français
Aquaculture Feed and Fertilizer Resources Information System
 

North African catfish - Clarias gariepinus

(Burchell, 1822) [Clariidae]

FAO official common names: Fr - Poisson-chat nord-africain; Es - Pez-gato

Taxonomic and biological features:

Distinguishing characters
Body strongly compressed towards caudal. Colour varies from almost black to light brown, often marbled in shades of olive green and grey; underparts of head and abdomen white, often with red flush to extremities of fins, especially when spawning (Teugels, 1986, 1996; Skelton, 1993). Head large and depressed, heavy boned and completely encased above (Figure 1). The species has 61–75 dorsal rays and 45–60 anal fin rays. Dorsal fin extends from behind head nearly to base of caudal fin. Anal fin extends from base of anus to base of caudal fin. No adipose fin. Caudal fin rounded. Pectoral fin with barbed spine, used for defense or "walking" overland. Eyes small, lateral. Mouth large, subterminal, jaws with broad band of fine, pointed teeth (Figure 1). Vomerine band of similar teeth. Four pairs of long filamentous barbels; maxillary barbels longest. First gill arch with numerous (24–110) close-set, slender gill rakers. A large chamber above gill arches contains the suprabranchial organs (multibranched accessory air-breathing organs). These function like a lung and render clariids capable of aerial respiration and thus able, under conditions of low dissolved oxygen, to still meet 80–90 percent of their oxygen requirements (Moreau, 1988).The species is an obligate air breather.

Distribution
The species ranges from the Gariep (Orange) River in South Africa northwards through Central, West and North Africa, through the Middle East and into Eastern Europe. Of all freshwater fishes it is the species with the widest latitudinal range in the world (about 70 degrees latitude) (de Moor and Bruton, 1988). The species has been widely distributed for aquaculture purposes to many parts of the world (Welcome, 1988, Na-Nakorn and Brummett, 2009).

Reproduction
The species is a gonochorist. Size and age at first maturity vary greatly (150–750 mm TL between one and four years), although the average size at sexual maturity is around 300–350 mm TL. The elongate and pointed urinogenital papilla of the male and the more rounded papilla of the female are the only external features (Figure 2) upon which the sexes can be distinguished from each other (Bruton, 1979a). Average relative fecundity is in the region of 20 000–25 000 eggs/kg body weight. Fecundity is related exponentially to total length in mm (Fecundity = 0.000004TL mm3.563) and linearly to weight in grams (Fecundity = 45.18W (g) + 5 786).

Spawning normally takes place in spring and summer (at night) in newly inundated, shallow water. Pair formation takes place and prenuptial aggression may be intense. Courtship behaviour is fairly complex and culminates in the release of gametes. Fertilized eggs are adhesive and are distributed vigorously and adhere to submerged vegetation. Under natural conditions, a pair may consecutively mate 2–5 times (Bruton, 1979a). In rivers large migrations may take place before spawning (Merron, 1993), although potamodresis appears not to be obligatory. There is no parental care of the young except for the careful choice of a suitable spawning site. The shallow, recently flooded, highly vegetated areas usually chosen for spawning are typically free of predators and rich in food resources. Egg and larval development is rapid. Depending on temperature the larvae hatch after 24–48 h. Exogenous feeding commences within 80 h of hatching. The larval period lasts for 7–10 d. Larvae and juveniles are cryptic and seek out dark, confined microhabitats where they feed on small invertebrates in shallow inshore areas (Bruton, 1979a).

The genetic implications of domestication are discussed by Na-Nakorn and Brummett (2009).