Survey of growth performance, antioxidant enzyme activity and bacterial community in recirculating, biofloc-recirculating, and biofloc common carp culture systems

In this study, growth performance, antioxidant enzymes activity, and bacterial load were investigated in recirculating aquaculture system (RAS), biofloc-RAS (BRAS) and biofloc system. Common carp juveniles with initial body weight of 70.99±0.91 g and stocking density of 6.25 kg/m3 were farmed in nine designed systems for three months. The mean weight, specific growth rate (SGR), weight gain, and food conversion ratio (FCR) were measured once every 15 days, bacterial load at the beginning, middle and end, and antioxidant enzymes at the end of the study period. Results showed the mean weight, weight gain and SGR in the biofloc system were significantly lower than other systems (p<0.05). However, the fish in the RAS and BRAS did not show any statistical difference in terms of the mentioned indicators. The FCR in the biofloc system (1.96) was significantly (p<0.05) higher than the RAS (1.59) and the BRAS (1.55). The highest amount of total antioxidant capacity and catalase enzyme activity was observed in the biofloc system and the lowest amount of superoxide dismutase enzyme activity was in the BRAS. In terms of bacterial load, a significant difference was observed amongst the three systems. So that the lowest value was observed in the RAS and the highest value was in the biofloc system. In general, it can be concluded that growth performance and feeding efficiency of common carp in the RAS and BRAS were better than the biofloc system in conditions of low water exchange.