Recirculating Aquaculture Systems (RAS) and Biofloc Technology (BFT) are promising approaches that reduce water usage and promote sustainability in aquaculture production.
A study published by researchers from the Institute of Oceanography, Federal University of Rio Grande, and the Virginia Seafood Agricultural Research and Extension Center at Virginia Polytechnic Institute and State University compared RAS and BFT systems for super-intensive farming of Pacific white shrimp Penaeus vannamei, evaluating water quality, shrimp growth, and economic feasibility.
Background
RAS provides precise environmental control, efficient resource utilization, and reduced water consumption. It employs mechanical and biological filtration to remove waste and control water chemistry. Biofloc technology (BFT), on the other hand, leverages a diverse microbial community within the culture water to process organic matter and maintain water quality. This system minimizes water exchange, reducing environmental impact.
Nitrogenous compounds, primarily ammonia and nitrite, are major concerns in intensive aquaculture. These compounds can accumulate due to shrimp excretion and the decomposition of organic matter, negatively affecting shrimp health and survival.
Methods
The 69-day study, published in MDPI’s Sustainability journal, compared RAS and BFT systems in 100-L units, each with three replicates. P. vannamei shrimp (initial weight: 0.10 ± 0.04 g) were stocked at 500 shrimp m-3.
BFT maintained a C:N ratio of 15:1, adding dextrose when total ammonia nitrogen (TAN) reached 1 mg L−1. Probiotics were administered daily to both groups. Water quality parameters, shrimp growth (weight, length, survival), and feed conversion ratio (FCR) were monitored throughout the culture period. A partial budget analysis (PBA) was also conducted to assess the economic feasibility of each system.
Results
Key Findings
- Water Quality: BFT initially experienced a spike in total ammonia nitrogen (TAN) levels, which stabilized after 36 days. RAS effectively controlled nitrogenous compounds. The abundance of Vibrio was initially higher in RAS but increased in BFT towards the end of the trial.
- Productivity and Growth: BFT was more productive than RAS, yielding higher final weights (13.56 g vs. 8.14 g), weekly growth rates, and shrimp yields (5.62 Kg/m³ vs. 3.58 Kg/m³). Survival rates were slightly higher in RAS (88%) compared to BFT (83.33%). This suggests that adopting the BFT system could lead to greater shrimp production in the industry.
- Operational Costs: The partial budget analysis (PBA) indicated that BFT is more economically advantageous due to lower operational costs and higher shrimp yields. Transitioning from RAS to BFT resulted in a net benefit of $2,270.09, demonstrating that shrimp farms adopting BFT could reduce production costs and increase profits.
- Vibrio Management: Although Vibrio abundance was initially higher in RAS, it increased in BFT by the end of the trial. BFT demonstrated better overall Vibrio management. Probiotics and bioflocs are essential for controlling Vibrio and improving production indices. Producers should adopt best management practices, use probiotics, and develop bioflocs to maintain optimal Vibrio levels and ensure shrimp health.
- Water Usage: BFT demonstrated greater water-use efficiency, using 1.82 m³ of water per kilogram of shrimp produced, compared to 2.13 m³ in RAS. Efficient use of natural resources and reduced water dependency are critical aspects of sustainability. Shrimp producers may consider adopting BFT to reduce their environmental footprint and enhance sustainability.
Implications for Shrimp Production
The study highlights that BFT is more productive and uses fewer natural resources, supporting the concept of sustainable development, which integrates ecological prudence, economic efficiency, and social equity. The shrimp industry, increasingly concerned with environmental issues, can turn to systems like BFT to achieve more responsible production.
In summary, adopting the BFT system could offer the shrimp industry higher productivity, lower operating costs, better Vibrio management, more efficient water use, and a move toward more sustainable practices. These combined factors contribute to the long-term economic and environmental viability of the shrimp industry.
Conclusion
Biofloc technology emerged as a more productive and economically viable option than RAS for the super-intensive farming of P. vannamei under the conditions of this study. However, due to the delayed maturation of nitrifying bacteria in the BFT system, it would be beneficial to initiate stable biofloc development before introducing shrimp. The results also highlight that outcomes are tied to local water, climate, and regulatory conditions in the U.S., where the study was conducted.
The study concludes that under the experimental conditions, the BFT system is technically and economically superior for Penaeus vannamei production compared to RAS. The natural productivity of bioflocs in BFT provides better zootechnical parameters, offering valuable insights for improving intensive shrimp farming management.
The study was funded by the National Council for Scientific and Technological Development (CNPq), the State of Rio Grande do Sul–FAPERGS, and the Coordination for the Improvement of Higher Education Personnel (CAPES).
Reference (open access)
Ramiro, B. D., Wasielesky, W., Pimentel, O. A., Sun, T., McAlhaney, E., Urick, S., Gonçalves, F. H., Van Senten, J., Schwarz, M. H., & Krummenauer, D. (2024). Assessment of Water Quality, Growth of Penaeus vannamei, and Partial Budget in Super-Intensive BFT and RAS: A Comparison Between Sustainable Aquaculture Systems. Sustainability, 16(24), 11005. https://doi.org/10.3390/su162411005
