Do Fish Suffocate or Drown in the Air?

Unlike aquatic animals with lungs, like whales, dolphins and turtles, fish don't breathe air because they don't have lungs. Instead, fish use gills to extract the oxygen they need from the water. Just as any other living organism that needs oxygen to survive, if a fish is deprived of oxygen, it can suffocate and die.

  1. Drowning vs. Suffocation

    • Suffocation, regardless of whether an organism uses lungs or gills to breathe, is death from oxygen deprivation. The medical definition of drowning, according to Merriam-Webster.com, is suffocation in water or in another liquid, or suffocation due to excess body fluids interfering with oxygen passing from lungs to other tissues in the body. A fish can't drown in the air, because the air is not liquid. Also, a fish has no lungs, so they can't fill with excess body fluids. However, a fish that finds itself unable to take in enough oxygen through the gills will suffocate if left out of water -- in the air -- for too long.

    How Fish Breathe

    • While they don't have lungs to pull oxygen from the air, fish are still able to breathe by using their gills to absorb dissolved oxygen from the water. To breathe, fish take in water through the mouth and push it back out into the open water through the gills. There are many blood vessels in the gills, and as oxygen-rich water passes over them, the blood vessels absorb the oxygen from the water where it then enters the fish's bloodstream.

    How Gills Work

    • Blood flows through the vessels in gills in the opposite direction than the water passing over the gills, allowing for maximum diffusion of oxygen into the bloodstream. In order for this diffusion to take place, water needs to be moving over the gills. While swimming, water flows through the fish's open mouth and over the gills, but while stationary, the fish must pull the water in through the mouth while gills are shut. Once water is in the fish's mouth, the mouth shuts, and through contraction, the water is forced into the gills, which then open to let the water out as it flows over the gill surfaces.

    Out of Water

    • A fish out of water can still take in oxygen through its gills from the air, just not enough to survive. This is because gills don't function the same in the air as they do underwater. Out of the water, gills collapse, decreasing the surface space needed for oxygen diffusion to take place. Without sufficient oxygen being taken in, the fish will eventually suffocate. Fish can also suffocate in the water if oxygen levels have been depleted. If your fish tank has no aerator or water feature to help keep oxygen cycling into the water, you may notice your pet fish is spending a lot of time gulping at the water's surface. If this happens, it's quite possible your fish is seeking a source for oxygen.