Do Fish Sleep?

Fish do rest, but their versions of sleep doesn't look the same as ours. Learn more in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/fish/do-fish-sleep.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeart Radio, Hey
brain Stuff Lauren Bogle bomb here goldfish of the animals,
not the crackers, are beautiful and inexpensive pets, and they're
known for being pretty hardy, which is why many of
us received one as an early pet, perhaps with less

(00:22):
preparation and equipment than is actually required, which is why
blacking an appropriate tank with a filter and water pump.
Many of us checked in on our fish a few
days later to find it floating upside down, motionless. In
our youthful innocence and curiosity, we might have wondered, is
that how fish sleep? It's hard to tell when a

(00:43):
fish is sleeping because they don't have eyelids, at least
not ones that close completely over their eyes, obscuring their
vision like ours do. But scientists know that fish do rest,
and some have very interesting ways of doing it. A
fish don't sleep the same way that you, or your dog,
or any other mammal does. Most don't seem to experience

(01:05):
cycles of rapid eye movement or r e M, though,
to be fair, we might just not know how to
recognize dream stayed activity in these animals. For example, research
on zebra fish suggests that they experienced similar brain activity
to R. E. M sleep, and other researchers have observed
an octopus changing colors while sleeping, which may suggest that

(01:26):
it was dreaming. Still, scientists have observed that many species
of fish rest. This is a period of restoration when
their metabolic functions slow and they're less active. A sufish,
like reef sharks, lay still at the bottom of the
ocean or inside caves when they sleep. These sharks have
a unique anatomical feature called a spiricle that forces water

(01:49):
out of the sharks skills so that they can continue
to breathe while they're resting, they're not as responsive to
their surroundings, but some species of sharks and tuna must
keep swimming to breathe because they don't have spircles to
keep water flowing over their gills. In their cases, scientists
hypothesized that they shut off half of their brains, which

(02:10):
is what dolphins do. They slow their breathing and move
more slowly, but are still somewhat responsive to their environment.
But some fish species, like the Spanish hog fish, are
known to sleep very soundly, so soundly in fact, that
divers can touch them and even move them to the
surface without disturbing their slumber. Some relatively deep sleepers create

(02:33):
their own protection. A parent fish, for instance, create enough
mucus to form a cocoon around themselves at night when
they stop moving. This mucus blanket is likely used to
keep blood sucking parasites from clinging to them while they sleep,
and clownfish bury themselves in sea enemies to protect themselves
from predators while they sleep. Like humans, fish have biological

(02:57):
clocks that tell them when to be alert and awake
and when to rest, and some sleep during the day
and some sleep at night. These tendencies primarily evolved based
on when they're more or less likely to be attacked
by predators or what the best times are to find
a meal. One of the more bizarre sleeping habits of
the ocean is experienced by loaches, which float to the

(03:18):
top of the water and remain completely still when they
sleep for short periods. So if your pet fish is
a loach and it's motionless at the top of the tank,
it could very well be sleeping. Unfortunately, the same cannot
be said about that pet goldfish, which tend to rest
towards the bottom of their habitat, not upside down near
the surface. Today's episode is based on the article do

(03:45):
fish Sleep on how stuff works dot Com, written appropriately
by Allison Troutner. Brain Stuff is production of I Heart
Radio in partnership with how stuff works dot com, and
it's produced by Tyler Klang. For more podcasts my heart Radio,
visit the heart Radio app, Apple Podcasts, or wherever you
listen to your favorite shows. M