Avaliação da tecnologia de bioflocos no desempenho zootécnico de alevinos de Tilápia (Oreochromis niloticus) cultivados em diferentes densidades

Abstract

The Bioflocs Technology system (BFT) offers the possibility of producing fish with low water cost, since it does not require large partial water exchanges. In this system, ammonia is assimilated by the action of heterotrophic microorganisms, unlike conventional systems of cultivation. The microorganisms present in the BFT agglomerate with other particles forming flakes which are held in suspension by means of aerators. The maintenance of microbial biomass occurs by controlling the relationship between carbon and nitrogen (C: N) concentrations in water. Tilapia is the most cultivated fish in Brazil and offers great productivity due to rusticity and rapid growth also feeding on microscopic organisms in the water column presenting as a very promising species for cultivation in bioflocs. The present work had as objective to evaluate the zootechnical performance of Tilapia fingerlings in BFT. The inoculum was obtained in 62 days, the recovery of the system lasted 87 days and the final stage, with the presence of the fingerlings, 64 days. A completely randomized design (DIC) was used, in which the weight gain of Tilapia fingerlings was evaluated in a biofloc system at different densities (200, 400, 600, 800 and 1000 copies per m3), with four replications in each density. As a control, water recirculation system (SRA) was used with four replications containing 62 fish in each tank, totaling 24 experimental units. The fish were fed commercial feed containing 35% protein, and the brown sugar (carbohydrate source) was used in a C: N ratio of 20: 1. The chemical physical parameters of dissolved oxygen (OD), ammonia (NH3), pH and temperature were monitored daily, nitrite and alkalinity were monitored weekly and biometrics were performed. As a result of the tests and analysis of the data of weight gain of the individuals in the five densities, the linear function Y = - 0.0017X2 + 3,724X - 87,77, with r2 = 0,864 and CV = 14,23% was obtained. No significant difference (p <0.05) was found between the survival data between the different treatments. At the end, the planktonic community in the system was also identified, presenting great variety, predominating rotifers and diatoms. In addition to the variation of the measurements of the physical and chemical parameters of the culture water, we considered the density of 800 fish / m3 the most indicated among the tested ones, exhibiting average weight gain of 1,891.25  151.24 g, with the BFT productive efficiency index (274.96) approximately three times higher than the index found in the control treatment (87.43), demonstrating that the bioflocosis system improves the zootechnical performance of Tilapia (Oreochromis niloticus), in high density, in the initial phase of cultivation.