Discovery of Iron Grapnel Anchors in Early Modern Ryukyu and Management of Underwater Cultural Heritage in Okinawa, Japan
Early Modern Maritime Archaeology in the Ryukyuan Islands
Bibliographic Data
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), which were originally produced in Okinawa Island from the 16th to the 19th centuries, during the Edo Period in Japan and the Early Modern Ryukyu Kingdom Period in Okinawa. They are the first grapnel anchors found in Okinawa and grapnel anchors have not previously been found in the region. Thus, these remains provide the opportunity to investigate both the past anchor types that equipped Ryukyuan and other vessels that navigated around the Ryukyu Islands and maritime trade during the Early Modern Ryukyu Kingdom Period. Based on this preliminary survey, our aim was to locate the site with more accuracy, to find evidence for a precise date, and to attempt to characterize the site to determine, for example, if it was a harbour, anchorage, or shipwreck site. Accurate and detailed recording is the essential first step to understand a site. Moreover, geographical and topographical data can greatly contribute to reconstructing site formation. Therefore, multiple methodologies were employed including GPS positioning (Table 1), a broadband multibeam sonar survey, the creation of a high-definition video record using a small-sized, lightweight underwater robot, and a record and analysis of each artefact. A bathymetric map was provided by the Geospatial Information Authority of Japan (GIS) and is shown here with the location of artefacts plotted (Fig. 3). However, this map proved to be insufficiently detailed and did not accurately represent seafloor topography. To solve this problem, we conducted a multibeam echo sounding (MBES) survey around the site to visualize the bathymetric results at a lateral grid resolution of one metre. The MBES survey was conducted in August 2011, using Sonic 2022 (R2 Sonic, LLC) and its accessory system which had been introduced to the laboratory at Okayama University in 2011, where H. Kan was affiliated. The Sonic 2022 has a variable ultrasonic frequency of 200–400 kHz with 256 ultrasonic beams and provides selectable swath coverage of 10–160°. The typical ultrasonic beam width, parallel and orthogonal to the direction of travel, is within one degree of each other when an ultrasonic frequency of 400 kHz is selected. We used a VS111 GPS compass system with A20 and A30 antennas (Hemisphere Inc.) combined with a dynamic motion sensor (DMS-10, Teledyne TSS Ltd), a sea surface sound velocity sensor (miniSVS, Valeport Ltd), and a sound velocity profiler (MicroSVP, AML Oceanographic Ltd). The sounding method is similar to that used in the Nagura Bay survey (Kan et al., 2015) but the ultrasonic frequency of 400 kHz was selected for the entire area of the Yarabuoki underwater site. The depth of the surveyed area (Fig. 3B) ranges from 0.5 to 51.0 m. The HYPACK2010 software was used for both hydrographic survey and data processing. IVS3D Fledermaus was used for three-dimensional visualization with a grid size of one metre for the entire area. The MBES bathymetric map enabled us to create a high-resolution site map on which to plot the artefacts (Fig. 3C). An experimental part of the underwater survey at Yarabuoki, conducted by N. Sakagami and F. Takemura, used a purpose-built low-cost, portable remote operating vehicle ROV (Fig. 4) with a high-resolution digital video camera. Its use had the great advantage of saving time; as the survey area ranges in depth from 15 to 30 m, SCUBA divers could work for only limited periods. Anomalies could thus be captured and viewed on board via the video screen without entering the water. The ROV is 0.7 m long, 0.55 m wide and 0.3 m high, and weighs about 15 kg. It can reach a maximum depth of approximately 30 m. The robot is equipped with four thrusters to achieve surge, heave, and yaw motion: each generates a force of 2.2 kgf under water. The cylindrical waterproof housing contains equipment including a high-resolution camera, a small computer, depth sensor, magnetic compass, LED lights and batteries. We have also developed software so that an untrained user can manoeuvre the ROV easily using a video-game controller. The aim of this system was to invite public involvement and the promotion of the site to non-divers through the experience of operating the ROV and viewing the site. Two separate areas of artefact concentrations have been recorded at Yarabuoki (Fig. 3). The grapnel anchors can be divided into an eastern and a western zone, some 400 m distant from each other. anchors are located in the eastern at a depth of m, with the ceramic in the western at a depth of m and The of anchor m. The