海洋魚類地理分布關聯性之長期變化

Abstract

不同的海洋物種的地理分布差異很大，其主要會受到物種的特徵，演化及生物地理學相關的因子，如：遷移能力和不同魚種演化相關性所影響。環境改變下，適應能力較弱的物種選擇離開原有的棲地，遷移到更適合的環境居住。物種的遷移，不僅造成個別物種地理分布的改變，同時也將造成魚類群聚組成的變化，進而可能影響海洋生態系統的平衡。但是，對於物種地理分布之間的關聯性如何影響區域性群聚結構和如何進一步造成群聚的不平衡和功能性的改變的了解還非常有限。本篇研究探討從1982至2011年，中緯度美國東北沿岸，高緯度北海以及百令海東部三個不同海洋區域群聚内的成魚之間地理分布的關係，著重了解在不同時間段，地理區域和魚種分群下，物種之間地理分布的變化。研究結果發現，所有物種和根據魚種分群的穩健性（其他物種對其依賴程度，robustness）和敏感性（對其他物種的依賴程度，sensitivity）都會隨著時間增加。另結果發現中緯度美國東北沿岸的魚類群聚結構有相對較多的對稱性結構且物種之間的相關性較強，高緯度的北海和百令海東部則大部分呈現不對稱性結構且物種之間的相關性則較弱；但是在三個10年的時間段卻未發現顯著變化。根據共同出現物種對的不對稱性貢獻，發現中緯度美國東北沿岸的常見物種（common species）在30年間有逐漸偏向對稱分布。總結，海洋魚類在這30年内的地理分布關聯性會隨著時間增加且不同緯度的魚類群聚在地理分布不對稱重疊模式會不同。根據中緯度美國東北沿岸有較多對稱性結構的結果推測此區域的群聚結構比較不穩定，在環境變遷下將會面臨更大的危機。本研究加入海洋魚類地理分布之間的關聯性，探討並了解環境變遷下魚類群聚的變化，對未來海洋魚類群聚受到環境變遷影響的評估和漁業管理提供了新的觀點。

The geographical distributions of individual marine species vary substantially in extent, and this variation can be determined by its current traits and by phylogenetic and biogeographic factors such as dispersal ability and phylogenetic relatedness of different marine fish species. Species with low adaptive ability will no longer stay in their current habitat and migrate to a new geographical location with more suitable environment under environmental change. The migration of species not only cause changes in their geographical distribution but also changes in the composition of the fish community, which may further affect the balancing of the whole marine ecosystem. However, there is still relatively limited knowledge of how the correlation between the geographical distribution of species affects regional community structures and how they further cause community imbalances and functional changes. Here, I investigated geographical interactions of marine adult fish species in the mid-latitude Northeast US coast, the high-latitude North Sea and the Eastern Bering Sea from 1982 to 2011 and focused on exploring the geographical distribution changes between species in different time periods, geographical regions and fish species groups. The results of overall species and different fish species groups indicated that robustness and sensitivity of the three time periods increased. More symmetrical structure and stronger species interactions were found in the mid-latitude Northeast US coast than the high-latitude North Sea and the Eastern Bering Sea marine fish communities, but there were no significant differences over three decades in each community. According to the contribution of cooccurring species pairs to asymmetry, asymmetry structures of common species pairs in mid-latitude Northeast US coast were tended to be symmetrical over three decades. We concluded that results of long-term geographical interaction within 30 years and both robustness and sensitivity in species groups had increased with time and their geographical overlapping asymmetry may vary in the aspect of latitudes. The finding of highly symmetrical community structure in the Northeast US coast suggests that the mid-latitude marine fish community may be more unstable and particularly face a high risk under environmental changes. Taking the geographical interactions of marine fish species into account will provide a new perspective on exploring the changes in marine fish communities under environmental change and crucial for the development of climate change impact assessment and also fisheries management in the future.