The Baltic Sea is a unique ecosystem and the largest body of brackish water in the world. It is inhabited by several originally freshwater fish species, one of them being pike (Esox lucius), which is adapted to the mesohaline conditions of the southern Baltic Sea and colonises its south‐western bays and lagoons. Using twelve microsatellite markers, we analysed the genetic structure of 407 Baltic Sea pike collected from ten locations in the coastal zone of the southern Baltic region and adjacent rivers and nearby lakes. We used traditional F‐statistics and a Bayesian approach implemented in STRUCTURE to investigate spatial structuring. Our results show an overall isolation by distance pattern with two distinct coastal clusters. The border area between the two clusters is characterised by a sharp salinity leap, indicating that the dispersal barrier is not physical, but physiological in nature. A third cluster was formed by three lake populations, presumably as a result of past stocking measures. Additional otolith microchemical studies demonstrate the brackish origin and residency of the majority of the pike from the coastal lagoons, supporting previous studies which suggest that the anadromous pike “ecotype” is scarce in this area of the Baltic Sea. Our results contribute to current knowledge on the population genetics of Baltic Sea pike in a previously unsampled area.

中文翻译：

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波罗的海南部咸咸泻湖中的长矛（Esox lucius Linnaeus，1758）的遗传种群结构

波罗的海是一个独特的生态系统，是世界上最大的微咸水。它栖息着几种原始的淡水鱼类，其中一种是梭子鱼（Esox lucius）），适应波罗的海南部的中盐环境，并在其西南海湾和泻湖定居。我们使用了十二个微卫星标记，分析了从波罗的海南部地区沿海地区的十个地点以及邻近的河流和附近湖泊收集的407波罗的海梭的遗传结构。我们使用传统的F统计和在结构中实施的贝叶斯方法来研究空间结构。我们的结果表明，按距离模式将整个隔离起来是两个截然不同的沿海集群。两个簇之间的边界区域的特征是盐度急剧上升，这表明分散障碍不是物理的，而是生理上的。第三群是由三个湖泊人口组成的，大概是由于过去的放养措施造成的。额外的耳石微化学研究表明，来自沿海泻湖的大多数派克微咸的起源和居住地，支持先前的研究，表明波罗的海这一地区稀缺的派克“生态型”稀缺。我们的研究结果有助于了解以前未采样地区的波罗的海派克种群遗传学。