## 3 Results and Discussion
### Ecological Conditions of the Caspian Sea
#### 3.3.3.1 Pesticide Contamination
The presence of DDT observed in the _Acipenser stellatus_ and middle number in the muscles of the _Huso huso_. In spring 2005, no DDT metabolites were founded in the organs and tissues of _Acipenseridae_. However, the accumulation of HCH isomers has become more widespread, although their concentration is not as high. In the muscles of _Acipenseridae_ the occurrence of these toxicants was in the range of 25% for _Acipenser stellatus_ to 100% for _Huso huso_, in the liver from 37 to 60%, the maximum is also characteristic of _Huso huso_, and the minimum is for _Acipenser stellatus_. The detected concentrations of toxicants are generally low, from 1.0 to 2.0 \(\upmu\)g/kg in the fish muscles and from 1.2 to 2.8 in the liver. Unlike _Acipenseridae_, the presence of HCH isomers and DDT metabolites was registered in the muscles of small fishes. HCH isomers are found in rare cases mainly in the muscles of fish caught in shallow waters adjacent to the Volga Delta. The presence of these toxicants in higher concentrations (0.70-2.5 \(\upmu\)g/kg) was found mainly in the muscles of _Cyprins carpio_. DDT metabolites were registered in almost all analyzed fish particles, the percentage of their occurrence was from 50 to 100. The highest concentrations of DDT were detected between 60 and 140 \(\upmu\)g/kg in _Cyprins carpio_, _Abramis brama_, and predatory species in _Silurus glanis_ and _Esox lucius_. From these data it follows that the shallow Caspian Sea area is influenced by Volga River runoff. The accumulation of pesticides in fish there is much higher than in other parts of the Northern Caspian Sea. Consequently, the increased pesticide contamination of the Volga River runoff is the reason for a fairly high accumulation of these toxicants in the organs and tissues of fish. The organochlorine pesticides accumulation in the ichthyofauna of the Kazakh sector of the Caspian Sea, according to our research in 2008-2010, is briefly characterized by the following data. Dichlorodiphenyltrichloroethane (DDT) at the highest level between 369 \(\upmu\)g/kg and 449 \(\upmu\)g/kg was registered in the muscles of _Clupeidae_ and _Acipenseridae_ respectively. It accumulates in the tissues of the _Rutils rutilus_-up to 40 \(\upmu\)g/kg significantly less, in frequent cases it was not detected. 200 \(\upmu\)g/kg DDT, that means an excess of the MPL standard for Caspian Sea fish, in three cases for _Acipenseridae_ and _Clupeidae_ species was detected. Maximum DDT accumulation was registered in _Acipenseridae_ caught in the pre- estuary sections of the Ural River and Volga River (Figure 17). Its maximum concentration \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Species of Fish**} & \multicolumn{3}{c}{**2004**} & \multicolumn{3}{c}{**2005**} \\ \cline{2-7}  & **HCH** & **DDT** & \multicolumn{3}{c}{**HCH (Isomers)**} \\ \cline{2-7}  & **Muscle** & & **Muscle** & & **Liver** \\ \cline{2-7}  & \(\upmu\)g/kg & & \(\upmu\)g/kg & _Occurrence \%_ & \(\upmu\)g/kg & _Occurrence \%_ \\ \hline _Acipenser stellatus_ & Not up & 0.0–40 & 0.0–1.60 & 25 & 0.0–2.0 & 37 \\ \hline _Acipenser_ & & & & & & \\ _gueldenstatedtii_ & Not up & Not up & 0.0–2.00 & 60 & 0.0–2.0 & 60 \\ \hline _Huso huso_ & Not up & 10.0 & 1.0–2.0 & 100 & 0.0–1.2 & 50 \\ \hline _Acipenser nulvientris_ & & & 0.0–1.70 & 75 & 0.0–2.80 & 50 \\ \hline MPL, \(\upmu\)g/kg & 200 & 200 & 200 & & & \\ \hline \end{tabular}
\end{table} 
Table 5: Pesticide accumulation in muscles and liver of _Acipenseridae_ species in 2004 and 2005.  
in _Clupeidae_ was observed in the eastern water section, although this toxicant accumulation is at an increased level throughout the whole Northern Caspian Sea. Hexachlororocyclohexane (HCH) was not detected in 50% of _Acipenseridae_ and 30% of _Clupeidae_ fish. The highest concentration of the toxicant reached 194 ug/kg in _Acipenseridae_ muscles and 160 ug/kg in _Clupeidae_ muscles, i.e., below the MPL.