Why are there no dolphins in the Caspian Sea

The absence of dolphins in the Caspian Sea causes surprise and raises many questions. Despite being the largest enclosed body of water on Earth, rich in various species of fish and other aquatic animals, there are no dolphins here. Why?

The main reason for the absence of dolphins in the Caspian Sea is its isolation. Historically, the Caspian Sea was part of the ancient Tethys ocean, but after tectonic changes, it became completely isolated from the world ocean approximately 5 million years ago. This factor played a key role in forming the unique ecosystem of the sea, which lacks many common marine mammals, including dolphins.

Additionally, the Caspian Sea is characterized by significant fluctuations in water salinity and sharp temperature changes. These conditions are unfavorable for most dolphin species accustomed to stable marine environments with moderate temperatures and ocean salinity. The salinity of the Caspian Sea is significantly lower than oceanic, which complicates the survival of animals adapted to seawater.

Another important factor is the absence of migration routes for dolphins. Unlike other enclosed seas, such as the Black or Mediterranean, the Caspian has no natural straits connecting it to the ocean, making it impossible for dolphins to naturally populate its waters.

Thus, the combination of geographical isolation, specific natural conditions, and lack of migration routes has resulted in the absence of dolphins in the Caspian Sea, although this sea is a rich ecosystem with unique fauna, including, for example, the famous Caspian seal.