Comparative efficacy of neem (Azadirachta indica) and non-neem supplemented biofloc media in controlling the harmful luminescent bacteria in natural pond culture of Litopenaeus vannaemei

Impacts of two different biofloc media with and without neem (Azadirachta indica) leave in reducing the pathogenic abundance of luminescent bacteria (Vibrio harveyi, V. parahaemolyticus, V. alginolyticus and V. fisehri) through probiotic development of Bacillus cereus and Lactobacillus sp. were investigated both in summer and autumn seasons in white leg shrimp (Litopenaeus vannaemei) natural grow-out ponds at Rasulpur (21.83 N, 87.86 E), West Bengal, India. Though, the population density of Bacillus cereus and Lactobacillus sp. significantly increased in both the media, biofloc with neem negatively impacted upon them as significantly lower population size in both the seasons was recorded in the water phase and even during autumn in the sediment. Reduction of luminous bacterial population mediated through the probiotic effect of Bacillus cereus and Lactobacillus sp. under both the media (R2 = 0.54-0.90) was more pronounced in summer when increase in total dissolved solids and salinity of water played synergistically with the former. Application of neem as media component of biofloc should be avoided during the low temperature regime like autumn.