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, there are monsters swimming unseen.

While most freshwater fish are smaller than counterparts in the salty ocean, there are some that can grow to mammoth sizes. You may think twice about that dream of one day catching "the big one" after you take a look at these freshwater giants.

Here are the largest freshwater fish in the world.

Not to be confused with the beluga whale, which shares no relation whatsoever to this fish, the beluga is a species of sturgeon that inhabits the rivers and seas of central Eurasia.

Because they continue to grow throughout their lifetime (which can last for 118 years), the beluga might be the world's largest freshwater fish. Some of these monsters have been found that are nearly 30 feet long and weigh over 6,000 pounds — numbers that also put them in contention for being the largest bony fish in the world by mass.

Species of these fish can grow to mammoth sizes anywhere, but none compare to the Mekong giant catfish of Southeast Asia.

Capable of growing to over 10 feet long, this is one fish you probably wouldn't want to feel slither past your leg while taking an afternoon dip. Unfortunately, their large size also makes them a prize catch, and these giant catfish have nearly been fished to extinction.

Though they are now protected from fisherman, they are likely to remain critically endangered due to the construction of upstream dams on the Mekong.

Due to a dual row of large teeth and a snout like an alligator, these carnivorous fish might be the scariest thing lurking in the rivers of North America. Measuring as long as 10 feet, alligator gars are fish right out of a horror movie. They can survive for short periods of time out of water.

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 ambush prey. Despite their intimidating appearance, they are passive toward humans.

Found in the Amazon river, these giant fish are as ancient as they are large. Capable of growing to a length in excess of 10 feet, Arapaima have been around since the Miocene, and are considered living fossils.

These fish are also incredible leapers and can propel themselves above the water if they feel threatened. Unfortunately, record-sized arapaima are difficult to come by today since they have been so widely hunted.

These freshwater fish can grow to massive sizes, with some weighing in excess of 1,000 pounds and measuring nearly 15 feet across.

Found in the rivers of Southeast Asia, they have a serrated spike on their tails that can measure 15 inches long and is capable of piercing bone — not the sort of thing you want to swim with.

Unfortunately, though, like many of the unique river species endemic to Southeast Asia, the giant freshwater stingray is critically endangered due to fishing and habitat loss.

Easily recognizable by their paddle-shaped snout, these shark-like river giants aren't actually related to sharks at all. In fact, paddlefish are harmless filter-feeders, opening their mouths to capture zooplankton.

There are two extant species of these creatures, the Chinese paddlefish and the American paddlefish (shown here). Unfortunately the Chinese paddlefish, which inhabits the Yangtze River, has been declared extinct. It was the larger of the two species, measuring as long as 9 to 10 feet in length. American paddlefish inhabit the Mississippi River valley and once inhabited the Great Lakes as well. They can grow to around 5 feet in length.

Carp of all varieties can grow to formidable sizes, but none are as large as the giant barb found in Southeast Asia.

These behemoths regularly grow to as long as 10 feet long and adults are rarely found under 5 feet. Despite their namesake, giant barbs actually carry no barbels. And although they grow to such large sizes, giant barbs are as harmless as your pet goldfish. They prefer to eat small organisms like algae, phytoplankton and, occasionally, fruit.

Easily the largest freshwater fish in North America, the white sturgeon has been known to grow to an incredible length of 20 feet though not in modern times.

Found along the West Coast of North America, and as far north as the Aleutian Islands, sturgeon are ancient fish that have kept the same form for at least 175 million years.

Due to their size, sturgeon are a popular target for fishermen, and there is concern among conservationists that they may be overfished. In fact, some populations are even classified under the Endangered Species Act of 1994.

Native to the tropical rivers and lakes of Africa, the Nile Perch is Africa's largest freshwater fish. Reaching six feet in length, these fish have mammoth mouths.

Due to their popularity among fishermen, the Nile Perch has unfortunately been introduced to many non-native lakes and has become a dangerous invasive species. This has been especially tragic in Lake Victoria, where several hundred native species have been driven to extinction due to the introduction.

The taimen, found in freshwater rivers and lakes of Russia, Mongolia and Central Asia, is the largest species in the salmon family.

Because they can grow to over six feet in length and have been known to gulp up creatures like rodents and birds, they have been referred to as the "Mongolian Terror Trout" by National Geographic. According to Chinese folklore, monster fish weighing upwards of 3,000 pounds have been found, though taimen that large have never been confirmed.

If you think that just because you're swimming in freshwater that you're safe from sharks, think again.

Not only do bull sharks roam as freely through freshwater as they do in saltwater, but bull sharks have been found as far inland as Indiana in the Ohio River and Illinois in the Mississippi River. Along with the great white shark and the tiger shark, bull sharks are among the top three species most likely to attack humans.

There are also at least five other species of true river sharks that are exclusive to freshwater rivers in Southeast Asia and Australia. All river sharks are capable of growing to over 10 feet in length, and are more than capable of consuming a human.