Effects of stocking density on growth, antioxidant enzyme activity and related gene expression of juvenile Siberian hybrid sturgeon Acipenser baerii (♀)×A. schrenckii (♂)

In order to study the effects of aquaculture density on the growth performance of juvenile Siberian hybrid sturgeons Acipenser baerii (♀)×A. schrenckii (♂) in Jinggangshan region, this study took juvenile Siberian hybrid sturgeons with an initial body weight of (7.89±0.45) g as the research object. Three density groups low density group (1.16 kg/m³), medium density group (1.74 kg/m³) and high density group (2.32 kg/m³) were set for 90 days of production test. Through the comparative analysis of different density groups of Siberian hybrid sturgeon growth indexes and body composition content, antioxidant enzyme activity and related gene expression levels, it was found that low density group of larval final body weight, weight gain rate and specific growth rate of low density group was significantly higher than those of medium density and high density group (P<0.05), the density experiment fish survival rate had no significant difference; water content and ash content increased with the increase of culture density, and there were significant differences, but crude fat and crude protein did not show significant differences. The activities of superoxide dismutase (SOD) and glutathione sulfur transferase (GSH-ST) in liver in low and medium density groups were significantly higher than those in high density group at the end of experiment (P<0.05). With the increase of breeding density, the content of MDA in liver of juvenile fish increased continuously, and the activity of catalase (CAT) decreased. There was no significant difference between MDA and CAT during the trial. The results also showed that the expression levels of growth-related growth hormone receptor gene (GHR), insulin-like growth factor-1 gene (IGF-1) and insulin-like growth factor-2 gene (IGF-2) were significantly decreased in the high-density group (P<0.05). The expression level of stress-related heat shock protein 70 gene (HSP70) in high density group was different after 45 days (P<0.05), and after 90 days, high density group was significantly higher than low density group (P<0.05).The expression level of heat shock protein 90 gene (HSP90) in low density group was significantly lower than those in medium and high density groups on day 30 (P<0.05). At the end of the experiment, there were significant differences among the three density groups (P<0.05). The results showed that the juvenile Siberian hybrid sturgeon showed good growth performance under medium and low density conditions. Therefore, it is suggested to control the breeding density of juvenile Siberian hybrid sturgeon in Jinggangshan Mountains region between 1.16 and 1.74 kg/m³.