Acute Toxicity of Nitrite to Various Life Stages of the Amazon River Prawn, Macrobrachium amazonicum , Heller, 1862

This study determined the effects of nitrite on different life stages of the Amazon river prawn Macrobrachium amazonicum . Prawns of each life stage (postlarvae, juveniles and adults) were stocked in 24 experimental units (n = 10 prawns), under a complete randomized design. Individuals were exposed to nitrite (0, 1, 2, 4, 8 and 16 mg L −1 ). The median lethal concentration after 96 h (96 h LC 50 ) was calculated through the Weibull I. The mortality results showed that M. amazonicum is slightly less tolerant to nitrite than other species of Macrobrachium . The 96 h LC 50 for postlarvae, juveniles and adults of M. amazonicum were of 1.49, 2.36 and 2.34 mg nitrite/L, respectively. Nitrite intoxication risk quotient suggest moderated risk to low risk to the species. Usually in production systems nitrite values are lower than safe levels suggested in this study (0.1 mg L −1 to postlarvae and 0.2 mg L −1 nitrite to juvenile and adults), which makes our results appropriate for the production of this species.