author(s)
Ajay Kumar, AK Reddy, AM Babita Rani, Gaurav Rathore and WS Lakra

abstract
The experiment was conducted to assess the effect of different C/N ratios in bio floc systems on growth performances and digestive enzymatic activity of Litopenaeus vannamei. The experiment was carried out using inland ground saline water at 15 ppt salinity fortified with potassium and magnesium ions. Bio floc developed with different C/N ratios as treatments T1 (5:1), T2 (10:1), T3 (15:1), T4 (20:1) and T5 (25:1) respectively by manipulating the C/N content in feed and water by adding rice bran as carbon source and without bio floc used as control. After optimum floc produced in experimental tanks the juveniles Litopenaeus vannamei (avg wt. 3.37±0.03 gm) were stocked. At the end of the experiment the weight gain % and SGR was found higher (p<0.05) in treatments T3 (641.07c±12.55 and 3.29d±0.03) and T4 (650.00c±5.88 and 3.35d±0.01) respectively and in the treatment T1 and control group the growth rate was showed significantly similar (p > 0.05). A better FCR T4 (1.04a±0.01), T3 (1.12a±0.02) and T5 (1.16a±0.03) was observed significantly lower from control (2.23d±0.04) and T1 and T2. Similarly, significantly higher FER and PER was registered in T4 compared to control, T1 and T2 respectively. However, no significant difference in FER and PER was observed between T3 and T5. The 100% survival reported in treatments T1,T2, T3 and control groups with 99.33% and 94.33% survival reported in T4 and T5 groups.The different levels of C/N ratios in bio floc improved (p<0.05) the digestive enzymes activities in hepatopancreas and intestine like amylase, lipase, cellulose and protease in the treatment groups compared with control. The present study elucidates the suitability of optimum C/N ratios in bio floc for enhancing the growth and digestive enzyme activities in L. vannamei in inland ground saline water. The finding could help in reducing the environmental concern saline waste water discharge from the shrimp pond to the land.