Background: Aquatic ecosystems including fish in rivers may be widely contaminated by heavy metals released into waters from industrial, agricultural and other human activities.This study aimed to investigate the level of contamination of theses heavy metals (mercury, cadmium and lead) in fish caught in Khersan river, the largest tributary of Karun river.
Methods: The heavy metals level of mercury, cadmium and lead was investigated by atomic absorption spectrometry using Perkin Elmer 4100ZL in rainbow trout, pike and common carp species caught in Khersan river.
Results: The average concentration of mercury, cadmium and lead in muscular tissue of trout, pike and common carp in all three breeding areas were (0.023,0.110, 1.12), (0.026, 0.162, 1.34) and (0.027, 0.155, 1.45) mg/kg, respectively and only lead metal was more than the level determined by the World Health Organization and European Commission
regulations. The concentration of cadmium and lead in muscular tissue of caught fishes indicated an inverse and significant relationship with increasing weight and reducing fish metabolism (r=-0.568 and r=-0.517). The concentration of heavy metals of fishes in the river reduced by an increase in fish age, length and weight.
Conclusion: The level of mercury and cadmium in fishes of Khersan river was shown not to be threatening for their consumers, but the increase for lead concentration reflects the fact that the entry of urban, rural and agricultural wastewater affects the concentration of heavy metals in fishes of the river that may be threatening for their consumers.