Backgrounds and Aim: The simultaneous presence of environmental contaminants in the aquatic environment could be more different effects to separate them on fish and other organisms. The aim of this study was to evaluate the simultaneous effects of mercury and silver nanoparticles on the oxidative stress of laboratory fish gill tissue.

Material and Methods: In this study of 180 laboratory fish were used. To determine of superoxide dismutase and catalase in the gills of fish, a non-lethal dose of mercuric chloride, a non-lethal concentrations of silver nanoparticles, the composition of mercury chloride and silver nanoparticles with control group were used. To evaluate for significant differences in different groups one-way ANOVA was used.

Results: The levels of superoxide dismutase showed no significant difference in different groups (p>0.05), while the levels of catalase in different groups was statistically significant (p<0.0). The results showed that the simultaneous presence of mercury and silver nanoparticles enhances the concentrations of superoxide dismutase and catalase index in the gill of fish, but this increase was not significant differences (p>0.05).

Conclusion: According to this study, in the short term, simultaneous presence silver nanoparticles with mercury in the aquatic environment can have a synergistic effect on the catalase index in fish.