Challenges of fish diversity in the Caspian Sea

Biodiversity includes the composition, abundance and richness of species and is studied at genetic diversity within species, between species and ecosystem level. Species diversity is vital for maintaining the flexibility of an ecosystems results in greater stability. The presence of more species in an ecosystem makes natural ecosystems more complex and therefore ecosystems are more resistant to unfavorable environmental changes with their stable communities. The Caspian Sea is poorer in biodiversity than other seas such as the Baltic and Black Seas, and due to growing pressure of environmental challenges, the population of valuable aquatic species has declined radically including all sturgeon representing the Caspian Sea and are in danger of extinction. On the other hand, rivers and lagoons leading to the Caspian Sea, which are suitable spawning grounds for spawners and safe nursery grounds for offsprings of several bony fishes often do not have appropriate conditions due to irresponsible fishing and heavy loads of various pollutants. Therefore, practically there is no sound spawning migration into these water bodies by bony fishes which means the stocks of anadromous species are severely threatened. Restoration of stocks of these bony fish species should be practiced in large scale similar to that of Kutum (Rutilus kutum). Appropriate river management and restoration and providing conditions for migration to at least some of these rivers and providing conditions for natural reproduction will play a key role in rehabilitation of stocks of these fish and preserving the biodiversity of the Caspian Sea.