Dugong

A dugong is a marine animal in Okinawa that suddenly attracted attention in 1998. Pictures of them swimming offshore of Camp Schwab (Henoko – Nago, Eastern coast in the northern part of the main island), one of the candidates for the relocation of Futenma Air Station, were widely reported by the media. Combined with the disputes regarding the construction of an offshore air base, the apparition of this nationally designated protected species (also listed in Article 1 of CITES which strictly restricts commercial trade) exposed the issue. Despite the attention it gathered, little is known about the dugong itself. 

Dugongs used to be called Zan or Zannuiyu in Okinawa. As old as the times of the Ryukyu, dugong fishery was a custom on Aragusuku Island in Yaeyama. They also appear in folk tales related to tsunamis and thus, are a familiar presence.

Dugongs are marine mammals belonging to the Dugongidae family of the order Sirenia, less than 3 meters long and weighing about 250-350kg. Their distribution range is fairly wide: from Mozambique on the western coast of Africa to the Red Sea in the West, the eastern coast of Australia, Indonesia, and the Philippines to the East, and as north as Southwest Islands. Dugongs only eat limited species of seaweed such as Ryukyu sugamo and beniamamo. The growth of these seaweeds in the Southwest Islands is apparently the factor accounting for their distribution. According to rearing precedents, dugongs eat seaweeds of about one-tenth of their body weight everyday. In 1998, the media reported the meandering feeding trail found in the shallow sandy seaweed bed. As they inhabit such shallow water, they have been affected by humans’ fishery, and are apparently shifting to nocturnal activity by staying outside of the reef during the day, and only coming to the seaweed bed at night. They were spotted near Amami Island in 1960, however, no reports were made ever since, and consequently, the present-day northeastern periphery is thought to be around Okinawa. In addition, 13 individuals were seen as part of its population research and most of them were sighted off the east coast of the main island. We also sometimes hear of some people who saw them. Although it is unknown how many dugongs were originally in the Okinawan waters, it is estimated that the number greatly decreased due to post-war dynamite fishing. We also hear of people eating dugongs at that time.

That dugongs’ field of living overlapping with that of humans is now their matter of life and death. Most of the sighted individuals mentioned earlier were caught in gill nets or fixed nets. In that sense, it seems necessary to take measures to set up conservation areas; however, no basic or organized research has been conducted so far to determine where and how many dugongs there are. Every time I see the reported photographs, I can’t help but feel that the dugongs are saying, “hurry up and do a thorough investigation,” whatever happens to the sea bases. If no actions are taken now, it is well possible that they become extinct in the Okinawan sea.