中国东南沿海日本鳗鲡幼体的发育时相及其迁徙路径分析

Developmental stages and migratory routes of larvae Japanese eel from southeast coastal estuaries of China

对2008年1—3月采自中国广东至江苏沿海9个河口的534尾日本鳗鲡幼体鉴定发育时相,分析了其中104尾玻璃鳗的日龄、柳叶鳗龄和抵岸龄。结果显示,中国大陆东南沿海玻璃鳗的柳叶鳗龄平均为102（90~112）d,并呈现出地域性的从南至北逐步增大的趋势。Scheffe′s多重比较可将9个群体按柳叶鳗龄的大小归为3个组,南部的新会和汕头归为第1组;中间的福清、宁德、温州、台州归为第2组;北面的慈溪、九段沙和大丰归为第3组。同样,群体的R-聚类和个体的Q-聚类分析也显示出与上述分组相一致的结果。研究表明,从产卵场随北赤道洋流迁徙至菲律宾东北部并进入黑潮接近中国东南沿海的柳叶鳗,分成3个群体迁徙。变态最早的进入了南方的水域,抵达广东沿海;变态较早的进入了中部的东海水域,抵达闽浙沿海;变态最晚的则被送到长江口及其以北的沿海河口。结果还显示,最北部大丰的平均柳叶鳗龄[（106.00±3.22）d]比最南部新会的平均柳叶鳗龄[（91.87±1.36）d]大14.13 d,其与黑潮流速（约96 km/d）的乘积（1 350 km）同两地的距离大致相等,研究表明,我国沿海的玻璃鳗在柳叶鳗阶段是随着黑潮暖流自南向北被动地迁移。

A total of 534 larvae of Anguilla japonica were collected from 9 estuaries in Guangdong,Fujian,Zhejiang,Shanghai and Jiangsu,China,during Jan.-Mar.of 2008.Their pigmentation stages were determined according to the distribution of pigments on the body surface.The age of leptocephali at metamorphosis（Tm）,time between metamorphosis to arrival at estuaries（Tt.m）,and age of glass eels（Tt） arriving at the 9 sites were counted according to the number of daily growth increments in the sagitta.The mean Tm was 102 d（90 d to 112 d） and progressively increased from south to north.The homogeneity tests for Tt,Tm and Tt-m among nine estuaries were conducted by Scheffe＇s multiple comparison method.According to sampling location and Tm value,leptocephali were divided into three homgeneous groups.Group I was located in two southern sampling sites（Xinhui and Shantou） and had the lowest Tm.In contrast,group III in the 3 northern sampling sites（Jiuduansha,Cixi,Dafeng） had the highest Tm.Group II were in the four mid-sites（Fuqing,Ningde,Wenzhou,Taizhou）.Similar result was acquired by R-cluster dendrogram of nine sampling sites and Q-cluster dendrogram of every sample based on Tm.These results indicated that the leptocephalus might migrate in three populations along the North Equatorial Current from their spawning ground to the northeastern continental shelf waters of Philippines,to Kuroshi Current and then to the estuaries of China for metamorphosis.The fast-growing leptocephali metamorphosed earlier,and migrated to the southern estuaries and then entered into Guangdong coastal rivers,while the slow-growing ones metamorphosed later,migrated to the Changjiang estuary and the northern estuaries of the range.The remaining leptocephali migrated to the middle coastal waters of East China Sea.The difference of leptocephali metamorphosis age between Xinhui [（91.87±1.36） d] and Dafeng [（106.00±3.22） d] was 14.13 d.If the leptocephali were drifted by the Kuroshio Current at a velocity of 96 km/d,the dispersal distance of the leptocephali for 14.03 d would be 1 350 km,approximately equal to the distance between Xinhui and Dafeng.These results suggest that glass eel of Chinese estuaries was passively transported by the Kuroshi Current from the south to north at their leptocephali stage.