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This study aimed to investigate the effects of stocking density on Litopenaeus vannamei at the nursery phase in low-salinity biofloc system. Post-larvae of L. vannmei were cultured for 28 days at 2000, 4000 and 6000 shrimp m-3, and the water quality, plankton composition and growth performance were evaluated. The water quality variables remained within the ideal range for the shrimp culture, and only total suspended solids showed a significant difference between treatments -- the highest stocking density has increased the levels of total suspended solids. In regarding to zooplankton structure, the Protozoa group had the greatest diversity regardless of treatment, and also the greatest abundance (> 66%). For phytoplankton structure, Bacillariophyta (Navicula sp. and Cyclotella sp.) was the dominant class in phytoplankton structure throughout the culture, although a Cyanobacteria bloom has reported at the end of the cultivation at 2000 shrimp m-3. At the end of cultivation, the shrimp yield (0.133 ± 0.028 kg m-3) was significantly higher in the 6,000 shrimp m-3. In contrast, the shrimp survival was significantly higher in the lowest stocking density (71.66 ± 10.36%). Our findings suggest that a density of 6,000 shrimp m-3 should be used under these conditions, but an economic feasibility study should be considered in the future. [ABSTRACT FROM AUTHOR]

The present study aimed to evaluate the influence of different salinities on water quality, growth performance, and hematology of the Nile tilapia Oreochromis niloticus cultured in a biofloc system. Four different salinities with four replicates were evaluated: 2, 8, 15, and 22 PSU. The fish (200 ± 10 g) were stocked at a density of 15 fish m-3 in tanks with 800 L of useful volume for 56 days. Fish were fed with a 32 % crude protein commercial feed. Water quality remained stable throughout the study. The growth parameters differed, with the salinities of 2 and 8 PSU presenting higher growth and survival. The treatment of 15 PSU showed high survival, however, with reduced growth. The salinity of 22 PSU had lower results than the others for all parameters analyzed. The hematological evaluation showed differences in RBC, hematocrit, and glucose counts, indicating that salinity may have caused stress to animals cultured at higher salinities, thus, causing low growth and survival. These results indicate that Nile tilapia can tolerate high salinities when cultured in a biofloc system. However, salinities above 15 PSU may compromise its growth and weight gain. [ABSTRACT FROM AUTHOR]