台灣招潮蟹棲地保育之底質特徵探討：以麥寮為例

Abstract

台灣招潮蟹(Uca formosensis)為台灣特有種。近二十年來，其數量與分布區域逐漸減少，使對其棲地的了解與保護更為重要。本研究為釐清底質棲地環境對台灣招潮蟹族群之影響與關係。研究地區為雲林麥寮濕地(位於台塑六輕廠北側)，研究中共評比了八項環境因子，分別為：粒徑、粉泥/黏土含量、土壤篩選係數、土壤含水量、全有機碳、全氮、土壤氧化層深度與累積浸沒潮時；八項環境因子可歸納為底質顆粒組成、營養鹽組成與潮汐影響等三個面向。 根據研究結果，台灣招潮蟹棲地之底質特徵為：粉泥土或極細砂土(粒徑<0.125mm)，粉泥/黏土含量高於60%，累積浸沒潮時少於40小時(一次潮汐週期下)。以麥寮為例，台灣招潮蟹棲地之其餘底質環境表現為：土壤氧化層介於14.93~55.55cm、含水量介於20.576~26.321 %、土壤篩選係數介於0.806~1.308、全有機碳介於0.25~0.44、全氮介於0.07~0.09。本研究以麥寮地區為台灣招潮蟹棲地模式，應用判別分析以分析新竹海山罟與彰化伸港地區的台灣招潮蟹棲地表現。本研究根據累積潮水浸沒時間的長短，將台灣招潮蟹棲地分為三級：第一類(良好)、第二類(普級)與第三類(劣級)棲地。根據判別分析結果，伸港地區內83.3%(10/12)的樣點屬於第一類棲地，16.7%(2/12)屬於第二類棲地；麥寮地區內38.9%(7/18)的樣點為第一類棲地，38.9%(7/18)的樣點為第二類棲地，27.8%(5/18)的樣點為第三類棲地；海山罟地區內，16.7%(4/24)的樣點屬於第一類棲地；66.7%(16/24)的樣點屬於第二類棲地；16.7%(4/24)的樣點屬於第三類棲地。 本研究歸納出台灣招潮蟹的底質棲地特徵，並驗證累積浸沒潮時對台灣招潮蟹族群為具有影響力的因子。

Uca formosensis is an endemic species in Taiwan. The population size and habitats decreased continuously in the past twenty years. This study focus on the relationship between the sedimentary environment and Uca formosensis population. The study area is in northwest site of Mailiao township and eight environmental factors were analyzed: grain size, silt/clay content, sorting coefficient, water content, total organic carbon(TOC), total nitrogen(TN), depth of oxidation layer(DOL) and accumulated inundated-time. According to the results, grain size smaller than 0.125 mm, silt/clay content more than 60% and accumulated inundated-time less than 40 hours are the habitat characteristics of Uca formosensis. In Mailiao case, the other environmental factors showed that DOL between 14.93~55.55 cm, water content between 20.58~26.32%, sorting coefficient between 0.806~1.308, TOC between 0.25~0.44 and TN between 0.07~0.09. This study takes the sedimentary environment of Mailiao as a model and classify the substratum into three grades by the accumulated inundated-time to discriminate the suitability of Uca formosensis habitats in HaiShanGu and Shenkang. Mailao area has 38.9% best habitats, 38.9% common habitats and 27.8% bad habitats of Uca formosensis; Shenkang area has 83.3% best habitats and 16.7% common habitats of Uca formosensis; HaiShanGu has 38.9% best habitats, 66.7% common habitats and 16.7% bad habitats of Uca formosensis. This study generalized the habitat characteristics of Uca formosensis and demonstrated the accumulated inundated-time is an important factor to Uca formosensis.