Uptake and tissue distribution of dietary and aqueous cadmium by carp (Cyprinus carpio)

The aim of this study was to assess whether contaminated prey can be a major source of Cd for fish. For this purpose, the uptake and tissue distribution of dietary and aqueous cadmium by the carp (Cyprinus carpio) was studied. The fish were exposed to either Cd-contaminated food or Cd-contaminated water for 4 weeks in laboratory experiments. When exposed to contaminated food, the fish were kept in clean water and fed contaminated chironomid larvae, equilibrated with 99 micrograms Cd. liter-1. During exposure to contaminated water (nominal 100 micrograms Cd. liter-1; actual 80 micrograms Cd. liter-1) the fish were fed uncontaminated food. The Cd accumulation in the tissues of fish fed contaminated larvae was, in decreasing order, gut > kidney > liver = gill > muscle. In the water experiment this order was gut > gill > kidney > liver > muscle. In almost all tissues the Cd uptake was similar for both routes; only the gill had accumulated more Cd from Cd-contaminated water than from Cd-contaminated food. Considering the ongoing discussion of the importance of Cd transfer from contaminated food to predators, these findings suggest that uptake of Cd from Cd-contaminated prey by fish plays an important role in contaminated waters.