Anthropogenic environmental degradation has led to an increase in the frequency and prevalence of aquatic hypoxia (low dissolved-oxygen concentration, DO), which may affect habitat quality for water-breathing fishes. The weakly electric black ghost knifefish, Apteronotus albifrons, is typically found in well-oxygenated freshwater habitats in South America. Using a shuttle-box design, we exposed juvenile A. albifrons to a stepwise decline in DO from normoxia (>95% air saturation) to extreme hypoxia (10% air saturation) in one compartment and chronic normoxia in the other. Below 22% air saturation, A. albifrons actively avoided the hypoxic compartment. Hypoxia avoidance was correlated with upregulated swimming activity. Following avoidance, fish regularly ventured back briefly into deep hypoxia. Hypoxia did not affect the frequency of their electric organ discharges. Our results show that A. albifrons is able to sense hypoxia at non-lethal levels and uses active avoidance to mitigate its adverse effects.

中文翻译：

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弱电鱼Apteronotus albifrons在达到临界水平之前避免缺氧

人为环境的退化导致水生缺氧的频率和发生率增加（溶解氧浓度低，DO），这可能会影响吸水鱼类的栖息地质量。弱电黑色鬼刀鱼（Apteronotus albifrons）通常在南美充氧充足的淡水生境中发现。使用穿梭箱设计，我们使幼年的A. albifrons的溶解氧从常氧（> 95％空气饱和度）逐步下降到极端低氧（10％空气饱和度），在另一个隔室中逐渐升高。空气饱和度低于22％时，A。alfifrons会积极避开低氧舱室。避免缺氧与游泳活动上调有关。避免后，鱼定期短暂地回到深缺氧状态。缺氧并不影响其电器官放电的频率。我们的结果表明，A。alfifrons能够在非致死水平上感知缺氧，并积极回避以减轻其不利影响。