Can Fish Drown? Can you suffocate a fish in water?

Can Fish Drown in Water

Can Fish Drown in Regular Water?

Thinking about the lifetime of a fish, ends up in many questions like ‘can fish drown in water?’ or ‘how do fish mate?’ and ‘do fish sleep?’… Also, a general and common question people ask is: “can fish drown?”

It’s easy to take fish without any consideration. You forget how impressive it’s that they manage to live in a very vastly different environment to us.

Fish Need oxygen similar to humans do, but because they live in water, it doesn’t look like they’d be ready to drown. They’ve adapted gills that allow them to extract oxygen from the water so is it possible to drown once they can take a breath in water?

Here we will investigate the question by observing some important factors like do fish have lungs, how fish breathe, and many more…

Keep reading to search out everything you would like to understand about how oxygen is dissolved in water, how fish breathe, and what may lead to a fish drowning.

1. Do Fish Need Oxygen To Breathe

In order to know how oxygen levels in water affect fish, it’s important to see how oxygen moves from the air into the water in the first place.

Dissolved oxygen (DO) is the scientific measurement used to determine what quantity of oxygen is in the water and prepared to be utilized by living organisms. Dissolved oxygen is influenced by plenty of things, including depth, temperature, atmospheric exchange, outside sources, and photosynthesis.

As humans we want oxygen to breathe; fish are not any different. rather than taking oxygen from the air like us, they collect dissolved oxygen from the water as they swim.

There are tons more oxygen in the air than there’s in water. This makes it much easier to get oxygen when living on land, but fish have evolved gills to allow them to survive in water.

Taking a breath inside the water has its problems. The salt levels of water may vary a lot.

  • Saltwater fish absorb a huge amount of salt while respiring because it’s in the water. Consequently, they require a specialized mechanism to get rid of excess salt from their body.

  • Freshwater fish have an alternative problem. There isn’t much salt in the water, that’s why they need a mechanism to carry on to the maximum amount of it as they can.

Fish need oxygen for a similar reason as humans. Without it, they’ll struggle to breathe, and eventually, die.

Oxygen gets combined with other elements to form proteins and even form new cells.

When breaking down food inside the body, oxygen is utilized to convert and store its energy. This energy is used altogether by active processes within the body.

Fish don’t need quite the maximum amount of oxygen as us since they’re cold-blooded. Warm-blooded animals need extra energy to keep their body heated. Fish do not require this energy. So they can survive with a very less amount food and oxygen.

There’s a finite amount of oxygen inside a body of water. The larger the body of water, the larger the area, and as a result the more oxygen.

In an aquarium, this will be a very big problem. There’s only a little amount of water, meaning it can quickly run out of oxygen. This can be only one reason why tank size is so important.

Aquarists can use plants to introduce some oxygen into the tank as they photosynthesize. Air pumps are useful too as they convey oxygen-depleted water up to the surface, forming a little circulation.

2. Do Fish Have Lungs and What Are Labyrinth Organs of Fish?

Typically, fish don’t have lungs. Most of them that you’ll ever see or hear about will have a collection of gills on either side of their body; however, this isn’t the case for all fish.

There’s a bunch of fish called Lungfishes. As you may guess from the name, they have air-breathing lungs rather than gills.

They’re a tiny group of six freshwater species which can only be found in Africa, Australia, and South America.

African and South American species can survive their habitat drying out by burrowing into the substrate and entering a state almost like hibernation. They are doing this by slowing their metabolism right down to 1/60th of its normal rate.

There used to be tons more lungfish and they were spread throughout a bigger network of freshwater rivers and lakes. The number of Lungfishes has dropped down dramatically since Pangaea broke apart.

Lungfish aren’t the sole fish that can breathe air, some have a labyrinth organ. This organ acts as a lung, letting fish take oxygen from the air instead of water. It’s not usually present in juveniles, they begin with gills and later grow labyrinth organs.

Lots of aquarium fish have labyrinth organs, like crowntail bettas and kissing gouramis.

While breathing air could be a primitive trait for fish, it can allow them to live in waters that may not be survivable for any fish respiring inside the polluted water.

However in most places, the water is perfectly safe, so fish don’t need lungs to breathe the air because there’s enough oxygen in the water. Alternatively, fish have gills that are perfectly adapted for collecting this oxygen.

