Do Fish Sleep?

Fish do indeed sleep, but it may be hard to tell at a glance. Sneak up on your pet goldfish in the middle of the night and you may very well find him hovering near the bottom of his tank, his fins making just a few corrective movements to keep him in his place in the water. Goldy is indeed sleeping. If you drop his food pellets to him at that moment you will notice a far slower response time than normal, as if he’s having a problem waking up and getting out of bed.

Scientists believe that all species of fish enter into restorative periods that mimic human sleep. Some of the deep ocean dwellers seem to never quite stop moving; understandable perhaps given the nature of their environment, but they do limit their movements and slow down their bodily functions to help “recharge” their batteries, just like mammals do.

Researchers discovered an interesting fact back in 2007 when studying the habits of zebra fish. They concluded that they not only entered a sleep like state on a daily basis but some actually showed signs of being disturbed if they were deprived of their “nap time” (mind you, I might be disturbed if someone kept  disturbing my nap with mild electric shocks!)

When do fish “sleep”?  That is another question entirely. Many follow a set night and day pattern like a human might while others, such as sharks, seem to catch a bit of rest whenever they can. Some fish, like bass and perch, even “go to bed”, choosing to retreat beneath rocks and logs to try to get some uninterrupted rest.