Written by Fernando Lopez
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Published on May 1, 2019
TAGS: fish, underwater, Water
Whether you love snorkeling and diving or have an aquarium filled with fish at home, you’ve probably wondered at some point how long can a fish stay out of water. You’re either worried about keeping your fish out for too long while changing their water or are simply curious about how certain types of fish are able to hang out above the surface of the water and seemingly breathe the same air as humans.
The fact is, there are many different species, types, and sizes of fish, and they obviously don’t all have the same breathing capabilities. Therefore, there’s no universal time period for how long a fish can survive out of water.
Before exploring this question further, let’s learn more about how fish are able to breathe underwater.
How do fish breathe underwater?
Like all marine creatures, fish need water to survive, but what many people don’t understand is that they are just as dependent on oxygen as we are. Most fish, if not all, get their oxygen supply in the water—which is where gills come into the picture.
Fish’s unique respiratory systems make use of gills to let water in and extract the oxygen from it using the tiny blood vessels found on the gills’ surface before discharging waste gases back out. You can say that gills work like our lungs, which are also uniquely designed to absorb atmospheric oxygen.
Another odd similarity is when fish allow themselves to be swept away by water currents so they can conserve their energy and oxygen supply in the water, which is basically the same as what we do when scuba diving. So when a fish is out of the water, the gills would normally arch and collapse as it’s unable to find oxygen the way it’s designed to. While it’s still a matter of debate if fish feel intense pain, they will die of suffocation, sometimes in a matter of seconds, when separated from the water.
But here’s another interesting fact: Some species of fish can actually live for a few days on land and can breathe air or absorb oxygen with their skin. These are typically amphibious fish and larger underwater creatures that are capable of storing air so they can last out of the water. It’s just a matter of how long and what they do to survive for surprisingly long periods of time.
How long can a fish survive out of water?
It’s important to note that the chances of a fish surviving out of water is determined by the conditions that they’re in while out of the water. For example, if a fish jumps out of an aquarium and lands on a non-absorbent surface with some of that water, it can survive by breathing the water’s dissolved oxygen content as long as its gills stay moist.
Below are some types of fish that will survive the longest—and shortest—when separated from water.
Pet Fish
Pet fish, like goldfish and rainbowfish, are much weaker than saltwater fish, plus they have small bodies and more fragile gills. They can suffocate and die quickly without water (following three to four minutes of no gill movement), so it’s important that you don’t take them out unless the new water is ready for their transfer.
Large Ocean Fish
Remember those species of fish that are able to breathe above the surface of the water? We’re talking about short-beaked dolphins, blue whales, sperm whales, beluga whales, and other sizable underwater creatures. The truth is, these are actually mammals that are commonly confused with fish because they live in the ocean.
As mammals, they have lungs and can hold their breath for long periods of time underwater They can also live for months on land, but will eventually have to return to the water to provide support for their bodies, or else their weight will crush their organs. Fortunately, this allows our favorite whales, dolphins, and some species of pinnipeds to put on a show for us above water and on land.
Mangrove Killifish
The mangrove killifish, or mangrove rivulus, are amphibious in nature and can live for about a month without water. According to research, they can absorb oxygen through their skin when they’re out of the water and have the ability to store them. They simply go back to using their gills when they’re back in the water.
Mudskippers
Mudskippers are also small, amphibious fish that can live on land for most of their lives. They are born with skin that consists of blood vessels near the surface, so they can absorb oxygen into their bloodstream without actively breathing through gills or lungs.
Walking Catfish
This unique species of fish have an extra organ that helps their gills inhale oxygen from the same air we breathe. Not only that, they can even “walk” or wiggle on land by flexing their body and using their pectoral fins to propel themselves, so you might find them on roads after big rainstorms.
The duration of survival will depend on the species
There are other species of fish that can live without water longer than most. The bottom line is that the duration will depend on the species. Some will die in a matter of seconds or minutes (pet fish) while others can stay out of water for hours to months (amphibious fish). One thing’s for sure: Whether you’re going fishing or are simply changing your goldfish’s water, don’t allow it to suffer for long through water deprivation.
