[Make it Lady (OP)]

They have no eye lids and are constantly swimming so how do they sleep if at all?

[DoctorBeaver]

Like this...

[Make it Lady (OP)]

Twadle!!!

[DoctorBeaver]

 []

[Make it Lady (OP)]

Anyone got a serious answer. My goldfish can't nod off and is counting Neileps.

[atrox]

Yes, fish do sleep.
But with their eyes open. And not all of them swim around all the time.. just have a look in an watertank at night with fishes which are active at days. They are literally just hanging around, dont move much. I think most freshwaterfish rest like that.
Some fishes (like the parrotfish/Scarinae) rest between rocks, producing a bubble of slime around their body, to be scentless and not been found by the predators. Some sharks in coral reefs rest in big caves (or somewhere where is a lot of current..), where the oxygen-level is higher than in the surrounding ocian ...so they don´t have to move, but can really rest on the ground. But in fact, most sharks have to constandly move their body, to flood fresh water (not freshwater ;-) ) throught their gills. I read somewhere, that a great white shark have swim with at least 3 km/h (don´t know how much this is in miles per hour) all the time to get enough oxygen.

cu
aj

[DoctorBeaver]

Sharks don't sleep as such. They just rest.

They also have the ability to shut down each hemisphere of the brain separately. Plus, the Central Pattern Generator that co-ordinates their swimming movements is located in the spinal column, not the brain. This means that even if the shark is completely unconscious, it can still swim.

[Make it Lady (OP)]

Wow, now that is more like it.

[atrox]

sleeping/resting sharks in such a cave I mentioned

and sleeping parrotfish

[DoctorBeaver]

Wow, now that is more like it.

I know a bit about sharks.

[DoctorBeaver]

sleeping/resting sharks in such a cave I mentioned

Oooh - white tipped reef sharks. They're cute. Don't let them see the second video because they eat parrot fish (among other things).

[atrox]

hehe... I allways like the...dogfish(?? .. smaller sharks) the most

[DoctorBeaver]

The spiny dogfish is indeed a type of shark - Squalus acanthias.

[atrox]

oh yes...google my friend told me, thats the right one....but pretty confusing.. in Germany we call it "Katzenhai" >> Catshark ... but eventually thats why i kept the common name in mind...

[DoctorBeaver]

No. This is a catshark...



There is a family of sharks known as catsharks - Scyliorhinidae. Strangely enough, many species in that family are known as dogfish.

The largest is the humpback cat shark, which can grow to 4m.

[atrox]

yeeeah...isn´t it cute  [:X]


ah...I see... dogfish are something else ... I meant the Scyliorhinidae/catsharks

uuuh...now its not that confusing anymore...you have both...dogfish and catsharks.... so are they chasing each other up the trees? []

[DoctorBeaver]

Maybe the catsharks go up trees to get the parrot fish!  []

[opus]

....on waterbeds ....?

[Alan McDougall]

Just to add. Whales although not fish, are mammals like us have to switch off one side of their brain at a time to give eah side a rest.

The reason is they are not automatic breathers like us and have to consciously breath or die. So if they were to fall asleep like we do they would stop breathing and die.

Regards

Alan

[omghalloz]

first of all, it depends on their species, fish can be very different when varying between species, if you look at mammals like whales, they are concious breathers, meaning that they 'decide' when to breath; they are able to shut down one side of their brain (allowing it to rest) and use the other half to control their movements (to continue surfacing to breathe).
for fish like sharks (yes, a type of fish), then the utmost important thing to realise is that they must remain moving in the water to push water through their gills thus allowing more oxygen in to breath; there is one theory that they sleep something like whales (see explanation above). sharks do seem to enter this 'half rest state' (something like a nap), having been observed to be less responsive during this state (i.e. less attentive to things going on around them, not actively hunting/searching for prey, appearing tamer to humans etc). also, since most predatory sharks (unlike the calmer nurse shark) have a main hunt at night, therefore it would be useless for them to cuddle up on the ocean floor for the night as they'd lay prey to other sharks!
for other fish, such as the common goldfish, the fish can be observed to enter a 'resting' state at the bottom of their tanks overnight and sometimes during the day, somewhat like a nap. wild fish such as the tropical varieties found on coral reefs can be observed to enter such a state while hiding between crags and holes to avoid being eaten at night.
as with most things to do with sleep, there is no determined answer about what exactly goes on in an someone's/something's brain, but many theories suggest that yes, fish 'rest' but do not enter an unconciousness that humans do while we sleep.