Ecology and Conservation of Sea Turtles in the Nansei Islands
|
Date: 29th October 2016 13:00 – 17:00
Place: Room 203, The Interdivisional Education and Research Building, 2ed
Floor, Kagoshima University
Simultaneous reporting on the Internet: Amami Station, Research Center
for the Pacific Islands, Kagoshima University (Naze Yanagimachi 2-1, Amami
City) |
●Aim
Sea turtles are very familiar to people in Japan, which is surrounded
by the sea, from the ancient times, and they appear even in Japanese fairy
tales. Their meat and eggs are also very important as food especially on
small islands. Sea turtles have been endangered due to its overhunt and
decrease of their spawning grounds, i.e. pollution or removal of sandy
beaches as a result of human activities. For these reasons, there is an
increasing momentum among people in the world to conserve sea turtles in
many ways. The loggerhead turtle, green turtle, and hawksbill turtle are
often seen in the waters around Japan, and it is known that the sandy beaches
of the Nansei Islands are very important for spawning grounds. In this
symposium, we have invited three presenters who conduct research on sea
turtles in different disciplines in various regions, and we focus on global
and local activities of conservation and ecology to understand the present
situation of sea turtles.
●Program
13:00 Opening
13:05 「Overview of Sea Turtle Conservation and Biology」
● MATSUZAWA Yoshimasa
(Sea Turtle Association of Japan, Suma Aqualife Park KOBE)
- Sea turtles are marine reptiles and a part of the order Testudines. There are 8 species of living sea turtles, which consist of one species placed in the family Dermochelyidae and 7 species in the family Cheloniidae. Five of the 8 are widely distributed in tropical, subtropical and temperate waters through the world. Although they are well adopted to life in the ocean with their paddle-like flippers, flattened and streamlined shells, and salt glands, they are not ovoviviparous and females must return to land in order to lay their eggs. In Japan, nesting sites for loggerhead are distributed mainly along the Pacific coast in the south of Fukushima, those for green in the Ogasawara and Nansei islands, and those for hawksbill in the Ryukyu Islands. Irregular leatherback nesting has also been observed in Amami-Oshima Island. There had been variety of relationships between human sand sea turtles, which come ashore for nesting. Local people who observe turtles laying eggs would feel compassion for them whereas others especially in islands that traditionally utilize turtles and their eggs, see them more as a food resource. Due to overexploitation and other threats –including fishery bycatch, beach erosion, coastal development, and oil leakage– that rose in the late 20th century, many of the sea turtle species and populations have declined and become in danger of being extinct. With growing support for conservation since the 1970s, a variety of conservation actions have been taken and some of them have led to recovery of some populations. However, subsequent studies found that some did more harm than good. Some of the turtle’s inherent biological characteristics, such as long-distance migrations and generation time as long as 4 decades, make it difficult to conserve sea turtles comprehensively and effectively without long-lasting practical actions on regional scale, including sea turtle nest monitoring, and understanding and cooperation among communities and nations over migration routes for each population.
13:55 「Sea Turtles in the Nansei Islands」
●ISHIHARA Takashi (Suma Aqualife Park KOBE)
- Sea turtles are significant in the Nansei Islands in several ways. Firstly,
the area is one where three sea turtle species, namely loggerhead turtle,
green turtle, and hawksbill turtle, nest constitutively and sympatrically.
While the southern nesting limit of the loggerhead is the Yaeyama Islands
and the northern nesting limit of green and hawksbill is the Osumi and
Amami islands, respectively, nesting sites of these three sea turtle species
overlap only in the Nansei Islands. Secondly, it is has recently been revealed
that the loggerhead genetic population structure of the Nansei Islands
differ from that of mainland Japan. It is significant that about 20-40%
of the haplotype from the Nansei Islands have the same unique haplotype
of the South Pacific loggerhead population. In addition, the rate of the
haplotype tends to increase as towards the southern nesting sites. This
fact suggests that there is or was a genetic exchange between the North
and the South Pacific populations through the Nansei Islands. For green
and hawksbill turtles, juveniles with a carapace length of approximately
20cm are only rarely found in the Nansei Islands. This size is called a
‘lost year size’ because their habitats are still unknown. Clarification
of their ecology is awaited in near future. It also seems that the frequency
and number of sightings of green and hawksbill turtle by scuba divers is
increasing in recent years and it is said that greens and hawksbills are
increasing in numbers. In addition, it is also said that because it has
also been lost to be captured for food or stuffed, the number or individuals
of turtles who do not fear the people are increasing. It is now easy to
take underwater photos during scuba diving. The underwater sea turtle photographs
could reveal various ecology of sea turtles especially in the Nansei Islands,
the dominant sea turtle habitat.
14:45 Break
15:00 「Preservation Activity of Turtles in Amami-Oshima Island」
●OKI Katsuki (Amami Marine Life Research Group)
- There are over 130 nesting beaches of sea turtles at Amami-Oshima Island.
Only about 30 beaches have been researched by the by administration, and
we have shared in researching about 100 remaining beaches with a local
resident and related groups since 2012. The sea turtles nesting situation
of Amami-Oshima Island whole area became clear for the first time in 2012.
The results showed there to be 1081 nests of sea turtles (605 nests of
loggerhead, 327 nests of green turtle and 149 nests of unclear species).
- Research on Tokunoshima Island was undertaken in 2013, and the research
of sea turtles in the Amami Archipelago whole field was also performed,
identifying 1932 nests (1141 nests of loggerhead, 662 nests of green turtle
and 129 nests of unclear species), with the Amami Archipelago accounting
for about 10 percent of the general laying number of times in the whole
country.
However, the total number of nests of sea turtles decreased after 2012
at Amami-Oshima Island, with the number of nests of the loggerhead decreasing,
and on other hand, the number of nests of the green turtle increasing.
We started the satellite tracking of the females which nested at Amami-Oshima
Island from 2015 and found that loggerheads are using the East China Sea,
and that green turtles are using the coast of Kyushu, south-side of Honshu
and Izu-islands as feeding areas. The predation of turtle eggs by Ryukyu
Wild Boar, which is a native species, was confirmed at Amami-Oshima Island,
and 89 nests were affected –about 25 % of the number of general nests are
preyed on in 2015, and a preservation measure by the prefecture is proposed.
Talk and observation turtle meetings are being held periodically by our
research group for the purpose of preserving the sea turtle and its nesting
beaches.
15:50 Discussion
17:00 Closing
●Poster
（Poster pdf） |
トップページヘ 
cpi.kagoshima-u.ac.jp
