Re: Does colder water have more oxygen than warmer water?

Well Laura, you're both right.  

Not only do different fish have different metabolisms, but water has a 
greater capacity for holding oxygen as it gets colder.  

There's a great table in an environmental reference called "Standard 
Methods for the Examination of Water and Wastewater" (Eaton, et al).  In 
my edition, from 1995, the table's on page 4-99.  That'll tell you how 
much oxygen the water CAN hold at certain chlorinities.  If you can't find 
the same edition, look in the index of almost any chemical or 
environmental reference for "solubility- oxygen in water" and if it 
doesn't give you a table, it should give you a fairly simple algebraic 
problem to help you figure out the solubility of oxygen in water.  

But each fish's metabolism is different, depending on what they eat and 
where they live.  For instance, I'm betting you've gone fishing a few 
times.  If you live in a place where it's safe to eat the fish, you've 
probably noticed a difference in taste between say, trout and bass. This 
is one of those great ecological problems like the chicken and the egg- 
bass eat bugs and live in warm water- they also require less oxygen than 
trout, which eat other fish and occasionally bugs or worms.  Both fish 
taste very different.  And yes, because of the cold, trout tend to grow a 
bit slower and use more of the calories they aquire from their food.  I'm 
sure someone's done it already, but it couldn't hurt for you to check 
their theories, but you could compare the diets of certain fishes with how 
much oxygen they need or the average O2 concentration at the depth they 
like to live.   

Quick experiment you can try to express gas solubility in a liquid is to 
pour ginger ale into two of the same kind of cup- the closer to a perfect 
cylendar, the better 'cause solubility also relates to the surface area of 
a liquid.  So pour your two glasses from the same bottle at the same time 
to the same levels, and leave one cup on the counter and one in the 
fridge.  Taste them about every hour and see which one goes totally flat 
first.  Dollars to donuts the one in the fridge will stay fizzy longer.  I 
recommend ginger ale because it's got the most carbon dioxide of all the 
sodas, with the exception of seltzer water and that just tastes wierd when 
it's flat.  

Even though the fizzies are carbon dioxide, not oxygen, it's the same 
principle as the solubility of oxygen in water, and water in your fridge 
is about as cold as the bottom of a lot of healthy lakes.  But for the 
most part, the bottom of a lake won't get much colder than 4 degrees C.  
Ever wonder what happens to the fish every winter when the top of the lake 
freezes over?   :)