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How do fish sleep?

How do fish sleep?
Talis Maisey Edwards from Carmarthenshire (Age 5-14)

Answer:Yes fish sleep. But it’s not sleep as we know it. They don’t have eyelids to close, they sometimes do it during the day, they don’t show the characteristic brainwave patterns like REM sleep seen in humans, and some, including most sharks have to keep swimming in their sleep.

But fishes do have a period of reduced activity and metabolism which seems to perform the same restorative functions as nocturnal sleep does in humans. Some are more obvious about it than others and actually rest on the bottom or in coral crevices, and parrotfish secrete a mucus “sleeping bag” around themselves before they go to sleep. If you get up quietly in the middle of the night you will find your goldfish in an almost trance- like state, hovering near the bottom of the tank making just the minimum correcting motions with its fins to maintain its position in the water column. If you put food in when they’re like this they take noticeably longer than usual to respond, as if they have trouble waking up.

Mr. Oliver Crimmen, Fish Curator, Department of Zoology, The Natural History Museum

Answer2:How can you tell if  a fish is asleep? In human terms, they don’t have the type of day / night lives that we recognise on the old 9 to 5 routine. Some fish are active by day,  others by night. Many fishes live quite still  lives on  a regular day / night  cycle. (Deep down it’s pretty dark anyway!)

Some deep ocean fish appear never to stop moving (often said of some sharks who have to keep water and oxygen flowing through their gills).
Most fish do rest. A bit of ‘shut eye’ is difficult for most fish as they don’t have eyelids except for sharks. Most fish  ‘switch off’ when safe to save energy and go into daydream mode. You can see this in a fish tank or aquarium – some float motionless in place, some float near the bottom of their tanks, some build nests or nestle  themselves into the seabed or coral for safety and camouflage.
They might look  but like most resting animals are alert for danger whilst resting or “sleeping” saving energy. What exactly is going on in their brain (and human type sleep / brain waves) would be harder to tell. I’ve no idea if they dream either. However a recent bit of research (featured in a Times article in October 16 2007) suggest they even get sleepless nights if you keep annoying them!
“Researchers have now been able to show not only that [zebra] fish sleep, but that they can suffer from sleep deprivation and insomnia. By repeatedly disturbing the fish using mild electric shocks, researchers were able to keep zebra fish awake at night. Those fish that had suffered a disturbed night were found to catch up on their sleep as soon as the opportunity arose.”
Mark Norris, Education Officer, Newquay Zoo

22 Responses

  1. My friend keeps fighting with me and saying that fish don’t sleep but i believe that they do so there.

  2. fishe sleep but don’t close there eyes the only shut do

  3. fishes are very interesting.

  4. i dint know that!

  5. pls send me a full detail about a fish to my mail above

  6. All fish sleep in a way. Its more like when we rest though. All fish sleep in different ways. Some Fish will lay on the bottom of a still or slow moving water bed, on or under log, in cracks and plants. Or some will just float in one spot But fish like sharks MUST keep moving to breath. So they just move enough to breath and rest (sleep) If you have an aquarium with fish, the easiest way to tell if they are sleeping is 1st it is night and kinda dark, 2nd if you can walk close to the tank with out any real reaction from the fish… This is why it is always good to turn off you aquarium lights when you go to bed…

  7. This helped me on a report I had to do for science it was very informative. We had to watch a video in class, but I didn’t pay attention, and the report was due on Monday along with another one about the rainforest. THANKS

  8. wow thats so cool i dident know fish could sleep but now i know!!!!!!! 🙂

  9. O.K. Fish do sleep but not how you think a human would sleep. They can’t close their eyes cause they don’t have eyelids, but they do go into kinda like a coma for a few hours when it is the right time to wake up they are fully awake.
    Hope this helped : )

  10. Thank you very much 4 the info. This thing was in my mind since my new aquarium in the house.
    How ignorant is this that what we think is an innovative thought in our mind is actually a well processed discussion of the world.

  11. this is very interesting!!!!!!!! esp sharks very fascinating!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  12. Yes, I witness my Beta fish wake up from sleep, when I aproach the tank you can see his eyes dialate when he wakes up.

  13. I now believe that fishes do sleep

  14. lol i was worried because sometimes my fish would stay motionless at the bottom of the tank, what a relief.

  15. Thanks for the info. I find it hard to take seriously considering you used the word fishes. Just FYI “fish” can be used in a plural form just like dear and mice.

  16. Cool didn’t know dat fish are cool I have two

  17. Thanks 2 giving tis great answer. My frnds r fighted to tis matter. But now its cleared. Thanks a lot.

  18. I have a salt water aquarium with a clown fish(the ones like “nemo” ) and a coral beauty. The clown fish literaly lays down and on its side during the night when the lights in the tank are off. It just lays there like it’s dead not moving at all. When the lights go on it wakes up and starts swimming normally going about it’s day. I guess it does because there are no predators or other agresive fish in the tank.

  19. i have 9 fish and everytime i turn the light of at night, they all float at the bottem of the tank! so fish do sleep.

  20. thank you so much for answaring me, i was thinking about it one day and thats when i decided to ask someone. now i have got an ansaw!
    cheers. also seeing as you are so smart do you now where santa originated from?

  21. i never knew that

  22. Thanks soooo much this info helped me out a lot.

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