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

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 D-0.5 = 0.5, D-1.0 = 1.0 and D-1.6 = 1.6 kg/m(3) for 53 days, and in Phase II, juveniles (150.61 +/- 0.58 g) were stocked at densities of D-1.5 = 1.5, D-3.0 = 3.0 and D-4.5 = 4.5 kg/m(3) 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/m(3) for each class. After the first 30 days of Phase I, final weight (FW) and daily weight gain (DWG) were highest for D-0.5, but feed conversion rate (FCR) was lowest. Daily feed intake (DC) was the lowest for D-1.6 and the highest for D-0.5. At 53 days, FW, DC and DWG were highest for D-0.5 and lowest for D-1.6. 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 D-0.5. After the first 30 days of Phase II, FW, DWG and DC were highest for D-1.5. After 60 days, D-1.5 had the highest FW and HSI and lowest values for glucose, triglycerides and Htc (P < 0.05). In Phase III, after 30 days FW, DWG and DC were highest for class L (P < 0.05), and FW remained highest for class L after 60 days. The HSI was highest for class S and lowest for class L (P < 0.05) while triglycerides, cholesterol, total proteins and Hg were lowest for classes S and M (P < 0.05). Stocking density must be evaluated according to the size of the individuals and, despite the best performance found for the lowest densities (phases I and II), higher densities produced greater biomass. The classification of animals is an important management strategy to maintain uniformity for commercialization because different densities and sizes of animals can interfere with some hematological and biochemical parameters, which can be used as indicators of animal welfare.

Automated summary

The study on Tambaqui showed that despite better performance at lower densities, higher densities produced greater biomass. The classification of animals is important for commercial purposes as different densities and sizes can affect hematological and biochemical parameters.