[Coral-List] Why do fish swim upside down in caves?

[Thomas Murphy]

Some  interesting views so far on why cave fish orientate towards the ceiling in overhang environments. I wonder if this  is a behavior that first develops as smaller fish enter overhang environments for protection. When sitting at the entrance to a cave/wreck, predators would have a better chance of catching a glimpse of their prey if they were situated normally, but by associating with the top you are able to minimize the angle which you are visible from. One could creep right up to the opening without becoming visible from above, increasing the likelihood  of avoiding and evade the more manageable head-to-head predation. 
I have seem many fish that orientate towards the top of overhangs, but this behavior is far more common with smaller fishes like gobies - so much so that some species have evolved specialized fins to maintain this position without expending much energy. Larger fish would then use potentially utilize the same strategy to prey on smaller fishes, but would be a more downstream effect of predator avoidance. 
Then again, I've never lived in a cave.... or been a fish... but it seems reasonable that it is a behavior that starts with the little guy fearing for its life.
Cheers,-Thomas Murphy


--------------------------------------------------------------------------------------------------------------------------------------- Thomas A. MurphyOregon State
University, Hatfield Marine Science Center

Department of Fisheries & Wildlife

2030 SE Marine Science Dr.

Newport, OR 97365

Phone - 631.241.1599



> From: exallias2 at gmail.com
> Date: Thu, 4 Feb 2016 09:58:54 -1000
> To: psammarco at lumcon.edu
> CC: Coral-List at coral.aoml.noaa.gov
> Subject: Re: [Coral-List] Why do fish swim upside down in caves?
> 
> I think of it this way:  if I’m lying on the floor, I have a very hard time eating if I’m on my back; roll over and it’s easy to eat.  OK, that’s not quite the same as this situation, but perhaps for the grouper there is a greater efficiency feeding if your ventral side stays oriented towards the substratum, especially if you’re a carnivore feeding on fish that might pop out of the holes.  I can’t quite imagine how they would feed efficiently with their back to the rock.   Other larger groupers that may not feed on little fish in holes would be better off just remaining in the “normal” orientation.  
> 
> Just guessing.
> Bruce
> 
> 
> > On Feb 4, 2016, at 5:25 AM, Paul Sammarco <psammarco at lumcon.edu> wrote:
> > 
> > Dear Charles,
> > 
> > Hello.  This is all a guessing game, but my suspicion is that the phenomenon may be a combination of two things.  Firstly, where is direct or reflected light coming from?  Which way is it light, and which way is it dark?  Also, perhaps it's also a matter of looking dorsally for predators..  They should certainly know which way is up and which way is down.  
> > 
> > Food for thought.  
> > 
> > Cheers,
> > 
> > Paul
> > 
> > Paul W. Sammarco, Ph.D.
> > Professor
> > Louisiana Universities Marine Consortium (LUMCON)
> > 8124 Hwy. 56
> > Chauvin, LA  70344-2110
> > 
> > 1-985-851-2876 (tel)
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> > 
> > -----Original Message-----
> > From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Charles Delbeek
> > Sent: Wednesday, February 03, 2016 3:22 PM
> > To: Coral-List at coral.aoml.noaa.gov
> > Subject: [Coral-List] Why do fish swim upside down in caves?
> > 
> > Our exhibit design consultant asked me this question concerning Cephalopholis polleni.
> > 
> > My thoughts were that since these fish are bottom oriented they feel more secure with something on their ventral surface, I also believe they can see more what is ahead and below them where most predators come from for bottom oriented fish?? Also when a fish swims into a cave or overhang they are swimming down a reef face and coming across the opening so it is safer to remain oriented to the rock face then twisting and turning as they enter to cave/crevice. Also the shelter holes are in the ceiling so it is easier to dart into them when it is below them then above their line of sight, but I am just guessing on these.
> > 
> > Anyone have something more definitive on this?
> > 
> > Thanks in advance!
> > 
> > Best regards,
> > 
> > 
> > *J. Charles Delbeek, M.Sc. *Assistant Curator, Steinhart Aquarium California Academy of Sciences
> > 
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> BRUCE CARLSON
> exallias2 at gmail.com
> BCarlson at GeorgiaAquarium.org
> 
> Carbon-dioxide concentrations hit their highest level in 4m years <http://www.google.com/url?sa=X&q=http://www.economist.com/news/science-and-technology/21577342-carbon-dioxide-concentrations-hit-their-highest-level-4m-years-measure&ct=ga&cad=CAEQAhgAIAAoATAAOABAg-SwjAVIAVAAWABiBWVuLVVT&cd=i9IW-ZD9Lxc&usg=AFQjCNFYqbjH-5nMF6If2GtXM1bbeZhjNQ>
> The Economist <x-msg://267/>
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> AT NOON on May 4th, 2013, the carbon-dioxide concentration in the atmosphere around the Mauna Loa Observatory in Hawaii hit 400 parts per million (ppm).
> 
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