Study on heavy metals (Chromium, Cadmium, Cobalt and Lead) concentration in three pelagic species of Kilka (Genus Clupeonella) in the southern Caspian Sea

Environmental pollution by heavy metals has been a matter of growing concern over the last decades. Heavy metals are toxic and tend to accumulate in living organisms (Devier et al., 2005). In many studies, fish has been used as a sampling item to monitor the quality of ecosystems because of two reasons: 1- Fish bio-concentrate and integrate contaminant load both in time and space leading to more representative results compared to water samples, and 2- Fish represent the bio-available fraction of environmental contaminants, unlike water and sediment samples. On the other hand, humans consume fish species which makes attention to these fauna even more important (Danielsson, 2007).