Growth performance and physiological parameters of Colossoma macropomum in a recirculating aquaculture system (RAS): Importance of stocking density and classification

Abstract Tambaqui (Colossoma macropomum) is the main freshwater species produced in South American aquaculture and is also produced in several Asian countries. The objective of the present study was to evaluate the growth and physiology of juvenile Colossoma macropomum submitted to different stocking densities and classified by size in a recirculating aquaculture system (RAS) to maximize the production and enable the fish rearing in colder regions. In Phase I, juveniles (34.88 ± 0.60 g) were stocked at densities of D0.5 = 0.5, D1.0 = 1.0 and D1.6 = 1.6 kg/m3 for 53 days, and in Phase II, juveniles (150.61 ± 0.58 g) were stocked at densities of D1.5 = 1.5, D3.0 = 3.0 and D4.5 = 4.5 kg/m3 for 60 days. In Phase III, the animals were classified according to size as S = 300–400 g; M = 400–500 g and L ≥500 g for 60 days with an initial biomass of 3.9 kg/m3 for each class. After the first 30 days of Phase I, final weight (FW) and daily weight gain (DWG) were highest for D0.5, but feed conversion rate (FCR) was lowest. Daily feed intake (DC) was the lowest for D1.6 and the highest for D0.5. At 53 days, FW, DC and DWG were highest for D0.5 and lowest for D1.6. From day 31 to day 53 there was a decrease in hemoglobin (Hg) and hematocrit (Htc) and an increase in the hepatosomatic index (HSI) for D0.5. After the first 30 days of Phase II, FW, DWG and DC were highest for D1.5. After 60 days, D1.5 had the highest FW and HSI and lowest values for glucose, triglycerides and Htc (P