Lethal copper concentration levels for Clarias gariepinus (Burchell, 1822) @ a preliminary study

Abstract

Lethal copper concentrations were determined for both adult and juvenile Clarias gariepinus at representative mean summer and winter temperatures. Fish were exposed to copper for 96 hours in an experimental system and mortalities monitored. Toxicity curves of percentage mortality versus actual copper concentration were drawn, and the LC50 calculated for winter and summer temperatures. The lethal copper concentrations, expressed as LC50, found in laboratory exposures, ranged for adults from 1,29 mg/1 during summer to 1,38 mg/1 in winter. These values are considerably higher than the levels of copper in the water of the Olifants River in the Kruger National Park during summer (0,055 @ 0,016 mg/1) and winter (0,085 @ 0,032 mg/1). The derived LC50 values predict the level of copper which should be prevented at all cost. The fish in the Olifants River are already exposed to sublethal concentrations (40 of LC50) of copper. The results can be used as an indication of what the safe concentrations of copper should be.