6 Fish That Can Survive Without Oxygen — And How They Do It

Most fish need oxygen-rich water to survive. But there are a few remarkable species that have figured out how to live when that oxygen runs low– or disappears altogether. From ponds that go still and stale to floodplains that dry up completely, these fish have found clever ways to adapt. Some breathe air, some use their skin, and a few can even leave the water for short periods.And no, this isn’t science fiction. These are real fish, living in real, often extreme, environments. Their survival skills are the result of slow and steady evolution, shaped over millions of years. In the face of changing conditions, they’ve learned how to thrive– making them some of the most adaptable creatures in the freshwater world.Here are six such fish that break the usual rules of aquatic life– and the surprising ways they do it.African LungfishIn parts of Africa where rivers dry up seasonally, the African lungfish has an incredible way to stay alive. When water disappears, it buries itself in mud and creates a protective mucous shell. Inside this cocoon, it slows down its body functions and breathes using its lungs– not gills. This state, known as estivation, helps it survive long dry spells until water returns.Mangrove RivulusThis tiny fish from the Americas doesn’t panic when oxygen runs low– it just leaves the water. When tidal pools dry up, the mangrove rivulus crawls into moist leaf litter or decaying wood. There, it absorbs oxygen through its skin. This clever trick helps it stay alive in tough conditions that would kill most other fish.Walking CatfishOriginally found in Southeast Asia, the walking catfish lives up to its name. It uses its fins to “walk” on land, especially when its pond starts drying up. It has a special organ that allows it to breathe air, giving it enough time to find a better spot with water. It can stay out of water for several hours while on the move.Amazon MollyThe Amazon molly, found in parts of Texas and Mexico, is used to living in warm, slow-flowing waters where oxygen is scarce. Its gills are specially adapted to absorb more oxygen than usual, helping it stay active and healthy in conditions where other fish might struggle.Siamese Fighting Fish (Betta)Known for their bright colours in aquariums, these fish are native to Thailand and nearby regions. In the wild, they live in shallow waters like rice fields and ditches, which often lack oxygen. Luckily, they have a unique “labyrinth organ” that lets them gulp air from the surface– a major advantage in low-oxygen environments.BichirThe bichir is a prehistoric-looking fish found in parts of Africa. It has real lungs and regularly comes to the surface to breathe air. This ability helps it live in swampy or slow-moving waters that don’t have much oxygen, especially during the dry season.