Formerly three types of dolphins, short-beaked common dolphin, common bottlenose dolphin and harbour porpoise, regularly visited the Sea of Azov from the Black Sea although the common dolphin usually avoided the basin and Kerch Strait due to low salinity. One type of harbour porpoise, "Phocoena phocoena relicta", used to live in the Sea of Azov and was therefore called "Azov dolphin" () in the Soviet Union. Nowadays, dolphins are rarely observed in the Sea of Azov. This is attributed to shallowing of the sea, increasing navigation activities, pollution, and reduction in the fish population.