Do Fish Sleep?

I’m not sure what prompted Kam to ask this question.  Perhaps it’s because we saw fish in the pond at the park, (see our post do fish have ears?).  Nevertheless it’s a question asked – several times now.

Fish and Brain Patterns

imageFish do rest, but whether they sleep depends upon how you define sleep.

When people sleep there are specific changes which occur to brain wave patterns and ar processed in the brain’s neocortex area.  Fishes don’t have advanced neocortical development, they don’t display the associated brain-wave sleep patterns. 

So, as far as brain-wave patterns go, fishes don’t sleep.

Fish and Rest

Fishes have periods of reduced metabolic rate, slowed physical activity, lowered response to stimuli and the assumption of a resting posture.  If this is a definition of sleep, then fishes do sleep but not as we define it.  Still, they definitely do rest.

How do Fish Rest?

Parrotfish with protective mucus envelope
Parrotfish with protective mucus envelope

Some fish such as parrot fish rest on the sea bottom.  They encase themselves in a secreted mucus envelope to spend their night.

Fish have various ways to disguise their presence.  Some examples include hiding in plant growth, under logs, in rock or coral crevices, or they may buried in  a layer of sand.  Some even float motionless in open water!

A Note to You and Me

Thank you for reading.  If you like it or have anything to add please let us know, we’d love to hear from you.

We’ve written another post about fish and their hearing and a couple of poems.  Here are the links:

Do Fish have Ears?
Fish and Sleep – a poem
Fish and Ears – a poem.


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