Transcript Duke-Myrtle-poster - SEATRU UMT | Sea Turtle Research Unit

How do captive-raised hawksbill turtles perform
when released back into the wild?
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
Introduction
It 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?
REDANG ISLAND
Duke-Aziz’s locations
VIETNAM
Peninsular Malaysia
Myrtle-Adi’s locations
Percent time spent at given depth(m)
Juvenile hawksbill fitted with a satellite tag
Depth
Duke- mean
Aziz
stdev
Myrtle- mean
Adi
stdev
0 - 10m
92.99%
8.55%
60.69%
32.16%
11 - 20m
5.59%
8.31%
23.60%
29.53%
21 - 30m 31m - 100m
0.05%
0.05%
0.00%
0.00%
10.00%
1.44%
16.31%
2.75%
Methodology
Discussion
To 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.
Controversy 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. Headstarted 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.
Results
Both 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.
1 Presently with www.turtleconservationcentre.org
References
Allen, 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.
Acknowledgements
Aquaria KLCC, The Body Shop, Berjaya Air, WWF Malaysia