The African sharptooth catfish was introduced all over the world in the early 1980s for aquaculture purposes, so is found in countries far outside its natural habitat, such as Brazil, Vietnam, Indonesia, and India.
The African sharptooth catfish is a large, eel-like fish, usually of dark gray or black coloration on the back, fading to a white belly. In Africa, this catfish has been reported as being second in size only to the vundu of the Zambesian waters, although FishBase suggests the African sharptooth catfish surpasses that species in both maximum length and weight.
C. gariepinus has an average adult length of 1–1.5 m (3 ft 3 in–4 ft 11 in). It reaches a maximum length of 1.7 m (5 ft 7 in) TL and can weigh up to 60 kg (130 lb). These fish have slender bodies, flat bony heads, notably flatter than in the genus Silurus, and broad, terminal mouths with four pairs of barbels. They also have large accessory breathing organs composed of modified gill arches. Also, only the pectoral fins have spines.
It is a nocturnal fish like many catfish. It feeds on living, as well as dead, animal matter. Because of its wide mouth, it is able to swallow relatively large prey whole. It has been known to take large waterbirds such as the common moorhen. It is also able to crawl on dry ground to escape drying pools. Further, it is able to survive in shallow mud for long periods of time, between rainy seasons.
African catfish sometimes produce loud croaking sounds, not unlike the voice of the crow.
Spawning mostly takes place at night in the shallow, inundated areas of the rivers lakes and streams. Courtship is preceded by highly aggressive encounters between males. Courtship and mating takes place in shallow waters between isolated pairs of males and females. The male lies in a U-shape curved around the head of the female, held for several seconds. A batch of milt and eggs is released followed by a vigorous swish of the female's tail to distribute the eggs over a wide area. The pair usually rests after mating (from seconds up to several minutes) and then resume mating.
Parental care for ensuring the survival of the catfish offspring is absent except by the careful choice of a suitable site. Development of eggs and larvae is rapid, and the larvae are capable of swimming within 48–72 hours after fertilization.
The rearing of the African sharptooth catfish in Africa started in the early 1970s in Central and Western Africa, as it was realized to be a very suitable species for aquaculture, as:
Disadvantage of the Hetero-clarias hybrid:
North African catfish have been widely introduced around the world. They are found as far south as South Africa and north into northern Africa. They have also been introduced in Europe, the Middle East, and in parts of Asia. They are potamodromous, which means they migrate within streams and rivers (Teugels 1986).
Biogeographic Regions: palearctic (Introduced ); oriental (Introduced ); ethiopian (Native )
North African catfish are elongate with fairly long dorsal and anal fins. The dorsal fin has 61-80 soft rays and the anal fin has 45-65 soft rays. They have strong pectoral fins with spines that are serrated on the outer side (Teugels 1986).
This species can attain sizes of up to 1.7 meters including the tail and can weigh up to 59 kg when fully grown. They posses nasal and maxiallary barbels and somewhat smallish eyes. Their coloring is dark grey or black dorsally and cream colored ventrally. Adults posses a dark longitudinal lines on either side of the head; however, this is absent in young fish. Adult's heads are coursely granulated, while the head is smooth in the young. The head is large, depressed, and heavily boned. The mouth is quite large and subterminal (Skelton 1993).
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: male larger
gill openings wide; air-breathing labyrinthic organ arising from gill arches; first gill arch with 24 to 110 gillrakers;
cleithrum pointed, narrow with longitudinal ridges and with sharpness. Mouth terminal, large. Four pairs of barbels present.
Long dorsal and anal fins; without dorsal fin spine and adipose fin. Anterior edge of pectoral spine serrated. Caudal fin rounded.
Colour varies from sandy-yellow through gray to olive with dark greenish-brown markings, belly white.
Can be confused with: The morphology of the cleithrum appears as a useful character to distinguish the closely related catfish species, Clarias anguillaris and C. gariepinus . Elsewhere, the difference seems less distinct, although the presence of a pointed cleithrum is typical for C. gariepinus (Benech et al ., 1993).
North African catfish live in a variety of freshwater environments, including quiet waters like lakes, ponds, and pools. They are also very prominent in flowing rivers, rapids, and around dams. They are very adaptive to extreme environmental conditions and can live in pH range of 6.5-8.0. They are able to live in very turbid waters and can tolerate temperatures of 8-35 degrees Celsius. Their optimal temperature for growth is 28-30 degrees Celsius (Teugels 1986).
