EFFECTS OF ARTIFICIAL SUBSTRATES ON THE CARP GROWTH PERFORMANCE AND WATER QUALITY IN PONDS EQUIPPED BY USING A POLY-CULTURE SYSTEM

To investigate the influence of artificial substrates (AS) on the growth performance of fish in pond poly-culture systems, a feeding experiment was conducted in six individual earthen ponds, which were divided into two groups. The ponds with AS in the water were labeled as the " AS group” and that without the use of AS were labeled as the " control group” (three ponds per group). A total of 3867 common carp Cyprinus carpio, (310±11) g, being artificial-feeds feeding fish, and 370 bighead carp (Aristichthys nobilis) and silver carp Hypophthalmichthys molitrix, (810±15) g, being plankton filter feeding fish, were divided into six groups and cultured in the ponds respectively. The common carp in each pond were fed with commercial particle feeds three times a day and the feeding period was 62 days. Water quality, concentration of plankton and the bacterial community presenting in the water and sediment were monitored during the experiment. At the end of the experiment, all fish were harvested and the growth of the fish and feed efficiency ratio were determined. Results showed that the weight gain rate and feed efficiency ratio of common carp in AS group was significantly higher than that of the control group. Final body weights of bighead carp and silver carp in the AS group were significantly lower than that of the controls. Water transparency and diversity indices of the bacterial community in the AS group were significantly higher than that of the control (P<0.05) and the concentration of plankton in the AS group was lower than that of the control. Results showed that the application of AS in poly-culture ponds was beneficial for the growth of common carp, being artificial-feeds feeding fish, while it was not beneficial for the growth of bighead carp and silver carp, being plankton filter feeding fish.