臺灣西海岸中華白海豚族群之時空變異

Spatial Distribution and Temporal Variation of Indo-Pacific Humpback Dolphins (<i>Sousa chinensis</i>) in Western Taiwanese Waters

郭毓璞(Yu-Pu Kuo)

指導教授 ： 周蓮香

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02211

摘要

中華白海豚(Sousa chinensis)主要分布在印度東岸至澳洲東部的近岸淺水區域，其中分布在臺灣西海岸的族群被認為是數量稀少且獨立封閉的族群，且在IUCN紅皮書上被列為「極度瀕危」等級。本研究採用海上穿越線調查法以及「標記-再捕捉」法進行該族群豐度之估算，並分析其空間分佈和族群動態。穿越線設計方面，除了2008年到2012年共執行394天趟的傳統平行海岸穿越線調查外，本研究在2012年至2013年期間另外執行26天趟的Z字型穿越線調查以擴大調查範圍，橫跨海豚所有可能棲地，最後進行兩種方式之比較。此外，就過去五年研究所累積之75隻非嬰幼個體照片資料庫，採用標記-再捕法的「穩健設計模式」來估算歷年族群豐度、死亡率、出生率之變化。海上調查Z字型穿越線的結果顯示中華白海豚呈現近岸淺水分佈，出現於平均水深7.9±0.79 (SE)公尺的水域，有些河口偏好傾向，且其可能棲地範圍可能超出本調查之南北界。族群密度方面，相對於Z字型調查估算結果為0.103隻/平方公里 (CV=42.0%)，平行海岸線則為0.31 隻/平方公里 (CV=11.5%)；豐度估算方面，兩方法的結果則相當接近，分別為64隻 (95%CI: 29-144)或 68隻 (95%CI: 54-85)，因此就這個近岸淺水分布的小族群，近岸平行海岸線可以視為一種合適的穿越線設計。族群的近五年間動態分析方面，結果首度明確顯示族群數量從2010年的75隻下降到2012年的64隻，還伴隨下滑的族群存活率和出生率，尤其是粗出生率從2009年的7.14%到2012年急遽下降至零。針對臺灣狀況如此危急的小族群，在區域性滅絕之前，急需針對此警訊深入研究起因，並展開有效的保育行動。

關鍵字

中華白海豚 ； 穿越線調查 ； 標記-再捕捉法 ； 分布 ； 族群動態 ； 保育

並列摘要

Indo-pacific humpback dolphins (Sousa chinensis, a.k.a. Chinese white dolphins), are widely distributed in inshore shallow waters between eastern India and Australia. The population off the western coast of Taiwan is considered to be a small isolated population, categorized as “Critically Endangered” in the IUCN red list. The purpose of this thesis is to estimate the abundance of this population by two commonly used methods, the transect line survey and mark-recapture method, and to investigate the dolphins’ spatial distribution and population dynamics. Two designs of transect line surveys were used-- 394-day inshore parallel transect line surveys conducted between 2008 and 2012, and 26-day zigzag transect line survey was conducted between 2012 and 2013 that covered the whole possible habitat of this dolphin species, and their results were compared later. In addition, based on the photo-ID data assembled over the past 5 years’ researches that consisted of 75 identified individuals, a robust design mark-recapture method was used to estimate the yearly changes in abundance, as well as mortality and the crude birth rate. The results of zigzag transect lines confirmed that the Chinese white dolphins were concentrated in inshore shallow waters, with average water depths at 7.9±0.79(SE) m, showing some indication of preference for estuarine environments, while their potential habitat range could extend further north and south than previously assumed. The population density was estimated by the zigzag survey as 0.103 individual/km^2 with CV=42.0%, and 0.31 individual/km^2 with CV=11.5% by the inshore parallel surveys. The estimates of population abundance were quite similar, as 64 individuals (95%CI: 29-144) by the zigzag survey and 68 individuals (95%CI: 54-85) by the inshore parallel surveys, respectively. Thus it was concluded, as for the distribution of the Chinese white dolphins in Taiwan is limited to inshore shallow waters, the inshore parallel surveys could serve as an effective and valuable transect line design for density and abundance studies on this population. In addition, the analysis of the robust design mark-recapture model showed a significant declining trend in the dolphin’s population, with the annual abundance dropping from 75 individuals in 2010 to 64 individuals in 2012, while the survival and birth rates decreased. In particular, the present study revealed for the first time the dramatic drop of the animal’s crude birth rate from 7.14% in 2009 to zero in 2012. For a population as small as the one in Taiwan, this finding requires special attention, and further researches and effective conservation actions must be taken place soon before the Chinese white dolphin population in Taiwan becomes regionally extinct.

並列關鍵字

Chinese white dolphins (<i>Sousa chinensis</i>) ； transect line ； mark-recapture ； distribution ； population trend ； conservation

參考文獻

Williams, Byron K., James D Nichols, and Michael James Conroy. 2002. Aanalysis and Management of Animal Populations: Modeling, Estimation and Decision Making. Access Online via Elsevier.

Yu, H. Y., T. H. Lin, W. L. Chang, S. L. Huang, and L. S. Chou. 2010. “Using the Mark-recapture Method to Estimate the Population Size of Sousa chinensis in Taiwan.” Workship on Population Connectivity and Conservation of Sousa chinensis off Chinese Coast, Nanjing, China.

Yu, H. Y., T. H. Lin, W. L. Chang, S. L. Huang, and L. S. Chou. 2010. “Using the Mark-recapture Method to Estimate the Population Size of Sousa chinensis in Taiwan.” Workship on Population Connectivity and Conservation of Sousa chinensis Off Chinese Coast, Nanjing, China.

Chapter 1

Barros, Nelio B, Thomas A Jefferson, and ECM Parsons. 2004. “Feeding Habits of Indo-Pacific Humpback Dolphins (Sousa chinensis) Stranded in Hong Kong.” Aquatic Mammals 30 (1): 179–188.