That's an important question! About 21% of the
air we breathe is composed of oxygen. Even though
fish live in water, they need oxygen too. Unlike
us, fish do not have lungs, but instead uptake
dissolved oxygen from the water using their gills.
The concentration of dissolved oxygen in water is
much lower than the amount of oxygen in the air.
Fish do best in water that has dissolved
oxygen which is at least five parts per million
(=0.005 grams of oxygen in 1 liter of water). If
the dissolved oxygen drops below about 2 parts per
million, most fish will suffocate and die.
Therefore, it is important that lakes, rivers, and
streams remain relatively oxygen-rich. Things that
can affect dissolved oxygen concentration include:
temperature (colder water will hold greater oxygen
concentrations) and pollution (things like sewage
in water can cause blooms of bacteria that use up
the dissolved oxygen, hurting fish).
Click Here to return to the search form.