Toxicity of copper and zinc to Puntius parrah (Day, 1865)

•The toxicity of copper and zinc on Puntius parrah was assessed.•Zn and Cu in water and sediment showed high level in the highly industrialized area.•Several histopathological alterations are induced by the trace metals.•There was a decrease in erythrocyte count after exposure to Cu and Zn.•WBC count increased whereas hemoglobin, hematocrit, MCV and MCHC decreased.

The toxicities of the trace metals copper and zinc on the fish Puntius parrah were assessed based on standard renewal bioassay methods, and the 96 h LC50 values for copper and zinc were 0.5 mg/L and 9 mg/L, respectively. The zinc and copper concentrations in water and sediment were high in a highly industrialized area compared with those in non-industrialized zones of the Periyar River. The fish exposed to a sublethal concentration of 0.05 mg/L of Cu and 0.9 mg/L of Zn showed a higher accumulation of both of the metals in the liver than in the kidneys, gills, and muscles. The histological changes induced by copper and zinc on the test organism under sublethal concentrations on the 3rd, 7th, 14th, and 28th -days of exposure were also studied. There was a significant decrease (p < 0.001) in the erythrocyte count after exposure to sublethal concentrations, whereas the hemoglobin, hematocrit, and mean corpuscular hemoglobin concentrations were significantly decreased after 28 days of exposure. Effective management strategies need to be developed and implemented to protect water bodies and aquatic organisms from trace metal pollution and its toxic effects.