Environmental amelioration in biofloc based rearing system of white leg shrimp (Litopenaeus vannamei) in West Bengal, India

The potential of biofloc media in in-situ environmental amelioration mediated through the removal of nitrogenous metabolites, reduce the dominance of disease-causing Vibrio to beneficial Bacillus community and reduction of costly commercial feed was investigated in white leg shellfish (Litopenaeus vannamei) farming. Three treatments viz. biofloc without neem + commercial feed (B), biofloc with neem +commercial feed (NB), only commercial feed without biofloc (F)and, one control (C) withno biofloc and no feed in triplicate was applied with a stocking density of 60 PL-20 m−3 in outdoor earthen ponds (1000 m3). Two biofloc media (C:N = 15–10:1) with and without neem leave extract were applied with reduction of feed supplement from 50% to 100%. The significant difference was observed in final body weight (33.82 ± 0.18 g) in neem based biofloc media than the other tested shrimp with the survival percentage above 87%. Superiority of biofloc based rearing system over the traditional feed based one was established as live weight gain was 28.48–137% more with a reduction of feed conversion ratio by 7.60% to 8.18% in the former. Moreover, feed cost was reduced both in B (8.1%) and NB (8.77%) compared to conventional feed −based culture system (F). The nutrient profile of floc and shrimp also improved as higher protein content was recorded in floc (18.65–19.63%) and shrimp (24.58–26.29%). The development of biofloc within the culture system resulted in cumulative increase of Bacillus population with concomitant decrease of luminous Vibrio population. The findings of the study strongly indicated that biofloc technology could be a potential tool of ecosystem approach towards in-situ environmental amelioration in shrimp farming ponds with substantial reduction of cost towards feed, aqua chemicals used for disease and environmental health management and other operational cost like water exchange.