綠島椰子蟹Birgus latro (L.) 復育之研究：幼生人工養殖、幼蟹棲地調查及社區宣導

Restoration of the Coconut Crab Birgus latro (L.) in Green Island： Artificial Cultivation of Larvae, Investigation of Juvenile Habitat and Community Education

王芳琳(Fang-Lin Wang)

指導教授 ： 陳章波

國立臺灣大學/生命科學院/漁業科學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00688

摘要

椰子蟹是唯一成長到一至二年後就不需要背負螺殼的陸寄居蟹，也是國內唯一的保育類甲殼動物。為了保育此珍稀物種，本研究主要進行綠島地區椰子蟹幼生人工養殖、幼蟹分布棲地調查與社區保育宣導等三個方面的研究。
2003年與2004 年七至八月大潮的夜晚，我們於綠島海岸利用洗卵的方式共採得二隻雌蟹孵化之幼生，並將幼生養殖於溫度24-25℃、鹽度34-35‰之過濾海水中，餌料以豐年蝦無節幼生為主。2003年之結果發現蚤狀幼生共經歷三到五期，需25~38天；300隻蚤狀幼生中，共13隻變態成大眼幼生，分別有7隻第三期及6隻第五期蚤狀幼生變態為大眼幼生。每個階段的形態特徵變化如Reese(1968)所描述。大眼幼生於孵化後第38 天即可離開海水區域，過水陸兩棲的生活，無背殼行為。2004 年以PUFA, (n-3) HUFA, EPA, DHA 等養分滋養豐年蝦後投餵蚤狀幼生，對第三期蚤狀幼生個體有顯著的增長，並且可有效提升第四、第五期蚤狀幼生之存活率。共20隻第五期蚤狀幼生於第25~34天變態成大眼幼生，其中15隻來自投餵滋養豐年蝦組別。大眼幼生於第36天開始有背負螺殼的行為。幼生養殖的結果可做為未來椰子蟹幼生大量養殖之依據。
2002年10月至2004年8月約二年的期間，共調查6個樣區，於沙岸上方之海岸林與農田區共發現4隻頭胸甲長約19~22mm、未背螺殼的幼蟹，但未發現背殼的幼蟹個體。椰子蟹幼蟹與成蟹族群數量低，已嚴重影響綠島地區椰子蟹族群之補充。綠島四種陸寄居蟹的族群分布有重疊的情況，故椰子蟹與其它陸寄居蟹共同的棲地特徵為高濕度、具有許多岩石縫隙能提供躲藏，以及充足食物來源的區域。此一結果可做為棲地復育與人工養殖之幼蟹放流之用。
本研究結合社區、公部門與學界，推動「綠島椰子蟹保育推動工作小組」的成立，共商可行之保育策略，並進行社區學生、教師與居民之教育宣導，藉由社區的參與，永續綠島椰子蟹族群之保育。

關鍵字

椰子蟹 ； 陸棲寄居蟹 ； 復育

並列摘要

The coconut crabs Birgus latro (L.) are terrestrial hermit crab which only occupy discarded molluscan shells during the post-larvae and early juvenile phases of their life history, and then discard shells after about 1-2 year and move further inland. To protect this rare species, our study focused on artificial cultivation of larvae, investigation of suitable features of habitat, and community education at Green Island.
Zoeae from two female crabs were collected at higt tide on July and August in 2003 and 2004 respectively, and were reared in filtered seawater at temperature 24-25℃, salinity 34-35‰, fed on Artemia nauplii. The results in 2003 showed that duration of 3~5 zoeal satges lasted 25 to 28 days. There were 13 glaucothoe metamorphosed from 300 zoeae, 7 of them were early metamorphosis from the 3rd zoeal stage, and 6 metamorphosed from the 5th. The characteristics of larvae at each stage were similar to those described by Reese (1968). Glaucothoes started their amphibian life at 38th days after hatching without carrying shells. In 2004, zoeae which fed on enriched Artemia nauplii with PUFA, (n-3)HUFA, EPA, and DHA increased size of 3rd stage zoeae and survival rate of 4th and 5th zoeae. A total of 20 5th stage zoeae metamorphosed to glaucothoes, and 75% of them from feeding on enriched Artemia groups. The glaucothoes carried shells at 36th days after hatching and lived amphibiously. The results on larval cultivation will pave the way for mass cultivation.
We found 4 juvenile crabs of B. latro which cephalothoracic length were 19-22 mm without carrying shells in the coastal shrubs beyond beach and farmland after sampling 6 sites in 2 years. Low number of juvenile and adult population of B. latro have reflected low recruitment in Green Island. The distribution of B. latro and other land hermit crabs tend to overlap. So the common feathers of habitat for these land hermit crab were high humidity, more crevices to provide hiding, and the area with sufficient food source. These results will provide the basis of habitat conservation and releasing artificial-reared juvenile crabs in hope to improve the recruitment of natural coconut crab population in Taiwan.
In addition, we initiated a conservation team composed of local residents and officials to plan and execute restoration works. Moreover, environmental education was carried out on local teachers, students, and residents. Participation of local communities is the key to sustainablely conserve the population of coconut crabs in Green Island.

並列關鍵字

coconut crab ； Restoration ； terrestrial hermit crab

參考文獻

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