Stocking densities of Colossoma macropomum in the initial grow out phase using biofloc technology

Abstract

The objective was to identify the best stocking density in the initial fattening phase of tambaqui (Colossoma macropomum) using biofloc technology (BFT) and evaluate the effects of the densities on water quality, zootechnical performance and the metabolic profile of fish and production costs. Juveniles (56.5 ± 1.69 g) were reared in the densities: 15 (BFT15), 30 (BFT30) and 45 (BFT45) fish.m− 3, in triplicate, for 80 days. The use of BFT inoculum at the beginning contributed the maintenance of adequate ammonia and nitrite concentrations at all densities, though with a higher nitrite concentration in BFT45. Electrical conductivity (EC), nitrite, total suspended solids (TSS), pH, alkalinity and hardness were different (p < 0.05) between BFT15 and BFT45. EC and TSS increased according to the increase in density, and were higher in BFT45. The highest final weight, weight gain, daily weight gain and specific growth rate were observed in BFT15, while the apparent feed conversion was lower for BFT15 and BFT30 compared to BFT45 (p < 0.05). Biomass and productivity were higher (p < 0.05) in BFT45. The values of hematocrit, number of erythrocytes and the hemoglobin concentration were higher in BFT45 (p < 0.05). Regarding production costs, the highest average feed expenditure occurred in BFT45; however, expenditure with electricity was lower at this density. The increase in biomass in BFT45 generated the reduction of the partial average cost (ACp). It can therefore be concluded that the best stocking density for initial fattening of tambaqui is 45 fish.m− 3, since it presents better productivity and biomass, lower ACp and average expenditure on electricity when using BFT.