How long can a fish live out of water?

Whether it be out of curiosity or concern for our fish, something that we all have wondered is how long a fish can live out of water.

Whether it be from fascination by this creature that is so different from ourselves or ensuring that you don’t accidentally suffocate your goldfish the next time you change its water. Either way, there isn’t a solid answer to this question. 

There are so many different types of fish out there, different species, different breeds, different sizes. All of which will have different breathing abilities. So there is no specific period in which a fish can live out of water.

But to get a better understanding, you should understand how fish breathe and how this differs from species to species. 

How do fish breathe?

Just like the majority of creatures on this planet, just like human beings, fish are dependent on oxygen to be able to breathe and survive. But as fish live underwater they cannot get their oxygen by simply breathing in air from the earth’s atmosphere. This is why they have gills. 

The gills allow water in and in the process extract the oxygen from the water. They do this using the small blood vessels that coat the fish’s gills, with all discharge water and waste gases being released back into the ocean. So on a basic level, the gills work very similarly to our lungs. They inhale, take all the nutrients they need then exhale all the necessary gases. 

We may view fish as being the complete opposite of us as human beings. We have legs, they have fins. We have lungs, they have gills. We can only survive on land, they can only survive in water. But we have a lot more in common with fish than we realize. 

We’ve already discussed the similarities between their breathing abilities and ours, but it stretches further than this. To conserve energy and oxygen fish will stop actively swimming and allow themselves to be swept away by the current. Similar to how we will rest when we need to conserve energy. 

Once a fish has been removed from water their gills will still attempt to find oxygen. This process is observable as you will be able to see their gills rising in an arch then falling back flat when they are unable to take in any water. Eventually, the fish will die from suffocation as they are unable to access oxygen. But the time this takes will depend on the fish. 

How long do fish breathe out of water?

As we’ve already explained, the amount of time that a fish will survive out of water depends on the type of fish.

Some fish will suffocate within minutes, even seconds, while others can live for hours and sometimes even months. It is unsure exactly how much pain or discomfort this causes the fish, but you shouldn’t let a fish suffer from water deprivation. 

The species of fish affects the amount of time that they can breathe out of the water, but the conditions also make a difference. A fish does not need to be fully submerged in water to be able to survive, as long as their gills have access to water this might increase the amount of time they can survive.

So if a fish who lives in an aquarium manages to jump out of its tank and finds itself beached on a surface outside of the water it could survive. This would depend on the surface being non-absorbent and there being water on its surface. The water would allow the fish’s gills to stay moist and prolong their life. 

However most fish will not be able to survive out of water for very long, and you should try and avoid your fish speeding any time out of the water at all. 

Different Species

There are lots of different types of fish that will be able to survive for different amounts of time out of the water. 

For example, fish that we keep as pets tend to be a lot weaker than fish who live in the ocean. They are a fragile species and because of this they typically live much shorter lives than some saltwater fish species.

Without water, your pet fish, whether it be a goldfish or rainbow fish, will suffocate quickly and die within minutes. This is why you must be careful when cleaning the tank. Your fish should go immediately from their original tank into another tank of water, and you should keep the time they are out of water down to seconds. 

Some people may be deceived into believing that some fish breathe oxygen from the air as humans do. It is a common misconception that whales and dolphins are fish, but they are mammals and have lungs just like ours. This is why they need to leave the water to be able to breathe. They do not have gills so they have to hold their breath while underwater and come up for air regularly.

But even though they are mammals, these species cannot survive out of water. Mammals that live in water tend to have larger bodies that cannot be supported out of the water, leaving them mid-way between fish and mammals. 

But there are some fish which can survive for long periods out of water. These are mostly amphibious fish that have adapted to be able to get oxygen through other ways than their gills.

One species that does this is the mangrove killifish. These fish can absorb oxygen through their skin, as well as through their gills, which allows them to survive out of water for up to 1 month. 

Summary

So in short, there is no precise answer to the question ‘How long can a fish live out of water?

As is often the case, the answer differs depending on the species and size of fish. But for most fish, excluding amphibious fish, any period of time out of water is not a good thing.

Being out of water is actively killing the fish and they should return to the water as soon as possible in order to survive.