Can Fish Drown? Find Out Here

can fish drown

Fish live underwater. We humans would drown underwater. Can fish drown under water? How do the fish do it?

Here is the paradox. Fish need oxygen to breathe. So why do you need to spend money on pumps and filters? Can fish drown? Even through they have gills and live comfortabley under water?

Why don’t fish drown?

Can fish drown? They live underwater. We humans would drown underwater. How do the fish do it?

It is actually strange that fish cannot breathe on land. The reason for this is surprising

Our air has a much higher proportion of oxygen than water. But why can’t fish still breathe on land? Fish also need oxygen. To do this, fish absorb oxygen through their gills and give off carbon dioxide. Fish the size of the red neon require around 10 to 30 mg of oxygen per day.

There is about 30 times less oxygen in water than in air. One liter of air contains about 260 mg of oxygen, one liter of water 8.5 mg at 25 ° C and sea level.

However, they do not have lungs, but gills through which they absorb the oxygen dissolved in the water. Gills are designed to be constantly filled with water. They don’t work on land. Therefore, fish can suffocate in the air.

Sure, they don’t have lungs like humans do, but gills. But oxygen from the air can certainly be absorbed through the gills, some fish do that too if necessary. In principle, this would even be quite efficient for the fish, because the air we breathe has a much higher proportion of oxygen than water. Then why don’t fish do that?

This has to do with the fact that fish in the water not only absorb oxygen with their gills, but also get rid of metabolic end products such as carbon dioxide and nitrogen-containing ammonia. The fish inhales and exhales with one gulp, refreshing its blood and removing residues from it at the same time.

Fish breathing

Are there fish species that can drown?

Yes, there are fish species that can drown. They need to surface and breathe air regularly. If they don’t, they will suffocate and drown. 

But fish live in water and have gills. How can fish drown?

The fish species that can drown normally start to gasps for air as they suffocate.

The fish that can drown are called “surface breathers”. 

Just like human and most living things, they need oxygen. What is special about them is that over time they have developed a special organ with which they can breathe air over water.

Some of them have reduced their gills so much, even literally volute them, because they no longer needed them. That is why they have to go to the water surface. They do not breathe in enough oxygen through their gills, although the water in which they are romping might be rich in oxygen.

Which fish species can drown?

1. Labyrinth Fish

A good example if the labyrinth fish which is also referred to as climbing fish. The Labyrinth fish have to go to the surface of the water to take a breath.

Labyrinth fish are a pure freshwater fish and he likes water temperatures of 23-26 degrees Celsius. Examples of labyrinth fish are the Fighting fish and licorice gouramis.

The extraordinary thing about them is their so-called labyrinth organ, a special respiratory organ that consists of skin folds that are well supplied with blood and are arranged like a labyrinth and that lies above the gills. 

Where do labyrinths mostly habitate? 

They live mainly in the waters of Southeast Asia, Indonesia and Africa, as well as South Korea and China. Some species can grow to around two feet. Labyrinth fish belong to the group of carnivorous coarse fish, i.e. they feed on zooplankton, insects and various small crustaceans.

2. Lungfish

The Lungfish can drown. It is actually the case that the lungfish does most of its breathing through the lungs. It looks inconspicuous, a bit like a small eel. The lungs are a protuberance of the foregut and lie behind the gills. The paddle-like pectoral and anal fins are more noticeable. The latter resemble limbs with two fingers and make it clear what the lungfish is: the transitional form from fish to reptile that is still alive today.

3. Bichir (Raft fish or Pike fish)

The gills of this fish are not powerful enough on their own to absorb enough oxygen from the water. The swim bladder serves as a lung. The fish has to come to the surface of the water every now and then to take a breath. Probably this is even the genealogical older function of the organ.

can fish drown
Can fish drown?



Why don’t the rest of the fish species drown in water?

Fish have a so-called trap apparatus. This means that the water does not get into your stomach when you breathe or ingest food, but is drained away through the gills behind your head. The oxygen enters the bloodstream directly through the gills.

Many fish also have a swim bladder, which acts as a respiratory organ and is stored in the air. The swim bladder adjusts the weight of the fish to that of the water so that it floats in the water. In addition, the swim bladder has a connection to the gill intestine, through which oxygen is released and new air is taken in from outside. Fish that do not have a swim bladder have to create buoyancy by constantly swimming in order not to drown.

How do fish actually breathe?

1. Through Gills

Fish have gills on either side of their head. When the fish ingest water, the water flows in through their mouth and is pushed out of their gills.

can fish drown
Can fish drown?

The fish gills are composed mostly of chloride cells (involved in ion exchange) and densely packed capillaries for gas exchange. The water is pumped opposite to the blood flow, creating a counter-current exchange of oxygen from the water to the blood.

The deoxygenated blood is then pumped from the heart to the gills for the gas exchange. The oxygenated blood is pushed from the gills to the rest of the body, without returning to the heart.

That is why fish have a two-chambered heart.

2. Though basic “lungs”

Only the lungfish has these simple “lungs”.

The lungfish has basic lungs and must swim to the surface of the water to breath. They have evolved two specialized swim bladders that are surrounded by capillaries, which allows for oxygen to diffuse directly into their blood stream.

can fish drown
Can fish drown?

The capillary system allows them to use the same two-chamber heart as other fish, but with an added bonus; their lungs allow them to survive should their habitat dry up. When their habitat dries up they form a cocoon of mucus to cover the upper part of their body, which allows them to survive out of water for more than 20 weeks!

Fish suffocating (Fish gasping for breath): symptoms, causes, and treatment

Brief information on gasping for air

Main symptoms: fish hangs under the surface of the water gasping for air.
Causes: lack of oxygen, gill worms, gill parasites.
Cure: curable if diagnosed in good time.
Treatment: Lots of water changes, oxygen supply, remedies

Suffocating behavior

  • Fish hangs under the water surface
  • Fish gasps violently

Suffocating symptoms

Salmer swim head up for three days. The belly was curved to the side and a little darker. The tetra stopped eating.

Causes of suffocating in fish

The immediate cause of gasping for breath is always a lack of oxygen. This in turn can have different reasons

  • Too little oxygen in the water, e.g. B. at high temperatures
  • Mucous gills
  • Gill worms
  • Gill parasites

If, for example, several fish suddenly look for air on the surface of the water in summer, there is probably too little oxygen in the water. Possible causes:

  • Putrefaction processes in the soil use too much oxygen.
  • Putrefaction processes in the filter consume too much oxygen.
  • Too few plants produce too little oxygen.
  • Too many fish use too much oxygen.
  • Due to high temperatures, the water absorbs too little oxygen.

If only individual fish are affected, there is probably a problem with the gills so that too little oxygen can be absorbed. Gill problems that can lead to violent gasping for air:

  • Gill worms
  • Parasites on the gills, e.g. 
    • Ichthyo
    • Velvet disease
    • Epitheliocystis
  • The gills were corroded by the pH value being too low.

Take action to prevent fish from suffocating

In any case, it makes sense to enrich the water with an oxygen stone and by moving the water surface with oxygen. This definitely makes breathing easier. Water changes with plenty of fresh water can quickly bring oxygen into the aquarium water.

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