Conservation experts yesterday highlighted a worrying increase in the number of marine mammals that have washed up dead on the country’s islands and coastlines over the past week or so. The most serious incident reported by the Institute of Marine and Environmental Research of the Aegean Sea, also known as Archipelagos, was the discovery of a young female sperm whale on the northern coast of Samos. The mammal’s body bore no sign of injury, according to experts, who noted that early fall usually brings an increase in the migration of sperm whales into the area between the islands of the eastern Aegean and Turkey. Archipelagos researchers also reported finding two dead dolphins, one in Alimos, southern Athens, and another on Samos. The cause of their deaths was also unclear. A dead loggerhead sea turtle (Caretta-caretta), found on the coast of Icaria, had been knifed, conservationists said.