Data from: Oxygen and carbon isoscapes for the Baltic Sea: testing their applicability in fish migration studies

Conventional tags applied to individuals have been used to investigate animal movement, but these methods require tagged individuals be recaptured. Maps of regional isotopic variability known as “isoscapes” offer potential for various applications in migration research without tagging wherein isotope values of tissues are compared to environmental isotope values. In this study, we present the spatial variability in oxygen (math formula) and dissolved inorganic carbon (δ13CDIC) isotope values of Baltic Sea water. We also provide an example of how these isoscapes can reveal locations of individual animal via spatial probability surface maps, using the high-resolution salmon otolith isotope data from salmon during their sea-feeding phase in the Baltic Sea. A clear latitudinal and vertical gradient was found for both math formula and δ13CDIC values. The difference between summer and winter in the Baltic Sea math formula values was only slight, whereas δ13CDIC values exhibited substantial seasonal variability related to algal productivity. Salmon otolith δ18Ooto and δ13Coto values showed clear differences between feeding areas and seasons. Our example demonstrates that dual isotope approach offers great potential for estimating probable fish habitats once issues in model parameterization have been resolved.

传统个体标记技术曾被用于探究动物移动规律，但此类方法需要对已标记个体进行重捕方可开展后续研究。被称为『同位素分布图（isoscapes）』的区域同位素变异性图谱，无需对动物进行标记即可应用于迁徙研究的诸多场景，其核心逻辑为将生物组织的同位素值与环境同位素值进行比对。本研究针对波罗的海海水的氧同位素（math formula）与溶解无机碳（δ¹³CDIC）同位素值的空间变异性展开分析。本研究还依托波罗的海海域海洋摄食阶段鲑鱼的高分辨率耳石同位素数据，展示了如何通过空间概率表面图谱，利用此类同位素分布图推断个体动物的栖息位置。研究发现，氧同位素（math formula）与δ¹³CDIC值均呈现显著的纬度与垂向梯度特征。波罗的海海水的氧同位素（math formula）值在冬夏两季仅存在微小差异，而δ¹³CDIC值则表现出与藻类生产力相关的显著季节性波动。鲑鱼耳石的δ¹⁸Ooto与δ¹³Coto值在不同摄食区域与季节间均存在明显差异。本研究案例表明，一旦解决模型参数化相关问题，双同位素方法在估算鱼类潜在栖息生境方面具备巨大应用潜力。