An oil source packed with endemisms
As a Portuguese, I never had much interest on inland seas, such as the Black Sea, the Aral Sea, or Caspian Sea. But now, visiting Azerbaijan, a republic of the Caucasus region and having walked by the maritime water front at Baku, the capital city of the country, I wanted to know more. I only have heard about the existence of the Sturgeon, that fantastic mega-fish which has vanished along time ago from many EU rivers.
During my stay at the country I saw an article on the Caspian in a magazine I came across on business and development. It mentioned a rather low number of species, but also that it got closed around 5 million years ago, a unique salty lake, with a shallow morphology in the north and much deeper in the south. It is fed by several rivers, but there is no outflow to other oceans; it is isolated and the balance is kept by evaporation.
That made me think that even the Caspian might be quite polluted, there must be or at least have been a lot of endemic species. 5 million years is enough time for species to evolute into new ones.
I found the following data in World Lakes:
The Caspian Sea may be home to as many as 54 endemic fish species (out of 133 total), 190 endemic zoobenthos species (out of 380) and 64 endemic zooplankton species (out of 315 species).
Species in the Caspian listed in the Red Book as endangered include 63 birds, 41 mammals, and 27 fish.
125 thousand square km of the coast around the Caspian Sea is severely degraded. Parts of the Caspian coast are experiencing desertification due to overexploitation and poor management. Overgrazing and deforestation in the watershed have led to increased erosion.
Severe overfishing has decimated fish species and caused sharp declines in catches. Between 1920 and 1940, the most common commercial species were the Caspian lamprey, Volga shad, Caspian trout, and Caspian inconnu. The total catch of these species was about 80 thousand tons. All these species are now included in the Red Books of the Republic of Kazakhstan, Russian Federation, and other Caspian states.
In the Islamic Republic of Iran over-fishing of Caspian trout, bream, and zander, along with the damage of their habitats and spawning grounds, has resulted in an almost complete loss of these species. The Caspian zander disappeared due to massive catches in Azerbaijan and Turkmenistan.
During the last twenty years, the sturgeon catch has declined by 88 percent.
90% of the Beluga spawning grounds are gone due to dams. Poaching may take up about 12 times the volume of the official catch.
More research is needed on the impact of invasive species on the Caspian. The comb jelly Mnemiopsis leidyi has recently been discovered.