为了解长江靖江段两种刀鲚生态型长颌鲚与短颌鲚的生境履历的不同,利用X射线电子探针微区分析技术研究采集自长江靖江江段的长颌鲚和短颌鲚个体耳石的锶和钙微化学特征.定量分析结果显示,短颌鲚个体的耳石锶、钙比值(即Sr/Ca×10^3)稳定在2.00左右,反映了其在纯淡水生活的习性;而长颌鲚的锶、钙比值波动显著,不仅具有对应淡水生活的低值(1.18±0.48-2.11±0.94),还具有对应半咸水生活的高值(3.39±0.60-6.79±1.13),反映了其溯河洄游的生活习性.短颌鲚因在淡水生活,其淡水系数(FC)值均为1.00,2013年和2014年长颌鲚的FC值分别为0.36±0.06和0.50±0.11,证明了长颌鲚与短颌鲚群体间存在差异,而且长颌鲚不同年份群体间也并不相同.长颌鲚和短颌鲚的洄游模式存在显著差异,同时不同年份间的长颌鲚也存在生境履历差异.靖江段长颌鲚资源群可能来自不同出生地起源及生活史背景不同的群体.该江段是两类刀鲚的重要栖息地或洄游通道.
In order to explore the different ecotypes in the life history of tapertail anchovy between its Coilia nasus and C. brachygnathus which live in Jingjiang section of the Yangtze River,an electronic probe microanalyzer was applied to analyze the microchemistry patterns of element Sr and Ca in otoliths of these two fishes collected from the Jingjiang section of the Yangtze River. Analysis results on the line transect showed that the Sr / Ca ratio( i. e.,Sr / Ca × 10^3) in the otolith of C. brachygnathus was consistently low( around 2. 00),indicating that these individuals experienced in freshwater habitat during its whole life. In contrast,C.nasus had a fluctuation pattern of Sr / Ca ratio in the otolith from low to high,suggesting the individuals experienced not only in the freshwater,but also in the brackish water at different stages in their life history. All these differences could be well confirmed by the freshwater coefficient( FC). The value of FCin the C. brachygnathus was 1. 00,and in contrast,the values of FCin the C.nasus for the individuals collected in 2013 and 2014 were 0. 36 ± 0. 06 and 0. 50 ± 0. 11,respectively. It confirmed an obvious difference of life history between C. nasus and C. brachygnathus,as well as C. nasus collected between different years. The present study demonstrated that the migration patterns were significantly different between C. nasus and C. brachygnathus,as well as C. nasus collected in 2013 and 2014. The resource of C. nasus in Jingjiang section might originate from different stocks with different natal waters and life history background. The water ecotypes in Jingjiang section of the Yangtze River must be the important habitat or migration channel for both tapertail anchovy.