Aquaculture technologies have been developed over the last decade to increase productivity and reduce cost of fish and shrimp farming. Among different approaches, Biofloc technology (BFT) used as a promising technology to advance shrimp farming economically and environmentally. Biofloc technology is an efficient way to manage water quality conditions for cultured species by optimizing carbon and nitrogen concentrations in shrimp rearing system. BFT is a symbiotic process that includes confined aquatic animals, heterotrophic bacteria and other microbial species in the water to enhance animal growth. In the current study, we have utilized sugarcane bagasse as an economic carbon source to feed L. vannamei larvae for 90 days in a BF based system under two different shrimp densities (12 PLs/litre and 16PLs/litre). Water parameters and shrimp measurements were monitored on biweekly basis. Thence, water parameters during the experimental period were within the acceptable range for shrimp culture, as water temperature ranged from 27.91 to 28.76± 0.87 C, dissolved oxygen from 5.66 to 6.19± 0.52mg/L, pH from 7.14 to 7.25± 0.12, and salinity from 27.77 to 29.01± 1.25 ppt. Expectedly, total ammonia Nitrogen (TAN), Nitrite (NO2-N), nitrate (NO3-N) and phosphorus (PO4-P) concentrations have been increased with stocking density in control tanks, meanwhile interestingly, the values were significantly low in BF treated tanks compared with the control tanks. On the other hand, total suspended solids (TSS) have been increased with biofloc treated tanks than control ones. Furthermore, shrimp growth was higher in terms of growth and survival (SR%) (12BF and 16BF) than that fed the control diet (12C and 16C). Also, the mean shrimp weight (FBW) was significantly higher at biofloc treatments in both stocking densities compared to the control ones. Finally, enhanced shrimp growth, water quality and TSS in BF treated tanks were associated with a significant decrease in the percent of "total vibrio count/total heterotrophic count" in both densities in BF tanks than those in the control counterparts. This may refers to the flourish beneficial bacterial community under BF treated tanks.
Genuinely, in our study we have utilized a BF system-based Sugarcane bagasse as a direct food source to feed L. vannamei larvae. Sugarcane bagasse as an economic carbon source could not only enhance the heterotrophic bacterial community that was conjugated with enhanced water quality parameters of TAN, NO2-N, NO3-N and PO4-P but also enhance shrimp growth under intensive rearing. Results of our study strongly recommend using Sugarcane bagasse in intensive farming of L. vannamei.
Acknowledgements: The research was performed within the "Development and Research Application of bioFloc Technology for increasing shrimp production in Egypt (EGY-DRAFT)" project, which is financially supported, by the Science & Technology Development Fund (STDF), Ministry of Scientific Research, Egypt. (Agreement No. 25305, Reintegration Grants). The authors are grateful for all the support.