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Do fish sleep?

  1. Nov 11, 2004 #1


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    Just one of those random discussions but now I'm kind of curious. Do fish actually have an unconcious state similar to what we'ld call deep sleep? So that they wouldn't react to most stimuli, excepting a sudden pulse in the water?
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  3. Nov 11, 2004 #2
    This has also been one of the questions I've asked when I was younger. A quick google search gave me some information, although I do not know how legitimate and accurate this information is.

    It seems that fish can "sleep" (more like rest) in an energy-saving state. Some fishes that live near coral reefs actually hide in the spaces between the coral when they "sleep" to avoid predation. Other fish "sleep" under logs or large rocks to avoid predation.

    Just an aside, what is the definition of sleep? Some people sleep with their eyes open, most with their eyes closed, but they all sleep the same.
  4. Nov 11, 2004 #3
    I think he's talking about 'sleeping' in the way mammals do. Then again, I understand why he'd ask such a question because of the conflict with their aquatic environment.
  5. Nov 15, 2004 #4


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    Fish do sleep, but certainly differently than we do. I've observed (and read about) the semi-conscious state of their sleep. They still swim (like hovering in place) in a safe location and are generally oblivious to things, but still aware enough to snap back to attention if something threatening advances on them. I'd say it's a safe bet that different species of fish have different variations on sleeping.
  6. Nov 15, 2004 #5
    How well can fish unconsciously hold their position when ‘sleeping’?
    Last edited: Nov 15, 2004
  7. Nov 15, 2004 #6
    Position would be held by their boyancy. This would not need to be maintained through a conscious effort. Although, they can change this to change depth.

  8. Nov 16, 2004 #7


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    Of course fish can't sleep, they would drown...
  9. Nov 16, 2004 #8


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    Something underwater (maybe "fish" is too broad of a category) is said to have a brain that sleeps one-half at a time. Can't remember where I read that, though.
  10. Nov 19, 2004 #9
    in response to kalladin the term sleep is considered when all senses have been reduced by 80% and so energy is saved and is used for other things like growing. we can solve 30% of problems or questions during sleep because our brains turn off our senses it have less information to take in and we in turn become less aware of our surroundings. people day dreaming are people normally who don't get enough sleep and so their brains, at a time when they are not so active like in a lecture or boring class, reduce reactions from senses and so uses that energy conserved to provide the body with the much needed growth and energy and look to other people as sensless and away in another world as it were, that is where the term day dreaming comes from.

    if have anymore questions just ask

    day without sunshine ..........is like..........well...................night!!!
  11. Nov 19, 2004 #10


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    First two hits from Google on "fish + sleep"...


    :confused: joking? or are you thinking of sharks, as mentioned above?
  12. Nov 19, 2004 #11


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    Just kidding. Certain fish appear to spend most of their time in a state best described as sleep. I used to have an aquarium with this fish that stuck to the side of the tank. The guy at the fish shop sold it to me saying it would keep the glass clear of algae. I once calculated how long it to make one pass across the entire tank: about 11 years. It actually moved about four times a week. The rest of the time it spent pasted in place like a stunned slug. One time I saw it swimming around in the tank. My first thought was that it had died. That thing either slept 99% of the time or was the most easily amused creature I have ever encountered.
  13. Nov 19, 2004 #12
    you forgot to calculate how fast the algea and other things would grow on the tank...plus, those suckers (almost literal name) can grow pretty big, depending on how big the tank is.
  14. Nov 20, 2004 #13
    I thought fish turn off half of their brain and keep on going with half power. Like keeping on swimming, but not consciously.
  15. Nov 21, 2004 #14


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    :rofl: Maybe there's a business opportunity in breeding fish with brush-like fins to keep tanks clear of algae.

    FWIW, when I had aquariums, my sleeping fish would simply hover in a quiet corner. Perhaps I should have turned up the filter pump rate to push them around a bit more. :smile:
  16. Nov 23, 2004 #15
    i have an aquarium of gold fish and they move around quite alot even though the tank is small, i had to put a lid on the top of it to stop them jumping out. maybe they saw finding nemo?
  17. Nov 26, 2004 #16
    Well, i have observe that fishes do sleep - or at least, the species of the fish that I keep. At night, my fishes would remain motionless at a single spot with their eyes turned pale (Sometimes, they even lie down on their side when their sleep! ).
  18. Jan 20, 2009 #17
    I would say yes fish do sleep, but in a different way then we mammals. I have had fish since I was a young boy and now I can say that I have seen fish sleeping. Currently I have two small comet goldfish in a ten gallon tank. I remember getting up in the dark of night because I could not sleep or I needed a drink or bathroom ect. I remember looking at my two fish to feed them it was winter and I had been sleeping and the lights had been off for no less then 4 hours and there had been darkness out side for at least five hours. I remember having not feed the fish that day so I thought to feed them and when I turned on a dim light I saw one fish that looked like it might be dead or dieing. This fish was on the bottom of the tank in a spot where the current of the tank pump my have left a fish if it was dead, a spot in the tank of low current. I put some food in the tank and there was no responce from the fish at first. I saw the fish moving just enough to keep from drifting around in the tank. The goldfish looked like it was on auto pilot and sleeping. The goldfish did not even move when I put the food inside the fish tank, and the gold fish was nearly moving. Any one who is a big fan of goldfish will know that any goldfish that is not sick would never wait long to get food inless it had already eaten its fill. My goldfish had not been feed all day so they would be very hungry, as goldfish are always hungry and live to eat. After a minute and after I banged on the glass of the fish tank the fish "woke up", and became aware again and started smimming and looking alive and then hunted for food as it would normaly.

    So with the above said in mind I firmly believe that fish do have a form of sleep almost like deep transe where only the most basic outward actions of the fish take place, just enough outward action and responce that is done as an automatic brain responce as the fish essentially sleeps.

    Any coments or responces?
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