A Fishy Mystery

So admittedly I have never thought of this before, but do fish get out of breath?

Fish rely on their gills to remove oxygen from the water. Gills are feathery organs full of vessels. A fish breathes by taking water into its mouth and forcing out through the gill passages. As water passes over the thin walls of the gills dissolved oxygen moves into the blood and travels to the fish's cells.

All of the roughly 30,000 different types of fish need oxygen. However, different types of fish respond to exertion in different ways. For example, salmon must work hard to traverse rapids or waterfalls but they will tire before they run out of oxygen. Part of this is due to the cool water that they live in having more dissolved oxygen.

Tropical fish on the other hand live in warmer water with less oxygen and have made several adaptions to compensate for their environment. The types of fish that are sold for home aquariums will engage in "aquatic surface respiration." They swim upwards towards the top-most layer of water, which has been exposed to the air and therefore contains more oxygen. Fish such as sculpins and gunnels pop out of the water for gulps of air and others such as lung fish use internal organs as makeshift lungs, absorbing oxygen into the blood through the walls of their mouth, swim bladder, or even stomach. Image Credit

Luckily for fish, they will never get so short of breath that they pass out. The fish will rest near the sea floor to save energy or surface in search of oxygen first.