maximum of the is m and m. four in good with two of in the (Table is in with a of about m. The are and in A at the of the is m in is is than its m in with a maximum of m and of m. Of the four two in good two of are in the (Fig. The the and is in The are to be in with a possible of m. The is and m by m. An m in is to the is than and with a of only m. Of the four two of are in the only the of the other two are of the have been and are (Fig. The of anchor is one of the m in Of the four two are in the only the of the other two are and these are and (Fig. The is in but the can be to be in The is m by m. An of m is to the The has a The of anchor is m in four in good one of is in the (Fig. The m. An with a of m is to the The has a The of anchor is m in Its maximum is about m. the four in good of is in the (Fig. of the are The anchor is in but the of the is confirmed as An is to the of m The has a The of anchor is m in with a maximum near the of m and m Of the four are in good and are (Fig. one is in the The anchor is in but the of the can be confirmed as The are and in The is m. An is to the of m The of the anchors that at two or ships anchors at the site, as it is that of these anchors to a 3C). be a between the anchor sizes and The two anchors and are located as are the two anchors and 2). the in was located at some The ceramic cluster is to anchors and and thus these to a The ceramic jars are located to grapnel anchors and on the at the depth of about m. In jars have been recognized in size from about m to m in the jars are similar in and which can be as the Early Modern Okinawan known as originally produced on Okinawa Island (Fig. The jars were recorded and in for a small that was in the and easily The is in the Okinawa Prefectural Museum to the site and precise are the first iron grapnel anchors discovered in Okinawa and the Ryukyu Islands. The discuss the of and of the and possible of these In of we that these artefacts to the Early Modern between the and the 19th the Edo Period in Japan and the Early Modern Ryukyu Kingdom Period in on our historical and archaeological of Okinawan and it is to a more precise at this The Ryukyu Kingdom was an most of the Ryukyu Islands from to The Kingdom was by who was the of Kingdom from Ryukyuan for including and in In the Period from the to each of these into maritime and the Kingdom a with the Dynasty of China in the and 16th centuries, the Ryukyu Kingdom and was in maritime trade with and East Asia for years The Ryukyu Kingdom the Yaeyama Islands at the of the chain its maritime In the 16th the into with the increased of or Japanese other The and interest in the region. The that had Japan since the the of to an force to the Ryukyu Kingdom in The in the Ryukyu Kingdom in the In when the Dynasty the Dynasty in the Ryukyu Kingdom a The this in we the Early Modern Ryukyu Kingdom as with the of the of in and with the by the Japanese in were major types of during the Early Modern Ryukyu The ships were and Ryukyuan and were a of were used for with China and the Ryukyuan (Fig. were for local trade between and Ryukyu the had been were to (Fig. by Ryukyuan for within the Ryukyu Kingdom (for example A could also be or as were used for maritime trade between the of the Ryukyu and in and around vessels were to the Kingdom by the when Ryukyu a more than 30 vessels were to the Ryukyu Kingdom a of years ships to be in two types by vessels with a about or a of and vessels with a about 300 or a of about on Ryukyuan historical (for example However, when from China in the the Ryukyu Kingdom to have vessels at around the 16th the are some (for example or which recorded the of the Ryukyu Kingdom from to in a total of that the Kingdom and for from the Ryukyu Islands to and the to ships the Ryukyu Kingdom had to within the Ryukyu Islands, on Okinawa and when the Ryukyu Kingdom was by the (for example 2007; the historical these vessels in and in the Ryukyu Islands were than the previously vessels and can be at with maximum of or of The use of ships by the Ryukyu Kingdom during this also the of maritime trade with the the size of vessels and 300 or a of about and vessels to have to be or used after the Early Modern Ryukyu Kingdom Period. the Early Modern Ryukyu Kingdom the Kingdom also had to as well as similar ships 2012: The Ryukyuan and the as the and were used to the for local trade by between and the of in the part of Island. The of in the The sizes of these Early Modern Ryukyuan ships are by from the by National Museum shown in and are the with as as m, and m in the vessels are with a maximum of only m and beam of m. historical record Ryukyu dated to of Ryukyu originally by of Japan in and by the Ryukyu in the of and as or The also were vessels as the of more than about 300 a