2 Department of Food Science & Technology, Federal University of Technology, Akure, Nigeria.
3 Department of Forestry, Wildlife & Fisheries, University of Ado Ekiti, Ado Ekiti, Nigeria.
Nigeria is the second largest producer of farm-raised tilapias in Africa, after Egypt (Adesulu, 1997; Fagbenro, 2002; El-Sayed, 2006; Fagbenro et al., 2010). The first attempt at fish farming was in 1951 at a small experimental station in Onikan and various Tilapia species were used. Modern pond culture started with a pilot fish farm (20 ha) in Panyam for rearing the common/mirror carp, Cyprinus carpio, following the disappointing results with tilapias. Although the first years of Panyam fish farm's existence were hardly satisfactory, the trials nevertheless generated sufficient interest that regional governments established more fish farms. Tilapias are widely cultivated in ponds, reservoirs and cages in Nigeria (Satia, 1990; Fagbenro et al., 2004) and are suited to low-technology farming systems because of their fast growth rate, efficient use of natural aquatic foods, propensity to consume a variety of supplementary feeds, omnivorous food habits, resistance to disease and handling, ease of reproduction in captivity, and tolerance to wide ranges of environmental conditions (Fagbenro, 1987).
Tilapia culture in Nigeria remained largely a subsistence level activity until 2000, when it began to expand rapidly following the successful commercial farming of catfishes during the last decade (Alfred and Fagbenro, 2006; Afolabi et al., 2007). There are over 25 species of tilapias in Nigeria, out of which about six species are used for aquaculture, namely, Tilapia zillii, T. guineensis (substrate spawners, macro-phytophagous (generally herbivorous), Sarotherodon galilaeus, S. melanotheron (bi-parental mouth-brooders, micro-phytophagous (planktophagous), Oreochromis niloticus and O. aureus (maternal mouth-brooders, omnivorous). The natural feeding habits of cultivated tilapias in Nigeria are summarised in Table 1.
Table 1: Natural feeding ecology of tilapias used in fish culture in Nigeria.
Adults omnivorous. Fry feed initially on zooplankton. Exclusively phytoplanktivorous.
Omnivorous grazer. Feeds on algae but not higher plants.
Adults feed almost exclusively on phytoplankton. Juveniles feed on plankton.
T. guineensis, T. Zillii
Adults feed exclusively on higher plants. Juveniles consume plankton.
Sources: Idodo-Umeh (2003), Adesulu and Sydenham (2007)