Yes, fish do sleep. Fish spend part of each day sleeping. They don’t have eyelids that open and close. Fish are sleeping if they are at the bottom of the fish tank and don’t move, except for making the minimum correcting motions with its fins to keep it in position. They seem to be in a trance-like state of suspended animation. If you drop food in the tank while your goldfish is “sleeping”, you will perhaps notice the fish takes longer to respond.
Fish sleep is a bit different than the sleep we humans enjoy. For most fish, it is a period of rest and reduced activity, not the deep REM brainwave activity occurring in humans. Scientists have recorded brain waves (EEG) on catfish. They show a distinct difference in the patterns between being awake and being asleep.
Fish need the restorative nature of reduced activity and slower metabolism that comes with sleep. In that respect, they are the same as humans and most all others in the animal kingdom.
Researchers kept some zebra fish awake by repeatedly giving them a mild electric shock. They found the fish suffered from sleep deprivation and insomnia. These pestered fish tried to catch up on their lost sleep as soon as they were left undisturbed.
Fish sleep behavior varies widely. Some fish will wedge themselves in a spot in the coral or mud. Some build a little nest. The parrot fish secretes a mucus sleeping bag around itself. Other fish will change color slightly taking on a duller color, so they are less noticed. Sharks have to keep moving to have a flow of oxygen and water moving through their gills.
The behavior of minnows change when they are trying to get some zzzzz’s. They are very active in schools during the time they are awake. But they scatter and stay motionless during rest periods.
What do you call a fish with no eyes? Fsh
Sources: www.nefsc.noaa.gov/faq/fish and http://www.newton.dep.anl.gov