Strontium concentrations are low in fresh waters compared to seawaters. Therefore, wild-born river-spawning and stocked freshwater-reared whitefish Coregonus lavaretus L. display regions with low concentrations of strontium in the centre of their otoliths. Strontium in otoliths from wild-born river-spawning whitefish ascending the River Tornionjoki, river-spawning whitefish stocked as one-summer-old fingerlings caught ascending the River Kemijoki, and sea-spawning whitefish caught near the Åland Islands was mapped using µ-XRF. The strontium-depleted regions in the centre of the whitefish otoliths, measured using ImageJ, had mean sizes of 0.18 ± 0.2 mm² (River Tornionjoki) and 2.3 ± 0.3 mm² (River Kemijoki), whereas the otoliths from whitefish caught at sea lacked a strontium-depleted region altogether. Measurement of the area of the strontium-depleted region in whitefish otoliths provides a convenient method with which to differentiate between whitefish of different provenance and to determine the origins of whitefish in mixed catches.

中文翻译：

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耳石的微 X 射线荧光图像分析以区分在波罗的海捕获的野生和放养的河流产卵白鲑

与海水相比，淡水中的锶浓度较低。因此，野生河流产卵和放养淡水饲养的白鲑Coregonus lavaretus L.在耳石中心显示锶浓度低的区域。使用 µ-XRF 绘制了从野生河流产卵白鲑中上升到 Tornionjoki 河的耳石中的锶、作为一夏龄鱼种在 Kemijoki 河上捕获的河流产卵白鲑以及在奥兰群岛附近捕获的海产白鲑中的锶. 使用 ImageJ 测量的白鱼耳石中心的锶耗尽区域的平均尺寸为 0.18 ± 0.2 mm ² (River Tornionjoki) 和 2.3 ± 0.3 mm ²（River Kemijoki），而在海上捕获的白鲑的耳石完全缺乏锶耗尽区域。测量白鲑耳石中锶耗尽区域的面积提供了一种方便的方法，可以区分不同来源的白鲑，并确定混合捕捞中白鲑的来源。