以耳石微細結構與穩定性碳氧同位素組成探討深海底棲性魚類之發育垂直遷徙

Abstract

重建深海底棲魚類各生活史階段的深度變化有助於了解深海魚類的生活史策略，過去的資料多半依賴捕撈的紀錄，因此各生活史階段的深度分布依然相較缺乏。耳石的微細結構以及穩定性氧同位素，對於探討發育垂直遷徙是個有效的工具，本研究使用的材料包含由研究船採集自台灣東北部海域的魚類樣本、大溪漁港和委託長濱漁民採集的樣本，一共分析了7科10種深海底棲魚類，並且與先前的研究結果整合分析，從個體層次探討物種發育垂直遷徙之生活史。研究結果顯示耳石的δ13C與δ18O分別反映代謝速率與環境溫度的變化，且能夠重建個體的發育垂直遷徙行為，並推算各生活史之深度變化，而與過去研究相比，笛鯛科(Lutjanidae)、鰧科(Uranoscopidae)、青眼魚科(Chlorophthalmidae)及黃魴鮄科(Peristediidae)的模式較常見，大致上隨著成長，棲息深度逐漸增加，不過軟腕魚科(Ateleopodidae)，稚魚時會向深處遷徙，在日齡約63天時達到最深(600-1300 m)，隨後棲息深度回到較淺的200公尺海域、發光鯛科(Acropomatidae)的赤鯥(Doederleinia berycoides)有類似季節性的垂直遷徙行為與獅子魚科(Liparidae)的暗色微盤獅子魚(Elassodiscus obscurus)則是早期待在較深水域 (1500 m)，之後回到約600 m的深度。結合本研究結果與先前已完成的論文，發現魚類發育垂直遷徙的距離與成體棲息深度可依生殖模式(reproduction mode)區分：產浮性卵與胎生的物種多為正相關，而以大型卵為生殖模式的黑頭魚科(Alepocephalidae)與暗色微盤獅子魚則無相關。不過在本研究發現有少數的例外，如軟腕魚科的物種，其成體雖然棲息不深，但發育垂直遷徙的距離卻非常的大；黑首燧鯛(Hoplostethus melanopus)幾乎沒有發育垂直遷徙的行為。本研究顯示，發育垂直遷徙為深海魚類適應深海環境之重要策略，並且呈現多樣性變化。

Reconstructing ontogentic vertical migration (OVM) of deep sea demersal fishes is useful to understand their life history strategies. Nevertheless, information of the depth distribution at each life history stages of deep-sea fish is still scarce based on limited catching records. Otolith microstructure and stable isotope analyses are effective tools to study OVM of fish. Fish samples were collected by R/V Ocean Researcher I, from DaiShi harbor or by a fisherman in ChangBin. In this study, we analyzed the otolith microstructure and isotopic composition for 10 fish species belonged to 7 families. We compared our data to published data in order to provide a comprehensive understanding of OVM among species. The results suggest otolith δ13C and δ18O reflect metabolism and environmental temperature respectively, which can be used to reconstruct individual OVM. The residing depth distribution of the fish at each life history stages can be deduced from otolith δ18O. Lutjanidae, Uranoscopidae, Chlorophthalmidae and Peristediidae have OVM similar to other species analyzed in previous studies that showed a gradual migration to deeper water. Jellynose fish (Ateleopodidae), blackthroat seaperch (Doederleinia berycoides), and Elassodiscus obscurus showed unique OVM. Juveniles of jellynose fish migrated from ocean surface down to depths (600-1300 m) at around 63 days, then the fish rose quickly to around 200 m. D. berycoides showed up and down OVM among seasons and years. E. obscurus inhabited at 1500 m depth during early life stage then migrated to around 600 m depth. The relationship between distance of OVM and adult residence depth varied among species with different reproduction modes. Positive correlations were found for viviparous species and that produce pelagic eggs. However, no correlation was found in Alepocephalidae and E. obscurus that lay larger eggs. Some exceptions were found in jellynose fish and Hoplostethus melanopus. The formal had a long distance of OVM but depth of adult’s habitat is shallow and the latter did not showed OVM. This research revealed diversified OVM for deep sea fish, suggesting different strategies were evolved to cope with the harsh environments in the deep seas.