The study examined the growth performance and morphometric characteristics of a wild against a hybrid strain of Malawian Tilapia Oreochromis shiranus. The objective of the study was to compare growth rates and morphological variations between hybrid and local strain. Three strains were analysed-an F1 hybrid (O. shiranus male X Oreochromis karongae female), F1 (Local) and F1 of wild strain as a control. The fish were cultured for 84 days in (5 X 5m2) hapa nets, replicated three times. Formulated feed (30% Crude Protein) was supplied twice a day at 5 % body weight throughout the experimental period. The final mean growth weights were significantly different (p<0.05) across the treatments with hybrid strain showing higher growth rates (13.8g), as compared to wild strain (11.20g) and Local strain (6.90g). Apparent food conversion ratio was also statistically different (p<0.05) across the treatments hybrid (0.18), wild (0.22) and Local strain (0.45). The morphological results revealed a shape variation in head and caudal peduncle depth characteristics among the strains. The results from this study show that a hybrid strain is a good candidate for aquaculture industry in Malawi due to fast growing characteristics as compared to the wild strains. Apart from selective breeding, hybridization technique may be used to improve growth and feeding efficiency rates of local Malawian tilapias. However, the morphological differences due to hybridization present a good policy point on the conservation of wild species in Malawian aquaculture industry.
Keywords: Orechromis shiranus, Oreochromis karongae, hybridization, hybrid strain, local strain, wild strain, morphometric, growth performance.