Growth, Serum Biochemical Parameters and Flesh Quality of Tilapia Oreochromis Niloticus Exposed to Different Aeration Flow Rates

The application of the aeration plug-flow devices (APFD) in recirculating aquaculture system (RAS) in tilapia cultivation is an effective way to improve yield for farmers and the flesh quality for fish, where the aeration flow rate is the key factor for fish growth by affecting the water velocity and the dissolved oxygen concentration in the aquaculture water. To investigate the effect of aeration flow rate on the growth, serum biochemical indices and muscle texture of tilapia (Oreochromis niloticus), we designed an indoor RAS with a new kind of APFD. Experimental fish were exposed to 3 aeration flow rates: 0, 30 and 50 L min^-1 (small, moderate and fast, respectively) over 56 days. Then, growth indicated by the specific growth rate (SGR) and the condition factor (CF), serum biochemical indices suggested by alanine aminotransferase (ALT),aspartate aminotransferase (AST),lactate dehydrogenase (LDH), total protein (TP), triglycerides (TG), total cholesterol (TCHO), glucose (GLU) and blood urea nitrogen (BUN), flesh quality evaluated by some textural properties including springiness, resilience, chewiness, cohesiveness and hardness were measured. Significantly higher SGR and all textural properties were observed in the 30 L min^-1 condition. In addition, values of TP, TGand TCHO were higher at moderate aeration flow rate over the feeding time, while blood urea nitrogen was lower. Fast aeration flow rate resulted in higher CF and significantly elevated ALT,AST andLDH at the end of the experiment. Fish kept in the 0 L min^-1 condition had lower SGR, and fewer nutrients accumulated in the serum except for GLU. Our results suggested that the moderate aeration flow rate is ideal for fish growth with better growth performance and positive effects on textural properties, while the increased nutrients concentrations but decreased waste concentrations were observed in fish serum. At the high aeration flow rate, tilapia must withstand the stress from the fast water flow, which resulted in an impairment of the serum nutrients, and eventually inhibited fish growth, whereas the insufficient dissolved oxygen and slow water velocity at small aeration flow rate led to a decline in the growth rate and the potential damage of organs.