Hock-Chark Liew, Juanita Joseph, Eng-Heng Chan1,

Siti Norazliyana Ali, Lionel Harith Sebastian Sea Turtle Research Unit (SEATRU),

Institute of Oceanography, Universiti Malaysia Terengganu,

21030 Kuala Terengganu, Terengganu, Malaysia

How do captive-raised hawksbill turtles perform when released back into the wild?

IntroductionIntroductionIt is often said that only one in a thousand sea turtle hatchlings will ever survive to become adults largely due to high mortality rates in the early life stages. To increase the chances of survival for these threatened species, rearing them in captivity to a larger size before release has often been suggested and practiced. Counter arguments by conservationists to this practice is that little is known about whether these captive-reared turtles would be able to survive when released back into the wild. Moreover, sea turtle hatchlings, when first released into the sea, would undergo a pelagic phase during their early "lost years" before settling as juveniles in foraging habitats. We have often wondered if they were captive-raised for a few years until they attain juvenile size, would they circumvent this pelagic phase when released into the wild?

Percent time spent at given depth(m)

MethodologyMethodologyTo give insight to these questions, two juvenile hawksbill turtles, named Duke-Aziz and Myrtle-Adi, were raised in captivity for four years in the Aquaria KLCC public aquarium facility before release into the wild at the beach where they were born at Redang Island, Malaysia. Satellite transmitters (Telonics TGM4325) fitted with GPS and pressure sensors were mounted on them to relay information about their location and diving activity.

1 Presently with www.turtleconservationcentre.org

Juvenile hawksbill fitted with a satellite tag

ResultsResultsBoth of the head-started juvenile hawksbills remained within the vicinity of Redang Island during the first three days. Subsequently, Myrtle-Adi headed northeast towards the waters off Vietnam while Duke-Aziz remained at Redang Island. During the journey towards Vietnam, Myrtle-Adi did not just stayed close to the surface but made occasional dives beyond 30m. Duke-Aziz however, appeared to have circumvented the pelagic phase and decided to remain within the vicinity of Redang Island. Myrtle-Adi and Duke-Aziz were tracked over a duration of 13 days and 49 days respectively before no further transmissions were received.

DiscussionDiscussionControversy still exist as to whether head-starting sea turtles should be practised (Allen, 1992; Fontaine & Shaver, 2005; Woody, 1991). Head-starting would significantly reduce mortality in the early stages but put doubts on whether they could survive and adapt on release into the wild. Head-started hawksbills were seen to wander aimlessly as observed by Okuyama et al. (2005) though head-started loggerheads showed directed swimming offshore as in wild hatchlings (Nagelkerken et al., 2003). In this study, one head-started hawksbill headed offshore but the other did not. Perhaps individual preferences to stay or go do exist.

  Depth 0 - 10m 11 - 20m 21 - 30m 31m - 100mDuke- mean 92.99% 5.59% 0.05% 0.05% Aziz stdev 8.55% 8.31% 0.00% 0.00%Myrtle- mean 60.69% 23.60% 10.00% 1.44% Adi stdev 32.16% 29.53% 16.31% 2.75%

AcknowledgementsAcknowledgementsAquaria KLCC, The Body Shop, Berjaya Air, WWF Malaysia

ReferencesReferencesAllen, C. H. (1992). Itʼs time to give Kemp's ridley head-starting a fair and scientific evaluation. Marine Turtle Newsletter, 56, 21–24.Fontaine, C., & Shaver, D. (2005). Head-Starting the Kempʼs Ridley Sea Turtle, Lepidochelys kempii, at the NMFS Galveston Laboratory, 1978-1992: A Review. Chelonian Conservation and Biology, 4(4), 838-845.Nagelkerken, I., Pors, L., & Hoetjes, P. (2003). Swimming behaviour and dispersal patterns of headstarted loggerhead turtles Caretta caretta. Aquatic Ecology, 37(2), 183–190.Okuyama, J., Shimizu, T., Abe, O., Yoseda, K., & Arai, N. (2005). Dispersal processes of head-started hawksbill turtles ( Eretmochelys imbricata ) in the Yaeyama Islands waters , Okinawa , Japan. Proceedings of the 2nd International symposium on SEASTAR2000 and Asian Bio-logging Science (The 6th SEASTAR2000 Workshop) (pp. 63-68).Woody, J.B. (1991). Its time to stop head-starting Kemps Ridley. Marine Turtle Newsletter 54:7-8.

Duke-Aziz’s locations

Myrtle-Adi’s locations

REDANG ISLAND

VIETNAM

Peninsular Malaysia