2006-10-012024-05-18https://scholars.lib.ntu.edu.tw/handle/123456789/712188摘要：日本鰻為我國重要的經濟養殖魚類，因為鰻魚的人工繁殖尚未完全成功，養殖用的鰻苗仍然完全仰賴天然撈捕的鰻線。鰻線資源的多寡，便形成鰻魚養殖業成敗的關鍵。1980年代之後，日本鰻的資源量急速下降，僅剩1980年代的10 %，嚴重影響養鰻業的發展。鰻魚資源量下降的原因可能與過度捕撈、河川棲地污染等等因素有關。為了鰻魚資源的永續利用，必須加強資源管理的研究工作。台灣自1976年起實施種鰻放流，但適當的放流策略仍付之闕如。近年來的研究發現，日本鰻的性別比例嚴重的偏向雌性，而鰻魚的性別決定顯然受外在環境因子所影響。透過分析耳石中的鍶鈣比變化，發現根據鰻魚對棲地利用的不同，可將之區分為海水鰻，淡水鰻與半淡鹹水鰻三群。是否在不同鹽度的棲地中，鰻魚會有不同的性別分化比例或是不同的遺傳結構組成仍不清楚。因此，本計劃擬利用鰻魚耳石中的鍶鈣比變化，分析三型棲地利用的鰻魚是否存在顯著的性別比例差異，並利用微衛星DNA分析三群間之遺傳結構是否相同。此結果可應用在放流復育工作上，若鰻魚性別受鹽度影響，則選擇偏好雄性分化之棲地放流性別尚未決定之幼鰻，用以補充天然雄鰻之不足。若三群鰻魚之遺傳結構有差異，則選擇放流淡水鰻與半淡鹹水鰻之族群，以增加鰻線之收獲量與養殖量。<br> Abstract: Japanese eel (Anguilla japonica) is one of the economically important cultured fish in Taiwan. Since the eel artificial reproduction has not fully succeed yet, aquaculture needed elvers are caught totally from the wild. The abundance of the elvers caught annually thus becomes the key of success for eel aquaculture industry. Historical statistics prove that Japanese eel suffer a dramatic decline since the 1980s due to overfishing, habitat pollution and other extrinsic factors, making the recent abundance of eels to only about 10 % compared with that in the past two decades. Consequently, concerns for the decline of natural population lead to the establishment of eel fishery management that is meant to recover eel population and increase elver catch for aquaculture industry. In Taiwan, early endeavor has already been started like releasing of hormone-induced spawners which is conducted during 1976. However, the effectiveness is hard to identify and the suitable strategy for stock enhancement is yet unknown because efforts on the basic researches of eels are still lacking. Recent studies indicate that the strong female sex ratio bias is found all over Taiwan, and the eel sex determination is significantly affected by environmental factors. By analysis of the life history pattern of the otolith Sr/Ca ratios, eels can be divided into types of freshwater resident, brackish water resident and seawater resident. It is not clear if the habitat use of the eels is sex-dependent and could affect eel sex determination. In addition, it is also not clear if there exist any differences among genetic structures of contingents. Thus, the purpose of this project is to clarify the sex-dependent habitat use of the Japanese eel by analyzing their otolith Sr/Ca ratios and their population genetic structures by using microsatellite DNA. These results can be applied to the eel resource enhancement by releasing the sex-undetermined juveniles into habitat that prefers male development for supplement of the bias wild population if the eel sex is affected by salinity, and/or releasing juveniles of freshwater and brackish water contingents to maximize the catch and aquaculture abundance of the eel if there are significant differences of the genetic structure among eel contingents.日本鰻鍶鈣比性比族群遺傳結構微衛星DNA性別決定Japanese eelSr/Ca ratioSex ratioPopulation genetic structureMicrosatellite DNASex determination