Name: Jason S Kay
Dear Mr. or Ms. Scientist, why do fish come
to the surface and gulp like they're breathing air or
trying to eat when there's no food there?
I'm not sure of the correct answer but I can make some guesses.
First, are you sure there is no food? Second, fish are able to suspend themselves
in water by adjusting their buoyancy with an air bladder.
This is an organ that like a balloon, is filled with air. Some fish that are
deep living (e.g. lake trout) are rumored to stop fighting when caught
as they are brought near the surface because the decrease in water
pressure allows the air bladder to expand enough to shock the fish.
Third, could it be that the fish you were observing has an adaptation
to allow it to absorb oxygen from its stomach when there is not enough
oxygen in the water for the gills to extract?? If this is a pet, try
oxygenating the water and see if the behavior subsides. GOOD LUCK!
Michael B Lomonaco
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Update: June 2012