Abstract:Four hundred and fifty Nibea albiflora juveniles(10.0~10.7g) were randomly distributed in four experimental treatments at different culture densities: 15ind/tank (1.49 kg/m3), 30ind/tank (3.00kg/m3), 45ind/tank (4.84 kg/m3), and 60ind/tank (5.81 kg/m3). A 30-day feeding experiment was conducted to investigate the impact of density stress on growth performance, feed coefficient, plasma complement of C3 and C4, and activity of related enzymes of the fish. Weight gain (WG) did not show significant differences among treatments.The trend of specific growth rate (SGR) was similar to that of WG. Feed conversion rate (FCR) increased with the increasing density. FCR of G60 was the highest and significantly higher than the other treatments (P＜0.05). (2) Activity of lactic dehydrogenase (LDH) in G60 was the highest and significantly higher than other treatments（P＜0.05）. Glutamic pyruvic transaminase (GPT/ALT) activity increased with the increase of density, while there were no significant differences among the treatments (P＞0.05). Similar trend was found in activity of glutamic oxaloacetic transaminase (GOT/AST). (3) The activity of lysozyme in serum decreased with the increase of density. The activity of lysozyme in G60 was the lowest and significantly lower than the other treatments (P＜0.05). Both complement of C3 and C4 in G30 were the highest, but they were not significantly affected by density (P＞0.05). This study indicated that high stocking density may impact metabolism and non-specific immune functions of juvenile N.albiflora, while low stocking density would suffer a great waste of water resource. Thirty individuals per tank（3.00 kg/m3）was considered to be a suitable stocking density.
