How Long Can Fish Survive Out of Water? (Explained)

Anyone who has reared fish for long enough has encountered the brave jumper – the escape artist that finds, only too soon, it is unable to breathe out of water! Oftentimes, this jumping behavior may be the result of unfavorable pond conditions, rather than the sheer curiosity or the adventurousness of your fish. Unbeknownst to them, life out of water is harsh. 

Fish need oxygen, just as we do. Unlike us, however, they need water to breathe despite the availability of oxygen in the air. Unsurprisingly, given millions of years’ worth of evolution, there are a few fish species that can survive on land and have adaptations that allow them to live outside of water. These species are more amphibious, though still formally categorized as fish. Unlike your typical pond fish, they have physical features that allow them to breathe through their skin or store large amounts of air at a time.

Unfortunately, freshwater pond fish are not equipped to survive for a long time on land. If you see one venture out of your pond, don’t waste time before rushing to save it and then checking on your pond’s water conditions. How long a fish can survive out of water will typically depend on the species, the environment into which it jumps, its size, and any jump-related injuries. This length of time can range from just a few seconds to even hours, days, or months!

To fully understand this phenomenon, it is important to first familiarize yourself with how fish breathe and what factors propel them to leave the water.

How Do Fish Breathe?

Fish use their gills to breathe. These are equipped with structures that permit the continuous flow of water. Oxygen in its dissolved form is absorbed from the water and into the gill membrane, which is innervated with blood. The mechanism by which oxygen is able to enter a fish’s bloodstream is called diffusion, and is a truly ingenious and efficient means of breathing. This mechanism is employed by our own respiratory systems too, albeit deep inside our lungs.

Diffusion occurs because blood passes through gills in a direction opposing the flow of water. This way, the membranes that are first exposed to oxygen-rich water are oxygen-poor in blood. The difference in oxygen concentrations induces uptake through the gill membrane, as oxygen generally moves from a high-concentration environment to one with a lower concentration. This mechanism makes it possible for fish to potentially survive out of water if they jump onto an area with considerable moisture, like a puddle, that can still come into contact with their gills.

Species-Dependent Survival Times

1) How Long Can Pond Fish Survive Out of Water?

Typical pond fish species, such as koi carp and goldfish, are not equipped with special mechanisms for surviving outside of water. They will quickly deteriorate within a few seconds of gill exposure to air, and will seldom survive past the 3- to 5-minute mark without access to water.

Smaller fish, with more fragile gills, may be unsalvageable as opposed to larger fish with sturdier gills. In some cases, a quick response from the pond owner can save a fish escapee, but this will require a methodical approach and may involve the use of medication. For the largest and most hardy of common fish species kept as pets, the fish may survive up to 10 minutes but with possible permanent damage and lasting effects to gills and tissue.

2) How Long Can Amphibious Fish Survive Out of Water?

Amphibious fish, such as mudskippers and mangrove killifish, are able to live for months outside of water! These species have special adaptations that allow them to live and even move over considerable distances on land. They are able to absorb oxygen through their skin, which is packed with blood vessels. A humid habitat is still necessary for their survival, however, as they must keep their skin moist for oxygen diffusion to occur. These species are generally found in estuaries, mudflats, mangrove forests, and swamplands.

3) How Long Can Walking Catfish Survive Outside Water?

Walking catfish are airbreathing freshwater species that are capable of wriggling about on land in search of suitable aquatic environments and food. These fish have specialized gill structures that allow them to take in oxygen from the same air we breathe. Walking catfish can supposedly last for up to 18 hours out of water, during which they use their pectoral fins to “walk” over distances of up to 1.2 kilometers! They are able to navigate using chemoreception, which is akin to our senses of taste and smell.

4) How Long Can Lungfish Survive Outside Water?

Lungfish belong to a small group of freshwater fish species that are able to breathe air on land. Regarded as the descendants of the ancient Osteichthyes (bony fish), they are among a handful of extant fish species that are equipped with actual lungs! These rare fish alternate between using their lungs and gills to breathe, depending on their exposure to water. They can live for up to 4 years outside of water, as they enter a dormant stage called aestivation. This amazing adaptation allows them to survive in the event that their habitats dry up. 

Why Is My Fish Out of Water in the First Place?

In the same way that we gravitate towards spaces with clean air, fish instinctively shy away from poor water conditions. If your pond’s water quality is compromised by high concentrations of toxic nutrients, your fish may grow unwell and feel compelled to escape.

The same goes for low oxygen concentrations, which can initially be signaled by fish gasping for air or congregating at the water’s surface. If you observe this behavior, make sure to test your pond’s dissolved oxygen levels right away and provide a supplementary means of aeration. Parasites may also trigger fish escapes, though they are more difficult to test for.

In some cases, fish may jump out of your pond if they are being chased or threatened. This is usually rare, but can occur when they are threatened by predators or when females are aggressively being chased by males during the mating season. Even more infrequent are fish jumping out of ponds during intense earthquakes. When nothing is out of the ordinary and your fish energetically leap out of the water, they may also simply be playing with one another or eager to receive some treats from you!