Hypoxia refers to low dissolved oxygen (DO) in an environment while the hyperoxia occurs when DO is beyond saturation in water. This paper reviews how fish adapt to environmental hypoxia and hyperoxia, and describes fish behavioral and physiological changes under these conditions. No adverse effects and abnormal behavior are found when fish are exposed to hyperoxia (<200% saturation), though there are some changes in the acid balance of fish blood. The abilities of fish to tolerance temperature, salinity, stocking density and ammonia in different O2 conditions are discussed. Although the growth and physiological changes of fish in hypoxia have been thoroughly studied, research on how fish cope with hyperoxia is rare. In general, environmental hyperoxia is beneficial to fish growth especially at high ammonia and stocking density. However, it is necessary to further examine the implication of hyperoxia in fish culture in an attempt to improve aquaculture production efficiency. This review suggests future research be focused on the interaction between hyperoxia and other environmental factors to explore the feasibility of using hyperoxia in aquaculture.