以環境 DNA 分析日本鰻和鱸鰻於台灣河川之分佈

Abstract

近數十年來，因為過漁、棲地破壞及氣候變遷的影響，鰻鱺屬 (genus Anguilla)物種的族群數量發生了迅速的下降，國際間越來越關注它們的保育問 題，並將其中數種列入國際自然保護聯盟(IUCN)瀕危物種紅色名錄中。然而， 監測這些物種的族群動態卻面臨著非常多的挑戰，因為鰻鱺屬物種有著非常複 雜的生活史，難以捉摸的習性且不易於觀察及捕捉。為了評估台灣河川常見的 兩種鰻鱺屬物種:日本鰻 (Anguilla japonica)、鱸鰻 (A. marmorata) 的分佈，本 實驗使用環境 DNA (eDNA) 分析方法，針對台灣 36 條河川流域之中下游水體進 行樣本採集，並在鳳山溪與石門溪之上中下游流域，同時進行電氣採捕及分析 水體鰻魚 eDNA，並進行比較。在電氣採捕調查中，本研究發現日本鰻多選擇 棲息於中下游區域，而鱸鰻則偏好選擇棲息於中上游區域。通過eDNA 分析結 果也發現，中下游能檢測到日本鰻及鱸鰻 eDNA 的存在，中上游能檢測到鱸鰻 eDNA 的存在，支持日本鰻傾向棲息於河口及下游流域，鱸鰻則傾向棲息於中 上游流域。儘管在有些研究區域未捕捉到日本鰻及鱸鰻，但仍然可以檢測到其 eDNA，表明了 eDNA 分析對此兩種物種有高靈度，是檢測河流中日本鰻及鱸 鰻的有利工具。我們也在數據的分析中發現，鰻魚豐度與 eDNA 樣本濃度無顯 著的相關性，eDNA 分析可能無法有效分析野外物種的生物數量。 本實驗首次針對台灣各大河川，進行了日本鰻及鱸鰻 eDNA 的大範圍檢測， 發現有數條河川能檢測到 eDNA 的存在，且多數情況可以於同一條河川檢測到鱸鰻與日本鰻之 eDNA。西部河川相較於東部河川更難檢測到 eDNA 的存在， 其原因可能為棲地的破壞及河川的水文差異。本研究表明eDNA 分析對於檢 測鰻鱺屬物種，有著高靈敏度和潛力，是用於調查鰻鱺屬於淡水流域中分佈的 強大工具。eDNA 分析與傳統採集技術相比，大幅減少了時間及人力，可以為 瀕危物種的族群監測，提供重要的參考。

In the last decades, due to overfishing, habitat destruction and global climate change, genus of Anguilla species experiences a remarkable decline in population. International grows more concern on their conservation, therefore listing them in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. However, population dynamics monitoring of Anguillid species shows many challenges because they have a very complex life history, elusive habits, and not easy to observe and capture. In order to evaluate the distribution of two common eel species: Japanese eel (A. japonica) and Marbled eel (A. marmorata) in Taiwan’s river basins, we collected samples from water bodies in the middle and lower reaches of 36 river basins in Taiwan, and electric fishing and eDNA analysis were conducted from the upper, middle and lower reaches of Fengshan and Shimen Rivers for comparison. In this experiment, we found that Japanese eels mostly choose to inhabit the middle and lower river reaches, while Marbled eels prefer to inhabit the middle and upper reaches. eDNA of Japanese eels and Marbled eels could also be detected in the middle and lower reaches, supporting Japanese eels tend to inhabit estuaries and lower reaches, while Marbled eels tend to inhabit the middle and upper reaches. Although Japanese eels and Marbled eels were not captured in some study areas, their eDNA could still be detected, indicating that eDNA analysis has high sensitivity for these two species and is a useful tool for the detection of Japanese eels and Marbled eels in rivers. We also found no significant correlation between eel abundance and eDNA sample concentration, indicating that eDNA analysis may not be a valid method in analyzing the biomass of wild species. This experiment is the first to use eDNA analysis method in a large scale to detect the eDNA of Japanese eel and Marbled eel in multiple rivers of Taiwan. We found theexistence of eDNA can be detected in several rivers, and in most cases, the eDNA of Japanese eel and Marbled eel can be detected in the same river. The presence of eDNA was more difficult to detect in western rivers than in eastern rivers, which may be due to the habitat destruction and hydrological differences in the rivers. This study demonstrates the high sensitivity and potential of eDNA analysis for the detection of eel species in freshwater basins, and is a powerful tool for investigating the distribution of eel. Compared with traditional collection techniques, eDNA analysis reduces time and labor, and provides an important reference for managing the population of endangered species.