The Growth Performance, Haematological Parameters and Serum Biochemistry of the Flathead Grey Mullet Mugil cephalus Under Recirculating Aquaculture System and Traditional Culture Systems

The present investigation explored the growth performance, haematological parameters and serum biochemistry of flathead grey mullet under recirculating aquaculture system (RAS) and traditional culture systems. Nine hundred healthy fish, weighing 43.80 ± 3.55 g and length 16.54 ± 0.82 cm were randomly distributed to three treatments of RAS and traditional culture systems (T₁: 20% of water changed daily; T₂: once-through system 250 L/h; T₃: RAS—20% of water changed weekly) in nine concrete tanks of 4000 L at stocking density of 100 fish/tank and each treatment had three replicates. Fish were fed (33.1% crude protein, 3 mm pellets) twice a day at a rate of 3% for 12 weeks. These findings suggest that the T₃ followed by T₂ led to notable improvements in growth performance compared to other culture systems. Significantly elevated values of weight gain, length gain, specific growth rate, average daily gain and survival % were observed in T₃. The RBCs exhibited a significant decrease under T₂. Haemoglobin concentrations and WBC counts significantly increased under RAS. Significant values of mean cell haemoglobin and mean cell haemoglobin concentration were recorded in T₂. Total protein, albumin and globulin enhanced significantly under RAS, whereas the highest values of cortisol were observed in T₂ and T₃. These findings demonstrate that the RAS followed by once-through system significantly improve growth performance, feed efficiency and survival, as well as enhancing the haematology and serum biochemical status of flathead grey mullet. In conclusion, RAS provides ideal conditions for optimizing physiological functions, growth performance and fish health.