Home' Partners : Partners November 2013 Contents FISHeRIeS
invAsion by Alien
by Peter Gehrke
Air-breathing fish such as striped
snakehead, walking catfish and
climbing perch have a distinct
advantage when it comes to invading new
territory: they can survive out of water for days.
It is a trait that entices fishers to transport
live fish between villages and islands. But
even without this assistance, the air-breathing
fish are known to waddle crudely between
water systems in the manner of intrepid, semi-
amphibious missing links.
In their native range—which covers
Southern and South-East Asia from China to
Pakistan—they are an important food fish of
considerable economic importance. But since
their introduction in Indonesia, the species
have proven voracious predators with a natural
talent for spreading southward.
They entered Papua New Guinea’s Western
Province from Indonesia during the 1980s and
rapidly established wild populations in the Fly
River system and surrounding catchments,
where they are proving difficult to control and
appear to be spreading. All three species were
recorded in the Kikkori River, 150 kilometres east
of the Fly, and unconfirmed reports also place
climbing perch in the Port Moresby region.
From here, they are moving towards
northern Australia, where they pose a threat
to native species such as barramundi. Already
climbing perch is established on the Australian
islands of Saibai and Boigu in Torres Strait.
To better grasp the biosecurity implications
of this alien invasion, ACIAR commissioned the
Snowy Mountains Engineering Corporation
(SMEC) to undertake a scoping study and assess
the policy implications for Papua New Guinea.
Arresting An Alien invAsion
Snakeheads are the most voracious of the three
species, able to grow up to 1 metre long. They
are expected to affect recruitment of species
such as barramundi by preying on juveniles in
Climbing perch are smaller, growing to
about 25 centimetres, and use strong fin spines
and flexible sub-opercula to pull themselves
over land. They feed on aquatic plants, shrimps
and small fish. Predatory Australian species such
as large fork-tailed catfish and barramundi have
been found dead with climbing perch lodged
in their throats.
Walking catfish grow to about 50 centimetres
and have an omnivorous diet, feeding on insects
and insect larvae, earthworms, shells, shrimps,
small fish, aquatic plants and detritus.
If these species establish populations
in Australia, potential effects on aquatic
ecosystems and fisheries are likely to be
significant through predation, competition for
food, habitat damage, disease and parasites.
In addition to effects on freshwater species,
commercial species that spend time in estuaries
and coastal wetlands could also be affected.
For the time being, a strong public
awareness campaign by the Australian
Quarantine and Inspection Service appears to
be preventing their spread further south from
Saibai and Boigu islands.
Beside fishers, these predators have been
found to have other means of invading Australia
at their disposal. They can migrate along river
channels, through coastal waters in low-salinity
river plumes, overland between rivers and
wetlands or aquaculture ponds, and through
drainage channels alongside road networks.
Dead pelicans with climbing perch in
their throats have been found on other
islands, suggesting that birds may also be a
vector for transport.
Available information suggests that climbing
perch are spreading most rapidly, especially
into Torres Strait, but it is highly likely that
striped snakehead and walking catfish will
follow within the next 10 years.
Options in Australia to reduce the potential
impact on local environments and fisheries
have been identified. These include working
with Papua New Guinea to contain populations
and prevent their further spread, including
across Torres Strait.
Besides community education to reduce the
incidence of human-assisted spread, a need
was also identified to develop the capability to
eradicate populations where it is feasible and
practical to do so, especially at the island level.
While trade in invasive fish in Australia is
prohibited under existing legislation, continued
vigilance to prevent illegal importation of live
fish is recommended.
Following the completion of the project,
a workshop was held in Brisbane to raise
awareness of the threats posed by these
invasive species. Outcomes include a risk
assessment of existing policies in Australia,
identification of linkages between government
agencies, assessment of communication
processes, and identification of knowledge
gaps on potential rates of spread, biology and
PARTNERS NOvEMBER 2013
impacts of invasive species, and control options.
The project was conducted with strong
assistance from Boga Figa, formerly with James
Cook University, and Jacob Wani, National
Fisheries Authority of Papua New Guinea. n
More information: Peter gehrke,
Achievements over the years
n A rapid diagnostic test for foot and mouth
disease developed in an ACIAR collaboration
with Thailand allows the confirmation of
the disease in a matter of hours, saving vital
time in containing a disease outbreak.
n The development of a reliable and
accurate diagnostic test for bluetongue
disease in cattle and sheep facilitated a
change in Chinese quarantine policy to
allow the importation of Australian live
cattle. This ACIAR project provided the
basis of a mutually acceptable quarantine
procedure between Australia and China
relating to the export of live cattle.
n In Australia, ACIAR projects underpinned
methods now used for active animal
health surveillance in Queensland’s
extensive beef industry sector. This
includes the adoption by the Australian
Quarantine and Inspection Service
of a method to identify and diagnose
Trypanosoma evansi, a protozoan that can
infect a wide range of animals.
n graziers in Australia’s extensive cattle
grazing areas benefited from the
application of tick fever tests derived from
ACIAR projects that aid decision-making
regarding whether expenditure on
vaccines is warranted.
n ACIAR research contributed to the effective
papaya fruit fly eradication campaign in
northern Queensland. Research on fruit
flies in the South Pacific region contributed
towards the development of regional
quarantine strategies to manage fruit fly
problems within neighbouring countries.
A striped snakehead
caught near the Fly river,
Papua New Guinea.
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