Hypoxia can modify normal behavior. Parental behaviour meant to provide oxygen to the eggs is often affected by hypoxia. For example, fanning behavior (swimming on the spot near the eggs to create a flow of water over them, and thus a constant supply of oxygen) is often increased when oxygen is less available. This has been documented in sticklebacks, gobies, and clownfishes, among others. Gobies may also increase the size of the openings in the nest they build, even though this may increase the risk of predation on the eggs. Rainbow cichlids often move their young fry closer to the water surface, where oxygen is more available, during hypoxic episodes.
Behavioural adaptations meant to survive when oxygen is scarce include reduced activity levels, aquatic surface respiration, and air breathing.