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研究報告

更新日期: 2015-02-09
點閱數: 1,348

瀕危大型軟骨魚類調查研究

年度 2013
計劃名稱 瀕危大型軟骨魚類調查研究
中文摘要 本年度定置網共誤捕鯨鯊46尾,標識放流15尾,另有一尾臺灣首次紀錄到的初生幼魚,於綠島海域標識放流,此可能是臺灣東部海域為西北太平洋鯨鯊系群繁殖場的有力證明。在47尾鯨鯊裡面,宜蘭有16尾(34%),花蓮10尾(21.3%),臺東10尾(21.3%),屏東5尾(10.6%),澎湖4尾(8.5%),竹苗2尾(4.3%);整個東部地區有36尾(76.6%),西部則有11尾(23.4%),換算成每組定置網的年平均單位努力漁獲量來看,東部為0.77(尾/組/年),西部為0.86(尾/組/年)。從整體的性別結構分析顯示,雄魚較多於雌魚。今年度鯨鯊的平均體長及體長中位數,不論雌雄都比去年高,從年齡組成顯示來游至臺灣附近水域的鯨鯊多是十歲左右的未成熟個體。     標識放流的16尾鯨鯊裡面,有1尾於隔天進入附近海域的別組定置網中,再見率為6.3%,統計所有標識過的鯨其鯊再見率則為2.9%。本研究已完成標識2枚衛星定位籤,一尾為10月30日於澎湖被捕獲的未成熟雌魚,全長6.7 m,被放流之後一直南游至菲律賓西部沿近海域並停留多日,從其棲息溫度分佈情形來看,黃昏時有最高的比例會前往高溫水域,也就是接近水面位置,其他時候則除了接近水面的位置外,還會往較低水溫處(7 -10 °C)移動。另一尾則是在11月27日,同樣是誤入澎湖定置網的個體,為全長5.1 m的雌魚,截至目前為止還沒有收到任何衛星訊號。     本年度開始落實的象鮫、大白鯊及巨口鯊等三種稀有鯊魚的通報制度,至今尙無捕獲象鮫。大白鯊則於11月14日由流刺網混獲一尾雌性個體,體重550 kg,全長365 cm,並採集到肌肉、脊椎骨、腸寄生蟲等樣本。自巨口鯊被發現並命名以來,至今共記錄到77尾,其中33尾來自臺灣,今年就通報了22尾,為世界之最。所有巨口鯊都是被花蓮的流刺網漁業所捕獲,捕獲的地點多集中在花蓮近海處。該22尾巨口鯊皆有量測紀錄,其中5尾未採集到樣本,1尾整尾由海生館購得做為標本典藏,剩下的16尾有採樣生殖腺、肌肉、脊椎骨、胃內容物、寄生蟲等。在花蓮外海捕獲的巨口鯊以雌魚較多,有15尾(71.4%),體長範圍250 -710 cm TL,雄魚有6尾,體長範圍363 -484 cm TL,1尾未記錄到性別,體長500 cm TL,性比(雄/全部)為0.29;紀錄的16尾個體中,成熟的有2尾,皆是未懷孕的雌魚,成熟中的有11尾,其他的未熟。後續需要持續蒐集資料,可望建立全世界最齊全之巨口鯊研究資料庫。     其他瀕危大型軟骨魚目前僅針對紅肉丫髻進行調查及樣本蒐集。從南方澳、大溪及西北部地區數個漁港採樣記錄紅肉丫髻鮫,共記錄了833尾樣本,中大型樣本多來自南方澳的沿近海延繩釣漁獲,少數中型樣本來自大溪底拖網漁業,西岸所採得的多是小型被流刺網所捕獲的個體,樣本體長在45.6 -344 cm TL(尾前長31.5 -246 cm PCL)之間。紅肉丫髻鮫雌雄魚的體長與體重關係均呈現指數型迴歸,但雌雄間有顯著差異,其體重(kg)-體長(cm)關係式分別為雄魚:TW = 4.26 PCL3.25,雌魚:TW = 5.00 PCL3.23。     紅肉丫髻鮫脊椎骨共採樣到229尾樣本,將處理過後的脊椎骨置放於X光下拍攝,能清楚讀到成長輪紋,目前較欠缺為出現於夏天的個體,以致於判斷輪紋形成週期為一年形成一輪或一年形成兩輪還無法定論。
英文摘要 There were 46 whale sharks barged into set nets in 2013, and 15 of them were tagged and released. In addition, the first record of a neonatal whale shark was tagged and released in Green Island waters, suggested that eastern Taiwan waters might be breeding ground of the northwest Pacific stock. In 47 individuals, there were 16 (34%) from Yilan, 10 (21.3%) from Hualien, 10 (21.3%) from Taitung, 5 (10.6%) from Pingtung, 4 (8.5%) from Penghu, and 2 (4.3%) from Hsinchu and Miaoli; there were 36 (76.6%) from the east, and 11 (23.4%) from the west, converted to catch per unit effort as being calculated to be 0.77 individual per set net per year in the east and 0.86 individual per set net per year, respectively. The amount of male whale sharks was significant bigger than which of female in sex structure analysis. Both the mean TL and median TL in 2013 were larger than which in 2012, and most whale sharks which occurred in Taiwan waters were near 10 years old based on age structure analysis.     