Abstract Carbon (δ13C) and nitrogen (δ15N) stable isotope analyses are used in marine ecology to study trophic relationships and migrations of species since they reflect dietary sources consumed which may vary geographically. However, better estimations of isotope incorporation rates and trophic discrimination factors (TDF) under controlled conditions are required. Moreover, variability of isotope incorporation rates and TDF among and within populations has been poorly described, especially in fish scales, whereas the use of non-lethal method is becoming a standard. This study aimed to experimentally assess whether carbon and nitrogen isotope incorporation rates (λC and λN, respectively) and TDF of scales vary in the European sea bass (Dicentrarchus labrax) among (1) Atlantic, West Mediterranean and East Mediterranean populations, (2) sexes and (3) individuals. Fish were reared under controlled conditions and switched from a diet 1 to a diet 2 with different δ13C and δ15N values. Scales were sampled repeatedly on 16 fish within the three populations, from the day of diet change (day 0) to the end of the experiment (day 217). Isotope incorporation rates of scales and TDF were determined using a time-dependent model. Isotopic carbon and nitrogen half-lives (t50C and t50N) were similar among the three populations but males had significantly lower t50C and t50N than females (29 ± 2 and 35 ± 2 days vs. 53 ± 7 and 80 ± 11 days, respectively). Females had higher growth rates but lower catabolic rates than males. Variability of λC and λN was large within sexes: t50C ranged from 17 to 159 days and t50N ranged from 18 to 342 days among individuals. Thus, variability between sexes and among individuals must be considered to avoid misinterpretation in field-based studies. For the 48 fish, TDF were 4.91 ± 0.03 and 2.46 ± 0.06‰ for carbon and nitrogen, respectively, and similar between sexes and among populations. Besides, TDF varied among individuals from 2.95 to 5.59‰ and from 0.93 to 3.55‰ for carbon and nitrogen, respectively. Empirical mixing models were run to estimate how different TDF influenced estimation of the contributions of food sources to diet of their consumer. The output differed considerably when using TDF from fish literature or those estimated herein, which confirms that a tissue-specific TDF must be used to avoid misinterpretation in field-based studies. Individual variation in TDF did not, however, influence estimation of the contributions of food sources, confirming that scales are a valid tissue for non-lethal sampling.

中文翻译：

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三个欧洲鲈鱼（Dicentrarchus labrax）种群尺度中碳和氮稳定同位素的同位素掺入率和营养鉴别因子的变化

摘要 碳 (δ13C) 和氮 (δ15N) 稳定同位素分析用于海洋生态学研究物种的营养关系和迁移，因为它们反映了可能因地理而异的饮食来源。然而，需要在受控条件下更好地估计同位素掺入率和营养鉴别因子 (TDF)。此外，种群之间和种群内同位素掺入率和 TDF 的可变性的描述很差，尤其是在鱼鳞中，而使用非致死方法正在成为一种标准。本研究旨在通过实验评估 (1) 大西洋、西地中海和东地中海种群中的欧洲鲈鱼 (Dicentrarchus labrax) 的碳和氮同位素掺入率（分别为 λC 和 λN）和 TDF 是否不同，(2) 性别和 (3) 个人。在受控条件下饲养鱼，并从饮食 1 切换到具有不同 δ13C 和 δ15N 值的饮食 2。从改变饮食的那天（第 0 天）到实验结束（第 217 天），对三个种群中的 16 条鱼进行了重复采样。使用时间依赖模型确定标度和 TDF 的同位素掺入率。三个种群的同位素碳和氮半衰期（t50C 和 t50N）相似，但雄性的 t50C 和 t50N 显着低于雌性（分别为 29 ± 2 和 35 ± 2 天 vs. 53 ± 7 和 80 ± 11 天） . 与男性相比，女性的增长率较高，但分解代谢率较低。λC 和 λN 的变异在性别中很大：t50C 的范围为 17 至 159 天，t50N 的范围为 18 至 342 天。因此，必须考虑性别和个人之间的差异，以避免在实地研究中产生误解。对于48条鱼，碳和氮的TDF分别为4.91±0.03和2.46±0.06‰，性别之间和种群之间相似。此外，碳和氮的 TDF 因人而异，分别为 2.95 到 5.59 ‰ 和 0.93 到 3.55 ‰。运行经验混合模型来估计不同的 TDF 如何影响对食物来源对其消费者饮食贡献的估计。当使用来自鱼类文献或本文估计的 TDF 时，输出有很大不同，这证实必须使用组织特异性 TDF 以避免在实地研究中产生误解。然而，TDF 的个体差异并不影响对食物来源贡献的估计，