How do fish breathe?

Fish breathe with the help of gills, specialized organs to take in oxygen from water. 

  • Step 1: Fish open their mouth and take in water
  • Step 2: The water flows over the gills on either side of its face.
  • Step 3: The gills have thin filaments called lamellae through which oxygen flows into their blood.
  • Step 4: The carbon dioxide in the blood goes out through the gills.
  • Step 5: The fish exhales, and the water goes out through the gill covers carrying the unwanted carbon dioxide.

What happens when you take a fish out of the water

There are several impacts to taking a fish out of water.

  • Loss of Oxygen: They lose their source of oxygen, the water. Lack of oxygen leads to suffocation.
  • Dry Out: The slimy layer on their scale dries out without the water.
  • Movement: Their body and fins have adapted to moving in water. Mobility is affected.
  • Temperature Shock: Water regulates the body temperature of fish. When taken out, they can experience shock based on the temperature of the air.

Do all species of fish breathe the same way?

The majority of fish are gill-breathers. There are some other unique breathing adaptations among fish.

  • Labyrinth Fish: Besides gills, they have a specialized labyrinth organ to breathe air from the surface.
  • Lungfish: They have both gills and lungs. During the dry season, they can survive by breathing air through their lungs.
  • Electric Eels: Have a modified respiratory system to breathe in air from the surface.
  • Mudskippers: Use gills to breathe underwater and their skin to breathe when on land.

Fun Fact: Only the deep sea coffinfish has been known to hold its breath for up to 4 minutes! 


Let’s quickly recap what we learned about how fish breathe:

  • What special organ does a majority of the fish use for breathing? Gills
  • What is the primary source of oxygen for most fish? Water
  • How does oxygen flow into the blood of the fish? Thin filaments in the gills
  • How do mudskippers breathe on land? Through their skin
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