The Cat-fish, Clarius carsonii

Clarias carsonii is a potential bioindicator of metal pollution since it is commonly found in pristine and metal-contaminated environments. This study utilised a biokinetic model to investigate the physiological processes controlling zinc (Zn) and copper (Cu) uptake and elimination in C. carsonii. A transplantation experiment assessed Zn and Cu bioaccumulation in the gills, gut, liver, and muscle under four treatment regimens: uncontaminated water and food, uncontaminated water with contaminated food, contaminated water with uncontaminated food, and contaminated water and food. Over 70 days of exposure followed by 70 days of elimination, the dissolved Zn and Cu uptake rates (ku) ranged from 0.04–0.54 Lg⁻¹d⁻¹ for Zn and 0.05–0.84 Lg⁻¹d⁻¹ for Cu, with the highest uptake in the gills and lowest in the liver. Efflux rates (ke) were faster in the gills and gut, with values of 0.84 d⁻¹ and 0.51 d⁻¹ for Cu, and 0.35 d⁻¹ and 0.28 d⁻¹ for Zn, respectively. The model further indicated that >90% of metal accumulation in the gills was due to dissolved metals, while dietary exposure was the main pathway for the gut, muscle, and liver.