曾萬年臺灣大學：漁業科學研究所曲有為Chu, Yu-weiYu-weiChu2007-11-282018-07-062007-11-282018-07-062005http://ntur.lib.ntu.edu.tw//handle/246246/59353台灣河川中的日本鰻(Anguilla japonica)，因過度捕撈及棲地惡化，所以族群量日益減少，而且雌性比例偏高。但是2004年7月2日敏督利(Mindulle)颱風之後，高屏溪的鰻魚族群量卻突然升高，而且性比偏向雄性。推測其原因，可能是養殖池的鰻魚流入所造成的現象。為了瞭解高屏溪鰻魚族群結構變化的原因，本研究嘗試建立野生及養殖鰻之識別方法，並探討性比變化的原因以及養殖鳗進入河川之後的命運。 1998年5月起至2004年12月止，每個月在高屏溪河口進行野生鰻採樣，並且在2004年2月及8月分別在鹿港地區及高屏溪沿岸的養殖池採集養殖鳗。標本採集之後，便進行性別、外部形態(體長、體重、胸鰭長、眼徑及體色)、體長組成、體長-體重關係、肥滿度、以及生殖腺和肝臟指數等之測定，並利用電子微探儀(EPMA)及感應耦合電漿質譜儀(ICPMS)分析耳石的鍶鈣比(Sr/Ca ratio)及微量元素組成，然後利用變異數分析(ANOVA)及判別函數分析法(Discriminant function analysis)分辨野生鰻和養殖鰻，並比較颱風前、後高屏溪的日本鰻之差異。 結果發現野生鰻和養殖鳗的外部形態以及耳石的微細構造、Sr/Ca比和微量元素組成有顯著性的差異。野生鰻的族群密度低，雌性比例偏高；而養殖鰻的族群密度高，雄性比例也偏高，顯示鰻魚的性別分化與族群密度有非常密切的關係。另外，發現2004年冬季高屏溪河口的雄性銀鰻比例偏高，銀化程度與野生雄鰻沒有差異，顯示颱風時流入高屏溪的養殖鳗在天然環境中可以銀化，並準備進一步洄游至產卵場繁衍下一代。這些發現對於未來在河川中放流養殖鳗改善日本鰻的族群結構及其資源的復育將有莫大的參考價值。Due to over-fishing and habitat degradation, the population of wild Japanese eel (Anguilla japonica) in most Taiwanese rivers declined since 1980, and its sex ratio extremely skewed to female. However, the population density of the eel in Kaoping River was found to be abruptly increased and the sex ratio of the eel skewed to males after Typhoon Mindulle, July 2nd, 2004. This may indicate that the population structure of the eel in the river was affected by the immigration of cultured eel resulting from the typhoon. In order to validate the relationship between the drastic change of the Japanese eel population structure in the Kaoping River and the typhoon, we attempted to establish the methods of discriminating cultured and wild eels as well as to understand the sex-determination mechanism of the eel and the fate of the eel escaped from the eel farm. The wild eels collected monthly in the Kaoping River estuary since May 1998 through December 2004, and cultured eels collected respectively from Lukang and Kaoping eel farms in February and August 2004 were examined. The sexes of the eel were determined, the biological characteristics including somatic length and weight, condition factor (CF), gonadosomatic index (GSI) and hepatosomatic index (HSI) were measured, skin tone, fin index(FI), ocular index(OI), length-weight relationship were analyzed, and otolith microstructure, Sr/Ca ratio and trace elemental composition were measured via EPMA and ICPMS. The data were analyzed with ANOVA and discriminant function analysis to discriminate wild and cultured Japanese eels. It was found that external morphology and the Sr/Ca ratios and trace elemental composition in otolith can effectively separate the wild eel from the culture eel escaped after typhoon in the Kaoping River. The wild eel was lower in density and dominated by female, but the intensively-cultured eel was dominated by male. This indicated that the sex determination of the eel was highly related to their