日本周边海域的深海底栖性鱼类之群聚构造

日本周边海域的深海底栖性鱼类之群聚构造 日本周邊海域的深海底棲性魚類之群聚構造、深度帶狀分布及生物地理與環境因子之相關研究 *1, 2葉信明 12 中央研究院動物研究所,東京大學海洋研究所 hmyeh@gate.sinica.edu.tw 了解群聚結構隨著梯度變化而改變的現象和原因是群聚生態學研究上的重要題目之一,其中群聚結構隨著深度而改變的現象一直是深海生物學研究的重點。1970年代以來深海生物群聚隨深度改變的現象陸續被發現並加以描述,但是對群聚結構改變的因子,卻一直很少有人提出合理的解釋。本研究的目的是對日本週邊海域的深海底棲性魚類群聚隨著深度以及水平方向的變化情形描述並對此群聚結構提出一個合理的假說,並對1970年代以來的深度帶狀分布觀念做修正。 群聚資料係以聚類和空間排序法來判斷魚類群聚在深度及地理分布方向是否有變化。在環境因子影響方面,以Detrended Correspondence Analysis(DCA) 所得的空間轉換軸上的測站座標與環境因子做Spearman rho type的Randomization test來檢驗群聚結構的梯度變化方向與環境因子是否有相關性。群聚分析的相似性指數使用Morisita-Horn Index並用non-combinatorial method來做測站間連結。 在深度方向,以群聚分析的相似性指數0.15為基準在日本東北部沿岸從大陸棚邊緣水深200公尺以下至海溝底部水深9000公尺為止共分出6個深度帶狀分布。而日本西南部沿岸從大陸棚邊緣水深200公尺以下至海盆底部水深3000公尺為止共分出4個深度帶狀分布,但是日本海的大陸棚邊緣水深200公尺以下至大陸坡(continental slope)水深1800公尺的測站間之相似度皆在0.15以下,故日本海的深海底棲魚類只有一個深度帶狀分布,與太平洋岸的2000公尺以淺有3-4個深度帶狀分布有明顯的差別。在地理分布方面,日本海形成一個獨立的生物地理區而太平洋岸在水深500公尺以淺的群聚大致以黑潮、親潮流域和黑潮、親潮的混合區一致,分為三個地理區。超過水深500公尺後,此地理區隔漸漸消失而水深超過1000公尺以下,太平洋岸變為同一地理區。日本周邊海域的深海底棲性魚類群聚結構在深度及地理分布方向變化與水溫和鹽份濃度具有非常顯著的相關性,而水溫和鹽份濃度同為水塊(water mass)的重要指標。對日本周邊海域的已知水塊構造和深海底棲性魚類群聚結構做比較時發現兩者非常吻合,故推測決定深海底棲性魚類群聚結構的因子應該為水塊構造。 COMMUNITY STRUCTURE, FAUNAL ZONATION AND BIOGEOGRAPHY OF THE DEEP-SEA DEMERSAL FISHES AROUND JAPAN, AND THEIR RELATIONSHIPS WITH ENVIRONMENTAL PARAMETERS *1, 2H.-M. Yeh 1Institute of Zoology, Academia Sinica, Nankang, Taipei 115, TAIWAN hmyeh@gate.sinica.edu.tw 2Ocean Research Institute, University of Tokyo Minamidai 1-15-11, Nakano-ku, Tokyo 164-8639, JAPAN To understand the gradient-controlled distribution is one of the principal interests in the community ecology. The depth-related faunal change is usually termed zonation. The causes of this pattern remain one of the most difficult and elusive problems faced by deep-sea ecologist. The concept of zonation has apparently been accepted among various taxonomy groups since 1970s. However, few studies have proposed the hypothesis to interpret the pattern of zonation. In this study, the vertical and horizontal patterns of deep-sea demersal fishes around Japan were discussed, and the modified concept of zonation of deep-sea demersal fish was presented. Data analysis was performed by means of a clustering technique, Morisita-Horn index and non-combinatorial method, and an ordination technique, detrended correspondence analysis (DCA). Then the correlation between the main gradients (DCA axes) and environmental variable was tested by the randomization test for Spearman’s rho correlation. The similarity level of 0.15 was used as reference points for identifying communities. Cluster analysis indicated three geographical areas; Japan Sea, North Pacific Ocean and Philippine Sea. Though the North Pacific Ocean and Philippine Sea have several typical faunal zonation deeper than 200 m, Japan Sea showed no faunal zonation and has a uniform faunal composition. Correlation of DCA axes with environmental variables showed that temperature and salinity explain main faunal groupings. Major latitudinal faunal break shallower than 500 m in the eastern coast of Japan took place in the Kashima-Soma area and was related to the frontal area between the warm, northeastward-flowing Kuroshio Current and the cold, southwestward-flowing Oyashio Current. The latitudinal faunal shift deeper than 500 m until 1,000 m takes place in Sagami Bay and is related to the southern limit of the Oyashio waters.