以衛星標籤研究日本鰻、鱸鰻及太平洋雙色鰻之降海洄游路徑

Study of the seaward migration routes of Anguilla japonica, A. marmorata and A. bicolor pacifica via satellite tag

張清榮(Ching-Rong Chang)

指導教授 ： 韓玉山

國立臺灣大學/生命科學院/漁業科學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201702998

摘要

日本鰻是屬於降海洄游型的魚類，已知日本鰻的產卵場位於馬里亞納海脊西側，但實際洄游路徑仍未證實，生殖洄游過程及路徑仍充滿著神秘感。台灣常見的三種鰻鱺屬之物種有日本鰻、鱸鰻以及太平洋雙色鰻。為了保育日本鰻之族群數量，並且制定適當的管理策略，對於其降海洄游行為的研究是不可或缺的。上浮式衛星標籤能記錄深度、溫度、光照以及衛星定位之資料，常用於海洋生物之追蹤研究，前人也成功將衛星標籤運用在歐洲鰻及美洲鰻之洄游追蹤上。利用衛星標識放流，觀察放流鰻在大洋中的移動。在宜蘭地區放流之9筆回傳數據顯示，無論養殖鰻或野生鰻均順著黑潮進行移動，最遠到日本九州之東方海域；小琉球地區放流之成鰻沒有一致的移動方向，推測可能是受到附近的環流影響所致。所有放流鰻均表現出晝夜垂直洄游行為，在大洋中之水平移動速度介於12.93至65.21公里/日，白天洄游之平均深度為518公尺，平均溫度為9 ℃；夜晚洄游之平均深度為125公尺，平均溫度為21 ℃。在潛水能力的比較中，鱸鰻具有最佳的潛水能力（平均5.05公尺/分）。雖然設定之上浮時程為1至4個月，但所有衛星標籤都早期脫離上浮，僅記錄2至32天，而早期上浮的事件也以長期困擾著海洋生物之追蹤研究。洄游中的鰻魚會以固定的模式在海中移動，而根據數據的模式改變，有發現到兩件掠食事件，紀錄之深度分布於表層海水，且紀錄之溫度範圍較正常洄游模式狹窄，經文獻比對後判斷太平洋黑鮪是掠食者的可能性較高。本研究雖無紀錄到成功洄游至產卵場之個體，但研究結果顯示養殖鰻與野生鰻之洄游行為及路徑並無顯著差異，且路徑也與近年日本相關研究結果相符合。本研究結果也能提供日本鰻人工放流之效益評估作業一個參考依據。

關鍵字

日本鰻 ； 鱸鰻 ； 太平洋雙色鰻 ； 上浮式衛星標籤 ； 降海洄游

並列摘要

The spawning migration of the Japanese eel Anguilla japonica to the western of the Mariana Ridge is such a great animal migration. However, the migratory routes of anguillid eels in Taiwan are still uncertain. A. japonica, A. marmorata and A. bicolor pacifica are three common species in Taiwan. To set up an appropriate conservation policy, a complete life cycle study is necessary. Pop-up archival transmitting tag has been used for tracking marine animals for decades which can provide records to display the oceanic behavior of the host. In East Asia, most silver Japanese eels start their oceanic migration in autumn and winter. Twenty silver eels were tagged and released at the water of Gueishan Island and Liuchiu. In Geishan group, fourteen data were received, but only seven data provided detail records. Nine eels released at Gueishan Island entrained in Kuroshio, and the farthest pop-up distance of tag was about 1500 km at the southern water of Yakushima, Japan in 23 days. Tags used at Liuchiu had an opposite pop-up location, eels may be influenced by a recirculation at southwestern water of Taiwan. Migration speed of the eels were reported 12.93 km/d in minimum and 65.21 km/d in maximum. The average depth of daytime migration was 518 m, the average temperature was 9 ℃; the average depth of the night migration was 125 m, the average temperature was 21 ℃. All eels established diel vertical migration behavior, moving from deep water (600 m) during day time and ascended to shallower water (200 m) at night. In the comparison of diving ability, A. marmorata had the best diving ability (5.05 m/min at average). Predation event occurred on #150540 and #150545, which displayed a clear change on habitat occupation. The temperature recorded by the tags rose from 10-24 ℃ to more than 25 ℃ but under 35 ℃, so the predator were probably tuna. This study suggested that silver Japanese eels may migrate in Kuroshio, once reach Izu-Bonin Ridge they swam towards south ahead to the spawning site at the western Mariana Ridge. No significant difference on migration behavior and routes between wild eels and farmed ones. Even though the tracking study did not record an individual that successfully migrated to the spawning area, this study still showed that migrating eels chose to entrain in Kuroshio during their early migration. The results of this study can also provide a reference for the benefit assessment of releasing cultivated Japanese eel.

並列關鍵字

A. japonica ； A. marmorata ； A. bicolor pacifica ； pop-up satellite archival tag ； seaward migration

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