| 中文摘要 |
本研究針對2004-2006年台灣遠洋鮪延繩釣漁業觀察員所蒐集資料進行分析，包括作業水域的掌握、各洋區漁獲努力量、各洋區漁獲種類組成、混獲鯊魚種類組成及種類別單位努力漁獲情形、大西洋區混獲鋸峰齒鮫CPUE季節變化情形等。為了評估歷年鋸峰齒鮫CPUE變動趨勢，本研究首先針對2002-2006年觀察員所得資料進行分析，根據所得之鯊魚混獲比率，首先將大西洋水域區分為A、B、C、D、E五個區域，A區域為低緯度水域，是5°N-15°S的區域，B區域是15°S-50°S西經20°以西的水域，C區域是15°S-50°S西經20°以東的水域，D區域係5°N-20°N水域，E區域為20°N以北的水域。利用觀察員在大西洋區所得的鯊魚混獲比例資料來修正歷史漁獲資料(Task 1)，並進一步估算該區鋸峰齒鮫及灰鯖鮫的混獲數量。結果顯示熱帶水域(A區和D區)混獲鯊魚數量有明顯高於較高緯水域(B、C、E三區)，各區所混獲鯊魚當中皆以鋸峰齒鮫及灰鯖鮫為大宗。鯊魚混獲數量自1981年的3,490公噸逐年增加至1990年的11,170公噸，2002年更達歷史高點的20,521公噸，隨後則呈逐年下降的趨勢。鋸峰齒鮫混獲重量自1981年的3,107公噸逐年增加至1990年的10,148公噸，2002年是歷史高點達18,586公噸，隨後則呈下降趨勢。 |
| 英文摘要 |
In this study the data collected by observers from distant waters tuna longline fishery between 2004 and 2006 were analyzed. The data of operation area, fishing effort, species composition, shark by-catch species composition, catch per unit effort by species, seasonal variation of CPUE in blue shark from Atlantic Ocean were presented. For the purpose of analyze the CPUE trend of blue shark, the observers’ records of Taiwanese tuna longline fishing vessels operating in the Atlantic Ocean from 2002-2006 were analyzed firstly. According to shark catch rate, five areas namely, A (5oN-15oS), B (15oS-50oS, west to 20oW), C (15oS-50oS, 20oW-20oE), D (5oN-20oN) and E (north of 20oN), were categorized. The shark catch data reported by observers were used to adjust the historical shark catch in Task I and to estimate blue shark and mako shark catches for Taiwanese longline fishery in the Atlantic Ocean. The shark bycatch in tropical area (areas A and D), is higher than that in temperate area (areas B, C, and E). The blue shark, and mako sharks are the dominant species of shark bycatch in all areas. Shark bycatch in weight increased from 3,490 tons in 1981 to 11,170 tons in 1990, peaked in 2002 of 20,521 tons and decreased thereafter. Blue shark bycatch in weight increased from 3,107 tons in 1981 to 10,148 tons in 1990, peaked in 2002 of 18,586 tons and decreased thereafter. |