Biofloc technology (BFT): An alternative aquaculture system for piracanjuba Brycon orbignyanus?

Freshwater aquaculture in Brazil is already well established and some studies have been conducted aiming to intensify the activity in a sustainable manner using alternative technologies such as biofloc technology system (BFT). Piracanjuba (Brycon orbignyanus) is a Brazilian native species with important economic and ecologic values. Nevertheless, dramatic reduction in natural stocks has been raising the interest of its aquaculture. The objective of this study was to assess the growth performance of piracanjuba raised in BFT, contrasting water quality and planktonic profile as compared to clear-water recirculation aquaculture system (CW). A 34-day trial was carried out using piracanjuba juveniles with 35.25 ± 5.64 g of initial weight. Fish were stocked in six 500-L polyethylene round tanks (350 L useful volume), three per treatment. Water temperature, dissolved oxygen, pH and settling solids (measured in Imhoff cone) were monitored daily. Ammonia, nitrite, nitrate, alkalinity and orthophosphate concentrations were monitored twice a week. Microorganism profile in BFT was monitored throughout the study. At the end of the trial, proximate composition of the biofloc and fish carcass was analyzed. Survival and feed conversion did not differ between CW (86.1% and 1.38) and BFT (77.8% and 1.7) (P > 0.05). Fish final weight, final biomass, yield and feed intake were higher in CW (P < 0.05). Twelve groups of microorganisms were observed in the biofloc, in which the most abundant were protozoan Euplotes (5.6 ind mL− 1), microalgae (1.2 ind mL− 1), and rotifers (0.15 ind mL− 1). Crude protein and lipid content of the biofloc were 21.31 and 0.80%, respectively. Biofloc technology could be an alternative system for piracanjuba cultivation, although such system did not improved growth performance as compared to RAS clear-water. Further research could imply a simpler technological setup for water quality control and potentially reducing feeding ratio for piracanjuba intensive culture.