Assessing Uptake Kinetics and Natural Depuration of Lead and Cadmium in African Catfish Juvenile

Abstract

This study was carried out to assess the uptake kinetics of two heavy metals lead and cadmium in African catfish juveniles and their ability to  depurate during subsequent exposure to clean water. Catfish juveniles with average weight and length of 5.3g and 5.8cm respectively were  randomly selected and acclimatized for two weeks. A 24-hour range finding test was carried out. In the definite test, the fish were stocked in 24 tanks containing 5litres of water with lead and cadmium treatment separately labeled according to predetermined concentrations 5, 10, 15, 20, 25 mg for lead and cadmium with 4 fish in each treatment. The water and fish were analyzed for the metals after 5 days to show percentage uptake of the metals from the water. The fish were transferred back into clean water to access the rate of depuration and water was changed continuously. After 4 days the fish were analyzed again to see if they were purged of the heavy metals. Based on these findings catfish have shown to be good accumulators of heavy metals but can be depurated if allowed to swim in clean water. Uptake percentage after the period of exposure to 5mg,  10mg, 15mg, 20mg, 25mg concentrations were 18.68, 10.17, 5.95, 1.41, 8.26 for cadmium and 20.47, 10.17, 8.76, 9.92, 10.08 for lead; Percentage of metals depurated after 4 days were 40.00, 80.70, 90.00, 77.78, 45 for cadmium and 73.045, 20.413, 41.425, 37.580, 61.141 for lead. Lead was readily taken but cadmium was readily depurated.

Keywords: Heavy metals, juvenile catfish, exposure, uptake and depuration