澎湖群島凶狠圓軸蟹分布調查及其棲地底質初探

Distribution of Cardisoma carnifex in Penghu Islands and Preliminary Study of Its Habitat Substrate

本研究敘述澎湖群島凶狠圓軸蟹的分布現況，並進行棲地土質粒徑分析及洞穴內水質鹽度測量。調查結果發現其確切棲地共17處，包含馬公市1處、湖西鄉3處、白沙鄉7處、西嶼鄉2處、望安鄉4處、以及推測棲地9處。在土質粒徑分析方面發現，凶狠圓軸蟹棲地土質粒徑範圍主要為極粗砂（1.000mm）及中等粗砂（0.250mm），二者合計皆占土樣總乾重的50%以上，反之，凶狠圓軸蟹棲地極細砂（0.125mm）含以下之粒徑分布較少，都不超過土樣總乾重的10%。另外本調查發現其棲地水樣大多為淡水，占了總棲地的43%，其餘海水及半淡鹹水各占了總棲地的28.5%。

This study is a description of the distribution of Cardisoma carnifex and substrate composition of its habitats in Penghu Islands, as well as an estimation of its populations in Chinglou wetlands. Totally 17 habitat sites were recorded, including one in Magong City, three in Husi Township, seven in Baisha Township, two in Siyu Township and four in Wangan Township. In addition, there were nine presumed habitats. The main particle sizes of substrates in the habitats ranged from very coarse sand (1.000mm) to medium sand (0.250mm). The summed dry-weight of both substrates was higher than 50% of the total weight of all substrate samples. On the contrary, the smaller particles that include very fine sand (0.064mm) and silt (＜0.064mm) in the substrate samples were less than 10% of the total weight. In addition, salinity of most water samples in the habitat caves showed they were freshwater. However, a few of the water samples were seawater and brackish water, accounting for 43% of the total habitat, and the remaining seawater and brackish water habitat accounted for 28.5% of the total habitat.