## 3 Results and Discussion
### Ecological Conditions of the Caspian Sea
#### 3.3.2 Heavy Metal Contamination
The over the years concentration of copper as shown in Table 2, with rare exceptions, was recorded significantly higher than the level of fisheries management MPC (5 \(\upmu\)g/L) for sea water. The cadmium concentration did not reach the MPC standards during the studied period. In contrast to zinc, copper and lead, higher concentrations of cadmium were registered mainly during the autumn period. In addition, increased concentrations of this element are more widely distributed in the Kazakhstan sector of the Caspian Sea. Figure 12: Spatial distribution of heavy metals in water of the north-eastern Caspian Sea. Before presenting the accumulation levels both of heavy metals and pesticides in the ichthyofauna, we consider to provide the standards that are in force for this issue (Table 3), given in a number of sources [58; 59; 60], for subsequent comparison with the obtained results. In 2003-2005, a number of priority metals were determined in the muscles and livers of _Huso huso_, _Acipenser stellatus_, _Acipenser gueldenstaedtii_, _Acipenser nudiverntris_ caught during the spawning period. A general pattern is revealed: for most metals and all types of _Acipenseridae_, there is a higher concentration of toxicants, including metals, in the liver of fish, than in the muscles (Figures 13-15). The accumulation level of the analyzed elements in the organs and tissues of _Acipenseridae_ varies markedly over the years. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Toxic Substance**} & \multicolumn{2}{c}{**Fresh Fish, mg/kg**} & \multirow{2}{*}{**Sources**} \\ \cline{2-3}  & **Freshwater Fish** & & **Seawater * Fish** \\ \hline Lead & 1.0 & 1.0 & [57] \\  & 1.0 & 2.0 & [58] \\ Cadmium & 0.2 & 0.2 & [57; 58] \\ Arsenic & 1.0 & 5.0 & [57; 58] \\ Mercury & 0.3 & 0.4 & [57] \\  & 0.3 & 0.5 & [58] \\ Copper & 10 & 10 & [57; 58] \\ Zinc & 40 & 40 & [58] \\ HCH & 0.03 & 0.2 & [57; 59] \\ DDT & 0.3 & 0.2 & [57; 59] \\ PCBs & - & 2.0 & [58] \\ \hline \hline \end{tabular}  
* Due to the fact, that there are no standards, especially for fish species in the Caspian Sea, seawater respectively marine water standards were used.  
\end{table} 
Table 3: Maximum permissible level (MPL) of toxicants in fish food products. Figure 13: Heavy metal accumulation level in muscular and liver of _Acipenser stellatus_. It is known that individual metals have a different ability to accumulate in the organs and tissues of aquatic organisms [10; 14; 55; 58]. Analysis of the metal ratio series by the level of their concentration in the organs of certain species of studied fish in general shows their similarity. Based on the obtained material, the following most characteristic series of metals were identified in descending order of their concentration for _Acipenser gueldenstaedtii_ muscular tissue Cr > Zn > Cu > Pb > Co > Ni > Cd, and for the liver of these fishes Cr > Zn > Cu > Ni > Pb > Co > Cd. The composition of more active migrants, consisting of three elements (Cr, Zn, Cu) is constant in the liver and muscles. Cobalt and lead accumulate more actively in the muscles, and nickel in the liver. The results of the metal analyses in the muscles of small fishes, caught in the north-western desalinated zone of the Caspian Sea, showed a similar level of metal concentrations  
Figure 14: Heavy metal accumulation level in muscular and liver of _Acipenser gueldenstaedtii_. Figure 15: Heavy metal accumulation level in muscular of small fishes from the north-western desalinated zone of the Caspian Sea. in the muscle tissues of all fish species taken for analysis. The Cyprinus carpio caught in the shallow zone had maximum concentrations of lead (1.01 mg/kg) and zinc (8.36 mg/kg) in the muscles. Comparing these results with the standard values (Table 3), the accumulation of most metals is lower than the MPL. Only in the muscles of carp from the shallow zone, the concentration of lead reaches the standard level.