A fisherman in Ginoza, Okinawa Prefecture, on Monday found a dead dugong trapped in a fishing net some 2 km to 3 km off the village coast.
People at the fishing port lamented when they saw the 2.2-meter female dugong, which weighed some 240 kg, according to Seishu Tanahara, head of Dugong Network Okinawa, a local citizens' group working to protect the endangered mammal.
The carcass was immediately taken to the Okinawa Expo Aquarium in the neighboring town of Motobu for examination, he said.
"It is extremely regrettable that a dugong died this way," Tanahara said. "Measures such as devices that use sound (to scare off the dugong) should be installed in fishing nets to prevent more deaths."
News of the dead dugong came about a week after the Defense Facilities Administration Agency spotted one of the mammals during a survey of the sea around Okinawa.
Agency officials said they spotted a 3-meter dugong about 1,500 meters off the east coast of Nago, about 10 km from where a planned civilian-military airport is to serve as the relocation site for the helicopter operations now handled by the U.S. Marine Corps Futenma Air Station.
The spot where the dugong was seen is about 10 km northeast of the airport site.
The agency has been conducting an aerial study since Oct. 30 to determine the number of dugongs ahead of the construction.
The survey began after the city of Nago made a request for the dugong to be protected. The Switzerland-based World Conservation Union also adopted a resolution to that end.