Download Invasive crayfish alert!

The colour of C. quadricarinatus ranges from dark brown to blue-green and adult males have a distinct red patch
or stripe on the outer margin of the chelae (claws) and may measure up to 20cm in length.
WHY SHOULD WE BE WORRIED?
• There are no native freshwater crayfish in mainland Africa and this
species can out-compete and even eat native freshwater crabs; it is also
capable of affecting the many endemic crustaceans, molluscs and small
fish of Lake Tanganyika causing (in the extreme) significant changes in
populations and even extinctions.
• These Crayfish are omnivorous and veracious feeders. In areas where
this species has been introduced, it has been able to impact native fauna
through direct competition and predation.
• The species may also modify the habitat thus making it unsuitable for
native species.
• Freshwater crayfish may spread previously unknown parasites into
native populations of crustaceans and other animals. They have been
reported (in other places) to carry a number of pathogens, including
viruses, bacteria, fungi, protozoan and metazoan parasites.
CONTROL OPTIONS:
Crayfish are extremely difficult to control and while predatory fish
have been tried, none has been very successful. The use of reproductive
hormones in small water bodies is being tested, but otherwise only drainage
and physical removal have been effective. It is next to impossible to drain
natural wetlands and certainly true of large lakes. Other management
strategies include creating barriers to prevent its spread, prohibiting the
transport of live crayfish, and improving public education about its risks
to the environment. Freshwater crayfish should not be kept in aquaculture
systems anywhere in the entire Lake Tanganyika catchment and especially
not in the lake itself.
WHAT IS MY ROLE IN
PREVENTING SUCH
INVASIONS?
• Do not introduce any species of
freshwater crayfish into wetlands
(for aquaculture or aquarium
trade) as this aids their spread.
• Report any sightings of
these crayfish to appropriate
authorities (Lake Tanganyika
Authority or Fisheries and
Environment Agencies of the
four riparian states).
• Freshwater crayfish have
already been recorded in the
neighbouring Zambezi basin,
the Lake Victoria and Nile River
basins. Mapping their spread
is important in order to issue
alerts of threats to freshwater
systems not yet invaded and to
prevent threats to the endemic
and indigenous freshwater
biodiversity of Lake Tanganyika
and its catchment.
IUCN Global Invasive Species Initiative
IUCN ESARO Regional Office, Nairobi, Kenya
For more information: contact: [email protected] or [email protected] or [email protected]
Photo by: Geoffrey Howard
Cherax quadricarinatus
(Australian red-claw crayfish)
Photo by: Geoffrey Howard
Photo by: Harris Phiri
Invasive crayfish alert!
Procambarus clarkii (Louisiana crayfish)
This freshwater crustacean, native to Southern USA, has become a big threat to African wetlands since its
introduction several decades ago. Adults are dark red-brown in colour and may measure up to 15cm in length. It is
considered to be one of the most adaptable freshwater crustaceans (Order Decapoda) and is able to grow quickly,
even in only seasonally present water, being tolerant of dry conditions that last up four months.
WHY SHOULD WE BE WORRIED?
This alien freshwater crayfish has a destructive feeding
behavior. It feeds on: submerged and emergent water
plants, semiaquatic vegetation, snails and other molluscs,
small fish, other crustaceans found in lakes, rivers and both
natural and man-made wetlands (dams, reservoirs, farm
ponds, swamps and floodplains) in shallow water and on
the edges of deeper water bodies.
• Procambarus clarkii can destroy native wetland vegetation
and the snail and crustacean fauna of freshwater
ecosystems. It has been held responsible for the
disappearance of water lilies and submerged vegetation
as well as many species of snails in wetlands of Eastern
and Southern Africa where it has become invasive.
• It is possibly a threat to the existence of smaller fish of
biodiversity value.
• Its burrowing habits can damage dams and reservoirs.
• It may out-compete the native freshwater crabs and other
aquatic species, and carry crayfish virus vibriosis and a
number of worms parasitic on vertebrates.
PATHWAYS OF SPREAD:
•In some cases P. clarkii was introduced to manmade wetlands to control bilharzia-spreading
snails from where it spread to other wetlands.
•This species has been introduced to fish ponds in
the adjacent catchments from where it has spread,
initially upstream in rivers bit also across wetlands.
•As it can function as an ‘air-breather’, the adults
can travel considerable distances across land
(especially in damp grass) and so spread from one
wetland to another and even from one river or lake
catchment to another.
