Stable isotope ratios of nitrogen (δ15N) have been used to estimate trophic position (TP) of organisms due to the predictable enrichment of nitrogen‐15 in consumer tissues relative to their diet. We explored estimates of trophic position using liver and muscle δ15N and stomach content analysis in a broad size range of Arapaima sp. from Amazonian floodplain lakes. Estimates of TP based on liver δ15N were more closely related to the stomach content data than estimates based on muscle δ15N, possibly because of the higher turnover of nitrogen in liver. Total length and season explained most of the variation in TP values estimated from δ15N, showing that they have more effect than prey trophic position on δ15N values. The TP estimated by identification of stomach content was 3.6 and was unrelated to the size of the arapaima. This highlights the need for a better understanding of the factors that affect values of δ15N and stomach content analysis is still needed to unravel the trophic ecology of predatory fishes.

中文翻译：

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与营养鉴别因子和体型相关的不确定性使巨骨舌鱼中 δ 15 N 衍生的营养位置的计算复杂化。

氮的稳定同位素比 (δ15N) 已被用于估计生物体的营养位置 (TP)，因为相对于其饮食而言，消费者组织中可预测的氮 15 富集。我们使用肝脏和肌肉 δ15N 以及胃内容物分析在广泛的巨骨舌鱼物种中探索了营养位置的估计。来自亚马逊河泛滥平原湖泊。与基于肌肉 δ15N 的估计值相比，基于肝脏 δ15N 的 TP 估计值与胃内容物数据的相关性更密切，可能是因为肝脏中氮的周转率更高。总长度和季节解释了从 δ15N 估计的 TP 值的大部分变化，表明它们比猎物营养位置对 δ15N 值的影响更大。通过识别胃内容物估计的 TP 为 3.6，与巨骨舌鱼的大小无关。