Produção de juvenis de tilápia do Nilo (Oreochromis niloticus) em sistema com bioflocos: efeito do momento de transferência dos alevinos para o sistema

Abstract

Among the production systems used in aquaculture, biofloc systems are gaining prominence due to little or no water renewal, high stocking density and predominant formation of an aerobic and heterotrophic biota that compose the aggregates or microbial flakes. Considering the great potential of this system for the production of tilapia, the goal of this study was to evaluate the transfer effect of Nile tilapia fingerlings at different times of cultivation to biofloc system. 1400 Nile tilapia fingerlings weighing 1.40 ± 0.04 g, divided into 20 rectangular tanks with a useful volume of 150 liters were utilized, in a completely randomized delimitation, including five treatments (T1 control; T2 - 1st day transfer; T3 - 15th day transfer; T4 30th day transfer, T5 45th day transfer) and four replications. The study lasted 76 days and the animals remained under the same control conditions until the transfers time. Furthermore, the data obtained were submitted to analysis of variance and the means were compared by SNK test (p < 0.05). The final weight (46.16 g), daily gain (0.59 g) and feed conversion rate (1.08) have not differed. Thus, the final stocking density was higher in T1, with the value of 17.44 kg / m³. Additionally, the other treatments has resulted in 10.20, 12.47, 12.68 and 11.49 kg/m³ at T2, T3 , T4 and T5, respectively. The median survival was not differed by Kruskal-Wallis test (P<0.05). The water quality parameters has oscillated over time, with peaks of N-NO2- in the treatments transferred to the biofloc system. Body composition was affected by the treatments assessed. As a result, the control and other treatments that were transferred in some time to the biofloc system has differed. Microbial flakes has not shown differences in CP content nor the ethereal extract. Also, it has indicated an increasing trend in mineral content. With these results, the transfer of fingerlings of Nile tilapia with 1.4g for the system with biofloc is suggested. Furthermore, the previous cultivation period is not necessary in another type of system.