Serious Declines of Nesting Populations of the Hawksbill Turtle (Eretmochelys Imbricata) in the Java Sea, Indonesia.

Hiroyuki Suganuma, Akil Yusuf, Shinichi Tanaka, Naoki Kamezaki

Introduction

Six sea turtle species, the green (Chelonia mydas), loggerhead (Caretta caretta), hawksbill (Eretmochelys imbricata), olive ridley (Lepidochelysolivacea), flatback (Natator depressus), and leatherback (Dermochelys coriacea), inhabit Indonesian waters (Siswonartono 1997). All except the green turtle are protected under Indonesian law through presidential decrees (Siswomartono 1997). Indonesia is a member of CITES, and the international trade of all sea turtles which are all on Appendix I, is prohibited.

According to the information from WWF-Indonesia (pers. com.), some 30 hawksbill rookeries are known in the Java Sea (Fig. 1). However, information on the reproduction of this species is very rare. The population dynamics of hawksbills is also unknown in Indonesia. For these reasons we have studied the nesting tracks of this species on beaches at 17 rookeries since 1995 (Suganuma & Kamezaki 1996, Suganuma 1997, Suganuma 1998).

Methods and Materials

From 1995 to 1998 we conducted nesting beach surveys at these 17 rookeries, and counted body pits and clutches of hawksbill turtle eggs (Table I).

Results and Discussion

We have noted significant declines in nesting activity over last 10-15 years. The overall regional decline was estimated to be about 70 %, and the maximum decline rate at a single rookery was 91 %.

These declines have been driven by the following factors: (1) export of numerous raw shells (bekko) and stuffed turtles to Japan until 1991; (2) increase in human population and coastal development of the islands, and; (3) increase in the numbers of eggs collected by local people with a rise in economic value.

Fig 1: Map showing the location of 30 hawksbill rookeries in the Java Sea. Seventeen rookeries which (indicated by closed circles) were surveyed during 1995 and 1996.

 Table I: Estimated annual clutch production by hawksbill turtles at various rookeries in the Java Sea.

Most of these rookeries are already on verge of extinction. If the egg collections are allowed to continue at the present level, the hawksbill turtles in this region will disappear in the near future. A conservation strategy for hawksbill turtles in the Java Sea id urgently needed, and it should be immediately implemented to take specific action for conserving turtle populations.