Performance and fitness consequences of hypoxia and thermal stress in fishes

如果种群数量减少，没有足够的时间适应，或者如果减少的捕食/竞争使种群尽管对当地条件的适应能力较差，但减少捕食/竞争，环境压力，无论是自然的还是人为的，都可能限制当地的适应。低氧(低溶解氧，DO)是人类对内陆和沿海水域的一种严重和普遍的应激表现，其原因是废物和化肥的大量涌入，加速了富营养化和污染。在严重缺氧的情况下，氧气可能是与健康相关的表现特征的强大限制因素，如耐力游泳或逃避捕食者。气候变化可能会加剧低氧对鱼类的影响，因为氧的溶解度随着温度的升高而下降，而外温动物(冷血生物)的新陈代谢则会增加。相反，低氧可能会限制在较高温度下的有氧运动，从而加剧热应激。

Environmental stress, whether natural or human-induced, may constrain local adaptation if populations decline, have not had sufficient time to adapt, or if reduced predation/competition allows populations to persist despite poor adaptation to local conditions. Hypoxia (low dissolved oxygen, DO) is a serious and widespread manifestation of anthropogenic stress to inland and coastal waters driven by influx of wastes and fertilizers that accelerate eutrophication and pollution. Under severe hypoxia, oxygen can be a powerful limiting factor on fitness-related performance traits, such as endurance swimming or escaping predators. Climate change is likely to exacerbate the impacts of hypoxia on fishes, because oxygen solubility decreases with rising temperature while metabolism of ectotherms (cold-blooded organisms) increases. Conversely, hypoxia may exacerbate thermal stress by limiting aerobic performance at higher temperatures.