Subject: Re: Do fish sleep? Explain night fishing?

From: Philip Deitiker <[email-masked]>
Date: 24 Jul 1995 20:54:12 GMT

Ward

  I am no expert on this matter, but fish certainly have a diurnal cycle, 
and many types of fish become quiescent at night while others become 
active. My discus become catatonic at night and move around in very slow 
graceful motions. I have seen the same thing with many types of marine 
damselfish, anglefish. 
   There are fish that feed at night as well as in the daytime; however, 
they may be using olfactory and lateral line information which other 
types of fish cannot take advantage of. These fish may select periods in 
which food or oxygen is scarce to become quiescent. These fish feeding 
behavior would be similar to the large cats (lions, tigers), which feed 
and rest in the daytime and the night time.
  Since fish don't have eyelids its hard for them to 'sleep' as we do. If 
you wan't a better question, Do fish have dream or have nightmares? I 
frequently will have an unexplained explosion of activity in a tank.

Philip

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From: [email-masked] (Hector Cruz-Lopez)
Date: 25 Jul 1995 13:30:51 -0400

[email-masked] wrote:
: The title is pretty self explanitory. Do fish sleep?

: 						Ward

Parrotfish envelop themselves in a sack of bubbles and mucus secreted by 
them during the night and actually sleep.  The sack protects them from 
predation and from drifting as they usually attach themselves to fixed 
structures along coral reefs.  Many other fishes actually go into a 
quiescence state in which they are suspended in the water column.  
Sharks, because of their lack of an air bladder, do not sleep as they 
would otherwise sink and die from lack of circulation of water through 
their gills.

Fish do not have eye lids and therefore can not close thair eyes.  Their 
brain activity is, however, significantly diminished and in some cases 
you can approach them, touch many species, and even move them without 
triggering a reaction.

Hope this helps
hector "che" cruz-lopez