太湖及洪泽湖太湖新银鱼耳石元素锶钙比的比较研究

Comparative study on otolith Sr:Ca ratios of Neosalanx taihuensis from Taihu Lake and Hongze Lake of China

利用元素电子显微探针分析技术,对南太湖(白雀乡水域)、北太湖(吴塘门至乌龟山水域)以及洪泽湖(老子山水域)的太湖新银鱼(Neosalanx taihuensis)的矢耳石进行了元素微化学分析,如锶及钙元素分布、积累、浓度比等特征的比较研究。元素定量线分析和面分布分析结果均直观而明显地表明,北太湖太湖新银鱼的个体可以分为两种类型,一类耳石具高锶钙比(21.41±0.50,N=4),另一类耳石具低锶钙比(1.64±0.12,N=5);南太湖个体耳石的锶钙比值居中(3.12±0.07,N=10);而洪泽湖个体耳石的锶钙比普遍偏高(5.42±0.32,N=9)。这些个体类别间锶钙比值的差异均显著(P<0.05)。此外,洪泽湖个体耳石标本有高锶环的存在,而太湖个体耳石中锶的分布水平较均一化。上述结果显示,一方面太湖和洪泽湖太湖新银鱼耳石锶钙比类型差异明显;另一方面太湖不同水域太湖新银鱼耳石的锶钙比类型亦不尽相同;反映出耳石锶钙比特征具有可以用来区别太湖新银鱼不同水域资源群体的潜力。

An electron probe microanalyzer was used to analyze the microchemistry of Sr and Ca in sagittal otoliths of the Salangid icefish Neosalanx taihuensis from southern（area of Baiquexiang） and northern（area between Wutangmen and Wuguishan） Taihu Lake,and Hongze Lake（area of Laozishan）.The results of both the life history transect analysis and X-ray intensity mapping analyses clearly showed that there were two different patterns in otolith samples of N.taihuensis from northern Taihu Lake.One was characterized by high Sr：Ca ratios（Sr：Ca×1000） with a mean value of 21.41（SD,0.50;N=4）;whereas another showed low Sr：Ca ratios with a mean value of 1.64（SD,0.12;N=5）.In contrast,mean otolith Sr：Ca ratios of the fish from southern Taihu Lake was 3.12（SD,0.07;N=10）.That of N.taihuensis form Hongze Lake was 5.42（SD,0.32;N=9）.The difference of otolith Sr：Ca ratio values was statistically significant at a 5% level among the icefish from different water areas.In addition,the X-ray intensity maps showed that the otolithes of N.taihuensis from Hongze Lake presented high Sr concentric rings,while Sr distribution in those of the icefish from Taihu Lake were almost homogeneous.The results of the present study indicated that different microchemistry patterns of otolith existed not only between the icefishes from the Taihu Lake and Hongze Lake,but also existed between the icefishes from different water areas of Taihu Lake,suggesting a possibility to separate different geographic resources of N.taihuensis by means of the different features of otolith microchemistry.