of about or with 15 those in the vessels are as and Two are as The are more in The for the is about the is about in the also that was a total of of these with in with not also at this with with and with 2012: that the anchor types that equipped a have been discovered as but are some the screen the during by the Okinawa Prefectural Museum and Art Museum, seven are with anchors and anchors are than iron The use of anchors can be on other including screen dated to the 19th by Okinawa Prefectural and the record of the under the of which Ryukyu on in The size of anchors used with has been by Okinawa Prefectural Museum at m in and m in maximum between each (Fig. of the Ryukyuan also in the historical by which that a Ryukyuan but in its and to in Prefecture in in was equipped with both anchors and iron grapnel Ryukyuan were it is possible that were also equipped with both anchors and iron grapnel by who was the of a for the of and in Ryukyu in also vessels that Ryukyu were equipped with both and iron grapnel and a detailed (Fig. the Early Modern Ryukyuan ships were the it is that the Ryukyuan anchors were to the Early Modern the historical and and anchors are limited in the screen Ryukyu a vessel with iron grapnel anchors Therefore, it is that types of Early Modern Ryukyuan ships were equipped with both and iron grapnel ships from both China and that the Ryukyu Island were equipped with iron grapnel to of the on a screen (Fig. by Okinawa some ships were also equipped with iron grapnel anchors (Katagiri, the Ryukyu Kingdom was by after are some that the Ryukyuan ships to between and or and the Yaeyama Islands shown in the ships were as Early Modern vessels in also which is from the Ryukyuan The of used in and many other in Japan were originally as ships during the Early Modern times. the vessels from both and China were equipped with iron grapnel the anchors found at Yarabuoki could be from Japan or grapnel anchors were originally in China during the Dynasty have been in the has a total of m and was found in in The anchor has an on the that that it was in Two other grapnel anchors in China are also as one from in m in and weighs (Fig. one from in is m in and weighs (Fig. In Japan, the historical iron grapnel anchors are the or of and the of by these iron anchors were used in with anchors and anchor the by the iron grapnel anchors had the anchors used for Japanese ships as or during the Edo Period of the vessels that in the in western Japan, had the major in Early Modern Japan by (Fig. one of the ships of Japan, in on the to the in Prefecture, Japan, was equipped with iron grapnel anchors (Fig. the which in the to be used from for the of various from western Japan to Edo or other eastern of Japan In the were approximately 1200 to vessels of this in Japan 2012: The is or a of used during the Edo or with a The for a is around 1200 which is the size as a Ryukyuan were equipped with seven iron grapnel anchors as the first anchor to the The was m in and 300 with each of the the anchor about 2012: (Table This that 1200 vessels were equipped with anchors from to 300 kg. vessels (for example the have been equipped with and example, an iron grapnel anchor about with a total of m was from Island underwater site, with a number of Early Modern and dated to the Island anchor weighs more than 300 it is to be the first known anchor for a Based on this the grapnel anchors at Yarabuoki, which about m in were those of one or more that the jars found at the site are Early Modern Okinawan originally produced in on Okinawa the Yarabuoki grapnel anchors and could have equipped a or from or However, could have also to vessels to Ishigaki Island when between and and the other islands in the Yaeyama It is also known that some of the Early Modern vessels ships from to were equipped with iron grapnel In are two local dated to that record the of possible vessels in the sea off the to Yarabuoki underwater site. The of the the that a small to China on with the of to the but was and off the coast of with the of many of the of the the or that a small on the and in China on the in It on the to to but was around on the The that the was between and the that the did not ships off in during the in historical that ships to the Yarabuoki underwater site, thus the anchors could to Ryukyuan or or detailed including precise of each anchor for and with other Early Modern iron anchors in China and Kyushu, in to be In to the of Yarabuoki underwater site and its this the results of our survey with the local and the of maritime in the Ryukyu In the Yaeyama Islands including Ishigaki was recorded under the of the Ryukyu Kingdom and and was off the by ships in the and between the and the Nagura Bay and Bay on the coast of Ishigaki as well as other