Abstract

The effects of different stocking densities (StDs) on growth and stress resistance rate (Rs) to air exposure (to evaluate the health condition of fish) of juvenile Colossoma macropomum in a recirculating aquaculture system (RAS) were investigated. A total of 1064 juveniles (0.35 +/- 0.10 g) were stocked in 0.5 (D-0.5), 1 (D-1), 3 (D-3), and 5 animals/L (D-5) in four different RASs of four circular tanks (28 L) each, and fed at 10% biomass/day. Growth and survival were assessed at 15, 30, 45 and 60 days. After 60 days, a 75-min air exposure test was conducted for each StD treatment and Rs determined. Regression analyses were performed for growth parameters. At 15 days, weight (W), weight gain (WG), daily weight gain (DWG), feed intake (FI), feed conversion rate (FCR), and specific growth rate (SGR) were highest for D-3. At 30 days, FI was highest at the StD values estimated through the derivation of the equation of 3.55 animals/L. At 45 days, WG, DWG, and SGR decreased with increasing StD. At 60 days, W was inversely proportional to StD. Biomass was directly related to StD at the end of all periods. Air exposure stress test found that after 48 h, 72 h, and 96 h, Rs values for D-3 and D-5 were highest and for D-0.5 lowest. Stocking densities of between 3 and 4 animals/L are recommended for the first 30 days, while higher StDs affected weight between 30 and 60 days. Animals at StDs between 3 and 5 animals/L are more resistant.