They are bottom dwellers and do most of their feeding there. They are also obligate air breathers, which means they do spend some time on the surface. This species can live in very poorly oxygenated waters and is one of the last species to live in such a uninhabitable place (Pienaar 1968). They are also able to secrete mucus to prevent drying and is able to burrow in the muddy substrate of a drying body of water (Skelton 1993).
Range depth: 4 to 80 m.
Habitat Regions: tropical ; freshwater
Aquatic Biomes: pelagic ; benthic ; lakes and ponds; rivers and streams; temporary pools; brackish water
North African catfish are omnivores. They are not specific in their food requirements. They are known to feed on insects, plankton, snails, crabs, shrimp, and other invertebrates. They are also capable of eating dead animals, birds, reptiles, amphibians, small mammals, other fishes, eggs, and plant matter such as fruit and seeds. Because they are mobile on land, they are able to prey on terrestrial organisms. This species may also hunt in packs on occasion by herding and trapping smaller fish. They are also refered to as sharptooth catfish because of fine, pointed bands of teeth (Skelton 1993).
Animal Foods: birds; mammals; amphibians; reptiles; fish; eggs; carrion ; insects; terrestrial non-insect arthropods; mollusks; aquatic crustaceans; other marine invertebrates; zooplankton
Plant Foods: seeds, grains, and nuts; fruit
Primary Diet: omnivore
North African catfish are an important player in certain ecosystems. In Thailand, they have been introduced as a farm fish. However, in these marshes and swamps where they are raised, there is a native catfish, walking catfish, that is nearing extinction. This is due to the population expansion of the the North African catfish. It is also due to the back-crossing of the walking catfish and the hybrid of the two species. This is also reducing the genetic variation of the native walking catfish (Na-Nakorn et al 2004). This species is also important in nutrient recycling in conjuction with rice fields. The transfer of nutirents takes place from the pond to the rice via fish feces, which increases rice yields (d'Oultremont and Gutierrez, 2002).
Because of the abundance of this species and its lack of mobility on land and in water, it is preyed upon widely. Man is the primary predator, but others include leopards, crocodiles, and birds. The fish eagle and marabou stork are very common predators (Skelton 1993)
It is not known whether this species in particular uses its pectoral spine to make sounds, but in other species of catfish this is very common behavior. This species has also been know to generate electic organ discharges, but it is not known if this behavior is communicative (Teugels 1986).
Communication Channels: acoustic ; electric
Perception Channels: visual ; tactile ; acoustic ; chemical
North African catfish lay their eggs in vegetation. The eggs hatch within 25-40 hours. The larvae are able to swim and are able to feed within 2 or 3 days. Growth is very rapid, with males reaching an ultimately larger size than females (Skelton 1993).
Development - Life Cycle: metamorphosis
North African catfish live 8 or more years (Skelton 1993).
Status: wild: 8 (low) years.
This species participates in mass spawning.
Mating System: polygynandrous (promiscuous)
This species in known to breed in the summers after the rainy season. Vast numbers migrate to "flooded shallow grassy verges of rivers and lakes" (Skelton 1993). The eggs are laid in the vegetation.
Breeding season: Summer
Average gestation period: 25-40 hours.
Key Reproductive Features: seasonal breeding ; sexual ; fertilization (External )
Further research should be done on the amount of parental care given in this species.
Parental Investment: no parental involvement
US Federal List: no special status
CITES: no special status
Because north African catfish are heavily farmed around the world, there are some adverse effects on native populations of fishes. North African catfish breed with native walking catfish, which produce some sterility when back crossing occurs (Na-Nakorn et al, 2004). Another adverse effect of fish farming in general is the effect of fish farm waste on the surrounding ecosystem. There are large amounts of feed and fecal matter near fish farms. This waste is further spread by wild fish and deposited an even further distance from the farm. This kind of dispersal has great effects on the environment. It affects the feeding behavior and performance of other aquatic animals, including other fishes, crustaceans, and mussels (Sara et al., 2004).
North African catfish are a very good food source for humans. They are farmed extensively all over Asia. Because of this, this species and other farmed catfish are involved with extensive diet experiments. These experiements are meant to find the best diet for optimal yield. One such study is attempting to find the optimal dietary carbohydrate to lipid ratio in the fish's diet (Ali and Jauncey, 2004). Another similar study is testing the digestibility of oilseed cakes and meals for use in the fish's diet (Fagbenro, 1998). There are many other studies that are testing similar ideas about the African catfish's diet to improve the success of the farms.
Positive Impacts: food