Diferentes fontes de carbono no cultivo intensivo da tilápia do nilo Oreochromis niloticus (Linnaeus, 1758) em sistema de bioflocos

Abstract

Biofloc technology has brought advances in traditional aquaculture, mainly in shrimp and tilapia. The main advantages are low water use, recycling of nitrogen compounds and production of supplementary food rich in protein. Various carbon sources are employed in the biofloc culture, as sugars, starches, alcohols and fibers. So the aim of this study was to evaluate the effects of organic carbon sources on water quality, growth performance and acceptance of Nile tilapia fillets (Oreochromis niloticus) cultured in biofloc systems. Were adopted three treatments involving the sources of carbon, as sugar (AÇU), liquid molasses (MEL) and powder molasses (MEP), with five replicates each and a control treatment (CTL) without biofloc, with four replications. Fish (72.6 g) were stocked in 19 circular tanks (800L) at a density of 35 fish/m3 and grown by 145 days. They evaluated the water quality variables, growth performance and acceptability of tilapia fillets. The dissolved oxygen concentration was significantly higher (P≤0.05) in the tanks without bioflocs (CTL) in the absence of bacterial biomass. Total ammonia nitrogen (NAT) showed statistical significance (P≤0.05) between the AÇU treatment and the other with bioflocs, displaying the lowest concentration of 2.53 mg NAT/L. Already nitrite, showed no statistical difference (P>0.05) among treatments with mean values ranging from 0.74 to 2.3 mg of N-NO2/L. The final weight ranged from 339 to 409 g, with feed conversion ratio between 1.61 and 1.89, survival 80-99% and showed no statistical difference between treatments (P>0.05). Productivity ranged from 9.72 (AÇU) to 14.22 Kg/m3 (CTL) (P≤0.05). The tanks without bioflocs (CTL) consumed 9 m3 of water to produce 1 kg of fish, while the bioflocs used only 0.68 m3, which represents a 13 times lower consumption. The percentage of protein in fillets of tilapia and analyzed bioflocs ranged respectively 17-20% and 31-33%.Tilapia fillets coming from biofloc with sugar showed to have the preference of the evaluators, with note 7.77 (like moderately to like very much). With these results, it is concluded that the carbon sources (molasses and sugar) can be used in the tilapia culture with biofloc without damage to water culture and productivity. Moreover, one should consider the ease of obtaining sugar.