Discovery of Iron Grapnel Anchors in Early Modern Ryukyu and Management of Underwater Cultural Heritage in Okinawa, Japan

摘要

The Yarabuoki underwater site contains seven iron grapnel anchors and Early Modern Okinawan ceramic jars and is dated to the 16th–19th centuries. The site lies at a depth of 12–32 m off the western coast of Ishigaki Island in Okinawa, Japan. Based on underwater archaeological and broadband multibeam surveys, as well as historical research of the artefacts and Early Modern Ryukyuan shipping, we discuss the possible anchor and vessel types in Ryukyu and Eastern Asia in Early Modern times. We also discuss the efficacy of low-cost ROV for assisting surveys in shallow-water environments and the value of educational programmes for promoting the management and conservation of underwater cultural heritage. 要約 屋良部沖海底遺跡は、16ཞ19世紀頃と推測される沖縄近世陶器群と7点の四爪鉄錨からなる。遺跡は沖縄県の石垣島西岸の水深12ཞ32mの海底に位置している。本論文では、この遺跡で発見された遺物群を対象としたこれまでの水中考古学的調査とマルチビーム探査の成果から、近世琉球王国における海運で利用されていた船や、それらの船が搭載していた錨のタイプについて論じる。このほかに本論文では、この遺跡調査で新たに開発した低コスト型のROVによる沿岸海域での効用、水中文化遺産の保全と活用を目的とした教育プログラム開発における新たな可能性についても論じる。 Academic and public interest in underwater cultural heritage (UCH) is increasing in Japan, partly because of the first designation of a permanently submerged site by the state government in 2011 at Takashima-Kōzaki. This site, in Nagasaki Prefecture in Kyushu, where 13th-century ships of the Yuan Dynasty China were discovered, was designated a National Historic Site after an extensive underwater investigation. Over the past two decades, the number of registered underwater archaeological sites subject to the Japanese Law for the Protection of Cultural Properties increased from only about 300 in 1998 to 512 sites in 2012 (Japanese Agency for Cultural Affairs, 2012: 32). Of these 512 listed sites, 34 are located in Okinawa Prefecture, one of the leading areas for underwater archaeological investigations. Okinawa Prefecture, or the Ryukyu Islands, consists of 199 islands in a chain that stretches some 1200 km between Kyushu Island and Taiwan (Fig. 1). Underwater archaeological surveys and research projects have been conducted in Okinawa since 1998. A total of 211 sites had been recognized by the Okinawa Prefectural Archaeological Center (the Center, hereafter) by 2014, many in a relatively good state of preservation (Katagiri, 2010; Okinawa Prefectural Museum, 2014). Research has been conducted by Kagoshima University and Nansei Islands Underwater Cultural Heritage Study Group (2010; 2011), the Center, Okinawa Prefectural Museum and Art Museum (for example Katagiri, 2007; 2009; 2010; Miyagi et al., 2005), and the Asian Research Institute of Underwater Archaeology (2012). The Yarabuoki underwater site near Ishigaki Island is one of those discovered by these recent surveys. Ishigaki is the most populated of the Yaeyama Islands, a subgroup of the Ryukyu Islands. The other major islands in the Yaeyama group are Iriomote, Taketomi, Kuroshima, Hateruma and Yonaguni. A total of 69 underwater archaeological sites are currently known off the coasts of these islands (Fig. 2). Our team is currently undertaking an interdisciplinary research project to evaluate the historical and archaeological significance and potential of the site as a cultural resource. This article presents up-to-date results of our current research and discusses the significance of the site in the context of reconstructing overseas trade routes in pre-Modern East Asia. We also report on cultural resource management practices for UCH in the Yaeyama Islands. The site was discovered in 2009 by a local professional diver, Mr Seiji Fujii, who has been running a diving service for more than 30 years from Ishigaki Island. He reported the approximate location of the site to the Center. In 2010, Katagiri (2010) conducted a site inspection survey as the chief investigator at the Center with the assistance of the Nansei Islands Underwater Cultural Heritage Study Group (2011). The survey confirmed the location of seven iron grapnel anchors of various sizes and a cluster of Early Modern Okinawan ceramic jars (tsuboya-yaki)