This study assesses the use of stable isotopes (δ¹³C and δ¹⁵N) and trace elements in gills (G), liver (L), and muscle (M) of the most commercially important migratory fish from the La Plata Basin, Prochilodus lineatus, as habitat proxies. With this purpose, fish and sediment (S) samples from the Paraná River and Río de la Plata Estuary were analyzed. Results showed differences in the stable isotopic ratios in fish tissue and sediments between the river and the estuary. In particular, δ¹⁵N values of the estuary samples were significantly lower (G = 7.38‰; L = 6.60‰; M = 8.61‰ and S = 4.36‰) than those from the river (G = 11.30–11.53‰; L = 11.03–12.35‰; M = 11.27–11.31‰, and S = 6.78–7.72‰), which could denote a shift in the isotopic baseline between these environments. Quadratic discriminant analysis effectively discriminates between sampling sites with high classification rates (L = 97.5%; G = 90%, and M = 82.5%), suggesting that combining stable isotopes and trace elements is useful to discriminate between fish populations. The liver was the most suitable tissue as a habitat indicator, using mainly δ¹⁵N, δ¹³C, Cr, and Hg as natural markers, and capable of discriminating between sites with a relatively high geographic resolution. Due to the spatial isotopic heterogeneity found in the La Plata Basin, these natural markers could be useful for studying other aquatic organisms' habitat use.

中文翻译：

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生物地球化学多标签方法通过河口系统揭示大型洄游鱼类的栖息地利用

本研究评估了稳定同位素（δ ¹³ C 和 δ ¹⁵ N）和微量元素在来自拉普拉塔盆地的最具商业价值的洄游鱼类的鳃 (G)、肝脏 (L) 和肌肉 (M) 中的使用，Prochilodus lineatus，作为栖息地代理。为此，对来自巴拉那河和拉普拉塔河口的鱼类和沉积物 (S) 样本进行了分析。结果表明，河流和河口之间鱼类组织和沉积物的稳定同位素比存在差异。特别是δ ¹⁵河口样品的N值（G=7.38‰；L=6.60‰；M=8.61‰和S=4.36‰）显着低于河流（G=11.30-11.53‰；L=11.03-12.35‰； M = 11.27–11.31‰，S = 6.78–7.72‰），这可能表示这些环境之间的同位素基线发生了变化。二次判别分析可有效区分具有高分类率（L = 97.5%；G = 90% 和 M = 82.5%）的采样点，表明结合稳定同位素和微量元素有助于区分鱼类种群。肝脏是最适合作为栖息地指标的组织，主要使用 δ ¹⁵ N、δ ¹³C、Cr 和 Hg 作为天然标记，能够区分地理分辨率相对较高的站点。由于在拉普拉塔盆地发现的空间同位素异质性，这些天然标记可用于研究其他水生生物的栖息地利用。