Effect of different C/N ratios on volume and potential microbial composition of flocs in freshwater prawn Macrobrachium rosenbergii culture system

Abstract

The present study was conducted to evaluate the effects of C/N ratio on the volume of floc formation as well as on the load of several potential microbes of the fresh water prawn (Macrobrachium rosenbergii) culture tanks. The experiment was designed with three different C/N ratios viz. 10:1, 15:1, and 20:1 as T1, T2 and T3 were applied with a control (C) at laboratory condition. It was observed that C/N ratio 15:1 (12.22 ± 1.08 ml/L) and 20:1 (15.33 ± 1.37 ml/L) gave higher floc development compared to control C (5.22 ± 0.62 ml/L) and T1 (7.22 ± .46 ml/L) (P<0.05). The loads of Enterococcus spp.was found to be highest in T2, followed by T1, C and T3 (P<0.05). Higher Lactobacilllus spp. load was found in T1 and T2 compared to T3 and C, which indicates that growth of Lactobacillus spp. require a fair range of carbon source. No Salmonella spp. was found in any treatment. The present findings indicate that C/N ratio 15:1 could be applied in sustainable freshwater prawn culture.