Effects of stocking density on growth performance and physiological and biochemical parameters of Pelteobagrus vachelli juvenile

Pelteobagrus vachelli, a native fish species of the Yangtze River, shows great developmental potential. To understand how it responds to varying densities in a land-based circulating water system, we investigated three density groups: Low density LD, (2.03±0.09) kg·m⁻³, medium density MD, (3.49±0.37) kg·m⁻³ and high density HD, (5.03±0.11) kg·m⁻³. After a 56-day rearing, we assessed the growth, physiological, and biochemical parameters of P. vachelli juvenile. The results show that MD group exhibited a significantly higher length gain rate but a lower food coefficient compared with the other groups, showingsuperior growth performance. There were no significant changes in the variation coefficients of body length and body mass (p>0.05), but the lowest values were found in MD group, indicating that the growth dispersion of P. vachelli in MD group was better and the specifications were more uniform. Serum glucose levels peaked in HD group (p<0.05), while serum triglycerides and total cholesterol were highest in LD group (p<0.05). Lysozyme activity decreased as density increased, but cortisol levelsremained relatively stable (p>0.05). The liver's superoxide dismutase activity was the lowest in MD group (p<0.05), while glutathione peroxidase activity was the highest (p<0.05). No significant differences were observed in the catalase activity and malondialdehyde content among the groups (p>0.05). The activities of intestinal enzymes such as trypsin, lipase, and amylase were the highest in MD group. The results suggest that P. vachelli juvenile grows best in a land-based circulating water system at a stocking density of 3.49 kg·m⁻³.