## 3 Results and Discussion
### Ecological Conditions of the Caspian Sea
#### 3.3.4 Biodiversity Conditions  
According to experts of the Caspian States [48; 50], the ecosystem status quo of the Caspian Sea including its northern part is under anthropogenic stress and ecological regression. A decrease in species diversity and the reduction in its biological productivity, especially stocks of _Acienseridae_ and _Pusa caspica_ have been observed as a result of contamination within both the Volga and the Ural River basins and by anthropogenic activities along the shorelines and the water body of the Caspian Sea. In the Kazakh sector of the Caspian Sea, sturgeon catches decreased by 10 times between 2008 and 2010. The status quo of Caspian seal stocks is of great concern. It is classified as the endangered species on the International Union for Conservation of Nature's (IUCN) Red List. At present, there is a critical situation for the further existence of _Pusa caspica_. The entire north-eastern Caspian Sea is covered by oil operations all year round--drilling wells, construction of artificial islands, marine structures, digging trenches and laying pipelines, movement of numerous ships and helicopters. All of them have changed the habitual way of life of _Pusa caspica_ with severe consequences for them. In addition, systematic chemical contamination of organisms has been increasing. Under these conditions, the number of deaths both seals and fishes has increased. Great number of seals deaths in the Kazakh sector of the Caspian Sea were registered in 1968, 1978, 1997, 2000, 2001, 2006, 2007 and in 2009 [78; 79; 80]. There is no clear answer yet about the reasons for the death of seals. The main cause of their death in 1997, 2000 and 2007, according to the Commission members, [79] is considered epizootic by canine distemper virus, although at the same time there was a mass death of sturgeon. At the same time, it was noted [81] that the infection of seals occurred against the background of the sharp decrease in their immunity due to long-term chemical contamination of the Caspian Sea and chronic polytoxicity, mainly by petroleum products and pesticides. According to full-scale visual observations of [PERSON] [78], during spring 2000, a next mass death of _Pusa caspica_ occurred. The number of dead individuals, according to Caspian Fisheries Management Research Institute, in the Russian coast approached 11 thousand. On the Kazakh coast, the number of corpses washed ashore reached 50 thousand. Along the northern border of Dagestan to Derbent (Russia) 15-20 thousand dead _Pusa caspica_ were counted. In addition, a significant number of dead fish, e.g., _Acienseridae_, _Rutilus rutilus_, _Clupeidae_, were observed on the Dagestan coast. Unfortunately, a systematic analysis of this tragedy, which is essentially for the ecological disaster for the Caspian region, has not been carried out. The fact of the accident was hidden, and the <<Environmental Information Bulletin of the Republic of Kazakhstan>> in 2000 stated that the main cause of the death of _Pusa caspica_ was an epizootic virus <<dog plague>> [78; 80]. At the same time, it should be noted that the mass death of seals is usually detected visually in the early spring period, after ice melting in the shallow south-eastern sector of the Northern Caspian Sea. Toxicological studies have proved [82; 83; 84; 85] that saturation of the aquatic environment with various contaminants leads to functional accumulation, that is, the increase in the degree of damaging effects of toxicants on the fish body. With prolonged exposure, harmful substances are able to accumulate to toxic levels in the fat tissue, internal organs and muscles of the fish. As a result, their resistance to infectious and invasive diseases, as well as adverse environmental factors, is weakened.