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Africa’s First Armoured Catfish Invasion
T
he South American armoured catfish
family Loricariidae includes more
than 700 nominal species. Some
are popular aquarium fishes in the global
pet trade. Releases by aquarists and escape
from fish farms have resulted in several
armoured catfish invasions in Central and
North America, Asia and now, Africa.
Exotic, or non indigenous species can be
extremely destructive to local environments
they may be introduced to. Often, such
species have no natural predators or means
of natural control when introduced to areas
outside their home ranges. While Africa
has seen some intentional fish introductions
(usually for sport) such as bass and carp,
some introductions have been motivated
Nseleni Reserve manager and Rhodes
University PhD candidate Roy Jones
measuring catfish samples.
P a g e 12
by commercial gain, such as kapenta
and more recently Niloticus bream. Still
other introductions have occurred when
unsuspecting individuals carelessly dispose
of aquarium fish in rivers and dams. All
effect indigenous species to some degree,
while some introductions such as the
Redclaw crayfish (from Australia) could be
absolutely disastrous over time.
In South Africa, C·I·B core team member
Olaf Weyl from the South African Institute
for Aquatic Biodiversity in collaboration
with Roy Jones (Ezemvelo KZN Wildlife
and Rhodes University PhD student), Ernst
Schwartz (SAIAB) and Martin Hill (Rhodes
University) have been assessing Africa’s first
documented armoured catfish invasion in the
Richards bay area. Armoured catfishes were
first reported from a lake near the town of
Empangeni in 2000. This was followed by
the formal collection of specimens from
the Mthlathuse River in 2004 and from the
adjacent Nseleni River system in 2007. This
indicated the need for a fuller assessment
because documented impacts of armoured
catfish invasions include destabilisation of
river banks by their breeding burrows. Says
a report from C.I.B “To do this we conducted
fish surveys using valve traps, fyke nets, gill
nets, electrofishing and habitat traps. We
also interviewed local community members
who were encouraged to report and donate
specimens. The information from interviews
and specimens collected during surveys and
from donations were then used to identify
the invading species and its invasion stage
according to unified invasion framework
criteria (see Blackburn et al. 2011, Trends
in Ecology and Evolution 26).”
Over two years of surveys, 346
specimens were collected, including 12mmlong juveniles, and adults measuring almost
50cm. Identification required both taxonomic
keys and DNA barcoding because selection
in the pet trade has resulted in invading
Email [email protected], [email protected]
A juvenile vermiculated sailfin catfish
sampled from the Nseleni River.
populations exhibiting a wide variety of
colour patterns that are not found in natural
populations. Specimens were identified
as vermiculated sailfin Pterygioplichthys
disjunctivus (Weber 1991), a native to the
Madeira River drainage of the Amazon basin
in Brazil and Bolivia and the main nuisance
species in Mexico, USA, Philippines and
Taiwan.
Interestingly, P. disjunctivus is not
on the draft list of fish species whose
importation is allowed under the National
Environmental Management: Biodiversity
Act (Act 10 of 2004), and is likely that
during importation it was identified as a
closely-related species which is allowed
in South Africa. Accidental or intentional
misidentifications are common in the pet
trade and often result in the importation
of invasive organisms. On escape from
captivity, this fish established first in the
Mthlathuse River and then spread to the
Nseleni River via an inter-basin water
transfer. The researchers characterised the
invasion as D2: “self-sustaining population
in the wild with individuals surviving and
reproducing a significant distance from their
original point of introduction”. The report
concludes “Containing this invasion will
require educating the public on the dangers
of fish introductions and discouraging
the trade in loricariid species with proven
invasion histories and their look-alike
species.”
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