3. How Do Fish Breathe and Get Oxygen In Water?

Firstly, we have to see how fish get oxygen, and how they breathe before we can answer the question “can fish drown?”…

Since there is a very less amount of oxygen in water compared to air, you require much more efficient surfaces to exchange gas in order to collect it.

Fish own gills that are able to take in oxygen when it is just at 5 only parts per million (ppm). We do breathe air, 21% of which is oxygen (210,000 ppm). These gills are an extensive network of capillaries that is filled with blood providing a large surface area for the exchange of carbon dioxide and oxygen.

It should be mentioned that there are invertebrates and fish which can breathe in both the water and out of the water, but, we will not be discussing the physiology of these species in this article.

For typical fish:

First, fish take in oxygen through their mouth. Then they generate pressure in their mouths which drives the water to cross the thin layers of the gills. Dissolved oxygen diffuses into the bloodstream. It is because of concentrations of oxygen being lower in the blood than in the surrounding water.

This is not only about efficiency although, gas exchange surfaces (like lungs and gills) required to be able to deal with the medium you are in ( water or air). Let’s take an example, our lungs can force air in and out, but we would suffocate if water filled the lungs.

So, how do gills work?

Firstly water is required to pass across them, which is regulated by the operculum (this is a flap of skin that acts as a boundary between the gills and the mouth). The fish reduces the floor of their mouth. It makes the pressure inside the mouth lower than the pressure outside. So water is drawn in.

When the fish increases the floor of their mouth, the pressure residing inside the mouth becomes higher than the pressure residing outside. It forces water out of the mouth through the operculum, and also across the gills.

If you have fish and keep them at home you can notice this happens, the operculum moves each breath. This site is one of the many reasons to keep fish.

The gills need a large surface area to extract oxygen from the water. The larger surface means as much water as possible may come into touch with the gills for oxygen to diffuse across.

When water comes into touch with the gills then the oxygen is transferred from the water to the blood through the edge of the lamellae. Each gill arch holds rows of lamellae and filaments, creating an appearance like a car radiator.

The anatomy of Gill can get a little bit confusing, but here is a basic overview.

4. So, Can Fish Actually Drown In Water?

To answer this question, we have to think about the definition of the word “drown”. This is a verb which is defined as when you “die through submersion in and inhalation of water”…

With humans, when water gets inside our lungs we can not get oxygen from it, so we can not breathe, and therefore, we die.

We already have learned that fish can extract dissolved oxygen from the water, so fish are physically not capable of drowning.

Fish will die if fish are taken out of the water, but not due to inhalation or submersion of water, so they are not drowning.

If there is not a sufficient amount of dissolved oxygen in the water, then they will die because they can’t breathe. You may argue that the fish has died through the“submersion in and inhalation of water” because the water inhaled does not contain enough oxygen. This does not fully meet the definition though.

So, if you have wondered if fish can drown, probably the answer is no.

A more perfect term is probably that fish “suffocate” when there is not a sufficient amount of oxygen for them to breathe. To suffocate is defined as to “die from lack of sufficient air or not able to breathe”.

5. Respiration System

However, the organisms which do not undergo photosynthesis and undergo respiration instead, where oxygen is transformed into carbon dioxide. This includes snails, fish, crabs, as well as the same phytoplankton that we discussed before!

One of the largest groups which use respiration is bacteria. As nutrients and minerals enter into a system, algae and other photosynthetic organisms start to thrive in this eutrophic situation; this is generally caused by the runoff of fertilizers and some other nutrient-rich-solutions that unnaturally enters into an ecosystem.

The algae may become so thick that the water is stained green. It blocks out all light from penetrating past the initial few inches of water. This eventually results in aquatic plants starving due to being unable to undergo photosynthesis.

Simultaneously, the algae start to die as the excessive nutrients are depleted and absorbed from the water. This is when bacteria begin to decompose the decaying algae and some other vegetation.

Because there is a lot of this food to keep the population of the bacteria thriving, numbers increases and that’s how respiration also increases, depleting the oxygen levels as they respire. As the levels of oxygen quickly reduce, the water becomes anoxic.

When there is such a shortage of oxygen, all organisms which need oxygen to survive generally die. These areas are called dead zones where aquatic life can’t be supported.

