numbers of
an IAS to below pre-set levels, or
containing its population within a defined
area.
• Preferable when eradication is not appropriate
or feasible
• Can be used for short-term relief from impacts,
or for ‘holding pattern while other options are
investigated
• Typically more practical, less damaging options
• More affordable in the short-term
– But require long-term funding
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Mitigation and Monitoring
Last Resort Strategies
•
Impact Mitigation
•
Monitoring / measuring change
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Key Points
• The ultimate goal of IAS management is to minimise threats to
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biodiversity, human health & welfare and economies
Once a species has become established, there are four options:
eradicate, control, mitigate or do nothing
Waiting for all possible information before deciding on how to
deal with a newly-reported IAS can be disastrous.
Use all sources of information about the IAS (local, national and
international) to help decide how best to manage it
An open and transparent process is more likely to win public and
governmental support
One agency or organisation should be responsible for the entire
process, with complete authority to make decisions and execute
them
Correctly identifying the alien species is the first step in deciding
how to manage it
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Local fishermen have reported that a different fish species has
been turning up in their catch during the current fishing season.
This species appears to be well-established and occurring in
large densities; and its presence has resulted in a decrease in
their normal catch.
1. How would you find out whether it is an invasive species or
an invasive alien species, while finding this out what steps
can you take?
2. Would you get the general public to assist? How?
3. How would you choose/ evaluate a method of control?
4. If you were to choose biological control, what factors should
you consider?
5. If you were to choose chemical control, what factors should
you consider?
6. What if all attempts to eradicate the species have failed, what
can you do?
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