Clarias gariepinus
North African catfish

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). (Teugels, 1986)

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). (Pienaar, 1968; Skelton, 1993; Teugels, 1986)

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). (Skelton, 1993; Teugels, 1986)

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). (Skelton, 1993)

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

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). (Pienaar, 1968; Skelton, 1993; Teugels, 1986)

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). (Teugels, 1986)

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). (Skelton, 1993)

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) (Skelton, 1993)

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). (d'Oultremont and Gutierrez, 2002; Na-Nakorn, Kamonrat, and Ngamsiri, 2004)

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). (Na-Nakorn, Kamonrat, and Ngamsiri, 2004; 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. (Ali and Jauncey, 2004; Fagbenro, 1998)

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