THESSALONIKI – The monk seal (Monachus monachus) might be considered the most endangered species in the Mediterranean, but the harbor porpoise (Phocaena phocaena) is perhaps the rarest. A small cetacean, for scientists it poses one of the mysteries of the Greek seas. Until 1999-2000, there was no evidence it existed in the Mediterranean. Since then, however, four dead harbor porpoises have washed up on the shores of the Thracian Sea. At the end of last month, another was found half-dead on the shore at Nea Heraklitsa, in the prefecture of Kavala, although until then it was believed that the species preferred deeper, colder waters. The appearance of a harbor porpoise so close to its headquarters at Nea Peramo, Kavala, astounded the staff of the Fishing Research Institute (which belongs to the National Institute for Agricultural Research, ETHIAGE). Staff members and researchers made every effort to save the porpoise, which was unable to stay afloat. It was impossible to move it elsewhere, so staff struggled on the beach for several hours to try and keep the animal alive, unfortunately to no avail. The carcass was taken to the institute’s headquarters to try and determine the cause of death. Scientists at Nea Peramo believe the laboratory tests will provide a great deal of information about this rare cetacean, which lived in the Aegean in antiquity. In «On the History of Animals,» Aristotle describes the biology of this species in detail. It later disappeared mysteriously, and for many centuries there were no reliable sightings in the Mediterranean until its recent reappearance in the 1990s. «The presence of this species in Greek waters, its behavior and the dangers it is subjected to are all an enigma,» said Manos Koutrakis, a researcher at the Institute. «The individuals found so far indicate the possible existence of a population in the Thracian Sea, but we are not sure.» According to staff member Aris Christidis, small populations have been found in the Black Sea and there are larger numbers in the Atlantic, although these are of a different length and weight. «Those found in the Thracian Sea are no more than 1.4 meters long, whereas in the Atlantic they range from 1.4 to 1.7 meters,» he said, adding that this could indicate the existence of a subspecies in the Mediterranean. Researchers do not yet know whether these individuals in the northern Aegean have arrived from the Black Sea or even from the Atlantic Ocean. Meanwhile, a group of biologists from Thessaloniki recently managed to rescue a harbor porpoise from a beach in Halkidiki and help it return to deeper waters.