How do fish sleep

But just fast-forward to that next morning! When the new day beckons, it seems like we all want just a little more sleep.

But what if you couldn't lie down , close your eyes, and snuggle into your warm, comfy bed? Would you still want to spend your time sleeping? Would you even be able to sleep? These are questions we thought of when we woke up and fed our pet goldfish.

Do fish sleep? And assuming they do, HOW do fish sleep? If you've ever watched fish for any length of time, you know they get plenty of exercise. They're constantly swimming around. It can seem like they never stop. Surely they need some rest from time to time, don't they? As a matter of fact, they do! If you watch fish long enough, you'll notice that they do take breaks.

There are definite periods of time when they seem to hover in place, almost like they're in a trance. But their eyes are open. Are they sleeping? The simple answer is yes! They are sleeping, and they can sleep at any time during the day or night. Fish do sleep with their eyes open , because they don't have eyelids except for some sharks to close! Fish sleep is not exactly like human sleep , though. For starters, they don't use pillows. They also don't have beds with sheets and blankets!

For fish , sleep is more like a resting period similar to a daydream that humans might experience. If you've ever owned a goldfish or watched one up close, you've probably noticed the times when it's sleeping. It might hover near the bottom of the tank in a trance -like state. If you put food in the tank during this time, you've probably noticed that it takes longer for the goldfish to respond, just like you might have a hard time waking up from a good night's sleep!

Sometimes people see fish when they're sleeping and assume they're awake because they're still moving. Most fish need to keep moving even when they're sleeping, so that they keep a constant flow of water moving past their gills to maintain a proper oxygen level in their bodies.

For some larger fish , like sharks, this can take the form of swimming at a slower rate when sleeping. Smaller fish might be able to do nothing more than occasionally move their fins. Certain types of fish are known for sleeping in ways that look more like traditional sleep to humans. For example, fish that live near a coral reef might stay active all day long and then hide in crevices in the reef at night to avoid predators.

We hope today's Wonder of the Day put you in a serene, restful mood. Before you take a nap, though, find a friend or family member to help you check out one or more of the following fun activities:. We're so glad to hear that you found this Wonder helpful, Flippy! It's very interesting to learn about how fish sleep, and why they may not eat duing this time!

What did you name your fish? Welcome back, jason! You're right! When a fish is sleeping, it's similar to our daydreaming. We hope you liked the Wonder, too! We hope you checked out the Wonder text above to learn how fish get rest, leilani!

Isn't it cool?! Ask a fish if it's not sleeping if fish don't sleep maybe they are one of. The eyes of God seeking how we treat them. Hi, Wonder Friend! Thanks for joining the discussion and sharing your thoughts. Hi, Justin! We all need sleep, including fish.

However, fish must sleep with their eyes open. Do you want to know why? Along with other cool facts, this Wonder explains that fish do not have eyelids! Weird, huh? Great, Zoe! We're glad that you learned something new today!

We agree, Hunter! That is pretty cool that fish do not have eyelids. Thanks for sharing with us today! Thanks, Vanessa! We think the fish with the "sleeping bag" is pretty cool, too! Ha, Alex! We think you may be referring to the "sleeping bag" made out of mucus. We agree, that sounds pretty gross! We're not sure, but that is definitely something to Wonder about! What did you like most about this Wonder? Hi, Sophia! Be sure to read the Wonder Article for the answer. Enjoy, Wonder Friend!

Still, fish do slow down metabolic processes in their resting state, much like humans. They physically slow down as well, with some fish floating in place. Since fish do not look very different when they are asleep, it can be difficult to determine whether a fish is resting or awake. However, during a state of rest, fish are much less responsive. Some may appear to stop moving completely, and can even be touched or handled without waking up. Moreover, some fish are more vulnerable to being attacked by predators at night, which suggests that they are diurnal, or resting and less alert at night.

Studies have found that certain fish species experience more deaths in the first two hours after sunset, which indicates that these fish tend to fall asleep at that time.

A lack of responsiveness is often a sign of fish sleep, but researchers have found additional markers of sleep that fish share with humans and other animals. For example, studies show that melatonin may regulate the sleep-wake cycles in zebrafish. Zebrafish also appear to have distinct stages of sleep like humans, and follow a circadian rhythm. Humans cycle through four stages of sleep, including two stages of light sleep, one stage of slow-wave, deep sleep, and one stage of rapid eye movement REM sleep.

Although fish do not have a neocortex like humans, researchers were able to monitor the brain activity, heart rate, and eye and muscle movement in zebrafish to document two stages of sleep that are similar to slow-wave sleep and REM sleep. When fish do not get enough sleep, they seem to be vulnerable to the effects of sleep deprivation. After a night of sleep deprivation, zebrafish experience a sleep rebound, in which they catch up on sleep.

This resting state is so essential to fish that they will find ways to maintain a bare minimum of sleep, just like other animals.

Many fish follow a regular sleep-wake cycle, similar to humans and other animals. The circadian rhythms of fish appear to be sensitive to light, similar to the human circadian rhythm that prompts us to feel alert during daylight and sleepy after dark.

Both types of interruptions woke up the fish, but only the light exposure significantly reduced the amount they slept for days at a time. Light-dark cycles are a common regulator of circadian rhythms in many animals. But there are fish that cannot see light, such as deep sea cavefish.

Cavefish live so deep in the sea that they live in darkness, and many have evolved without sight as a result. Even so, they display behaviors that are consistent with having a circadian rhythm, leading researchers to believe other environmental factors, like food, may help regulate their sleep-wake cycles. The sleep habits across and within different fish species are as varied as those of other animal species. For example, surface cavefish sleep significantly more than those of the same species that live in deep sea caves.

Fish species can also be diurnal, which means they generally sleep at night, or nocturnal, which means they are generally active at night.

For example, nocturnal sharks rest during the day and then swim and look for food at night. Fish need oxygen to survive, and they get it as water passes against their gills, which requires a certain level of movement.

Some fish can receive oxygen while in a nearly stationary position by facing a current, staying afloat and moving a fin every now and then as water passes around them.

Other fish, like some sharks and rays, need to make larger movements to move a sufficient amount of water over their gills. Due to unihemispheric sleep, these larger fish can keep swimming while they sleep. Unihemispheric sleep allows a fish to put one half of their brain to sleep at a time. The other half stays active, allowing the fish to keep swimming, albeit more slowly than when they are awake.

If they had eyelids, the eye connected to the sleeping side of the brain would close while the other stayed open, as it does with many birds and whales. Some fish occasionally enter estivation , a state of suspended animation that is similar to hibernation, but occurs in dry rather than cold climates.

However, species such as the stickleback make that sacrifice look small fry. The answer here varies between the sprawling species of fish around the globe an estimated 33,, according to leading body FishBase. With that said, many fish have been known to swim down to the bottom of the aptly-named seabed — or the bottom of a fish tank or river — to sleep on their side.

Species like the loach, however, have been known to sleep upside-down too and cause any owner a lot of undeserved panic. Believe it or not, fish sleep is being studied to help us better understand sleep in people. Most of these studies use zebrafish and try to understand things like the effects of sleep deprivation lack of sleep , insomnia trouble getting to sleep and circadian rhythm sleep cycles.

Here is a cool video about sleep in animals, including fish. Hello, curious kids! Ask an adult to send your question to curiouskids theconversation. Portsmouth Climate Festival — Portsmouth, Portsmouth. Edition: Available editions United Kingdom. Become an author Sign up as a reader Sign in.