6. Fish Suffocation and Drowning in Water

Fish will have access to oxygen when they are out of the water, and at a higher concentration. You may wonder what causes fish to die if they can still breathe. Well, the answer is they can’t breathe, however, it is not because of a lack of oxygen.

Fish can’t breathe, because the gills aren’t designed to process air, however, it does not mean that they can’t do it. The main issue is that the air dries them out. That’s why they can no longer work properly.

It’s like being dehydrated. A fish’s body stays moist when living in the water. Since the gills are designed to be moist, they will not work if they dry up out of water.

A fish may suffocate under the aquarium water as well as out of it. There are a lot of possibilities where this could happen. Any harm to the fish gills will decrease their capacity to collect oxygen, potentially to a particular point where they can’t get sufficient oxygen to survive. Damage could come through disease or fighting.

Some other causes of suffocation are things that reduce the concentration of oxygen in the water. The rise in population size is a good example, more fish are respiring and using up the amount of oxygen.

If oxygen is not being replenished fast enough then it can run out. In a fish tank, this may happen fast because they normally contain such a small body of water. Pollution can lead to a rapid de-oxygenation of water in a natural environment that can’t be replaced fast enough.

7. The Atmospheric Exchange

How does oxygen enter the water column in the first place? One of the important ways oxygen enters the water column is through the surface exchange.

For the major portion, it is accomplished by water mixing with atmospheric oxygen via waves and wind. It means rivers that are highly turbulent can usually have higher dissolved oxygen concentrations than stagnant lakes.

8. Depth and Temperature of Water

Coldwater can possess more dissolved oxygen, alternatively, warm water will hold less amount of dissolved oxygen.

It means that when the surface water temperatures are very low (so far there is no interference of exchange between the water and air due to ice), dissolved oxygen concentration may be much higher. When the surface water temperature is high, then the dissolved oxygen concentration will be below.

Altitudes and latitudes, as well as seasons mostly affect how much-dissolved oxygen is really available in the water column. Salinity can also influence saltwater systems versus freshwater concentrations.

These are the main reasons why there is a concern for the average temperature of the Earth is rising; as the atmosphere warms, the surface waters will also warm and the exchange of oxygen will slow down. The organisms which require oxygen to survive will face decreasing levels of dissolved oxygen.

9. The Outside Sources

Eventually, these rivers feed into larger bodies of water, although, bringing the dissolved oxygen with the water and influencing naturally occurring concentrations in those areas. Some of the streams are additionally fed by groundwater, which can also influence dissolved oxygen concentrations.

10. Photosynthesis

Lastly, unlike trees that undergo photosynthesis, vegetation and aquatic plants also convert carbon dioxide into oxygen at the time of processing their own food. One autotrophic plankton is known as the phytoplankton is especially necessary for contributing to dissolved oxygen levels by performing photosynthesis in the daytime in surface waters.

Can Fish Drown? (Summary)

Can fish drown? Absolutely Yes, fish can ‘drown’–for lack of a better word. And also having your fish drowning is surely not a pleasant experience. Although, it is good to think of it as a kind of suffocation where oxygen levels are too low or the fish is unable to properly pull oxygen from the water for one or some other reason.

If we are being critical then fish will not really drown, but taking a fish out of water is exactly the same as putting a human in it.

In both cases, the subject can’t breathe in a totally new environment. Lungs and Gills are designed for use in air or water, and they are much more active in their natural habitat than the other habitat.

Having considered the word “drown” you actually realize that fish do not die through the inhalation of water. So while fish can’t drown, they can go through the same experience when out of oxygen or water.

Always try to keep dissolved oxygen levels up in your aquarium by having lots of water movement and exchange with air at the surface level. Maintain water parameters, avoid fish that have modified bodies, and look out for disease and parasites and hopefully, you will not require to experience what happens when fish drown.

If you have any doubt regarding how fish drown, why fish need oxygen, or how air interacts with water, do not hesitate to leave a comment below!


Dibyajyoti Bordoloi is the creator and author of, a third-generation experienced fish keeper and owner of a successful pet breeding farm. He is also a member of the Center for Wildlife Rehabilitation And Conservation (Assam), the Marine Aquarium Societies of North East India, and the Kaziranga Nature Conservancy of Assam.