do fish breathe?
use a specialized organ called gills in order to breathe the
oxygen dissolved in water. The mouth and throat of a fish force
water over the gills. Gills have a lot of blood vessels. The
water has a higher concentration of oxygen than the blood. Therefore
the dissolved oxygen from the water moves through the thin walls
of the blood vessels and enters the blood. Once the blood is
fully oxygenized, it is pumped back into the body and used by
the fish for energy and for all metabolic processes in the body.