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2nd ASEAN Symposium
and Workshop on
Sea Turtle Biology and Conservation
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SESSION
3: Beyond the Beach....
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ABSTRACTS
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Swimming
Behaviour of Green Turtle Hatchlings in a Lagoon of Ishigaki Island,
Southwestern Japan.
Osamu Abe, Yoshitake Takada, Takuro Shibuno, Kazumasa Hashimoto, Hisakazu Ishii,
Yuji Funakura
Sea turtle
hatchlings use wave action as a cue to orient toward open waters after entering
the ocean. At tropical beaches that have fringing lagoon, offshore waves break
at the reef crest, while the surface of waters within the lagoon remain calm.
Green turtle Chelonia mydas hatchlings were followed during their frenzy
swimming period by snorkelling behind them to investigate how hatchlings in
lagoon conditions find the open sea. Swimming distance and body axis alignment
were noted, while a flowmeter and dive compass ivere used to predict the
positions the hatchlings would have reached if they were unaffected by water
movement. Water movement was calculated as the displacement between the
predicted position and the actual position, as determined by GPS records. Most
hatchlings swam directly offshore in an almost straight line, at a mean velocity
of 1.62 ± 0.18 km/h. In calm conditions, hatchlings swam toward a small channel
opening in the reef crest, but in rough conditions, water movements around the
complex topography of the lagoon altered their actual swimming path, and
hatchlings reached the open sea by crossing from the lagoon over the reef crest. |
