Caspian Sea
The Caspian Sea, like the Black Sea, Namak Lake, and Lake Urmia, is a remnant of the ancient Paratethys Sea. It became landlocked about 5.5 million years ago due to tectonic uplift and a fall in sea level. During warm and dry climatic periods, the landlocked sea almost dried up, depositing evaporitic sediments like halite that were covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin. (Comparable evaporite beds underlie the Mediterranean.) Due to the current inflow of fresh water, the Caspian Sea is a freshwater lake in its northern portions, and is most saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is one third that of Earth's oceans. The Garabogazköl embayment, which dried up when water flow from the main body of the Caspian was blocked in the 1980s but has since been restored, routinely exceeds oceanic salinity by a factor of 10.
Fauna of Azerbaijan
The country's fresh water basins and the Caspian Sea account for 97 species of fish of which eight introduced and seven of these have become widespread and over 15 thousand species of invertebrates in Azerbaijan. Most can be found in the Kura River, surrounding lakes, as well as in the Mingechevir reservoir. Most of fish are anadromous or semi-anadromous (the young grow up in salt water and migrate to fresh water to breed after they reach maturity). The most valuable of anadromous fish are salmon, sturgeon, stellate sturgeon and beluga. Aspius, Chalcalburnus and eel are also anadromous fish. Sturgeon meat and caviar are highly valuable. Beside, the water basins of Azerbaijan contain such valuable fish species as bream, sazan, rutilus kutum and others. Such fish species as herring are fished in the Caspian Sea. Due to the construction of a number of hydrotechnical plants on the Kura river after 1959, the regulation of the river water flow, as well as the Caspian water pollution led to the significant reduction in the number of valuable fish species. Three hatcheries (Kuragzi, Alibayramli and Kur experimental sturgeon hatchery) for melioration and fish-farming purposes were launched to restore the fish reserves and to increase the number of fish in species. Azerbaijan's fish-farming establishments and hatcheries account for breeding of 20 million sturgeons, 600 thousand salmons, over 800 thousand. A new hatchery with the capacity of 20 million sturgeons was put in commission in Khyly in 2000.