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Aquaculture Feed and Fertilizer Resources Information System
 

North African catfish - Feeding

For optimum growth and survival, larvae and early juveniles require live feed.  Early rearing of catfish larvae and fry normally takes place in a hatchery and lasts for 12–14 d at a temperature of 28 °C. Research has shown that live food in the form of enriched Artemia nauplii, small Daphnia, Moina or rotifers is essential for the first 4–6 d after the start of exogenous feeding (Hogendoorn, 1980; Uys and Hecht, 1985; Verreth and van Tongeren, 1989; Haylor, 1993; Hecht 1996; Awaiss and Kestemont, 1998) and is preferable to dry food only (Appelbaum and van Damme, 1988). Nwachukwa (1999) found that periphyton could also be used partially or wholly as an alternative to Artemia for larval rearing. Weaning onto a dry diet takes place gradually from 6 or 7 d after hatch to the end of day 10, where after the fry is fed exclusively on dry feed. Optimum pellet size during this period is 2.2 percent of mean total length of the larvae, and early juveniles should be fed at 25 percent of body weight per day at 2-hourly intervals (Uys, 1984). Predicted feeding rates are also provided by Verreth and Den Bieman (1987). Several protocols for larval and early juvenile rearing (up to fingerling size) have been developed and these are shown in Table 8. These protocols all result in good growth and survival rates. Costs can be reduced by replacing Artemia with small-strain Daphnia.

After 12–14 days, the fry are stocked into nursery ponds at densities between 65 and 2 000/m2 (Viveen et al., 1985; Hecht, Uys and Britz, 1988; Hecht et al., 1998). The density at which fry are stocked depends on fish age and the intensity of rearing protocols. Under pond farming conditions, it is recommended to feed the fry three times per day at 25 percent of body weight per day, using a 38–40 percent protein diet (Hecht, Uys and Britz, 1988). Under tank rearing conditions, the feed should have a protein content of around 50 percent. When the fish attain an average weight of 1 g, they are ready for stocking into ponds or tanks for grow out.

Grow out

Figures 9, 10, 11 and 12 illustrate aspects of rearing and feeding technologies for North African catfish.

Under intensive pond-farming conditions, with water exchange, the fingerlings (1g) are stocked into grow-out ponds (0.1 ha) at a density of 100 000/ha and fed according to the feeding schedule shown in Table 9. The population has to be thinned out at regular intervals to maintain a maximum biomass of not more than 40 tonnes/ha, at a water exchange rate of the pond volume once every 4 days. 

 

The production capacity of ponds under static water management conditions is lower than under flow through conditions. Under static conditions the critical standing crop is around 18 – 20 tonnes/ha as opposed to 40 tonnes/ha under flow through conditons. The critical standing crop is defined as the biomass of fish in the pond when the growth rate begins to slow (Isyagi, Veverica, Asiimwe and Daniels, 2009).  If the projected harvest weight of fish under static conditions is around 800g then 15g fingerlings are stocked at a density of  24 750 fish per ha. This allows for a 10 percent mortality rate during the grow out period.

Grow out under intensive tank culture conditions is somewhat different to pond culture (Oellerman, 1995; Oellermann and Hecht, 1996; Hecht, Oellermann and Verheust 1996; Akinwole and Faturoti, 2007; Ayinla, 2007). Because of the high densities at which the fish are reared (170–450 kg/m3), it is preferable to feed the fish 5–6 times per day, at a ration as recommended in Table 9. Daily ration table are guidelines at best and because of the high cost of feed, farmers are advised to monitor food consumption and to adjust daily rations accordingly. Other strategies to reduce feed costs should also be adopted and developed. For example, Ali (2001) found that alternating periods of restricted feeding (maintenance requirement) for three days and appetite feeding for the following four daysis a plausible way in which to reduce feed input costfor this species, although in a later study Ali and Jauncey (2004) showed that C. gariepinus only shows partial compensatory growth under periods of restricted and satiation feeding. A sample of fish should be weighed weekly or every 10 days to adjust the feed rations.