整合環境DNA與傳統採樣方法提升翡翠水庫魚類相解析及入侵物種偵測

Abstract

魚類相監測對於確保水庫水質與生態系統韌性至關重要，然而傳統調查方法容易低估隱蔽或稀有物種的存在。環境DNA（eDNA）技術具備更高靈敏度，但其可靠度需考量情境因素。本研究首度於台灣北部重要水源，翡翠水庫，應用eDNA技術評估魚類相變化，並整合長期傳統調查結果以驗證兩種方法的可靠性與互補性。eDNA共偵測出36種魚類，除涵蓋傳統方法記錄的全部物種外，更新增8水庫新紀錄物種。兩種不同方法呈現顯著魚類相結構差異：eDNA可全面偵測所有魚種，也偵測到原被認定已消失之原生魚種，傳統方法則傾向偵測大型入侵物種。其中原產於中美洲之外來入侵種—花身副麗魚（珍珠石斑，Parachromis managuensis）於2014年首次在翡翠水庫被記錄，其族群數量自2018年後顯著增加，顯示整體生態系統平衡可能正發生轉變。胃內含物分析顯示，其主要攝食原生甲殼類及小型魚類，顯示其可能對原生生物造成生態衝擊。生長分析結果顯示，其呈現負異速生長（negative allometric growth），且大型個體出現生長遲滯現象。透過eDNA進行調查不僅使調查到的魚種更為全面，更能從水生動物相的組成切合水質變化，以協助水庫建立更完整的基礎資料，並有利於以生物指標對應水質狀況的參數建立，作為提供水庫水源保護與管理策略之重要參考依據。

Assessing fish assemblage dynamics serves as a critical proxy for safeguarding reservoir water quality and enhancing ecosystem resilience. However, conventional capture-based surveys frequently fail to detect low-abundance or cryptic species. Environmental DNA (eDNA) offers a highly sensitive, rapid alternative for biodiversity monitoring. Here, we present the first application of eDNA metabarcoding in the Feitsui Reservoir to evaluate fish community composition and benchmark its performance against long-term traditional surveys (TD). A total of 36 fish species were detected using eDNA, including all species recorded by traditional methods and 8 newly recorded species. eDNA was more effective at detecting native and small species and covered all species collected by traditional capture-based methods, whereas traditional methods were biased toward capturing big sized invasive species. Among the invasive species detected, the jaguar cichlid (Parachromis managuensis) has expanded significantly since its first record in 2014, reflecting ongoing shifts in the fish assemblage. Stomach content analysis confirmed predation on native crustaceans and fishes, underscoring its potential ecological impacts. Furthermore, growth performance revealed negative allometric growth and growth retardation in larger individuals. Collectively, our results validate eDNA as a highly effective approach for capturing fish diversity and ecosystem alterations, offering a vital framework for reservoir biodiversity conservation and water quality governance.