To study the effects of different densities on the growth of large yellow croaker in flow-through systems, large yellow croaker with an initial body weight of (120±5) g was selected as the experimental object. Three density groups (low density group (4.92 kg/m3), medium density group (7.56 kg/m3), and high density group (10.08 kg/m3) were set for 150 days of production test. The growth indicators, nutrient components, serum biochemistry, digestive enzymes, and energy metabolic enzymes were observed at the end of the experiment. The results showed: the final weight gain rate of large yellow croaker in high density group was significantly lower than that in the medium density group and low density group, and there was no significant difference in the survival rate and fatness of experimental fish in each density group. Moisture and ash contents increased with the increase in culture density, and there was a significant difference. Crude protein and culture density were negatively correlated, and there was a significant difference, but there was no significant difference in crude fat. The activities of four metabolic enzymes in the liver were significantly lower in low and medium density groups than in high density groups at the end of the experiment. With the increase of culture density, the activities of five kinds of digestive enzymes in the stomach and intestine of large yellow croaker decreased, and there was no significant difference between medium and high density groups during the experiment. The results showed that high density culture in this experiment could affect the energy budget by increasing nutrient metabolism and weakening the digestion and absorption capacity of the body, thus affecting the growth, muscle nutritional quality, and physiological health level of fish.
