Chronic effect of nitrite on the rearing of the white shrimp Litopenaeus vannamei in two salinities

The aim of this study was to determine the effects of nitrite on the growth and survival of the white shrimp L. vannamei in two different salinities. Nitrite concentrations tested in salinity 8g/L were 0 (control), 2.5, 5.0, 10.0, and 20.0mg NO2--N/L, and in salinity 24g/L were 0 (control), 5.0, 10.0, 20.0, and 40.0mg NO2--N/L. For these experiments, 30 experimental units with 30 L of useful volume were stocked with 20 juvenile L. vannamei (8.0 +/- 0.50g), corresponding to a stocking density of 100 shrimp/m(2), and cultivated for an experimental period of 30days. A significant difference was found between the control and treatment groups with respect to growth and survival. The 2.5mg NO2--N/L treatment showed the best performance indexes in salinity 8g/L, while the best growth performance indexes were found in the control and 5.0mg NO2--N/L treatments in salinity 24g/L. Total mortality was observed in the 10 and 20mg NO2--N/L treatment groups from salinity 8g/L and in the 40mg NO2--N/L treatment group in salinity 24g/L. This study determined that concentrations of nitrite of up to 2.5 and 10mg/L are acceptable for the rearing of L. vannamei in salinities of 8 and 24g/L, respectively.