Intensive cultivation of whiteleg shrimp (Litopenaeus vannamei) under biofloc condition in land-based ponds

Land-based pond systems, as an emerging intensive aquaculture model, have encountered developmental constraints due to toxic nitrogen levels. This study aimed to develop and evaluate a biofloc-mediated aquaculture system in land-based ponds, focusing on water quality, bacterial composition of bioflocs, shrimp growth performance, and nonspecific immunity. Juveniles of Litopenaeus vannamei were stocked in three identical land- based barrel tanks at a density of 600 individuals center dot m- 2 for a 90-day cultivation period, with no water exchange. The results indicated that total ammonia nitrogen (TAN) concentrations were maintained between 0 and 4 mg center dot L-1, and nitrite (NO2--N) levels were kept between 0 and 1.0 mg center dot L-1. Bacterial community analysis revealed that the richness and Shannon index of bioflocs at 90 days were significantly higher, yet the dominant bacteria throughout the trial remained consistent, comprising Proteobacteria, Actinobacteria, Planctomycetes, Bacteroidetes, and Chloroflexi. Redundancy Analysis (RDA) demonstrated that Bacteroidetes were significantly positively correlated with TAN and NO2--N at 30 and 60 days, while Chloroflexi showed a positive correlation with nitrate (NO3--N) and phosphate (PO43-) at 90 days. Growth performance metrics indicated a survival rate (SR) of L. vannamei at (78.36 f 1.81)%, yield of (8.63 f 0.33) kg center dot m-3, specific growth rate (SGR) of (2.05 f 0.04)%center dot d- 1, feed conversion rate (FCR) of 1.53 f 0.25, and water usage of (192.29 f 9.01) L center dot kg-1 (shrimp). The relative expression levels of immune-related genes, including SOD, CAT, LZM, proPO, TLR2, and VEGF1L, exhibited an increasing trend over the course of the aquaculture process. Collectively, the findings suggest that bioflocs effectively regulated water quality and enhanced shrimp growth, production, and immune status.