While it is generally true that freshwater fish are smaller than their oceanic counterparts, there are also some significantly sized fish to see in lakes and rivers the world over.

Obviously, considerations like location, environment, climate, food supply and presence of fishermen all play a part in how big something can grow. There are plenty of examples out there that may not be as colorful as some saltwater breeds, but are just as hefty and interesting to learn about. Check out these ten biggest freshwater fish in the world.

1. Beluga Sturgeon

The Beluga Sturgeon, a needle nosed bottom feeder, is known for many things, not least the production of their roe, which goes on to become caviar. They are also the biggest freshwater fish in the world, achieving lengths of up to 18 feet. Their body is elongated, with a barrel-like midsection, and they also have barbs on their face which allow them to consume molluscs. They thrive in regular temperatures and in below arctic conditions, such as Eastern Europe. As they are slow moving bottom-feeders, as well as prized for their roe, they are vulnerable. Predictably, other elements such as pollution have an effect. Out of the 26 species of Sturgeon, most are currently considered in danger, and at threat of extinction.

2. White Sturgeon

Similar to the Beluga, the White Sturgeon is a big-hitter in another part of the world, the US. It really is big, too: one grew to 20 foot and 1799lb - definitely one of the world's largest freshwater fish, and considered the largest freshwater fish in North America. These are not unusual sizes for this behemoth, which can live up to one hundred years. But such a large haul brought with it fishing in earnest, and a restriction of a six foot maximum catch was instituted in the 1800s. Again, they are subject to dam construction and the threat to spawning that entails.

3. Freshwater Stingray

Found mostly in the rivers of South East Asia, these flat creatures can grow immensely large. They grow to over 1000lb and 15 feet across. One of the more disquieting features it possesses is the 15 inch long tail. Apparently, it has the capability to pierce bone. Like many other species on this list, these fish are declining in number due to overfishing and the construction of dams.

4. Catfish

Catfish are hard to pithily sum up, because the name covers so many breeds, sizes, and colors the world over. One thing they do not have in common is the barbs at their mouth that resemble the whiskers of a cat. As you would expect from such a diverse group, sizes vary widely. The longest and heaviest breed is the Mekong Giant Catfish. It can reach sizes of 660lb and a length of 10.5 feet.

The Mekong Giant Catfish enjoys a curious relationship with humankind and its habitat. In Thai folk lore, it is regarded with reverence, but in its own home the ongoing industrial work on the Mekong is forcing it out of its traditional habitat.

5. Alligator Gar

This is a fish to make you look twice. It has a long snout and dorsal covering to look remarkably like a gator. It grows up to 10 foot and 200lbs at maturity. Not hard to see mistaken identities could occur; there's an excellent chance this is the sort of places urban legends about 'a huge fish in the lake' come from. It's even more resilient than other fish when comes to being out of water, living up to two hours. The Alligator is carnivorous and a wily hunter, but there is no confirmation of human attacks.

6. Arapaima

This interesting big fish is generally found in the Amazon. The fish can be over eight foot in length, and weigh over 300lb. Some call it a ’living fossil’ owing to its long history, and curious habits, such as feeling the need to take in air from the surface. Owing to a number or reasons, ranging from a local predilection to its meat, to medicinal properties, to the always present over fishing they are in decline. They were mostly caught by nets or spear fishing, and it is thought there are around 2 million left in the wild today.

7. Paddlefish

Another odd-looking big fish is the Paddlefish. It's not hard to identify, and was named accurately. It has a long snout (longer than its head). The rostrum, as it's called, is actually there as an electro-magnetic guidance, similar to sharks. It also shares other similarities with sharks, such as fin shape and skeleton. These fish used to be plentiful in US streams and lakes, before overfishing. The Paddlefish can be used to harvest roe, but it is a long process.

8. The Nile Perch

The Nile Perch is native to many areas in Northern Africa, including the Nile itself. This fish can grow to reach over six foot in length and 200lb. Even though it has been introduced widely through Africa, some consider it one of the most invasive species - this may be because it is a voracious predator that also resorts to cannibalism. This is one species not in threat of being wiped out.

9. Taimen

Also known as the Siberian Salmon, this monster has been knows to gulp down birds and rodents. Growing to over six foot and weighing over 200lbs, these fish dominate these area they swim in. Even though they mainly are in Siberia, they also feature in Chinese and Mongolian folklore. Again, this is a species under threat, but the promotion of a catch and release policy for sports fishermen may be of help.

10. Carp

The perennial favorite of anglers and hobbyists alike. They are native to Europe and Asia, but were introduced to the USA. Carp have played a role as a sport fish and an ornamental one for breeders, but has more importantly been depended upon as a human foodstuff for many generations.

Their size can vary drastically depending on the, but 17kg Mirror Carp have been caught, and Koi Carp can grow to 36 inches long. There are a number of sub-species of carp that are generally plentiful, although the US believes them to be a nuisance to native fish stocks. So, if you’re looking for good meal, chow down on a carp, one of the largest freshwater fish in the world, and help native fish at the same time.