were recorded as in the and known as that were the first major of the Early Modern times. The at Japan to these in the the the produced detailed in an area from the coasts and the Ryukyu Islands including the Yaeyama Islands. of the between Ishigaki and Islands (Fig. It can be shown that most of the UCH sites around these islands are located the past (Fig. in the area of the This is not a but that these underwater sites are with maritime to these trade routes in the The Yarabuoki underwater site is located one of the major routes from the coast of that the Nagura Bay (Fig. The has been known to one of the used during the Early Modern times. In local historical that the was used as an in and from the by the or of the from the of or The also the of on submerged in Based on these the grapnel anchors from Yarabuoki could be from ships that on Okinawa the of Ryukyu or in ships to between and some and on to Ishigaki Island as after the ships as Japanese and Ryukyuan by or Ryukyuan between and Ishigaki via these types could have at or to the site is located in the coast of Ishigaki where a is at of the Kan et al., 2015) (Fig. 2). In the coast of Ishigaki Island is by from to one It located to the because the is not so developed in the area around the site as in the other areas around the (Fig. anchor is about m from a of only m and the to the is about m. the from and anchors to the is m, and m to the The MBES bathymetric map (Fig. the seafloor of this coast is by a a of m from the to the area. It that the around Yarabuoki underwater site provides for an and a for the seafloor the the lies of the and a to the Moreover, a depth of m, maximum m and m can be on the MBES bathymetric map (Fig. where two anchors and are located on its This was by some historical as The of the anchors in Yarabuoki that these anchors could to two or but not to a The of the site the remains of a Japanese equipped with seven anchors is not only because of the but also because of size between the anchors and This be if the of the Yarabuoki anchors can be in the Moreover, the historical report that ships are known to have around Yarabuoki in the we have not found and including in around the area with ceramic jars is the of the iron grapnel to the analysis of the and of the have a site of great The anchors could have when vessels the between and or and the or as a of in a recorded used for trade within the Ryukyuan It be if the site or artefacts including iron grapnel anchors and ceramic jars et al., a was found the ceramic jars (Fig. during our survey in This with the of anchors to around the ceramic jars in area of about m the potential for remains in the including In to this public and involvement are and a be to local who have to the site. part of our interdisciplinary we have public the Ryukyu Islands, including the Yaeyama Islands, are located in a with are the most diving area in Japan. is great potential for using including the Yarabuoki underwater site, as educational and if the local is to and the sites et al., The research in this article is the essential first step in the significance and potential of UCH The is the of research to the the local the we to the of educational and cultural programmes to historical significance and potential of this UCH to the local of Therefore, we by using low-cost underwater to investigate near the of Ishigaki Island. In these we provided local and with robot and in August and the had the to the to using video-game or to the underwater Moreover, we were to a survey using both diving and underwater on the Yarabuoki underwater site with the of some local who were part of the et al., Sakagami et al., 2014). We have also two public in Ishigaki in and and and of the local board of to discuss the potential of the UCH around Ishigaki including its use for educational and cultural Our step is to create a local group with who can work to UCH and the resource. by some Japanese (for example Katagiri, 2010, Katagiri et al., et al., the of underwater site that and UCH in be an to use and sites in the Yaeyama and Ryukyu Islands in the near This interdisciplinary research is part of the project in by by Research Institute for and Japan, and Japan for the of for Research of seafloor using and to and H. The educational programmes and of the are also partly by Research and Study of University Research We also to Mr Seiji Fujii, Mr Mr and Mr for the of our research and in the Yaeyama Islands
Ancient history · Archaeology · China · Cultural heritage · Geography · Underwater · Underwater archaeology · History · Maritime and Coastal Archaeology · Geology · Oceanography
| Citations per year | 0.13 |
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| Citation span | 2018 - 2018 (1) |
| Highly cited | No |