Freshwater fish face multiple challenges in human-altered rivers such as trace metal contamination, temperature increase and parasitism. These multiple stressors could have unexpected interactive effects on fish health due to shared physiological pathways, but few studies investigated this question in wild fish populations. In this study, we compared 16 populations of gudgeon (Gobio occitaniae) distributed along perturbation gradients in human-altered rivers in the South of France. We tested the effects of single and combined stressors (i.e., metal contamination, temperature, parasitism) on key traits linked to fish health across different biological levels using a Structural Equation Modelling approach. Parasitism and temperature alone had limited deleterious effects on fish health. In contrast, fish living in metal-contaminated sites had higher metal bioaccumulation and higher levels of cellular damage in the liver through the induction of an inflammatory response. In addition, temperature and contamination had interactive negative effects on growth. These results suggest that trace metal contamination has deleterious effects on fish health at environmentally realistic concentrations and that temperature can modulate the effects of trace metals on fish growth. With this study, we hope to encourage integrative approaches in realistic field conditions to better predict the effects of natural and anthropogenic stressors on aquatic organisms.

在人类改变的河流中，淡水鱼面临多种挑战，例如痕量金属污染，温度升高和寄生虫。由于共有的生理途径，这些多重应激源可能对鱼类健康产生意想不到的相互作用，但是很少有研究在野生鱼类种群中研究这个问题。在这项研究中，我们比较了16个种群的g体（Gobio occitaniae）沿扰动梯度分布在法国南部人为改变的河流中。我们使用结构方程建模方法测试了单一和组合压力源（即金属污染，温度，寄生虫）对与不同生物学水平上鱼类健康相关的关键性状的影响。仅寄生和温度对鱼类健康的有害影响有限。相反，生活在被金属污染的地方的鱼通过诱导炎症反应，具有更高的金属生物积累和肝脏中更高水平的细胞损伤。此外，温度和污染对生长有相互作用的负面影响。这些结果表明，痕量金属污染在环境上现实的浓度下对鱼类健康具有有害影响，而温度可以调节痕量金属对鱼类生长的影响。通过这项研究，我们希望鼓励在现实的野外条件下采用综合方法，以更好地预测自然和人为压力源对水生生物的影响。