Acute nitrite toxicity and methemoglobinemia in juvenile milkfish (Chanos chanos Forsskal)

Abstract

Nitrite was about 55 times more toxic to milkfish juveniles in fresh water than in 16% brackish water: the 48-h median lethal concentrations were 12 mg NO_2-N/l (95% confidence limit=7.4–19.6) and 675 mg NO_2-N/l (95% confidence limit = 435.8–1,045.4) respectively. Methemoglobin levels were higher for a given concentration of nitrite in milkfish kept in fresh water than in the brackish water. Methemoglobin decreased to a normal level within 24–26 hours of the removal of nitrite.