臺灣東北及西南海域底棲魚類之發育垂直洄游

海洋多數硬骨魚不論成魚是浮游型還是底棲型，幼魚通常屬於浮游型，幼魚的垂直分佈直接影響其生存(例如避敵、捕食)及運動(例如漂流至繁殖場)。就底棲魚類來說，產大量小型卵的物種一般預期幼魚屬於浮游型且會表現發育垂直洄游；相反的，產少量大型卵的物種及胎生物種一般預期幼魚屬於底棲型且未經歷發育垂直洄游。然而並非所有底棲魚類符合上述模式，本研究重建8種底棲魚類發育過程中的棲息深度及相對代謝率，包含日本尖牙鱸(Synagrops japonicus)、短鯒(Parabembras curta)、單棘躄魚(Chaunax fimbriatus)、黑口鮟鱇(Lophiomus setigerus)、小鰭新燈魚(Neoscopelus microchir)、單斑新鼬魚(Neobythites unimaculatus)、凹鰭牛尾魚(Kumococius rodericensis)、尖棘角魚(Pterygotrigla hemisticta)。樣本由臺灣東北或西南海域的商業性底拖漁船捕獲。耳石因為終生持續生長且沉積後的性質不易受代謝影響而成為理想材料，耳石碳酸鈣的穩定碳氧同位素比值分別為代謝率及水溫的指標，水溫可用於重建棲息深度。根據估計的棲息深度得知單棘躄魚(Chaunax fimbriatus)及尖棘角魚(Pterygotrigla hemisticta)的早期生活史屬於浮游型，8種底棲魚都會經歷發育垂直洄游(深度都在500公尺內)，符合浮游型早期生活史。發育垂直洄游的模式可分為5類，第一類：直接下沉至成魚深度，並無回升；第二類：下沉超出再回升至成魚深度；第三類：有兩次下沉，第一次會回升至表層，第二次會持續至成魚深度；第四類：先上浮再下沉至成魚深度；第五類：終生持續上下振盪。黑口鮟鱇(Lophiomus setigerus)、小鰭新燈魚(Neoscopelus microchir)、單斑新鼬魚(Neobythites unimaculatus)、尖棘角魚(P. hemisticta)的發育垂直洄游模式都存在個體差異。此外，沉降距離與成魚棲息深度呈現非常高度正相關(r > 0.9)，本研究除了揭露發育垂直洄游的模式存在種內多樣性，也顯示浮游型早期生活史伴隨發育垂直洄游是海洋底棲魚的一種生存策略。

關鍵字

底棲魚類；早期生活史；發育垂直洄游；耳石；穩定同位素

並列摘要

A large majority of marine teleostean fishes have a pelagic larval stage whether they’re pelagic or demersal as adults. The vertical distribution of fish larvae in the water column directly affects their survival (e.g. predator avoidance, prey capture, drift to nursery grounds). In terms of demersal fish, the species with numerous small eggs are associated with pelagic larvae and ontogenetic vertical migration (OVM). In contrast, viviparous species and the species with a few large eggs are associated with demersal larvae without OVM. However, not all demersal fishes follow this pattern. This study aims to reconstruct the ontogenetic shifts in residence depth and relative metabolic activity of 8 demersal fishes, including blackmouth splitfin (Synagrops japonicus), matron flathead (Parabembras curta), tassled coffinfish (Chaunax fimbriatus), blackmouth angler (Lophiomus setigerus), shortfin neoscopelid (Neoscopelus microchir), onespot cusk (Neobythites unimaculatus), spiny flathead (Kumococius rodericensis) and blackspotted gurnard (Pterygotrigla hemisticta). They were caught by the commercial trawlers operating in the northeastern or southwestern waters of Taiwan. Sagittal otolith is a proper material due to its continuous growth throughout ontogeny and metabolic inertness after deposition. The stable isotope ratios of carbon (δ13Coto) and oxygen (δ18Ooto) in otolith aragonite are the proxies of metabolic rate and water temperature (and thus depth) experienced by the fish, respectively. The estimated residence depths reveal the pelagic early life history of tassled coffinfish (Chaunax fimbriatus) and blackspotted gurnard (Pterygotrigla hemisticta). Each of the 8 fishes underwent ontogenetic downward migration within 500 m depth, which is consistent with the pelagic early life history. The pattern of OVM can be classified into 5 types. Type I: descend directly to the residence depths of adults without return; Type II: descend beyond and return to the residence depths of adults; Type III: descend and return before the final descent to the residence depths of adults; Type IV: ascend and descend to the residence depths of adults; Type V: continuously fluctuate throughout the lifetime of fish. Furthermore, individual variations in the pattern of OVM are found in blackmouth angler (Lophiomus setigerus), shortfin neoscopelid (Neoscopelus microchir), onespot cusk (Neobythites unimaculatus) and blackspotted gurnard (P. hemisticta). Moreover, a very high positive correlation (r > 0.9) exists between the distances of descent and the residence depths of adults. This study not only reveals the intraspecific diversity in the pattern of OVM but also demonstrates that pelagic early life history coupled with OVM is a survival strategy of marine demersal fishes.

並列關鍵字

demersal fish ； early life history ； ontogenetic vertical migration ； otolith ； stable isotope

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國際替代計量

臺灣東北及西南海域底棲魚類之發育垂直洄游

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