•Alien freshwater crayfish might enter the
catchment of Lake Tanganyika from the Lake
Victoria/Nile River catchment or from the Zambezi
River catchment along the major inflowing rivers
to the lake – Rusizi River, Malagarasi River,
Kalambo River, Lufubu River as well as smaller
tributaries of the lake
Cherax quadricarinatus
(Australian red-claw crayfish)
The colour of C. quadricarinatus ranges from dark brown to blue-green and adult males have a distinct red patch
or stripe on the outer margin of the chelae (claws) and may measure up to 20cm in length.
WHY SHOULD WE BE WORRIED?
• There are no native freshwater crayfish in mainland Africa and this
species can out-compete and even eat native freshwater crabs; it is also
capable of affecting the many endemic crustaceans, molluscs and small
fish of Lake Tanganyika causing (in the extreme) significant changes in
populations and even extinctions.
• These Crayfish are omnivorous and veracious feeders. In areas where
this species has been introduced, it has been able to impact native fauna
through direct competition and predation.
• The species may also modify the habitat thus making it unsuitable for
native species.
• Freshwater crayfish may spread previously unknown parasites into
native populations of crustaceans and other animals. They have been
reported (in other places) to carry a number of pathogens, including
viruses, bacteria, fungi, protozoan and metazoan parasites.
CONTROL OPTIONS:
Crayfish are extremely difficult to control and while predatory fish
have been tried, none has been very successful. The use of reproductive
hormones in small water bodies is being tested, but otherwise only drainage
and physical removal have been effective. It is next to impossible to drain
natural wetlands and certainly true of large lakes. Other management
strategies include creating barriers to prevent its spread, prohibiting the
transport of live crayfish, and improving public education about its risks
to the environment. Freshwater crayfish should not be kept in aquaculture
systems anywhere in the entire Lake Tanganyika catchment and especially
not in the lake itself.
WHAT IS MY ROLE IN
PREVENTING SUCH
INVASIONS?
• Do not introduce any species of
freshwater crayfish into wetlands
(for aquaculture or aquarium
trade) as this aids their spread.
• Report any sightings of
these crayfish to appropriate
authorities (Lake Tanganyika
Authority or Fisheries and
Environment Agencies of the
four riparian states).
• Freshwater crayfish have
already been recorded in the
neighbouring Zambezi basin,
the Lake Victoria and Nile River
basins. Mapping their spread
is important in order to issue
alerts of threats to freshwater
systems not yet invaded and to
prevent threats to the endemic
and indigenous freshwater
biodiversity of Lake Tanganyika
and its catchment.
IUCN Global Invasive Species Initiative
IUCN ESARO Regional Office, Nairobi, Kenya
For more information: contact: [email protected] or [email protected] or [email protected]
Photo by: Geoffrey Howard
Photo by: Harris Phiri
Invasive crayfish alert!
Procambarus clarkii (Louisiana crayfish)
This freshwater crustacean, native to Southern USA, has become a big threat to African wetlands since its
introduction several decades ago. Adults are dark red-brown in colour and may measure up to 15cm in length. It is
considered to be one of the most adaptable freshwater crustaceans (Order Decapoda) and is able to grow quickly,
even in only seasonally present water, being tolerant of dry conditions that last up four months.
WHY SHOULD WE BE WORRIED?
This alien freshwater crayfish has a destructive feeding
behavior. It feeds on: submerged and emergent water
plants, semiaquatic vegetation, snails and other molluscs,
small fish, other crustaceans found in lakes, rivers and both
natural and man-made wetlands (dams, reservoirs, farm
ponds, swamps and floodplains) in shallow water and on
the edges of deeper water bodies.
• Procambarus clarkii can destroy native wetland vegetation
and the snail and crustacean fauna of freshwater
ecosystems. It has been held responsible for the
disappearance of water lilies and submerged vegetation
as well as many species of snails in wetlands of Eastern
and Southern Africa where it has become invasive.
• It is possibly a threat to the existence of smaller fish of
biodiversity value.
• Its burrowing habits can damage dams and reservoirs.
• It may out-compete the native freshwater crabs and other
aquatic species, and carry crayfish virus vibriosis and a
number of worms parasitic on vertebrates.
PATHWAYS OF SPREAD:
•In some cases P. clarkii was introduced to manmade wetlands to control bilharzia-spreading
snails from where it spread to other wetlands.
•This species has been introduced to fish ponds in
the adjacent catchments from where it has spread,
initially upstream in rivers bit also across wetlands.
•As it can function as an ‘air-breather’, the adults
can travel considerable distances across land
(especially in damp grass) and so spread from one
wetland to another and even from one river or lake
catchment to another.
•Alien freshwater crayfish might enter the
catchment of Lake Tanganyika from the Lake
Victoria/Nile River catchment or from the Zambezi
River catchment along the major inflowing rivers
to the lake – Rusizi River, Malagarasi River,
Kalambo River, Lufubu River as well as smaller
tributaries of the lake