Water quality requirement of African catfish is similar to that of other catfish species in egg and larvae stage (Table 2). In first phase of nursing it requires environment similar to that of carp fry (Viveen et. al., 1986; Janssen, 1987). After development of accessory repitatory organ, it can survive in extremely poor conditions from fingerling stage. Upper limits of water quality tolerance of carps is shown in Table 3 and the data on water quality in an intensive and pond culture system of African magur is compared with that. It shows that, water suitable for rearing catfish is quite different from that for carp species.
Table 2 Water quality requirement of catfish hatcheries (After Tucker, 1988 in Boyd, 1990)
| Chemical and physical feature | Desired level |
| Salinity | 100–8000 mg/liter |
| Total dissolved gases | 105 % |
| Dissolved oxygen | min. 6 mg/liter |
| Carbon dioxide | max. 10 mg/liter |
| Calcium hardness | min. 20 mg/liter as CaCO3 |
| Ammonia (Un-ionized) | max.0.05 mg/liter |
| Iron | max. 0.5 mg/liter |
| Hydrogen sulfide | 0.0 |
Table 3 The upper limit of the water quality tolerance of carps and the prevailing water quality in a recirculated system and in a pond during African catfish rearing (After Haylor, 1989; Peteri et al. 1989)
| Parameters | Unit | Tolerance of carps | Water quality tolerated by magur | |
| Recirc* | Pond | |||
| Salinity | mg/l | 9–12000 | no data | 4300 |
| pH | 8.5 | 7.2 | 8.9 | |
| H2S | mg/l | 0.0 | 0.2 | 0.4 |
| NH4 | mg/l | 2.5 | 15.0 | 1.8 |
| NH3 | mg/l | 0.1 | 0.2 | 0.5 |
| NO2 | mg/l | 0.3 | 1.9 | 0.0 |
| COD(Pot. permanganate) | mg/l | 15 | 18 | 48 |
| O2 | mg/l | 4.0 | 1.7 | no data |
| Chlorophyll-a | mg/m3 | 80 | no data | 1942 |
This high tolerance of African magur makes it possible to stock it in significantly higher stocking density than any other fish species. High environmental tolerance and wide food spectrum are the main reasons why African catfish is excellent for tropical and subtropical pond fish culture (Haylor, 1989).
Though the fecundity of magur is less than that of carp broodfish, induced seed production of magur is easier. Incubation and larval rearing needs no sophisticated facilities. The simple non-sophisticated method of seed production (fingerling production in pond) is highly effective for this species.
As it develops the air breathing organ, transportation of the fish of any age group over 2 weeks is not difficult. No special equipment is necessary to keep the fish alive in the market.
Main disadvantage of the species is its high protein requirement in intensive culture. In the absence of adequate source of animal protein, only extensive culture of the species is suggested.
Important technical data relating to African magur, Tilapia and carp production are summarized for comparison in Table 4. Data are given from Woynarovich and Horvath (1980), Haylor (1989), Rana(1989).
Table 4 Relevant data on reproductive biology and rearing techniques of magur, tilapia and carps (After Haylor, 1989; Rana, 1989 and Woynarovich and Horvath, 1980)
| Species | Magur | Tilapia | Carps |
| Maturity in nature | 1–3 years | 1–2 years | 1–3 years |
in pond | 7–10 months | 5–6 months | 1–3 years |
| Fecundity | 10–200 000 | 200–1100 | 300 000–1 000000 |
| Embryonic development in 27–28°C | 30–35 hours | 90–100 hours | 20–45 hours |
| Firs food | 35–45 hours | 35–45 hours | 60–80 hours |
| Yolk absorption | 150–160 hours | 350 hours | 60–80 hours |
| Survival in pond nursing | 40–60 % | 70–90 % | 40–70 % |
| Protein requirement | |||
| Fry | 50 % | 50 % | 50 % |
| Fingerling | 40 % | 35 % | 40 % |
| Adult | 25–35 % | 25–30 % | 35 % |
| Food conv. ratio (FCR) | |||
| in tank | 0.7–1.2 | 1.4–2.2 | 0.9–1.2 |
| in pond | 1.5–4.0 | 1.8–2.6 | 4.0–7.0 |
| Growth (6 months) | 400–1000 g | 50–150 g | 300–1000 g |
| Pond production with manuring and feeding | 22,000 kg/ha/year | 6000 kg/ha/year | 4000–5000 kg/ha/year |
Attempts on semi-natural and artificial seed production of African magur were first made in the middle of seventies. Micha (1975) stimulated the spawning changing the environment. He stocked 6 females and 4 males in shallow ponds with water surface area of 400m2 and increased the water depth upto 0.5 m. This was the triggering factor of spawning for broodfish collected from natural water bodies in natural breeding season.
Hogendoorn (1979) released the broodfish in pond after injection with DOCA (Desoxi-Corticosterone Acetate ) at the rate of 50 mg/kg. This work was carried out in 1975–1976. In the same year he injected females with carp pituitary glands and stripped the eggs. The males were sacrificed for removing testis. The fertilized eggs were pasted on plastic sheet and sank in pond water. Later eggs were incubated and hatched in trays and fry were reared in tanks (Hogendoorn, 1980).
Sometimes 15–17 fingerling/ m2 were produced following above mentioned methods, but usually the survival was very poor due to damage caused by aquatic insects and tadpoles.
Main limiting factor for survival of African magur fry in tank culture was the lack of quality fish food. Survival and growth was always better after feeding Artemia and zooplankton. Feeding with other feed than natural one always decreased the growth and survival in initial attempts (Hogendoorn, 1980). With a well balanced feed containing high ratio of protein (55%) Uys and Hetch (1985) got better growth compared to that of zooplankton feeding. Nowdays, for artificial reproduction of African magur, pituitary glands of market-size catfish (Viveen et al., 1986) or carp PG (Janssen, 1987) or HCG are used. The results of Chinese fish culturists showed that LHRH is not a good agent for induced breeding (Wembiao et al., 1988) of this species.
Stripping of magur females is similar to stripping of other fish species. The milt is usually collected after removing testes, though there are methods available for stripping of male fish also (Van der Waal, 1985).
Special troughs (Viveen et al. 1986, 1985; Janssen, 1987) or Zoug jars(Peteri et. al., 1989) are used for incubation. The same troughs are used for larval rearing in hatcheries.
Most accepted method of fingerling production in Africa, China and Thailand is the pond production method. Fingerlings are produced in warm water recirculation systems or in raceways supplied with warm water of power stations, in cooler areas.