population density. The silver eel captured in the river during winter in 2004 was dominated by males, and their GSI values were similar to wild ones, indicating that the cultured eels escaped from the eel farms during typhoon can silvering in natural environment. These findings suggest that it is possible to restock the Japanese eel by releasing the cultured eel in the river in stead of releasing hormone-induced eel in the sea in the past time in Taiwan.中文摘要………………………………………………………..Ⅰ 英文摘要…………………………………………………………...II 前言……………………………………………………..………..1 1. 日本鰻之生活史……………...……………………….1 2. 鰻魚資源保育的隱憂…….…………...…………………..…2 3. 鰻魚性別的決定機制……………………...…………………..3 4. 養殖鰻與野生鰻生長環境的差異………...………………….5 5. 耳石的構造及化學組成………...…........................6 5.1 耳石的微細構造……..…………..…………….6 5.2 耳石的形成…………………………………………….7 5.3 耳石微量元素組成與水體環境之關係………………….8 6. 耳石在魚類生活史研究上的應用…….....................9 6.1 鍶鈣比(Sr/Ca ratios)之時序列變化……….…………….9 6.2 耳石微量元素組成分析……………………..…………..10 7. 研究動機及目的……………………...……………………..11 材料與方法……………………………………………..…13 1. 標本的採集………………………….………………...13 1.1 野生鰻標本…………..………………………..………...…13 1.2 養殖鰻標本………..……………………………..…13 2. 形態測定……….………………………………………...14 3. 野生鰻與養殖鰻的區別………………………………….14 3.1 性比………….………………………..………...…14 3.2 外觀體色……………..………………15 3.3 體長頻度分佈…………………………...………15 3.4 體長-體重關係……………………………………..15 3.5 耳石微細構造及微量元素………………...…………15 3.5.1 耳石微細構造觀察…………………………....16 3.5.2 利用EPMA分析耳石鍶鈣比……………………...16 3.5.3 利用ICP-MS分析耳石的微量元素組成………….17 4. 統計分析..…………………………...18 結果………………………………………………………..…20 1. 野生鰻與養殖鰻族群性比之差異性………..…………...20 2. 日本鰻野生族群性比的年間及月別變化………………...20 3. 野生鰻和養殖鰻體色的差異………………………….21 4. 依照黃鰻的體色差異而區分的鰻魚性比之比較………….21 5. 體長頻度分佈之月別變化…………………………….…22 6. 體長-體重關係之比較…………………………....22 7. 形態及生理指數………………………………….23 7.1 颱風前、後野生鰻各項指數之比較………………..…….23 7.2 日本鰻發育階段間生理指數之比較……………...…24 7.3 形態及生理指數的季節性變化………………………...24 7.4 颱風後銀鰻之成熟度………………………...24 8. 耳石鍶鈣比時序列變化………………………………….…25 8.1 野生鰻…………………………………………...25 8.2 養殖鰻………………………………………...25 9. 養殖鰻耳石的特異構造(Discontinuous Area, DCA)…..….25 10.野生鰻與養殖鰻耳石微量元素組成的比較……………….26 10.1平均值的比較…………………………………..26 10.2判別函數分析………..……………………………….27 11.耳石微量元素組成的發育階段變化………………….27 11.1不同群之間耳石微量元素比值的比較………………...28 11.1.1柳葉鰻期…………………..…………………..28 11.1.2黃鰻期................................29 11.2耳石微量元素比在分群上的判別函數分析………………...29 11.2.1柳葉鰻期………………………………………………29 11.2.2黃鰻期………………………………………...….29 討論…………………………………………………..…………31 1.野生與養殖日本鰻性比差異之探討………...………31 2.野生鰻與養殖鰻之識別………………………………33 3.耳石微量元素的時序列變化：LA-ICPMS的分析結果……...37 4.養殖鰻在天然環境中的命運…………………………37 總結..........................................39 參考文獻……………………………..…………40 表….…………………………………………………………….52 圖……………………………………………………………61 附錄…………………………………………………………891613919 bytesapplication/pdfen-US高屏溪日本鰻野生鰻及養殖鳗性比體色耳石微細構造及微量元素組成EPMAICP-MSKaoping RiverJapanese eel (Anguilla japonica)wild and cultured eelssex ratioskin toneotolith microstructure and trace elemental composition[SDGs]SDG10otherhttp://ntur.lib.ntu.edu.tw/bitstream/246246/59353/1/ntu-94-R92b45007-1.pdf