Due to its painful sting, dense blooms that clog fishing gear and pumps, and voracious Nitrite can accumulate in the water in natural and hatchery settings and elevated levels are toxic to many fish. This study evaluated effects of 1 mg/L nitrite on methemoglobin, PCV (packed cell volume), hemoglobin and plasma chemistry in Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus). Juvenile fish (0.544 kg ± 0.126 SD) were divided into two treatment groups of chloride concentrations of 0 mg/L and 50 mg/L. The percent methemoglobin in the 0 mg/L chloride group was 81.936 (68.182, 87.719), median (1^st quartile, 3^rd quartile), at 96-hours post exposure and was significantly different from the 50 mg/L chloride group which had a percent methemoglobin of 7.895 (4.762, 10.811) (P < 0.05). Two weeks after removal from nitrite, elevated methemoglobin was observed in the 0 mg/L chloride group with a percent of 71.429 (62.963, 90.476). PCV decreased significantly in both groups (P < 0.05). The 0 mg/L treatment group dropped in percent PCV from 30 (29, 32) to 7 (5, 9) and the 50 mg/L treatment group dropped in percent from 29.5 (28, 32) to 15 (13, 18) over the duration of the study. Total hemoglobin decreased significantly from 6.6 g/dL (6.2, 6.8) to 5.6 g/dL (5, 7.1) in the 0 mg/L chloride group and from 6.2 g/dL (5.9, 6.6) to 4.3 g/dL (3.5, 5.3) in the 50 mg/L chloride group (P < 0.05). Nitrite resulted in severe hemolytic anemia and mortality of 60% in the 0 mg/L chloride group and was less severe with no mortality in the 50 mg/L chloride group. Nitrite accumulation at a chloride level close to 0 mg/L is toxic and multiple stressors can result in significant mortality.

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