In the aquatic environment, fish are subject to different pollutants and environmental variations that favour stress on animals, making them vulnerable to pathogens. Fish parasites are excellent biological indicators of environmental quality, as their parasitic population may increase or decrease in response to changes in water parameters and/or the presence of pollutants. Ectoparasites are considered excellent indicators of environmental quality because they have a monoxenic life cycle with high reproductive rates that have been responsible for the immediate response to changes in aquatic biota. In turn, parasites with a heteroxenous life cycle are also responsive to environmental variation because, with the mortality of intermediate hosts, their population can be easily changed. However, studies with endoparasites and their relation with the environment are more numerous, as they are accumulators of pollutants, especially trace elements, either via fish or through stages of development outside the host that also contribute to the accumulation of metals. Moreover, Digenea, Acanthocephala, Nematoda and Cestoda parasites can compete for trace elements that are bioavailable in the environment, as fish with a greater abundance of parasites have a lower concentration of toxic metals in their tissues. Furthermore, they have a high affinity for trace elements that are toxic to human and fish health (arsenic, mercury, lead and cadmium). This review is a comprehensive overview of the use of fish parasites as environmental sentinels and describes their potential as bioindicators of effect and accumulation, and evaluates their application in fish farms environments.

中文翻译：

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鱼类寄生虫可以反映养鱼场的环境质量

在水生环境中，鱼类会受到不同的污染物和环境变化的影响，这有利于动物承受压力，使它们容易受到病原体的侵害。鱼类寄生虫是环境质量的极好生物学指标，因为它们的寄生虫数量可能会随着水参数的变化和/或污染物的存在而增加或减少。外寄生虫被认为是环境质量的极好指标，因为它们具有高繁殖率的单氧生命周期，是对水生生物群变化的直接反应的原因。反过来，具有异种生命周期的寄生虫也对环境变化有反应，因为随着中间宿主的死亡，它们的种群很容易改变。然而，对体内寄生虫及其与环境的关系的研究更多，因为它们是污染物的积累物，尤其是微量元素，无论是通过鱼类还是通过宿主以外的发育阶段，也有助于金属的积累。此外，Digenea、Acanthocephala、Nematoda 和 Cestoda 寄生虫可以竞争环境中生物可利用的微量元素，因为寄生虫数量较多的鱼在其组织中的有毒金属浓度较低。此外，它们对对人类和鱼类健康有毒的微量元素（砷、汞、铅和镉）具有很高的亲和力。本综述全面概述了使用鱼类寄生虫作为环境哨兵，并描述了它们作为效果和积累的生物指标的潜力，