Assessment of aeration plug-flow devices used with recirculating aquaculture systems on the growth of tilapia Oreochromis niloticus

Abstract

Aeration plug-flow devices (APFDs) have been used with recirculating aquaculture systems (RASs) to simultaneously improve water circulation and oxygenation. However, it is still unclear how aeration flow rates affect fish growth for better extension and application. Thus, a series of experiments were conducted to explore the water quality and growth performance of tilapia (Oreochromis niloticus, average body length 8.93 ± 0.34 cm, average body weight 23.61 ± 3.50 g) using three self-designed RASs with APFDs with three aeration flow rates for 56 days. Aeration flow rates were applied in triplicate with the values of 0 L/min (control treatment, C), 30 L/min (moderate treatment, M) and 50 L/min (large treatment, L). The results showed that the water velocity and dissolved oxygen (DO) concentration increased with the increase in aeration flow rates, and the non-aerated condition resulted in a low DO and low pH but higher values of NH4+ (3.22 ± 0.17 mg/L) and PO43− (5.78 ± 0.13 mg/L) for treatment C on the 56th day. The tilapia’s length gain rate, weight gain rate and specific growth rate for treatment M on the 56th day were 49.90 ± 4.07 %, 235.70 ± 19.80 % and 2.81 ± 0.54 %/d, respectively, which were 11.07 %, 20.2 %, and 41.4 % higher than that for treatment C, and increased compared to treatment L by 2.04 %, 19.5 %, and 8.49 %. Additionally, more nutrients (i.e., total protein, total cholesterol, glucose) accumulated in tilapia serum for treatment M compared to those in other treatments. Multiple regression analysis showed that growth rates are correlated with DO, NO3− and PO43−. This study gave a new try by combining water circulation and oxygenation into RASs with APFDs, and it is worth popularizing and applying to reduce the operational costs.