Growth performance of shrimp and water quality in a freshwater biofloc system with a salinity of 5.0‰: Effects on inputs, costs and wastes discharge during grow-out culture of Litopenaeus vannamei

Abstract

This study aimed to evaluate the effects of biofloc technology on inputs, costs and wastes discharge during grow-out culture of Litopenaeus vannamei under a low salinity condition. Two systems (water volume 5 m3, salinity 5‰) were designed: biofloc system (BFT) with addition of molasses (C:N 20:1), and clear water system (CW), for a 63-day culture experiment with shrimp juveniles (~0.80 g, 90 shrimp m−3). Water quality and zootechnical performance were monitored, and the costs and benefits were estimated. Results showed that the levels of pH (7.75 ± 0.01), carbonate alkalinity (86.6 ± 1.9 mg CaCO3 L−1), biofloc volume (29.1 ± 2.1 mL L−1), total suspended solids (588.7 ± 40.0 mg L−1) and total ammonia nitrogen (1.42 ± 0.12 mg L−1) in BFT treatment were significantly higher than those in CW (7.26 ± 0.07, 61.9 ± 1.2 mg CaCO3 L−1, 1.1 ± 0.7 mL L−1, 75.4 ± 9.4 mg L−1 and 0.62 ± 0.06 mg L−1, P < 0.05). Significantly higher survival rate (100%) and productivity (1.10 ± 0.02 kg m−3) were observed in BFT treatment, when compared to those in CW (92.6 ± 3.7% and 0.96 ± 0.01 kg m−3, P < 0.05). The total cost in BFT treatment were 9.51 ± 0.55 USD kg−1, significantly lower than that in CW (42.20 ± 0.67 USD kg−1, P < 0.001). The discharge of waste water, salt, ammonia, nitrite and nitrate in BFT treatment decreased 78.9–99.7% compared to that in CW. The results indicated that biofloc technology could be adopted for an environment-friendly and cost-effective culture of L. vannamei with a salinity as low as 5.0‰.