Claire Corlett

Fish Food, Fish Tanks, and More
Do Fish Sleep?

Do Fish Sleep?

Less like sleep and more like suspended animation,
most fish species do spend some time resting. And like us, if they don’t put in enough
downtime, they try to make up for it later. Sleep has a simple definition that includes
closed eyelids and a particular brainwave pattern in the neocortex; as a result, it’s
relatively easy for researchers to determine when a person, another mammal or a bird is
asleep. This definition is problematic, however, when
it comes to fish, since they have neither a neocortex nor eyelids. As such, researchers have to rely on behavior
observation to determine when they’re napping. Typically when a fish is “sleeping,” four
characteristics are observed: (1) inactivity for a long time; (2) a resting posture (like
a droopy tail); (3) a routine (like resting at the same time, and in the same manner,
each day); and (4) decreased sensitivity to its environment (hard to arouse). Different species of fish snooze in different
ways. For example, tilapia have been observed resting
at the bottom of their habitats, while brown bullhead catfish were found napping at a 10-30
degree angle along the bottom, with their tails flat and fins stretched out. In addition, some species of bass and perch
were seen sleeping on or under logs, while fish around a coral reef often hide in its
crevices at night In many fish species, during this period of
rest, lower cardiac and respiratory rates are observed, as are decreased mouth, gill
and eye movements. For several, like the bluehead and requiem
shark, the decreased sensitivity to disturbance is so profound that researchers have been
able to pick them up and haul them toward the water’s surface without stirring any
reaction. Interestingly, some fish species never seem
to sleep. Both mackerel and bluefish swim constantly,
and although they swim less at night than during the daytime, they remain responsive
to stimuli 24-7. Another night-owl, the California horn shark,
is far more active at night, although even during the day it remains responsive to disturbances. Others that never seem to sleep, but may actually
catch 40 winks now and then, include many fish that live in large schools. One theory holds that while some members of
the group have their eyes peeled, others are able to enter a kind of daydreaming restful
state. Other fish don’t give any signs of sleeping
when they’re young, but develop a sleep pattern once they reach adulthood; still others
that normally sleep at night, like the tautog, suspend any signs of sleeping during periods
of migration and spawning. Some chichlids and threespine sticklebacks
will forego sleep while their eggs are incubating – not necessarily to protect them, but to
fan them (thereby providing a continuous supply of oxygen to the brood). Some species of sleep-loving fish will work
to catch up on lost sleep. In a 2007 study, several researchers ruthlessly
pestered a group of zebrafish by alternately tapping on the aquarium and even piping noise
in through an underwater loudspeaker. Completely deprived of sleep during their
normal 6 hour dark period, the next day, the researchers left the tank dark and observed
that the zebrafish were significantly harder to arouse, and their normal mouth and gill
movements had been cut in half. Tapping on tanks seems to be a popular method
with fish-sleep researchers, and in 2011, some NYU biologists used the technique to
determine that cave fish don’t sleep much when compared with their surface-dwelling
neighbors. Observing four species of fish all indigenous
to northeast Mexico, a surface-fish species, Astyanax mexicanu, as well as three cave-dwellers,
Pachón, Tinaja and Molino, the scientists discovered that the surface fish slept about
4 times more than cave fish (800 minutes in 24 hours compared with 110-250). Easily as seemingly sadistic (to those of
us who love sleep) as the zebrafish researchers, the NYU biologists also experimented with
depriving the Mexican fish of sleep – by moving their containers once every minute. Sure enough, the fish lost sleep, and like
their zebrafish cousins, they caught up on it by sleeping more the next day. Seeking to learn why the cave fish sleep less,
the scientists with the 2011 study then bred cave fish with surface fish (to observe any
inherited sleep characteristics). Remarkably, each hybrid inherited the cave
fish’s need for less sleep, and as a result, the researchers concluded there is a genetic
basis that regulates sleep, and the cave fish’s gene (requiring less sleep) was dominant. After a review of over 300 scientific publications,
a panel of 18 scientists and researchers including representatives of the American Physiological
Society, American Academy of Pediatrics, American Psychiatric Association and American Geriatrics
Society, prepared a list of new sleep recommendations for the National Sleep Foundation. They concluded that newborns should optimally
get 14-17 hours of sleep each day, infants 12-15, toddlers 11-14, preschool kids 10-13,
grammar school kids 9-11, teenagers 8-10, adults (aged 18-64) 7-9, and older adults 7-8.

100 comments on “Do Fish Sleep?

  1. I am here 2:12 in the video I don’t know if you’re going to mention it but mackerel do sleep in some way. the thing with mackerel is that it always need to be in activities to get air because it don’t have a air/swim bladder to keep itself up so instead it does so bye swimming, so it can’t sleep normally however it turn off half of it’s brain leaving just the ability to swim to rest

  2. I'd like to offer a bonus fact of my own. When a person becomes sleep deprived for a long time – especially when they're just intentionally staying awake for a long period of time, to break a record or as part of an experiment – when they finally do sleep, they will generally sleep for about 14 hours and then be fine. Usually when you hear about someone sleeping longer than that there's some sort of illness involved (someone was once kept awake for a week due to fever, then slept for 3 days while recovering).

  3. Can a limb ever be trained to be equal or to or switch to become the dominant one. How is this affected by amputation?

  4. Huh I didn’t know blind cave tetra could be hybridized! It’s so cute when my neon tetra’s sleep at night. They turn off their neon and tuck themselves into little nooks in the decor. My banjo catfish sleep all day under the sand though hehe

  5. I have a question. When I face a desk fan from the front, I feel the air movement and hear the wind. But if I go to the back of the fan, I neither feel wind nor hear it. Whyizzzat?

