This study aimed to evaluate the e¡ect of low salinity on the water quality, microbial £ocs composition and performance of Litopenaeus vannamei juveniles reared over 40 days in a zero-water-exchange super-intensive system at 0, 2, 4 and 25 g L À 1 . At 0 g L À 1 , the mortality was total at the 26th day, and consequently, these salinity data were not included in the statistical analysis. Among the water quality parameters, only pH and the total suspended solids concentration were signi¢cantly in£uenced by salinity. However, a trend towards intensi-¢cation of the nitri¢cation processes was observed as the salinity increased, with the lowest ammonia and the highest nitrite and nitrate concentrations found at 25 g L À 1 . The concentrations of ciliates and £agellates diminished and increased, respectively, with the increase in salinity. Diatoms predominated at 25 g L À 1 , whereas at 2 and 4 g L À 1 , chlorophytes were more abundant. Microbial £oc crude protein content was reduced with the increase in salinity, whereas ash content demonstrated the inverse trend.The best overall growth performance and survival were observed at 25 g L À 1 . However, satisfactory productivity was also found at 4 g L À 1 , suggesting the viability of rearing L. vannamei at low salinity under zero-water-exchange conditions.

-The objective of this study was to evaluate the effect of salinity on the culture water quality, performance and body composition of Litopenaeus vannamei juveniles (1.16±0.30 g) reared for 36 days in a super-intensive system without water exchange at salinities of 4, 16 and 32‰. Groups of 200 animals (140/m 2 ) were stocked, with three replicates, in nine fiber-cement tanks (1.11 × 1.29 × 0.70 m) with a useful volume of 400 L. Physical and chemical parameters of water, such as temperature and dissolved oxygen before and after midday, pH, alkalinity, total suspended solids, total ammonium nitrogen, nitrite, nitrate, and phosphate, were monitored. Performance parameters like survival, weight gain, specific growth rate, feed conversion ratio and protein retention rate, were also evaluated. The proximate composition of the juveniles was analyzed through the moisture, protein, lipid and ash contents. The physical and chemical parameters of the water were influenced by the treatments. The increased salinity produced a significant increase in the alkalinity and the concentrations of total suspended solids, nitrite and phosphate. Of the parameters that were examined to evaluate the performance and proximate composition of the shrimp, only survival, protein retention rate and body lipid content were significantly influenced. The highest values were found at a salinity of 32‰. However, the analysis of the proximate composition of the bioflocs showed that the moisture, protein and lipid contents increased as the salinity decreased. Growth, use of feed and survival of L. vannamei juveniles reared in a super-intensive system without water exchange is positively influenced by an increase of salinity from 4 to 32‰.

No abstract

Ten isonitrogenous casein–gelatin‐based diets were formulated to contain five estimated metabolizable energy concentrations (10.92, 12.29, 13.63, 14.82 and 16.16 kJ g−1) at two carbohydrate‐to‐lipid ratios (CHO : L, 5.3 and 12.8, g : g) in a 5 × 2 factorial arrangement. Each diet was assigned to triplicate groups of 11 piracanjuba fingerlings (5.25 ± 0.14 g) and fed to apparent satiation twice a day for 90 days. Higher daily weight gain was obtained by fish fed the 13.63 kJ g−1 diets for both CHO : L ratios. There was a significant reduction of feed consumption when dietary energy concentration increased above 13.63 kJ g−1. Feed conversion ratio and apparent net energy retention improved as dietary energy increased. Apparent net protein retention tended to be lower in the highest and lowest dietary energy concentrations. The results suggest that dietary lipid energy was more efficiently utilized by piracanjuba fingerlings than carbohydrate energy. Body composition and hepatosomatic index (HSI) were not influenced by dietary CHO : L ratio. However, an increase in dietary energy concentration beyond 13.63 kJ g−1 resulted in a significant increment in lipid deposition, while body moisture and HSI decreased. Our findings indicate that at 300 g kg−1 dietary crude protein, a CHO : L ratio of 5.3 is recommended for piracanjuba, and the required energy is either 13.63 kJ g−1 if raised for aquaculture or 14.82 kJ g−1 if destined to stock enhancement.