C/N Ratio and its Effect on Biofloc Development, Water Quality, and Performance of Penaeus Vannamei Juveniles High-Density-Zero-Exchange-Outdoor Tank System

Increasing concerns over negative environmental impacts from shrimp farm effluent along with wide spread outbreaks of disease have led to the development of culture systems with minimal or zero water exchange. Biofloc-based systems have three pathways for nitrogen conversion: photoautotrophic uptake by algae, chemoautotrophic bacterial conversion of ammonia-nitrogen to nitrate-nitrogen, and heterotrophic bacterial assimilation of ammonia-nitrogen directly to bacterial biomass. Shrimp were fed a commercial feed which was specifically designed and formulated for biofloc-based super-intensive zero-exchange systems. Feed sample analysis showed a crude protein content of 36.1 %, crude lipid content of 7.3%, fiber content of 1.6%, and ash content of 9.5%. The community structure of biofloc and its development affect the microbial processes of metabolite assimilation and nutrient-recycling, creating different water quality dynamics in the culture system. The application of biofloc technology allows minimal or zero water exchange practice during the culture period, and thereby can improve sustainability, biosecurity and production in shrimp aquaculture.