A long and deep step in range expansion of an alien marine mammal in the Mediterranean: First record of the Indian Ocean humpback dolphin Sousa plumbea (G. Cuvier, 1829) in the Greek Seas

On 7 November 2017 a solitary Indian Ocean humpback dolphin, Sousa plumbea (G. Cuvier, 1829), was sighted in Karavolas Bay, near the port of Heraklion, Crete, Greece. On 14, 16 and 17 November 2017 another humpback dolphin sighting, likely the same individual, was recorded 100 km further west in Souda Bay, Crete. North Crete is the third area where this Lessepsian species was sighted in the Mediterranean Sea after records in Israel in 2001 and in SE Turkey in 2016. To reach the north coast of Crete, the dolphin crossed deep offshore waters that are theoretically incompatible with its typical coastal and shallow habitat. The distance travelled by this dolphin (1000-2330 km depending on the path followed) is the largest movement recorded for this species. Our observations show the potential of humpback dolphins to reach the shallow and coastal waters of the Cyclades in the Aegean Sea, where native populations of the vulnerable common bottlenose dolphin (Tursiops truncatus) and the endangered short-beaked common dolphin (Delphinus delphis) occur.