Sinergismo entre perifíton e bioflocos no cultivo intensivo de juvenis de tilápia do Nilo

Abstract

The work consisted of four consecutive experiments that were carried out with the objective of determining the degree of synergism between the periphyton and bioflocs without intensive cultivation of Nile tilapia juveniles. In the first experiment, a 2 x 2 factorial arrangement was performed, where the factors were perforated in bioflocs and periphyton, in two levels each, absence and presence. The tanks of the Control and Periphyton treatments had higher concentrations of NAT when compared to the BFT and Biophyton treatments. The feed conversion factor (FCA) of the fish was better in the tanks in which the bioflocos, when compared to the tanks without bioflocos. It was concluded that the bioflocos based fish culture system removes significantly more ammonia from the water than more traditional systems, such as in green waters and based they do not use submerged substrates (periphyton). (P <0.05) Our tanks were used to adjust the C: N ratio of water when compared to tanks without this adjustment. It was concluded that the fish farming system is not suitable for intensive farming in aquaculture. In the experiment it was not tested with the following substrates, submerged substrates (presence or absence) and food restriction (no and yes). The presence of submerged substrates in the tanks for development of periphyton did not significantly alter a concentration of nitrite in the water. Thus, as occurred for ammonia, the installation of submerged structures in the tanks did not present a water purifying effect, since nitrite is a toxic compound for cultured fish. Therefore, no zootechnical advantage was obtained without the work of installing submerged structures for periphyton in BFT tanks. The last experiment consisted of nine treatments, with four replicates each. The animals were cultivated in waste waters (green waters), with adjustment of the C: N ratio of water (bioflocs), and integration between bioflocs and periphyton (biophyton). In each cultivation system, there was a regular or restricted supply (-15% and -30%) of artificial feed. The installation of submerged structures in tanks with bioflocos is not able to raise the removal of water and nitrite from the water. In systems with bioflocs, the level of feed restriction of 15% did not cause damage to the gain in animal weight. The installation of submerged structures to the periphy;ton did not significantly affect the final body weight of the cultured fish.