The average human can hold their breath underwater for about 2 minutes. The record after breathing a lungful of pure oxygen first is 24 minutes and 3 seconds. However, we can’t survive long term under the water, and fish can’t survive for long out of it.
So, how long can a fish survive out of water?
The answer isn’t quite as simple as you would imagine. Since there are thousands of different types and species of fish, there are many times that fish can survive outside of the water for extended periods.
How Do Fish Breathe in the Water?
It is easier to understand how fish can’t survive out of water when you know how they survive in the water.
Fish rely on oxygen to be able to breathe, just like humans do. If you ever owned an aquarium, you probably had something that aerated the water for your fish. That machine’s purpose was to infuse the water with oxygen for the fish to continue to breathe.
Fish use a different respiratory system than humans. Fish use their gills to process all the water that they breathe in. There are tiny blood vessels close to the surface of the gills. These vessels work by extracting oxygen from the water and discharging waste.
Gills have a design that works somewhat similarly to our lungs. The crucial difference is that it involves absorbing atmospheric oxygen instead of sorting through various gases in the air and retaining the oxygen, as our lungs do.
So, when you take a fish out of the water, you will see its gills expanding and collapsing repeatedly. This movement is because they are trying to breathe in. Even though they are surrounded by oxygen, it is no longer usable for them.
Breathing on land is where the differences are between various species of fish. Some fish’s gills and respiratory systems will collapse within seconds. Others can live for a couple of days. They can do this because they have a way of absorbing oxygen through their skin or storing it inside them until they get back into the water.
The key for many fish is whether their gills stay moist. They can at least partially continue to absorb some oxygen while their gills are still wet. However, if a fish jumps out of an aquarium and lands on an absorbent substance, it will die much faster.
How Long Can a Fish Survive Out of Water?
Let’s break this answer into a few categories for accuracy’s sake.
Goldfish (and other pet fish)
How long your pet fish can last outside of water depends on whether they are freshwater or saltwater fish. Freshwater fish tend to be weaker than saltwater ones because they have fragile gills and smaller bodies. That adds up to a quick death outside of water. They will typically last a maximum of 10 minutes. However, if they panic, it can be less than 1 minute.
Saltwater fish will often survive longer, but not much longer than about 10 minutes, though sometimes they can last up to 20 minutes if they are on a non-absorbent substance.
Amphibious fish are unique compared to other fish species; they can leave the water for extended periods. Some spend more of their lives on land instead of under the water.
One example is the Atlantic mudskipper (Periophthalmus barbarus). They have adaptations that allow them to breathe oxygen through a special lining in their throats. They also have functioning gills that they use while under the water. They live almost 75% of their lives out of the water using these adaptations.
Depending on the amphibious fish species, they will have varying abilities to survive outside of the water.
Large Ocean Fish
This category is not about whales and dolphins. Although some people get them confused with fish, these animals are mammals. They require oxygen from the air to breathe. That is why they have to come up to the surface every once and a while before resubmerging themselves.
Sharks are excellent examples of large ocean fish. They can live outside of water for anywhere from a couple of minutes up to 11 hours.
The shark has adapted to staying out of water for that long because they spend most of their time hunting in the shallows, where it is more likely that they will get stranded when the tide goes out. But other fish, like the Great White Shark, will only be able to survive about as long as an average saltwater fish.
The walking catfish is unique. This species of fish has adapted to longer life outside of the water. They have developed an extra organ that allows their gills to absorb oxygen from the air.
They get the “walking” part of their name from wiggling on land and moving themselves using pectoral fins.
On average, fish can live about 10 minutes outside of water but can die faster if they land on an absorbent surface. However, saltwater fish will often live longer, and certain species, like amphibious fish, have particular adaptations that enable them to last for a long time outside of the water.
Featured Image Credit: Orla, Shutterstock