How do fish sleep?

Almost all animals need to sleep. Besides, some animals sleep most of the day. For example, the mice that everyone yelled at, although they ran around stealing food and destroying furniture at night, actually they slept for 20 hours in 24 hours a day.

Fish are no different. They need sleep to recover. But unlike mammals, fish sleep in a very unique way!

They don't rest like humans, but have their own way of sleeping. For example, some fish in the Pacific Ocean will sink into the water and hide behind sand dunes or corals when they need to rest, so as not to be disturbed by uninvited guests, and at the same time let themselves have a rest by reducing metabolism and activities. However, in this process, they remain vigilant in order to escape in time when they are in danger!

So this kind of fish will not enter the REM sleep stage, and their sleep is very shallow.

Most fish need to keep swimming when they are resting, because fish can't take oxygen like people. Only by constantly swimming and letting the water flow through the gills can we continuously absorb fresh oxygen. Some fish are smarter. For example, a nurse shark will find an ocean current, and it only needs to face the direction of the ocean current to get oxygen from the water through its mouth and gills, so that it can stay still all day.

There are also a few fish who enjoy deep sleep like humans, and even if they sleep, they are completely unaffected by changes in the surrounding environment. Sometimes even if they are fished out, they can't wake up, such as hairtail, which makes insomnia people envy and hate!

In addition, the sleep time of fish is related to the surrounding environment and its own habits. Take pet fish as an example. Some fish will start sleeping when the lights are turned off indoors and the light is dim. But some fish will become more active in the dark, but when the light gets stronger, they will go to sleep!