Avaliação do uso de substrato no desempenho e qualidade de água de camarão marinho (Litopenaeus vannamei) mantidos em berçário em sistema de bioflocos

Abstract

The increase in stocking densities of intensive and super intensive shrimp farming systems may have positive results on productivity. However, with harmful effects that mainly affect the water quality of the culture. In this scenario, the use of artificial substrates presents a mitigating potential in the depletion of water quality. With this aim, an experiment was carried out in the Aquaculture Laboratory of UFMG, using artificial substrate, during the nursery period of the marine shrimp Litopenaeus vannamei. The experiment lasted 40 days, and four treatments with four replicates were tested: Control, Virgin substrate, Matured substrate (MAT), Matured substrate + Biofloc (MAT+BIO) (10% inoculum). Post-larvae (PL) of 0.043 g were used. The culture density was 1500 PL.m-2 in salinity 17. As an artificial substrate, non-woven fabric (Needlona®) was used, in an amount corresponding to 100% of the bottom area of the tanks (100 L). Substrate maturation was carried out by the addition of ammonium chloride (NH4Cl) to reach concentrations of 3 mg.L-1 of NH4. The substrate was mature when the concentration of NO2- in the ripening water was observed. To analyze the water quality, measurements were carried out twice a day: temperature, dissolved oxygen, oxygen saturation and pH. Daily analyzes of total ammonia and nitrite were performed and alkalinity analyzes were carried out every three days. For analysis of the zootechnical performance were evaluated: mean weight, survival, final biomass, specific growth rate and feed conversion rate. The lowest alkalinity values were observed in MAT (150.50 ± 13.95 mg.L-1) and MAT + BIO (137.25 ± 11.97 mg.L-1) treatments. Nitrite concentrations were significantly lower (P<0.05) in MAT and MAT+BIO treatments, while total ammonia concentrations were not influenced by the treatments. Zootechnical performance was not benefited by the only addition of substrate in the growing environment, and the highest biomass was obtained in MAT+BIO treatment (105.39 ± 2.72 g). Precolonization of the substrate was efficient in the control of nitrite concentrations during the biofloc formation process. The use of substrate when associated to the 10% biofloc inoculum (preformed) was able to promote zootechnical gains during the nursery of L. vannamei.