Culture of Nile tilapia in a biofloc system with different sources of carbon

ABSTRACT The aim of this work was to evaluate the effects of using different sources of organic carbon on water quality, growth performance and the acceptability of Nile tilapia (Oreochromis niloticus) fillets grown in a biofloc system. The experiment was carried out over 145 days at the Aquaculture Station of the Federal Rural University of Pernambuco, Brazil. Fish of 72.6 ± 6.83 g were stored (35 fish m-3) in 19 circular tanks (800 L) in a completely randomised experimental design with three treatments, including as a source of carbon, sugar (SUG), liquid molasses (MOL) and molasses powder (MOP), each with five replications, and one control treatment (CTL) without bioflocs, with four replications. Dissolved oxygen concentrations were significantly higher (P≤0.05) in the tanks with no bioflocs due to the absence of bacterial biomass. Total ammoniacal nitrogen (TAN) showed a statistical difference (P≤0.05) between the SUG treatment and the other treatments with bioflocs, having the lowest concentration of 2.53 mg L-1. Survival was greater than 80%, with no statistical difference between treatments (P>0.05); productivity varied from 9.72 (SUG) to 14.22 kg m-3 (CTL) (P≤0.05). Water consumption in the tanks with bioflocs was 11.8 times lower than in the control (CTL). The tilapia fillets from the bioflocs with sugar were preferred by the evaluators, with a score of 7.77 (like moderately to like very much). The carbon sources used (molasses and sugar) can be employed in the culture of O. niloticus tilapia in bioflocs with no damage to the culture water or to productivity.摘要 本研究旨在评估不同有机碳源对生物絮团系统（biofloc system）养殖尼罗罗非鱼（Oreochromis niloticus）的水质、生长性能及鱼肉接受度的影响。本实验于巴西伯南布哥联邦农村大学水产养殖站开展，实验周期共计145天。试验初始均重为72.6±6.83 g的尼罗罗非鱼，以35尾·m⁻³的养殖密度放养于19个容积800 L的圆形养殖桶中，采用完全随机试验设计，设置3个碳源处理组与1个无生物絮团对照组（CTL）：碳源处理组分别为糖组（SUG）、液体糖蜜组（MOL）及糖蜜粉组（MOP），每组设置5个重复；对照组设置4个重复。无生物絮团的养殖桶因无细菌生物量，溶解氧浓度显著更高（P≤0.05）。糖组（SUG）的总氨氮（Total ammoniacal nitrogen, TAN）浓度与其余生物絮团处理组存在统计学差异（P≤0.05），其最低浓度为2.53 mg·L⁻¹。各组罗非鱼存活率均高于80%，组间无统计学差异（P>0.05）；养殖生产力介于9.72（SUG组）至14.22 kg·m⁻³（CTL组）之间，组间差异显著（P≤0.05）。生物絮团养殖桶的用水量较对照组（CTL）低11.8倍。经评价员评定，添加糖的生物絮团组所产罗非鱼鱼片接受度最优，得分为7.77（介于“中等偏好”至“非常偏好”之间）。本研究所用有机碳源（糖及糖蜜）可应用于尼罗罗非鱼的生物絮团养殖，且不会对养殖水质及生产性能造成不利影响。