Tropical earthen ponds for extensive aquaculture are characterised by daily fluctuations in the availability of dissolved oxygen in the water. Primary production during the daytime ensures excess oxygen availability with oxygen partial pressures (pO₂) exceeding 220 mmHg, while nocturnal respiration of fish, plankton and bacteria leads to nightly episodes of severe hypoxia (pO₂ < 20 mmHg), often persisting for several hours. To investigate how oxygen availability affects feeding, growth, digestive performance, metabolism and behaviour in Nile tilapia (Oreochromis niloticus), a series of experiments were conducted under different oxygen regimes. To assess growth performance, triplicate groups of fish were held either under constant normoxia (pO₂ 17.4 ± 0.4 kPa), constant hypoxia (pO₂ 8.1 ± 0.6 kPa), or diel-cycling between normoxia (pO₂ 17.1 ± 0.6 kPa from 6 a.m. to 11 p.m.) and severe nocturnal hypoxia (0.4 ± 1.0 kPa from 11 p.m. to 6 a.m.). Chronic hypoxia led to significant affected feed intake and FCR, compared to the normoxic group, whereas nocturnal hypoxia was associated with a compensatory increase in appetite later in the day. Overall, this resulted in a significant increased feed intake compared to the normoxic group. Interestingly, exposure of fish to 6-h nocturnal hypoxia (diel-cycling hypoxia) for 9 weeks resulted in the best growth performance indicators among the treatment groups. Respirometry showed that tilapia respond to nocturnal hypoxia by metabolic depression, allowing them to return to normoxia with a modest oxygen debt. Behavioural observations revealed that aquatic surface respiration is employed when pO₂ approaches 2.1 kPa.

用于大规模水产养殖的热带土池的特征是水中溶解氧的可用性每天波动。白天的初级生产可确保过量的氧气供应，氧气分压（p O ₂）超过220 mmHg，而鱼，浮游生物和细菌的夜间呼吸导致夜间严重缺氧（p O ₂  <20 mmHg），通常持续存在几个小时。研究氧的供应量如何影响尼罗罗非鱼（Oreochromis niloticus）的摄食，生长，消化性能，代谢和行为），在不同的氧气条件下进行了一系列实验。为了评估生长性能，将三组鱼置于恒定的常氧（p O ₂ 17.4±0.4 kPa），恒定的缺氧（p O ₂ 8.1±0.6 kPa）或常氧之间的diel循环（p O ₂从早上6点至晚上11点为17.1±0.6 kPa）和严重的夜间缺氧（晚上11点至下午6点为0.4±1.0 kPa）。与常氧组相比，慢性低氧导致饲料摄入量和FCR受到显着影响，而夜间低氧则与当天晚些时候的食欲补偿性增加有关。总体而言，与常氧组相比，这导致饲料摄入量显着增加。有趣的是，将鱼暴露于6小时夜间缺氧（迪尔循环低氧）持续9周，是治疗组中最佳的生长性能指标。呼吸测定法显示，罗非鱼通过代谢抑制对夜间缺氧作出反应，使他们以适度的氧含量回到正常状态。行为观察表明，当p O ₂时，进行水面呼吸 接近2.1 kPa。