Effects of stocking density on growth performance of Piaractus brachypomus reared in recirculating aquaculture system (RAS)

The intensification of aquaculture production in recirculating aquaculture systems (RASs) depends on the determination of appropriate stocking densities. However, such information remains scarce for many freshwater fish species, including Piaractus brachypomus. The objective of this study was to investigate the effects of stocking density on the zootechnical performance of Piaractus brachypomus juveniles reared in RASs during two independent growth phases. Experiment 1 used 270 juveniles (29.55 ± 3.10 g) reared for 90 days at stocking densities of 0.5, 1.0, and 1.6 kg m⁻³. Experiment 2 used 108 juveniles (250.35 ± 13.52 g) reared for an additional 90 days at stocking densities of 1.5, 3.0, and 4.5 kg m⁻³. Both experiments were conducted using a completely randomized design, and the fish were fed twice daily with commercial extruded feed containing 36% crude protein. In Experiment 1, the highest final biomass (11.84 ± 0.28 kg m⁻³) was observed at a stocking density of 1.6 kg m⁻³ (p<0.05). However, the lowest stocking density resulted in the highest feed intake (4.63 ± 0.49 g fish day^-1) and poorer FCR (1.97 ± 0.29; p<0.05), with no differences observed for these parameters at stocking densities of 1.0 and 1.6 kg m⁻³ (p>0.05). In Experiment 2, fish reared at densities of 3.0 and 4.5 kg m⁻³ exhibited similar final biomass (11.46 ± 0.26 and 13.89 ± 1.15 kg m⁻³, respectively; p>0.05). Furthermore, the lowest density tested in this experiment again resulted in higher feed intake (10.02 ± 1.07 g fish day^-1) and poorer FCR (1.38 ± 0.10) (p<0.05). However, in both experiments, final weight, weight gain, daily weight gain, and survival did not differ among the tested densities (p>0.05). Thus, the stocking densities tested can be considered suitable for rearing juvenile P. brachypomus weighing approximately 29.55 and 250 g in RASs for periods of 90 days.

Acknowledgments: CNPq-Brasil – 402840/2023-2, 310170/2023-0, 301816/2022-0, and 316901/2021-0).