Sleep plays a significant role in restoring energy and maintaining a healthy lifestyle for humans and every creature in the animal kingdom. Now, the question is – do fish sleep? The answer is ‘yes’, but one might wonder, how do fish sleep in water?
Technically, fish do not sleep the same way land animals do. However, they do rest once in a while by reducing bodily activity. This includes reducing movement, decreasing metabolism, and breathing slowly.
Some fishes float in the water to sleep while others have dedicated nests like birds do. Moreover, certain fishes look for safe and secure places like corals, caves, crevices, plants, and even mud that allow them to conceal themselves from predators.
Of course, even while sleeping fishes do some brain activity. This keeps them aware in case of an attack by a predator.
Unlike mammals which live on land and close their eyelids while sleeping, fish do not have eyelids. As a result, they sleep with their eyes open.
While land animals remain stationary while sleeping, some fish, like sharks, must keep moving during sleep to keep breathing by allowing their gills to ventilate.
When it comes to the sleeping time of fish, most fish are diurnal, which means that they are awake during the day and sleep at night. Some other fishes such as catfish, knifefish, and loaches are nocturnal.
In some exceptional cases, fish don’t sleep at all. This usually happens when they are looking after their young ones, migrating, or are too young to rest. An example of such fish is the young tilapia fish.
Absence of sleep has also been noted in certain species of fish, such as bluefish, Atlantic mackerel, tuna, and bonito.
