For completeness, it should also be noted that fish are cold-blooded and humans are warm-blooded. All other things being equal, warm-blooded critters need more oxygen.
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http://www.straightdope.com/mailbag/mfishbreath.html
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the report states :
that is water to Air. Given that oxygen concentration in water sits at about 10 to 15 ppm (parts per million), and in air at 200000 ppm, I think this qualifies as an undertatement!
Depends on how you’re doing the comparison. If you’re looking at mass of oxygen per mass of ambient material, then your figures are correct. But if you’re looking at mass of oxygen per volume, then you have a factor of the ratio of the densities, which is about a thousand, so water is up to about an order of magnitude short of air, as the Report said.
Supposedly there are warm blooded fish. The Encylopedia Britanica and the World Almanac say this but don’t seem to back it up. Any ideas?
Ian Thorpe?