Effect of different stocking densities on hematological parameters and zootechnical performance of pacu (Piaractus mesopotamicus) in the BFT system

This study evaluated the growth performance and hematological parameters of pacu (Piaractus mesopotamicus) juveniles (37.10 ± 0.35 g) subjected to different stocking densities (SD) in the biofloc technology (BFT) system. The individuals were distributed in five different SD: 200, 400, 600, 800, and 1000 fish m−3 (here called SD200, SD400, SD600, SD800, and SD1000, respectively) for 45 days. The experimental design was randomized entirely into five treatments and three replicates. The physical-chemical parameters of water quality remained stable. Survival was >94% in all treatments. Increasing SD had a positive linear effect on initial (R2 = 1.00) and final biomass (R2 = 0.87) and a negative linear effect on final weight (R2 = 0.93), final length (R2 = 0.92), weight gain (R2 = 0.93), specific growth rate (R2 = 0.92), and individual feed intake (R2 = 0.90). The SD600 showed higher values for hepatic somatic index according to quadratic regression (R2 = 0.95). According to quadratic regression, the highest SD had blood glucose values higher than the other SD (R2 = 0.95). Increasing SD had a positive linear effect on blood pH (R2 = 0.82) and mean corpuscular volume (R2 = 0.81) levels and a negative linear effect on hemoglobin (R2 = 0.81) and mean corpuscular hemoglobin concentration (R2 = 0.81) concentrations. In conclusion, pacu can be reared in a BFT system with an SD of 600 fish m−3 (final weight of 57.46 ± 1.60 g) since it increased the final biomass (34.16 ± 1.07 kg m−3) without compromising hematological parameters.