11 Largest Freshwater Fish in the World

The ocean isn't the only place where behemoth fish can be found. Hidden beneath the murky waters of our freshwater rivers and lakes are huge fish. While most freshwater fish are smaller than their counterparts in the salty ocean, there are some that can grow to impressive sizes.

From bull sharks to giant stingrays, here are some of the largest freshwater fish in the world.

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Beluga

The beluga is a species of sturgeon that inhabits portions of the Black Sea and the Caspian Sea. Because they continue to grow throughout their lifetime (which can be 100 years), the beluga might be the world's largest freshwater fish. Some of the largest belugas discovered have been nearly 24 feet long and weigh more than 3,500 pounds—numbers that also put them in contention for being the largest bony fish in the world by mass.

The beluga hatches its eggs in freshwater rivers, then lives its adult life in saltwater, returning upriver to spawn. Females do not reach maturity until 15 years of age. The beluga is also critically endangered, with a decreasing population.

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Mekong Giant Catfish

Eugene_Sim / Getty Images

Many species of catfish can grow to mammoth sizes, but none compare to the Mekong giant catfish of Southeast Asia. Capable of growing up to 10 feet long and weighing more than 650 pounds, their size makes them a prized catch, and these giant catfish have been fished to near extinction. They have a remarkably fast growth rate, reaching 440 pounds in six years—and living up to 60 years.

Though they are now protected by national legislation in Thailand and Laos, they are likely to remain critically endangered due to the construction of upstream dams on the Mekong River.

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Alligator Gar

Due to a dual row of large teeth and a snout like an alligator, these carnivorous fish are able to live in fresh and saltwater. Measuring as long as 10 feet and weighing as much as 350 pounds, alligator gars are the second largest fish in North America.

They live up to 50 years and have few natural predators. Found in the lower Mississippi River basin and in the waters of the Gulf Coast states, these fish tend to swim near the surface or among reeds where they can stalk and ambush prey, which they consume dead or alive.

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Arapaima

Found in the Amazon River, these giant fish are as ancient as they are large. Also known as pirarucu in Brazil and paiche in Peru, arapaima have been around since the Miocene and are considered living fossils. Once capable of growing to a length of 10 feet and a weight of 300 pounds, due to overfishing arapaima now reach about six feet in length and 275 pounds. These fish are able to breathe air and can survive up to 24 hours outside the water. It's found in Brazil, Peru, and Guyana.

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Giant Freshwater Stingray

One of the largest freshwater species in the world, the giant stingray was first identified by scientists in the 1990s. These freshwater fish can grow to massive sizes, with some weighing in excess of 1,300 pounds and measuring nearly 15 feet across—half the length of a bus. They've been known to pull boats up and down rivers, and even down into the water.

Found in the rivers of Southeast Asia, they have tails that measure up to 15 inches long with a serrated spike that is capable of piercing bone and injecting venom. Unfortunately, the giant freshwater stingray is endangered due to fishing and habitat loss.

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Paddlefish

There are two extant species of paddlefish, one Chinese and the other American. They usually range from five to seven feet in length and weigh in around 60 pounds. The Chinese paddlefish—the larger of the two species, sometimes measuring as long as 10 feet—is critically endangered and believed to be possibly extinct.

Inhabiting the Yangtze River, these fish are mostly threatened by overharvesting and habitat loss. American paddlefish, which are listed as vulnerable, once inhabited the Great Lakes in Canada but now exclusively live in the Mississippi River basin. They can grow to lengths of eight feet and weigh up to 150 pounds, living for 30 years in the wild.

Easily recognizable by their paddle-shaped snouts, these river giants are harmless filter-feeders, opening their mouths only to capture zooplankton.

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Giant Barb

Giant Siamese carp in clear blue water — Jurgen & Christine Sohns / Getty Images

Carp of all varieties can grow to formidable sizes, but none are as large as the giant barb, aka King of Fish, found in Southeast Asia. This species of carp regularly grows to 10 feet in length; adults are rarely found under five feet.

Although they grow to such large sizes, giant barbs are harmless. They prefer to eat small organisms like algae, phytoplankton, and occasionally fruit. The giant barb is critically endangered due to overfishing and habitat loss.

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White Sturgeon

Easily the largest freshwater fish in North America, the white sturgeon can grow to 12 to 20 feet in length and can weigh nearly one ton. It's an ancient fish whose appearance has not changed in 175 million years. Found along the West Coast of North America, and as far north as the Aleutian Islands, white sturgeon inhabit rivers, streams, estuaries, and the sea.

They migrate upriver to spawn and have a lifespan of 80 to 100 years. Due to their size, white sturgeon are a popular target for fishermen, and while not federally listed, they are categorized as a state Species of Special Concern in California.

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Nile Perch

Native to the tropical rivers and lakes of Africa, the Nile perch is the continent's largest freshwater fish. Capable of reaching a maximum length of six feet, these fish typically range from two and a half to three and a half feet. It looks similar to a barramundi.

Due to its popularity among fishermen, the Nile perch has been introduced to many nonnative lakes and has become a dangerous invasive species. This has been especially tragic in Lake Victoria, where more than 200 native species have been driven to extinction due to the introduction of the Nile perch.

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Siberian Taimen

Fisherman in lake holding a taimen above the water — Peter Zachar / Shutterstock

The Siberian taimen, found in freshwater rivers and lakes in Russia, Mongolia, and Central Asia, is the largest species in the salmon family. It is long-lived and slow growing, reaching lengths of up to six feet at maturity.

In addition to fish, Siberian taimen has a reputation for being an aggressive predator and feeds on creatures like rodents and birds. The Siberian taimen is listed as vulnerable with a decreasing population due to pollution and sport fishing.

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Bull Sharks

Bull sharks are coastal and freshwater sharks that spend their time in tropical and subtropical waters across the world. They can reach lengths of more than 11 feet, though most are six to seven and a half feet long.

Mainly found in shallow water, bull sharks are the only species of shark that can endure extended periods in freshwater, which brings it into more frequent contact with humans than other sharks. An aggressive species, bull sharks are known to attack humans. They are near threatened due to human interaction and development near their habitats.

Why Are Aquatic Animals Bigger Than Land Animals?

Aquatic animals often grow to sizes that are unprecedented on land (at least in our era) because the water is able to support their weight. If a land animal were to get as big as a blue whale, say, it might not be able to support its own weight with the pressures of gravity.

Temperature also plays a role, though. Some aquatic animals simply must get large in order to stay warm, as smaller animals have more surface area and are thus more susceptible to the cold. Water conducts heat, so aquatic animals need blubber to keep warm. Because many are filter feeders, they can eat a lot without expending much energy.