Clarias gariepinus

Geographic Range

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 palearctic
  • introduced introduced
• oriental oriental
  • introduced introduced
• ethiopian ethiopian
  • native native

Habitat

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).

• Habitat Regions
• tropical tropical
• freshwater freshwater

• Aquatic Biomes
• pelagic pelagic
• benthic benthic
• lakes and ponds
• rivers and streams
• temporary pools
• brackish water brackish water

Physical Description

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 ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Development

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 metamorphosis

Reproduction

This species participates in mass spawning.

• Mating System
• polygynandrous (promiscuous) 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.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• sexual sexual
• fertilization fertilization
  • external external

Further research should be done on the amount of parental care given in this species.

• Parental Investment
• no parental involvement

Lifespan/Longevity

North African catfish live 8 or more years (Skelton 1993).

Behavior

North African catfish are relatively poor swimmers that spends most of the time on the bottom of lakes and rivers (Pienaar 1968). They are, however, able to move across land to another water source during damp conditions (Skelton 1993). They simply extend their strong pectoral fins and spines and begin crawling through shallow pathways.

This species has been known, during intra-specific aggressive interactions, to emit an electric organ discharge that was head-positive and lasting 5-260 milliseconds (Teugels 1986).

• Key Behaviors
• natatorial natatorial
• motile motile

Communication and Perception

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 acoustic
• electric electric

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

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).

• Primary Diet
• omnivore omnivore

• Animal Foods
• birds
• mammals
• amphibians
• reptiles
• fish
• eggs
• carrion carrion
• insects
• terrestrial non-insect arthropods
• mollusks
• aquatic crustaceans
• other marine invertebrates
• zooplankton zooplankton

• Plant Foods
• seeds, grains, and nuts
• fruit

Predation

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)

Ecosystem Roles

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).

Economic Importance for Humans: Positive

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 food

Economic Importance for Humans: Negative

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).

Conservation Status

Additional Links

Encyclopedia of Life

Contributors

Hal Gunder (author), University of Michigan-Ann Arbor, William Fink (editor, instructor), University of Michigan-Ann Arbor, Matthew Wund (editor), University of Michigan-Ann Arbor.

References

Ali, M., K. Jauncey. 2004. Optimal dietary carbohydrate to lipid ratio in African catfish Clarias gariepinus (Burchell 1822). Aquaculture International , 12: 169-180.

Fagbenro, O. 1998. Short communication apparent digestibility of various oilseed cakes/meals in African catfish diets. Aquaculture International , 6: 317-322.

Na-Nakorn, U., W. Kamonrat, T. Ngamsiri. 2004. Genetic diversity of walking catfish, Clarias macrocephalus , in Thailand and evidence of genetic introgression from farmed C. gariepinus . Aquaculture , 240: 145-163.

Pienaar, U. 1968. The Freshwater Fishes of the Kruger National Park . Republic of South Africa: The National Parks Board of Trustees of the Republic of South Africa.

Sara, G., D. Scilipoti, A. Mazzola, A. Modica. 2004. Effects of fish farming waste to sedimentary and particulate organic matter in a southern Mediterranean area (Gulf of Castellammare, Sicily): a multiple stable isotope study. Aquaculture , 234: 199-213.

Skelton, P. 1993. A Complete Guide to the Freshwater Fishes of Southern Africa . Halfway House: Southern Book Publishers Ltd..

Teugels, G. 1986. A systematic revision of the African species of the genus Clarias (Pisces: Clariidae).. Annales Musee Royal de l'Afrique Centrale , 247: 1-199.

d'Oultremont, T., A. Gutierrez. 2002. A multitrophic model of a rice-fish agroecosystem: II. Linking the flooded rice-fishpond system. Ecological Modelling , 155: 159-176.