Abstract
This study evaluated the growth performance, water quality dynamics, and physiological responses of Asian seabass (Lates calcarifer) cultured in a locally engineered freshwater recirculating aquaculture system (RAS) over a 15-month production cycle at Sher-e-Bangla Agricultural University, Bangladesh. Juvenile seabass (initial weight: 5.67 ± 0.17 g) were stocked in 10-meter cube tanks and reared under controlled conditions. Fish were fed a diet formulated with 42% crude protein (CP) from locally available ingredients. At harvest, seabass reached an average final weight of 1227.0 ± 15.34 g, corresponding to a mean weight gain of 1221.33 ± 15.34 g, a specific growth rate (SGR) of 1.20 ± 0.01% per day, and an average daily gain (ADG) of 2.71 ± 0.03 g per day. Key water quality parameters, including temperature (29–30.5 °C), pH (7.2–7.5), total dissolved solids (750–850 ppm), ammonia (0.015–0.018 mg/L), dissolved oxygen (6.5–6.8 mg/L), nitrate (<45 mg/L), and nitrite (<0.1 mg/L), remained within optimal ranges for seabass culture. The formulated diet contained 40.53% CP, 11.87% crude lipid, 7.65% ash, and an energy content of 15.80 MJ/kg. Histopathological examination of spleen tissue revealed no major abnormalities, while hematological indices (WBC: 20.00 K/µL; lymphocytes: 80%; neutrophils: 15%) were within normal physiological ranges, indicating a healthy stock. Overall, the finding demonstrates the feasibility and biological suitability of culturing L. calcarifer in a locally engineered freshwater RAS, highlighting its potential as a sustainable, high-yield option for inland aquaculture diversification in Bangladesh.
