Feeding metabolism and feeding strategies in industrialized farming of Plectropomus leopardus

Research on fish metabolism is important in aquaculture physiology. As key physiological parameters, the oxygen consumption rate (OCR) and ammonia excretion rate (AER) are directly relevant to the design and management of recirculating aquaculture systems (RAS). To optimize precision management strategies for RAS aquaculture of the leopard coral grouper (Plectropomus leopardus), we systematically investigated the metabolic response characteristics of individuals of different sizes [Group A: (248±7) g, Group B: (358±19) g, Group C: (447±28) g] under feeding conditions. Using the standard static respirometry method, we measured the OCR and AER under fasting conditions and at different feeding levels (0.5%, 1.0%, 1.5% of body mass) and feeding frequencies (1−3 times per day). The results indicate that under fasting conditions, both OCR and AER decreased with increasing fish size, with OCR showing significant differences (p<0.05) and AER exhibiting distinct diurnal variations. Post-prandial OCR and AER increased with feeding level, showing significant differences (p<0.05) among feeding levels of 0%, 0.5%, and 1.0%. Furthermore, higher feeding levels resulted in an earlier occurrence of the metabolic peak. Increasing feeding frequency reduced the peak OCR per feeding event, but nighttime feeding had a minimal effect on AER. It is recommended a feeding strategy employing 1.5% feeding level combined with 2−3 daytime feedings per day in order to effectively mitigate metabolic load peaks. This study reveals the response patterns between feeding-induced metabolic dynamics and feeding strategies, providing a theoretical basis for constructing precision water quality regulation systems.