Do Fish Sleep? and if They Do, How Do They?

From Issue: Discovery 1/1/2004

Dear reader,

Most fish spend part of every day “asleep.” Being asleep can mean different things to
different fish. Some fish (like herring and tuna) are motionless in the water during the night. Other fish, like rockfish and grouper, don’t appear to sleep at all. They rest against the rocks, bracing themselves with their fins and have a calm period of rest (we think). Also, some freshwater fish (like catfish) swim up under a log or riverbank for shelter during the day.

 In the middle of the night, scuba divers have often handled fish that live around reefs, without the fish even waking up. Some fish have even been lifted out of the water before stirring.

By the way, fish can’t close their eyes when they sleep; they don’t have eyelids. This is one of the reasons why it  is hard to tell whether fish
are asleep or not.

All this writing is making
me tired. I think I’ll
close the eyelids God
made for me and
take a nap.


A copied sheet of paper

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