遺傳及耳石微化學標記在兩側洄游型及瀕危經濟性魚類族群管理的應用(1/3)

• Main Author: 曾萬年
• Format: Other/Unknown Material
• Language: Chinese
• Published: 臺北市：國立臺灣大學漁業科學研究所 2005
• Subjects: European eel; Anguilla anguilla; Otolith microchemistry; Migratory history; Restocked eel; 歐洲鰻; 耳石微化學; 洄游生活史; 放養鰻; Anguilla anguilla
• Online Access: http://ntur.lib.ntu.edu.tw/handle/246246/20572; http://ntur.lib.ntu.edu.tw/bitstream/246246/20572/1/932313B002114.pdf

Anguilla anguilla elvers have been restocked in Lithuanian waters and mixed with naturally recruited eels for several decades. Otolith Sr:Ca ratios were examined to evaluate the contribution of the exotic eels to the native eel population. Restocked eels were identified by the freshwater signature (Sr:Ca ratios < 2.24 × 10-3) on the otolith after glass eel stage. Naturally-recruited eels, that had migrated through the North and Baltic Seas, were characterized by an extended seawater signature (Sr:Ca ratios > 3.23 × 10-3) after the glass eel stage. Of 108 eels analyzed, 21 eels had Sr:Ca ratio profiles consistent with restocking while 87 showed patterns of natural recruitment. Eels from the inland lake Baluošai were all freshwater residents of restocked origin. However, restocked eels accounted for only 20% of the eel from the Curonian Lagoon and 2% of eels sampled in Baltic coastal waters. This finding does not support the hypothesis that eel fishery in the Curonian Lagoon mostly depends on restocking. This study demonstrates the application of otolith microchemistry in discrimination of mixed population and evaluating the stocking effectiveness of diadromous fishes. 由於歐洲鰻鰻苗資源不斷減少，使得波羅地海地區，包括立陶宛，幾乎已經沒有 天然的鰻苗，立陶宛為了提高國內的鰻魚資源，多年來向英國與法國購買鰻線放 流到內陸湖泊與波羅地海沿岸的瀉湖(Curonian Lagoon)。然而放流的鰻苗與天然 的鰻魚在外觀上無法區分，因此無法得知放流的鰻苗是否對鰻魚資源有所貢獻。 因此我們分析鰻魚耳石中的鍶鈣比，以區分放流的鰻魚與自然洄游到立陶宛的鰻 魚。放流的鰻魚在鰻線階段之後會呈現很低的鍶鈣比(Sr:Ca ratios < 2.24 × 10-3)，因為鰻線是直接被放入淡水環境中，鍶的含量在淡水中是很低的。而自 然洄游到立陶宛的鰻魚則是在鰻線階段後會有一段時間表現高鍶鈣比(Sr:Ca ratios > 3.23 × 10-3)，因為這些鰻魚必須游經北海與波羅地海才能抵達立陶宛， 而海水中的鍶含量是高於淡水的。在分析的108 尾鰻魚中，有21 尾是放流鰻， 而87 尾則是自然洄游到立陶宛的鰻魚。內陸湖泊的鰻魚全數都是來自放流鰻， 而放流鰻在瀉湖中佔了20%，在波羅地海沿岸則只佔2%。這項發現否定了瀉湖 的鰻魚主要是來自放流的說法。此研究成功地運用耳石微化學分析，用於區分不 同來源的鰻魚族群，並且評估放流對鰻魚族群資源的貢獻量。