In-situ environmental amelioration of biofloc supported Litopenaeus vannamei culture in West Bengal, India

In-situ environmental amelioration potential of biofloc media mediated through the removal of nitrogenous metabolites, reduction of pathogenic Vibrio with concurrent increase in Bacillus community and reduction of feed was studied in white Litopenaeus vannamei culture. 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 employed with a stocking density of 60 PL-20 m3 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 supplementary feed from 50% to100%. Final body weight in neem based biofloc media was higher than the others. with high survival (87%). Superiority of biofloc system over the feed based system was established as live weight gain was higher by 28.48-137 % with reduced FCR (7.60% - 8.18%) in the former. Ffeed cost was reduced both in B (8.1 %) and NB (8.77%) compared to feed based culture system (F). Biofloc system supported cumulative increase of Bacillus population with concomitant reduction of luminous Vibrio population.

本研究针对凡纳滨对虾（Litopenaeus vannamei，俗称南美白对虾）养殖体系，探究了生物絮团基质（biofloc media）通过去除含氮代谢产物、抑制致病性弧菌（Vibrio）、同时促进芽孢杆菌属（Bacillus）群落增殖并降低饲料投喂量所具备的原位环境改良潜力。

试验设置3个处理组与1个对照组，每组均设3个生物学重复：无印楝添加的生物絮团+商品饲料组（B组）、添加印楝的生物絮团+商品饲料组（NB组）、仅投喂商品饲料且无生物絮团组（F组）；对照组（C组）不添加生物絮团且不投喂饲料。试验于室外土池（单池体积1000 m³）中开展，放养密度为60尾第20期仔虾（PL-20）/m³。

设置两组生物絮团基质（碳氮比C:N=15-10:1），分别添加与不添加印楝叶提取物，并将补充饲料投喂量从全量下调至50%。印楝基生物絮团基质组的最终体质量显著高于其余各组，存活率达87%。相较于仅投喂商品饲料的传统养殖体系（F组），生物絮团养殖体系的活体重增益提升28.48%~137%，饲料转化率（FCR）降低7.60%~8.18%，由此证实生物絮团体系相较于传统饲料养殖体系的优越性。

相较于F组，B组与NB组的饲料成本分别降低8.1%与8.77%。生物絮团体系可促进芽孢杆菌种群的累积增殖，同时伴随发光弧菌（luminous Vibrio）种群数量的显著减少。