Influences of Aquaponics System on Growth Performance, Antioxidant Parameters, Stress Parameters and Gene Expression of Carassius auratus

Aquaponics is a new type of composite farming system, which combines aquaculture and hydroponics through ecological design to achieve scientific synergism. However, the effects of aquaponics on the welfare status and stress parameters of fish are unclear. In this study, 150 crucian carp with an average initial body weight of 7.06 ± 0.32 g were selected. Nine fish were randomly selected as the control group (NC group and hypoxia group) for stress, antioxidant and gene expression parameters after acclimation and hypoxia stress, respectively. The remaining crucian carps were randomly divided into three experimental groups with 20 crucian carps in each group (T0, T1 and T2, respectively), with three replicates. The fresh weight of the lettuce root in the T2 group had no significant effect (p > 0.05). Compared with the control group (T0 and T1), there were significant differences in the specific growth rate, the weight gain rate, the fresh leaf weight, the chlorophyll content and the water quality parameters in group T2 (p < 0.05). Regarding the biochemical parameters, superoxide dismutase and catalase showed significant differences between the T2 and T1 groups (p < 0.05). At the same time, the HSP70 and Prdx3 genes were upregulated in the liver of the T2 group compared to the NC group and the hypoxia group. The research suggests that aquaponics may reduce the hypoxia stress of crucian carp without affecting the growth of crucian carp and lettuce.