Background: Iron, manganese, and aluminum are three abundant metals on earth and their concentrations have increased in aquatic environments as a result of natural and industrial activities. This study was undertaken to report the median acute toxicity (LC50) and accumulation of the sub-lethal concentration (10% 96-h LC50) of iron (Fe), manganese (Mn) and aluminum (Al) in kutum (Rutilus kutum) fingerlings . Methods: For the 96-h LC50, the fish were exposed to concentrations of 105, 111, 117, 123, 129 and 135 mg/l of Fe and 40, 45, 50, 55, 60, and 65 mg/l of Mn and 18, 22, 26, 30, 34 and 38 mg/l of aluminum for 4 days. For sublethal exposure, they were exposed to mediums with concentrations of 12.3, 5.4 and 2.9 for Fe, Mn, and aluminum, respectively. Metal concentrations were determined by atomic absorption spectrophotometry in the gill tissues. Results: Probit analysis showed the 96-h LC50 values of 122.98, 54.39, and 28.89 mg/l for Fe, Mn, and aluminum, respectively. Sub-lethal tests were conducted with nominal concentrations of 12.3, 5.4, and 2.9 mg/l of Fe, Mn, and aluminum for four days, respectively. Significant accumulations were observed in gills for all tested metals as compared to the control groups in short-term exposure (P<0.05 .( Conclusion: Obtained results clearly show that aluminum is the most toxic metal among tested ones for kutum fingerlings and it has the highest branchial AF value during sublethal exposure.

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