What would you likely observe in fish due to nitrite toxicity?

Brown discoloration of the blood is a classic sign of nitrite toxicity in fish. Nitrite interferes with the ability of hemoglobin to carry oxygen by converting it to methemoglobin, which has a reduced ability to bind oxygen. This leads to a lack of adequate oxygen delivery to the tissues, causing the blood to take on a brown color, often described as chocolate brown. This is a significant and distinguishing characteristic of nitrite poisoning in fish.

In addition to the brown blood, fish suffering from nitrite toxicity may also exhibit signs of distress, such as lethargy or altered swimming behavior, but the definitive and notable indicator is the change in blood coloration. This alteration in blood property serves as a clear physiological response to increased nitrite levels in the aquatic environment.