Growth of 10 populations of O. niloticus under natural conditions is summarized by de Merona, Hecht and Moreau (1988). The von Bertalanffy growth function parameters range as follows; L∞ (cm) = 22.9 to 57.2, K = 0.14 to 0.51 and to = -0.85 to 0.54. The maximum recorded size is 64 cm TL (Lake Kyoga) and in Lake Turkana fish of up to 7 kg have been recorded (Trewavas, 1983). The range of von Bertalanffy growth function parameters for cultured Nile tilapia as modelled by Moreau and Pauly (1999) were: L∞ (cm) = 16.6 to 41.8, K = 0.637 to 4.566 and Ø’ = 2.93 to 3.43. The wide range of values reported for Nile tilapia under natural conditions reflects the phenotypic response to the prevailing environmental conditions of the species and under culture condition is determined by sex ratio, stocking density, culture systems, feeds, temperature and water quality (see Figures 5-7). With a “b” exponent value of 2.96 for a generalised length-weight relationship (FishBase), growth of O. niloticus is almost isometric.
