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海洋魚類通常在不同的棲息地之間過渡在他們的一生,這種棲地的遷移行為在仔魚期特別的顯著,棲地環境轉變對魚類的攝食及成長有顯著的影響。理解棲息地使用的性質、族群在棲息地間遷移行為是建立管理的關鍵,然而追蹤具有生態及經濟重要性的物種之棲息地極具挑戰性。傳統的標記方法需要耗費大量人力物力,並有高自然死亡率的問題。應用耳石微化學等生物追蹤技術是有利的工具,可應用於個體運動解析,近年來主要著重於探索分辨族群,而不是個別魚類的棲地選擇及移動模式。這個計畫主要在透過實驗室內模擬、觀察,制定一套新方法的理論模型,使用耳石微化學等生物追蹤技術來探索海洋魚類棲息地的轉變,本計畫第一年以鯖魚作為模式物種,探討耳石微化學的氧同位素作為標識器替代之可行性,收集ICES歷年產卵資料以阿麗亞娜執行海洋環流模型為尼莫(NEMO)進行洄游的路徑模擬,後估算耳石氧同位素數值,並進行分析不同之迴游路徑間之氧同位素是否呈現不同之趨勢。結果顯示,東北大西洋鯖魚可分為主要四個不同的洄游路徑,分別為第一型沿著愛爾蘭海往北海迴游,第二型則是順著沿岸流沿著愛爾蘭西岸迴游,第三型則是向南洄游,第四型為持續滯留於愛爾蘭島之南部,不同迴游型在夏季時所經歷之溫度差異不大,至秋季後始顯現明顯的區別,耳石氧同位素亦反應了明顯不同的趨勢,表明耳石氧同位素具有作為生物追蹤之潛力。

Marine fishes commonly transition between distinct habitats throughout their lifetime, particularly in larval and juvenile life stages. Such transitions are essential as the environmental demands and predation pressures experienced by fishes change dramatically with increases in body size. Understanding the nature of habitat use, habitat connectivity and ontogenetic timing of habitat transitions is key to establishing management practices covering whole life histories for commercially, recreationally and ecologically significant species. Tracing migrations of larval and juvenile fishes in coastal habitats are extremely challenging. Fishes are too small for most conventional tagging approaches and high natural mortality means large tagging programs are needed. Otolith reading and microchemistry is an attractive alternative for reconstructing high-resolution movements, where fishes move across chemical gradients. Until recently otolith microchemistry has largely focused on discriminating between populations rather than exploring temporal trends within individual fish. This project will build on recent collaborative experimental, observational and theoretical work to develop new approaches to using otolith microchemistry to explore habitat transitions in marine fishes. In the first year of the project, we used mackerel(Scomber scombrusas) as a model species to explore whether otolith oxygen isotope could be a replacement for the tag. Firstly, we collected egg surveys from ICES. Secondly, we used Ariane and the ocean circulation model Nemo (NEMO) to stimulate the migration path of mackerel and then applied the environmental data to calculate otolith oxygen isotope value. The last part is that we analyzed the differences between different migratory paths. The results show that the mackerel could be divided into four main type of migration routes. The first type of migration is traveling along the Irish Sea to the North Sea, and the second type is following the coast along the west coast of Ireland. The third type is migrate toward the south, and the fourth type is remaining in the southern part of the island of Ireland. The figure of temperature which was experienced by different types of migratory types shown little difference in summer. However, after the fall, the figure was clearly different. The otolith oxygen isotope also reflects the difference. It is indicated that otolith oxygen isotopes have potential as bio-tracking.