Successful spontaneous nesting of the hawksbill turtle (Eretmochelys imbricate) at Yaeyama Station, National Center for Stock Enhancement, Japan

Abstract

With a view to the conservation of the natural stock of the hawksbill turtle (Eretmochelys imbricata), we carried out studies on the propagation techniques of this species. This paper deals with the spontaneous nesting of this species under rearing conditions. Adult turtles that were captured off Ishigaki Island between 1999 and 2002 were brought to the center by licensed fishermen. One adult male and three mature females were selected from 29 turtles and they were stocked in a 250kL tank that was connected to a sandy beach for nesting. The females were examined by ultrasonography throughout experimental period. The mean diameter of the follicles ranged from 1.4 - 1.7 cm from January to April; and gradually increased to 3.0 cm from which shelled eggs were laid. The shelled eggs were first observed on 2nd June 2004, but were not observed after September. In contrast, non nesting individuals had not possessed shelled eggs during the experimental period. These results indicate that the formation of shelled eggs is an indicator of nesting. The first nesting was observed on 7th June, with a total of 7 nestlings observed until September. A total of 894 eggs were obtained from two females.