One of 16 released whale sharks entered into another near set net in the next day after release, indicated that re-sighting rate was calculated to be 6.3%, and 2.9% for total of released individuals. Two SPOTs were tagged on a 6.7 m TL immature female caught in Penghu on Oct. 30 and the other 5.1 m TL female also caught in Penghu on Nov. 27. The first one swam southward to the western waters off Philippines after release and remained there for many days. This individual usually moved to higher temperature as near surface regions in dusk time, and sometimes moved to lower temperature (7 -10 °C) regions based on time at temperature data. No signals were received from the other one until now.     Report system for catching the basking, white, and megamouth sharks was implemented in 2013, and not any basking shark was caught this year. But there was a 550 kg and 365 cm TL female white shark caught by the drift gill net on Nov. 14, and its muscles, vertebrae and intestinal parasites samples were collected. Since the megamouth shark was found and named, there were 77 individual records until now, and 33 of them were from Taiwan as top one region of the world, even 22 were reported this year. All megamouth sharks were caught by drift gill nets in Hualien and the locations were gathered in coastal and inshore waters. All of 22 individuals were measured and recorded, but 5 of them were not sampled, and one whole body was bought by NMMBA to be reserved sample. Remained 16 megamouth sharks were collected their reproductive organs, muscles, vertebrae, stomach contents, parasites, etc. There were more females as 15 individuals (71.4%) with 250-710 cm TLs, 6 males with 363 -484 cm TLs, and one 500 cm TL sex unknown individual for megamouth sharks caught in Hualien waters with sex ratio (male/total) of 0.29. For 16 individuals records, there were 2 mature but non-pregnant females, 11 maturing sharks, and others were immature. Keeping on collecting information and data further is needed, and the most complete megamouth shark data bank in the world could be hoped to be built.     In other endangered large chondrichthyan fishes, this study focused on investigation and sample collection for the scalloped hammerhead shark only. Total of 833 specimens were sampled/recorded from fish markets of Nanfanao, Tahsi, and northwest regions. Median and large specimens were caught mainly by coastal and inshore long-liners of Nanfanao, few median specimens were from bottom trawlers of Tahsi, and small specimens were collected from drift gill nets of the west. Sample lengths range distributed from 45.6 to 344 cm in TL, and from 31.5 to 246 cm in PCL. TW-TL relationships differed significantly between sexes, and as to be TW = 4.26 PCL3.25 for male and TW = 5.00 PCL3.23 for female respectively.Vertebrae of the scalloped hammerhead were sampled from 229 individuals. Growth band pairs could be read clearly from X-radiography of processed vertebrae. Periodicity of growth band pair formation is still unverified due to insufficient summer samples
計畫編號 102農科-11.2.1-漁-F3(2)
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