Comparative Growth Performance of Oreochromis Hybrids and Selectively-Bred Strain (F8) in Malawi

Most fish farmers in Malawi culture unimproved fish strains whose growth is slow and mature while still small. Four strains of Oreochromis, namely; selectively-bred/improved O. shiranus (F8), two reciprocal F1 Oreochromis hybrids, and O. karongae as a control (mean weight 2.5 ± 0.7 g) were stocked at a density of 5fish/m2 in 9m2 hapas replicated three times, and cultured for 90 days at Bunda Fish Farm. Fish were fed twice a day with feed formulated using maize bran and soybean containing 30% crude protein throughout the experimental period. The final mean weights were significantly different (p<0.05) across the treatments whereby; hybrid O. shiranus (male) X O. karongae (female) was 12.09g, hybrid O. shiranus (female) X O. karongae (male) was 9.72g, improved O. shiranus (F8) registered 9.23g, and O. karongae was the least with 9.00g. Apparent food conversion ratio was also statistically different (p<0.05) across the treatments whereby; O. karongae was 3.63, hybrid O. shiranus (female) X O. karongae (male) was 3.25, improved O. shiranus (F8) was 3.16 and hybrid O. shiranus (male) X O. karongae (female) was lowest with 2.26. There were no significant differences on the water quality parameters across the treatments throughout the experimental period and were within the required ranges for growth and survival of tilapias fish species. The results suggest that Oreochromis hybrids may be suitable candidates for aquaculture in terms of production as they performed better than the improved O. shiranus and the control O. karongae.