Comparative Analysis of Growth and Microbial Dynamics of Monoculture and Polyculture Shrimp Farming Systems in Sundarbans, West Bengal

Different sets of on-farm trials were conducted to standardize shrimp, Penaeus monodon monoculture at two stocking densities (6 and 12 post larvae [PLs] m-2) with conventional, organic principles and Bio-secured Zero Water Exchange (BZEST), and two shrimp-fish polyculture systems with different species combinations (TI - Mugil cephalus, Liza tade, L. Parsia and P. monodon and TII - Chanos chanos and P. monodon). The pond water was treated with 60 and 30 ppm of calcium hypochlorite before stocking in shrimp monoculture and polyculture ponds, respectively. Real-time microbial dynamics were studied throughout the culture and compared. BZEST average production was 3109 kg ha-1 with 7.95%, 6.96% and 10.24% gain in terms of production, survival rate and FCR in comparison to conventional ponds, respectively. The total production in polyculture was 687.44±27.64 and 717.08±43.75 kg ha-1 with FCR of 1.74±0.02 and 1.99±0.25 in T-I and T-II, respectively. Total heterotrophic bacterial (THBC) and Vibrio (TVC) counts in shrimp monoculture and polyculture ponds were significantly decreased immediately after bleaching. It revealed that the THBC and TVC in organic, BZEST and TI ponds were lesser than the conventional and T-II ponds, but not statistically significant throughout the culture. The influence of age of culture over the THBC in both monoculture and polyculture and TVC in monoculture ponds was highly significant. Further, it was observed that the treatment and age of culture interaction had a significant role in TVC in both the system of culture and THBC in polyculture ponds. Multiple comparisons of microbial dynamics in monoculture and polyculture ponds with reference to the age of culture revealed that there was a significant difference in THBC at the mid-culture and in TVC at the start and the end of the culture. Results obtained in this study would serve as a baseline real-time data on microbial dynamics in brackishwater aquaculture systems.