Many hypoxic freshwater springs have become havens for air-breathing, invasive, loricariid armored catfish. However, this does not seem to be the case for juvenile catfish, which are rarely seen. We wondered if hypoxia and air-breathing influenced habitat selection in juveniles, and so we designed an experiment to test the sensitivity of two size classes of juvenile catfish to varying concentrations of dissolved oxygen. Small and medium-sized juvenile Pterygoplichthys sp. were exposed to hypoxic, transitional, or normoxic conditions in the laboratory, and their air-breathing rates were measured and compared between fish size and dissolved oxygen category using a two-way ANOVA. We also measured air-breathing synchrony, which was assessed with a coefficient of dispersion and compared between fish sizes with a two-tailed, one-sample t-test, and with dissolved oxygen using linear regressions. We found that all fish air-breathed significantly more frequently under hypoxic conditions and smaller fish breathed significantly more frequently than medium fish at all dissolved oxygen levels, although there was no interaction effect. There was no air-breathing threshold oxygen tension, and only small fish exhibited synchronous air-breathing behavior. All of the behavioral changes we observed as dissolved oxygen decreased would put juveniles at greater risk of predation, and likely explains why so few juveniles are found in hypoxic waters.

许多缺氧的淡水温泉已成为呼吸空气，侵入性，loricariid装甲cat鱼的避风港。但是，似乎很少见到cat鱼的情况。我们想知道缺氧和呼吸是否会影响少年的栖息地选择，因此我们设计了一个实验来测试两种大小等级的少年cat鱼对不同浓度的溶解氧的敏感性。中小型少年翼龙sp。在实验室中暴露于低氧，过渡或常氧的条件下，测量呼吸速率，并使用双向方差分析比较鱼的大小和溶解氧类别。我们还测量了呼吸同步性，通过弥散系数对其进行了评估，并通过两尾一样本t检验和溶解氧通过线性回归比较了鱼的大小。我们发现在低氧条件下，所有鱼的空气呼吸频率均显着提高，而在所有溶解氧水平下，小鱼的呼吸频率均比中鱼显着提高，尽管没有相互作用。没有空气呼吸阈值的氧气张力，只有小鱼表现出同步的空气呼吸行为。