Fish are aquatic vertebrates that typically live and breathe underwater. However, the amount of time a fish can survive out of water varies greatly depending on the species. On average, most fish can only live for about 10 minutes outside of water before suffocating, but certain species have unique adaptations that allow them to survive for much longer periods.
Freshwater Fish
Freshwater fish, such as goldfish, tetras, and bettas, generally have the shortest out-of-water survival times. These fish are adapted to living in water with a consistent oxygen supply and can quickly suffocate when exposed to air. The average goldfish can only survive for up to an hour outside of water, while smaller species like neon tetras may only last for 10 minutes.
Saltwater Fish
Saltwater fish, on the other hand, tend to have a slightly longer out-of-water survival time compared to their freshwater counterparts. Clownfish, for example, can survive for a few hours out of water. Large saltwater fish, such as blue whales, can even live for several hours outside of water due to their larger body size, which allows them to maintain oxygen levels for longer.
Amphibious Fish
Some fish species have evolved unique adaptations that allow them to survive for extended periods out of water. These amphibious fish, also known as air-breathing fish, have specialized organs or behaviors that enable them to breathe air directly.
Mangrove Rivulus
One of the most remarkable examples of an amphibious fish is the mangrove rivulus. These small fish usually live in brackish pools, but when their habitat dries up, they have an amazing survival response: they hide inside logs. Mangrove rivulus can survive for up to 66 days without changing their metabolism while packed together inside moist cavities in rotten wood. Scientists believe these logs may also serve as boats, transporting the fish to new habitats during storms.
Snakehead Fish
Another air-breathing fish is the snakehead, which can survive out of water for several days. Snakeheads have a labyrinth organ that allows them to breathe air directly, and they can even move short distances on land using their pectoral fins.
Mudskippers
Mudskippers are amphibious fish that can spend up to 5 days out of water. These fish have adapted to life in the intertidal zones of tropical and subtropical regions, where they use their pectoral fins to “walk” on land and their skin to absorb oxygen directly from the air.
Lungfish
African lungfish are another remarkable example of an air-breathing fish. These fish can survive without water for up to five years by burrowing into the mud and entering a state of estivation (a type of dormancy similar to hibernation). During this time, their metabolism slows down, and they can survive on the small amount of oxygen they absorb through their skin.
Factors Affecting Out-of-Water Survival
Several factors can influence a fish’s ability to survive out of water, including:
Species: As discussed, some fish species are better adapted to life out of water than others.
Size: Larger fish tend to have a longer out-of-water survival time due to their ability to maintain oxygen levels for longer.
Water temperature: Fish in cold water generally have a longer out-of-water survival time because their metabolism and oxygen demand are lower.
Moisture: Keeping a fish’s gills and skin moist is crucial for survival out of water, as it prevents them from drying out and suffocating.
Handling Fish Out of Water
When handling fish out of water, it’s essential to minimize their time out of the water and keep them moist to ensure their survival. If a fish is caught for a photograph, it should be returned to the water as quickly as possible. If a fish appears to be struggling after being released, it may be necessary to perform “fish CPR” by moving the fish back and forth in the water to help increase its oxygen uptake and allow it to recover.
In conclusion, while most fish can only survive for a short time out of water, certain species have evolved remarkable adaptations that allow them to thrive in both aquatic and terrestrial environments. By understanding the unique characteristics of different fish species and taking appropriate precautions when handling them out of water, anglers and aquarium enthusiasts can help ensure the well-being of these fascinating creatures.