How Do Fish Breathe?

fish breathe

Do you know how a trout breathes?

Fish breathe oxygen just like people and other mammals.  But, do you really understand how fish do that when they live in water?

The other day I wrote a post about how some amphibians are able to breathe through their skin.  That got me wondering how other animals breathe, including us.  I know that we breathe air into our lungs and we get the oxygen out of the air to survive.  In contrast to us, fish live in water, which means they can’t breathe air like us.  Fish do need oxygen to survive just like us, but they get it in a much different way.

Why Do Animals Breathe?

All animals breathe because our bodies need oxygen in order to survive.

The organs throughout animals’ bodies need oxygen to function.  This includes everything from muscles to nerves.  Without that oxygen our bodies would suffocate and die.

How Do People And Mammals Breathe?

When we, people, breathe air into our lungs the oxygen in the air passes into our red blood cells.  That is the most important thing to keep in mind – the oxygen goes into our red blood cells.

That ‘oxygenated’ blood then gets taken throughout our body as our heart pumps the blood.  As the blood moves around the oxygen is taken out of our blood and used by all of the different parts of our body.  That oxygen is crucial for our survival.  Without that oxygen we would not survive.

fish breathe

The arrows point to the fish’s gills, just behind the mouth.

How Do Fish Breathe?

Fish, similar to mammals, need to get oxygen into their blood and then throughout their body.  However, fish do not breathe air nor do they have lungs (for the most part).

Instead fish take water in through their mouth.  Then they force the water out of their ‘gills’.  Gills are incredibly important for fish and serve the same role as lungs do for people and mammals.  The gills are able to take the oxygen out of the water and get it into their blood.

If fish are taken out of water their gills will not work with air.  This mean that similar to how people can’t breathe underwater, fish can’t breathe when out of water and would suffocate.

Extra Credit

*There are some fish that have lungs – lungfish.  These fish are able to get out of the water to travel over land for brief stretches of time.

*Sometimes you may see a fish’s gills working hard, opening and closing.  This is because it is trying to get more oxygen out of the water as if it is out of breath and needs to take big breaths.  This could happen because the water is dirty, polluted, or the fish has been out of the water for some time.