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Marine Turtle Newsletter 70:13-14, © 1995

Marine Turtle Newsletter-Online

SEA TURTLES AT DUNGSHA TAO, SOUTH CHINA SEA

Dungsha Tao, or Pratas Island (116°43.51' E, 20°42.5' N), is the northernmost coraline island in the South China Sea. Located on the western extreme of Dungsha Atoll, the island is 2500 m long and 865 m wide with an area of 1.74 km2, of which 0.64 km2 is a lagoon no deeper than 1.5 m. The entire island is sand, consisting mainly of moderately sorted coarse grains with an interstitial water content of 9.8% (by weight). The climate is subtropical marine, dominated by trade winds which blow from the southwest from May to August and from the northeast from November to March. Annual total precipitation is 1132.5 mm, with a maximum in June (226.0 mm) and minimum in December (3.3 mm). Sea surface water temperature averages 25°C, with a maximum in June (29-30°C) and a minimum in January (22°C). Tides are diurnal, with a maximum amplitude of 1.21 m (Central Climate Bureau, 1994). Dungsha Tao has been occupied by marines from the Republic of China since 1945. In general, 300-500 marines live in various buildings around the island.

Previous studies carried out at Dungsha Tao include substrate structure (Hwang et al. 1975), marine flora (Jung 1975), coral reef fishes and mollusks (Yang et al. 1975), deep sea fishes (Hwang and Yang 1983), and marine ecology (Council of Kaoshiung Government 1980). Two studies briefly mention sea turtles (Liang et al. 1990; Hwang et al. 1991); however, there are no previous records of nesting on the Island and very few details on the turtles. In April 1994, during the South China Sea Marine Biology Survey, photos were taken of a turtle (later identified as a hawksbill) swimming in the lagoon. In June 1994, the marines on the island reported rescuing a "big" sea turtle tangled in a long line. In July 1994, a 12-day expedition to the island was undertaken in collaboration with the Council of Agriculture and the Defense Department. During the expedition, three methods of investigation were employed. First, 100 marines were questioned about sea turtle nesting areas and the kinds of turtles that came ashore to nest. Second, all potential nesting beaches were inspected at least twice daily (1900-0500 hr) and some beaches were occasionally inspected earlier in the day as well (1600-1800 hr). Third, three patrol boat cruises of nearshore waters 2-3 km off the south shore were performed.

According to the marines, both "Daimo" (the common Chinese name for the hawksbill turtle, Eretmochelys imbricata) and "big" turtles nest on the northern and southern beaches. Further description of the "big" turtles indicated that these were green turtles (Chelonia mydas). The marines also reported that hatchlings emerged from nests on the northern beach and crawled toward street lamps in September and October. No nesting emergences were observed during the first five nights of the July expedition, but on July 20, two sets of fresh tracks were observed leading from the sea to bushes in the supralittoral zone on the inland side of a barbed wire barricade (the turtle crawled through the wire). The tracks measured 64 cm and 82 cm wide. On July 21, a hawksbill (90 cm curved carapace length, 84 cm straight carapace length) was encountered after it nested under a bush. Before returning to the sea, this turtle was tagged with two Inconel flipper tags (National Band and Tag Co., Style No. 681) on the right front flipper (numbers were TW218 and TW221; return address "P. O. Box 7-215, Keelung, Taiwan, 20224, R.O.C."). To reduce the chances of either marines or dogs digging into the nests, the nests were left in situ and undisturbed. No further nesting activity was observed, but two possible nests were found on the south shore.

In Chinese customs the sea turtle is a symbol of longevity and, for that reason, often revered. At times the Commander of the marine navy base on Dongsha Tao gives direct orders to the marines there to protect the turtles. Nonetheless, the sea turtle population in the region is reported to be declining. Senior officers recalled densely populated nesting beaches on the Island 10 to 20 years ago. Liang et al. (1990) reported that more than 2000 sea turtles have been slaughtered in the waters of Dungsha Tao since 1986. Today there are very few turtles nesting on the island. Because of political instability in the region of the island (various countries in the region claim Dungsha Tao), relatively few fishermen from Taiwan fish in this area. However, fishermen from numerous other countries (Hong Kong, Malaysia, People's Republic of China, Philippines, Vietnam) fish in the waters around Dungsha Tao. Fishing methods include the use of bottom trawls fitted with chain rollers, even though this has been outlawed. In addition, during a routine nearshore patrol last year, the Navy confiscated more than 200 kg of KCn solution which fishermen had been using for fish poisoning. These activities have had a devastating impact on local marine organisms and coral reefs.

Internal political instability further complicates conservation measures. Just before our expedition left the island, the base Commander ordered the enforcement of beach barricades for security reasons. Although he accepted our suggestion to use barricades which allow the turtles to crawl through them (enabling the turtles to reach the high beach for nesting purposes), access to these nesting areas by people became virtually impossible. Since 1995 is the "Year of Sea Turtle" in the Pacific [see Legal Briefs, this issue], we hope that SPREP (South Pacific Regional Environment Programme) will help those of us throughout the region who are seeking to protect and restore marine turtles in our part of the world.

Central Climate Bureau. 1994. 1994 Climate Data, Dungsha Station.

Council of Kaoshiung Government. 1980. The investigation of the marine ecology resources of the Dongsha waters. Kaoshiung, Taiwan, R.O.C. 61 pp.

Hwang, C-C., T. Y. Xiang and W. X. Yan. 1991. The status of research and conservation of marine turtles in China, p.101-102. In: Proc. Intl. Sea Turtle Conference, 30 July - 3 August 1988. Hiwasa-Cho, Toku Shima Prefecture, Japan. Himeji City Aquarium, Hiwasa Chelonian Museum.

Hwang, J-W. and J-J. Yang. 1983. The deep-sea fishes of the Dungsha Waters, p.234-255. In: . The Study of South China Sea Marine Biology. Guangdong, China, P.R.O.C.

Hwang, J-W., W-S. Jwang and Z-C. Chen. 1975. III. Substratum investigation, p.21-33. In:The Synoptic Investigation of Dungsha Tao. Institute of Oceanography, National Taiwan University, Taipei, R.O.C.

Jung, L-M. 1975. II. Marine flora, p.16-20. In: The Synoptic Investigation of Dungsha Tao. Institute of Oceanography, National Taiwan University, Taipei, R.O.C.

Liang, W-L., J-L. Dai, C-W. Liu, W-S. Liu, J-S. Wein, H-J. Sung, T-T. Chen, I-Z. Chen, Y-K. Shu, S-J. Lu, Z-S. Chang, C-Z. Chang and J-Z. Lin. 1990. The investigation of sea turtle resources in the South China Sea, and the development of the artificial hatching techniques of the sea turtles. Report of the Conservation Stations of Southsea Turtle Resources, Guangdong Province, China, P.R.O.C. 37 pp.

Yang, Z-J., S-J. Hwang, S-S. Li, J-H. Tsi and L-J. Shun. 1975. I. Coral reef fishes and molluscs, p.1-5. In: The Synoptic Investigation of Dungsha Tao. Institute of Oceanography, National Taiwan University, Taipei, R.O.C.

I-JIUNN CHENG, Institute of Marine Biology, National Taiwan Ocean University, Keelung, Taiwan, 20224, R.O.C.