Toxicity of Copper and Mercury to Caspian Roach Rutilus rutilus caspicus

Copper (Cu) and mercury (Hg) enter aquatic ecosystems from different sources threatening health of aquatic organisms such as fish. As such, in this investigation, determinaing, Cu and Hg toxic concentration in Caspian roach (Rutilus rutilus caspicus), was undertaken. Acute toxicity of Cu and Hg were determined in fish specimen under semi-static condition. Caspian roach fry (~ 1 g) were exposed to Cu or Hg at 6 concentrations (0.2, 0.27, 0.39, 0.47, 0.59 and 0.66 mg L-1 total Cu and 0.22, 0.26, 0.3, 0.37, 0.44 and 0.52 mg L-1 Hg). Control fish were exposed to water with no Cu or Hg. Mortality was recorded at 24-h-intervals for 96 h. Total Cu-LC50 values found to be 0.43 mg L-1 for 24 and 48 h and 0.42 mg L-1 for 72 and 96 h. The lowest observed effect concentration (LOEC) values for total Cu were 0.39 mg L-1 for 24 and 48 h, and 0.20 mg L-1 for 72 and 96 h. On the other hand, free-Cu-LC50 values found to be 0.22 mg L-1 for 24 and 48 h and 0.21 mg L-1 for 72 and 96 h. LOEC values for free Cu were 0.20 mg L-1 for 24 and 48 h, and 0.10 mg L-1 for 72 and 96 h. 24-72 h LC50 values for Hg were 0.37 mg L-1, while 96 h LC50 found to be 0.33 mg L-1. Likewise, LOEC values for Hg were 0.26 mg L-1 for 24- 72 h, and 0.22 mg L-1 for 96 h. The results showed LOEC values for Cu and Hg in Caspian roach were lower than these metal concentrations in Caspian Sea water, suggesting little risk of acute toxicity in the sea. Chronic toxicity test is suggested to illustrate the effect of current levels of contamination in Caspian roach.