2014年澎湖縣綠蠵龜（Chelonia mydas）繁殖與族群危機調查

Survey of Green Sea Turtle Reproduction and Population Threat in Penghu County in 2014

綠蠵龜（Chelonia mydas）是臺灣和附近離島地區主要上岸產卵的海龜。澎湖望安島綠蠵龜產卵棲地是臺灣唯一政府八告的海龜保護區，更是綠蠵龜繁殖保育的重要區域，當地提供綠蠵龜產卵繁殖的重要棲息環境。但是近年來上岸產卵的母龜數量有逐漸下降的趨勢，對海龜的族群保育出現嚴重的警訊，急需要深入探討和剖析。本研究自 2014 年 5 月綠蠵龜上岸產卵開始，直到 12 月底為止，共執行一整個海龜生殖季調查。本年度調查發現澎湖母龜產卵地區共有望安和嵵裡二處，各有一隻母龜上岸產卵。另外吉貝島僅有當地居民描述一隻母龜上岸產卵。望安保護區中母龜最早於 5 月 9 日產卵，共生下 6 窩蛋，總共產下 506 顆蛋，平均每窩卵數為 84 顆（n= 6；sd= 7.0），總共孵出 489 隻稚龜，總體孵化率為 96.6% （489/506）。在望安保護區內孵化稚龜的主要天敵為中華沙蟹（Ocypode sinensis）和角眼沙蟹（Ocypode ceratophthalmus），共有 21 隻稚龜被捕死亡，平均每窩被捕食 3.5 隻（n=6；sd=5.3），被捕食而死亡的稚龜最嚴重時可達該窩孵出稚龜數的 18.4% （14/76）。因熱休克死亡的稚龜共有 38 隻，其中有 33 隻是未爬出巢而在沙中死亡，有 5 隻是在沙灘上死亡。成功爬入海中的稚龜共有 428 隻，繁殖成功率為 84.6% （428/506）。裡沙灘一隻產卵母龜產下 7 窩，但在挖掘檢驗巢中蛋的發育後，發現均是未受精的蛋。其發生的原因為何？仍不得而知，需要深入持續的調查。 In Taiwan and on its nearby islands, the green sea turtle (Chelonia mydas) is the main species of sea turtle found to lay eggs on beaches. Wang-an Island of Penghu County is the single sea turtle refuge designated by the Taiwanese government, making the Penghu area also an important reproductive and conservation habitat of green sea turtle. In recent years the declining number of nesting turtles indicates a serious threat to sea turtle conservation. We studied nesting green sea turtles during their reproductive period on Wang-an Island and in Shi-li, Magong City, from May to December, 2014. Local people's accounts of green sea turtle on Ji-bei Island were also included in our study. There was only one nester in Wang-an in 2014. The earliest nesters laid six nests with a total of 506 eggs on May 9th. The average clutch size was 84 eggs (n= 6, sd= 7.0), which produced a total of 489 turtle hatchlings and amounting to a hatching rate of 96.6%. The main predators of the hatchlings in the Wang-an refuge were the Chinese ghost crab (Ocypode sinensis) and horn-eyed ghost crab (Ocypode ceratophthalmus), which accounted for a mortality rate of 3.5 individuals per nest (n= 6, sd= 5.3). In the most serious case, mortality from predation was 18.4% in one nest. There were 38 hatchlings that died from heat shock, with 33 individuals found in the sand of their nests while five individuals climbed out of their nests but died on the beach. A total of 428 hatchlings from 506 eggs successfully reached the sea, marking a breeding success rate of 84.6%. One nesting turtle on Shi-li beach laid seven nests but no eggs were found fertilized. The reason for unfertilized eggs remains unclear. More detailed researches are required to understand whether these populations are still declining.

In Taiwan and on its nearby islands, the green sea turtle (Chelonia mydas) is the main species of sea turtle found to lay eggs on beaches. Wang-an Island of Penghu County is the single sea turtle refuge designated by the Taiwanese government, making the Penghu area also an important reproductive and conservation habitat of green sea turtle. In recent years the declining number of nesting turtles indicates a serious threat to sea turtle conservation. We studied nesting green sea turtles during their reproductive period on Wang-an Island and in Shi-li, Magong City, from May to December, 2014. Local people's accounts of green sea turtle on Ji-bei Island were also included in our study. There was only one nester in Wang-an in 2014. The earliest nesters laid six nests with a total of 506 eggs on May 9th. The average clutch size was 84 eggs (n= 6, sd= 7.0), which produced a total of 489 turtle hatchlings and amounting to a hatching rate of 96.6%. The main predators of the hatchlings in the Wang-an refuge were the Chinese ghost crab (Ocypode sinensis) and horn-eyed ghost crab (Ocypode ceratophthalmus), which accounted for a mortality rate of 3.5 individuals per nest (n= 6, sd= 5.3). In the most serious case, mortality from predation was 18.4% in one nest. There were 38 hatchlings that died from heat shock, with 33 individuals found in the sand of their nests while five individuals climbed out of their nests but died on the beach. A total of 428 hatchlings from 506 eggs successfully reached the sea, marking a breeding success rate of 84.6%. One nesting turtle on Shi-li beach laid seven nests but no eggs were found fertilized. The reason for unfertilized eggs remains unclear. More detailed researches are required to understand whether these populations are still declining.