The fish were killed by cervical dislocation and weighed. The gill basket, skin, fins, head and gastrointestinal tract were removed from the carcass. The gills, carcass and water samples were analysed for Cd in a Searle gamma-counter.Nuclear Chicago, USA . The skin, fins and head were only analysed in the groups exposed to 0 and 16 µM Zn in experiment 2. The results were corrected for radioactive decay. The apical uptake of Cd from the water into the gill epithelium during the 24 h exposure period was calculated using the formula: