Effect of sublethal concentrations of copper on the critical thermal maxima (CTMax) of the fantail ( Etheostoma flabellare) and johnny ( E. nigrum) darters

Static 96-h copper LC 50 values determined for fantail ( Etheostoma flabellare) and johnny ( E. nigrum) darters were used to determine ranges of copper concentrations for sublethal tests. LC 50 values ranged from 330–392 μg · L −1 for fantail darters and 483–602 μg · L −1 for johnny darters. The CTMax method was used to determine the upper temperature tolerance of both species after a 96-h sublethal copper exposure. Copper exposure (concentrations above no-effect levels) for as little as three days significantly decreased the CTMax values for each species. A gradual increase in CTMax values was observed daily when fantail and johnny darters were removed from dosing water and placed into control water.