- 學位論文
台灣西部中華白海豚與沿岸漁業的食源潛在競爭
The potential competition for preys between Sousa chinensis and the coastal fisheries of western Taiwan
摘要
鯨豚與漁業之間的互動存在許多衝突，其中資源上的競爭往往成為漁民抱怨的主因。台灣西岸的中華白海豚族群，其棲息環境之沿岸漁業活動頻繁，因此本研究透過(1)漁民訪談的質性分析，與(2)資源利用重疊程度指標(Pianka's niche overlap index)，及(3)長期刺網漁獲量與漁獲種類的年間變化來探討台灣西部沿岸漁業與中華白海豚在資源上的重疊程度，並討論是否有地域上的差異。結果分述如下：(1)漁民訪談：自2010年5月至2011年4月完成苗栗、台中、彰化、雲林四地漁民訪談問卷共127人份。54% 漁民作業範圍包含中華白海豚主要棲息環境(離岸3海浬或水深20米以內)，其中刺網漁法占了94%。97%漁民表示從事漁業期間曾看過中華白海豚出沒，而多數漁民(91%)表示中華白海豚會遠離或不理會正在作業的船隻，約半數漁民(55%)表示中華白海豚的出現不會對漁獲量造成影響。許多漁民(42%)認為漁獲資源早在十年前即開始減少，而49%漁民認為工業汙染與違法三海浬拖網是造成漁獲量減少的原因。然而中華白海豚的目擊頻率與以往沒有差別(72%)。台灣西部沿岸漁民普遍對中華白海豚是否與他們搶奪資源的態度較為溫和，不如其他種海豚來得強烈(例如：瓶鼻海豚)，但仍有半數漁民表示中華白海豚的出現使得魚群被驅離，間接干擾作業。(2)漁業資料分析漁獲與中華白海豚食餌資源的重疊程度：不論在漁法上或各縣海域均有變異。由2009漁業年報結果顯示，沿岸刺網與一支釣漁法在資源利用上與中華白海豚的重疊程度較高(> 0.80)。另外由沿岸刺網漁業(1993–2009)資料顯示苗栗與彰化在中華白海豚的食餌資源利用上的重疊程度較高也較穩定。另外由底拖網採樣或刺網標本船漁獲資料，也顯示苗栗地區的主要食餌種類資源重疊程度較高(> 0.90)。(3)長期刺網漁獲量與漁獲種類的年間變化：整體而言在20年前(1990–1991)的刺網漁獲種類數較少，但漁獲總量比2010年度高，可能表示了漁民的目標漁獲轉向較小型的物種。另外由漁業年報刺網漁獲資料顯示，苗栗地區不論在中華白海豚的食餌資源利用上，或整體漁獲資源的捕撈量均較其它地區高。刺網漁業是台灣西部沿岸主要漁法，也是與中華白海豚食物資源高度重疊的漁業，為減輕漁業對中華白海豚的衝擊，更多相關的法規應予設立並確切執行。
並列摘要
The conflict between fisheries and cetaceans has been a universal issue in conservation. The population of Chinese white dolphins (Sousa chinensis) living off the western coast of Taiwan is facing survival challenges due to its small population size, as well as many other anthropogenic impacts including heavy coastal fishing activities. In this study, we investigated (1) the qualitative information from fishermen interviews, (2) the potential overlap in target prey (Pianka’s niche overlap index) between dolphins and fisheries, and (3) the long term trend of prey abundance for Chinese white dolphins, from the aspect of coastal gillnet fisheries. According to 127 fishermen’s interviews from May 2010 to April 2011, we found that 54% of the fishing operation range overlapped with the major habitat of Chinese white dolphins (less than 3 nm off shore or 30 meters water depth). Within this range, the main fishing method was the gillnet (94%). Most of fishermen (91%) said the dolphins had neutral or negative responses toward fishing boats and about half of the fishermen (55%) claimed that dolphin occurrence did not decrease their catches. Many fishermen (42%) claimed the fishery resources had declined over the past 10 years, and 49% of fishermen thought the industrial pollution and illegally trawling within three nautical miles were the main reasons that caused the decline. Most fishermen (72%) said the frequency of occurrence of Chinese white dolphins remain consistent over the years. According to analysis on the data from the 2009 Fishery Yearbook, we found that coastal gillnets and pole and lines showed higher overlap indexes (> 0.80), and the local variation in gillnets showed that Miaoli and Changhwa had higher and more stable overlap indexes than other areas. In addition, both bottom trawls and gillnets showed that Miaoli had a higher resource overlap in major prey (> 0.90). All in all, fewer catch compositions of coastal gillnets were recorded before 1990–1991, but the catch quantities were higher back then; this might indicate that fishermen changed their target preys to smaller fish. In addition, coastal gillnet catches from Fishery Yearbooks showed that Miaoli County had higher catch quantities than other counties. Although fishermen did not express strong averse attitudes toward Chinese white dolphins, half of the fishermen complained about the indirect interference caused by dolphins during operations. Nevertheless, the fish resource has been decreasing yearly, whether referring to fishermen interviews or long term fish logging data. Urgent regulation revisions are required to find a balance between gillnet fisheries and Chinese white dolphins.