GROWTH OF NILE TILAPIA Oreochromis niloticus STRAINS IN BRAZIL

The objective of this study is to evaluate the growth of Nile tilapia strains in Brazil, compared to genetically improved ones from Philippines, the Genomar Supreme. Tilapia fingerlings, male population, of approximately 8 g will be grown in water recirculation systems containing 0.5 m³ tanks, in initial density of 120 fish/m³, with four replicates (tanks). The fish will be fed three times a day with the same commercial feed for each particular growth phase according to biomass of each tank. Ten fish from each tank will be sampled at the 0, 60th, 120th, 180th and 240th days of cultivation. The study of the growth was conducted by fitting all data on fish weight for the Gompertz model given by y = Aexp(-Be^-Kx). The estimates were obtained by Weighted Least Squares. In addition it will be determined the absolute growth rates (AGR), the weight and age at inflection points (A/e and (lnB)/K, respectively).  

The initial weights were 8.72 (1.08), 8.60 (0.55), 8.70 (0.83) from Brazilian's strains and 8.14 (0.29) to Philippine's one and they were similar (P>0.05). The final weights from Brazilian's ones were 875.45 g (52.89), 732.88 (31.44) and 713.60 (57.24), 60% smaller tha Philippine's one (1302.19 g and 161.86, P<0.05). The model fitted and AGR are presented in Figure 1.

Genomar Supreme strain presented higher weight (723.8 g), age (161.5 days) and absolute growth rate (7.67 g/day) at the inflexion point when compared Brazilian's ones (370-420 g, 135 - 150 days and 4.2 - 4.95g/day, respectively).  

Data presented in this work don't represent the maximum growth of the tilapia strains. Genomar Supreme tilapia constitutes an important potential to improve tilapia farm in Brazil however, the use of this genetics needs to be concretized in this country.