*Yawn!* *Stretch!* Do you like sleep? Most kids do. Just ask their parents. Of course, it may not seem like it. For example, when it's close to bedtime and you'd like to stay up a bit longer to finish watching a movie or playing a video game, sleep may not seem like so much fun.
But just fast-forward to that next morning! Your alarm goes off, or your mom turns on your light with a cheery, “Time to get up, sleepyhead!" That's when you like sleep, isn't it? 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.
One peculiar fish doesn't use a pillow, but it does use a “sleeping bag" of sorts! The parrot fish is known for its ability to secrete a “sleeping bag" made of a jelly-like substance made of mucus. When it's time to rest, parrot fish surround themselves with a jelly “sleeping bag" to protect from predators when they're ready to snooze!