A Quantitative Analysis of Lead, Mercury and Cadmium Intake by Three Commercial Aquatics, Hypophthalmichthys molitrix, Onchorhynchus mykiss (Walbaum) and Fenneropenaeus indicus

At the present study, the distribution of Cd, Hg and Pb in water and their accumulation in fish species (silver carp, rainbow trout and shrimp) in three different farms. Totally 63 samples of three species and the water of their ponds were obtained during summer 2008 from Gilan, Mazandaran and ChabaharIran. The concentrations of three heavy metals in fish and shrimp flesh were measured by flameless atomic absorption spectroscopy. Only Lead was found in fish at mean concentrations above the permissible limits proposed by US FDA and EPA. Pb and Hg in the studied species showed the following pattern: silver carp > rainbow trout > shrimp, because Lead and mercury intake by species such as silver carp via phytoplankton consumption seems to be more logical. The accumulation of Cd in rainbow trout found to be more than it in silver carp. Metalloenzyme, an enzyme which found in plankton (the principle food diet of silver carp) that specifically uses cadmium to achieve its biological function, probably is a reason of cadmium increase in water and flesh samples of rainbow trout than that in silver carp. On the other hand, results showed that the significantly lower levels of contamination in shrimp, the main reasons of which might be the short period of feeding of the shrimp and an active mechanism of secretion.