  6. I think the sleep stats at the end would have benefitted from being listed more slowly, or having a number listed along with the photo. I went over it twice, then finally played it at .75x speed. It’s very interesting to me, and while it follows that as children get closer to maturity they need less rest, it was a lot of information flung out there.

    Loved the video as always. The captions on the fish were hilarious and spooky at the same time. “Or am I?” Shudder. 😖

  7. I've got a great pyrenees (livestock guardian breed for those unfamiliar) and he can be out cold and snoring, but will watch and follow you with one eye open. It's freaky. But it makes him a very effective guard dog.

  8. What would happen to a country that breaks the Geneva Convention. For instance, if the US started using dirty bombs or bio weapons, what would be the repercussions?

  9. What I actually found more interesting than fish sleeping is how birds do it. I heard on scishow tangents (a podcast) that some birds don't land for 10 months or even more as the research only lasted 10 months. And they told how some birds actually go limp in big parts of there bodies including the face and neck but their wings were still stiff and they were able to glide. So they would fly really high and then just glide for a long time while actually sleeping. Some birds go fully to sleep while others only have one of the brain sides go to sleep and then circling in a specific manner as they only have one working eye and fly in a group. Just thought it would be a fascinating topic for you to explore.

  10. Some parrotfish cocoon themselves in mucus for their nightly sleep. I've also observed some fish sleeping out in sandy areas vigorously move their fins to keep their balance in tidal surge, while being completely unresponsive to me. Occasionally the disturbed water from my passing has knocked fishes out of their perches on reefs or rocks and the completely stiff fish simply falling to the bottom. Bamboo sharks find a nice spot deep in under an overhang to sleep during the day.

  11. Imagine fucking with fish sleeping and calling yourself a "scientist"
    Maybe that's what all the birds outside my window are also doing, they're the dick scientists of the bird world not letting me sleep for "science"

  12. My 3 goldfish sleep at a bottom corner of the tank. They actually stay in group when this happens and one keeps watch for danger.

  13. I have an unrelated question. What would happen to the international space station if Russia and the US were at war?

  14. I think they do & they touch butts after they wake up😏

  15. I don't even need to watch the video because I have and aquarium and can see them sleeping, but I will cause I love this channel

  16. Well. In China, the fuckers actually implement a system of sleep deprivation on children and young people. No wonder so many Chinese kids are so fucking dumb.

  17. Please re edit the description of your video titled " What's the Difference Between BCE/CE and BC/AD and Who Came Up with These Systems?
    " Please change The first letters of The words " The Lord " to capitals also The word " Lord " with A capital L

  18. "orale ya dejen dormir a los pinches pececitos no mamen we" is translated "pray and let the little fish go to sleep" 3:40

  19. We were on a night dive and while we noted fish swimming around. Two of us came up upon a trumpet fish that appeared to be in a stasis. My dive buddy went up to it and it quickly reacted by swimming away from him and swam squarely into my mask thus stunning it and almost knocked me out. 😨😣

  20. My algae eater freaks me out because he has eyelids! We have starring competitions with each other and he DEFINITELY blinks. Thought I was imagining it but several others have seen him do it too. He spends the night in a hollow log though so don't know if he naps.

  21. I don’t care what science has to say. If I don’t get at least 10 hours, I’m cranky and don’t function as well mentally.

  22. Excellent video! I think it's interesting that dolphins, porpoises, and whales will sleep with only half their brain at one time in order to keep alert.

  23. I supposed that sleep has a genetic basis in humans too since my brother and I both have sleep disorders, although they manifest rather differently.

  24. Napoleon is said to have stated that “ a man needs six hours of sleep, a woman seven and a fool eight”. Just quoting. Don’t blame me.

  25. In this channel to speak of sleeping fish. When to talk of the awake ones you are in VisualPolitik EN

  26. Several of my guppies have distinct rest/sleep patterns from each other, some sleep up top, a few on the bottom with slow fin movement just to keep in place.
    The gold fish all seem to be the same, moving slowly in a forward direction

  27. Is it odd that I’ve only been getting 4 hours a night for years and feel fine? Like, sleeping too much makes me sick but 4-5 hours is great

  28. sooo…. does that mean hardcore gamers and coffee loving hipsters will be fish in their next lives, or were they fish in previous lives?

  29. my giant pet goldish sits on the gravel, holds his pectoral fins close, and lays his dorsal fin down lol

  30. When I kept fish, my gouramis would always park themselves on the gravel near the front glass; kissing gouramis would extend their pelvic and anal fins like a tripod, with the rest of their fins relaxed. In all cases, they would be completely insensate until the lights were on for a bit, unless I actually nudged them.

  31. My 12 year old clownfish sleeps in the corner of his tank, facing straight up.
    First few times I came in to see it I was convinced he died. But a few minutes after turning on the light, he'd slowly wake up and start swimming around. 🐠

  32. I typically sleep about two hours at night, sometimes as long as three, and sometimes I'll go days without any. Nope, not tired. I hate sleep. It's inactive time when I could be doing stuff. So I'm not complaining.

  33. My plecos will fall asleep while on the glass and fall off. They hit the substrate and wake up. Much like falling off the bed 😂

  34. İt was enough at "Yes, they do infact sleep." Everything afterward was unnecessary info. Thanks, though. İ can finally catch up on my sleep now.

  35. Two if my fish sleep side by side up against the airline tubing, and my other two just kind of float around at the bottom with their tail up.

  36. My Oscar has NIGHTMARES, he'll be completely out, just chilling , then dart 5ft. Hit a wall turn hit the opposite wall and shake like a dog when he wakes, lol, funny stuff

    I think karma fucks with him

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