Last Updated on February 22, 2025 by Falcone Dulce
When we think of giant fish, we often picture the oceans—those massive blue spaces teeming with titanic species like whales and sharks. But freshwater also hosts some magnificent giants, including the largest freshwater fish. In fact, a variety of gigantic fish species swim below the surface of rivers and lakes, each boasting its own unique characteristics and behaviors. These behemoths of the rivers and lakes — from the giant sturgeon to the bullhead catfish — are some of the most fascinating freshwater fish species in the world and fulfill essential ecological roles where they live. So explore with us and learn more about these giants of the fish world, the mysteries surrounding them, and what those fishily worlds are!
1. Beluga Sturgeon
The Beluga Sturgeon is one of the largest fish in the world. It is very famous for its size and extremely long lifespan. This species is primarily found around the Caspian and Black Seas, and has been around for a significant amount of time; thus is important to the biome.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Caspian Sea, Black Sea, and Azov Sea basins | Up to 100 years | Up to 6 meters | 450-1,000 kg | Mainly fish and bottom-dwelling invertebrates | A migratory fish that breeds in freshwater but lives in the ocean as adults. |
2. Mekong Giant Catfish
The Mekong Giant Catfish is a truly remarkable freshwater fish. It is one of the largest species of catfish in the world. This fish is native to the Mekong river and is heavily known for its massive size as well as for its value to the local cultures.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Mekong River basin | Up to 60 years | Up to 3 meters | 200-300 kg | Mainly plants and bottom-dwelling animals | A freshwater fish that usually lives in slow-moving waters. |
3. Alligator Gar
Alligator gar are often referred to as the ‘living fossils’ due to their primitive features as well as an ancient history. These fish are native to the lakes and rivers of North America, where they are best known for their impressive sharp teeth, powerful jaws, and fearsome appearance.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Freshwater lakes and rivers in North America | Up to 50 years | Up to 3 meters | 100-200 kg | Mainly fish and water birds | A carnivorous fish that can survive in low-oxygen waters |
4. Arapaima
Arapaima are colossal fish that reside in the warm waters of the Amazon River. Their distinctive shape and size make them crucial to the ecosystem and local fishermen.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Amazon River basin | Up to 20 years | Up to 3 meters | 200-400 kg | Fish and aquatic plants | A large freshwater fish that usually lives in deep waters. |
5. Giant Freshwater Stingray
Giant freshwater stingrays; perhaps the most marvellous of their species, can be found in Southeast Asia’s rivers. Their superb wingspan, combined with their ability to camouflage, renders them captivating in the aquatic world.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Mekong and Amazon River basins | Up to 50 years | Up to 4 meters | 200-300 kg | Mainly bottom-dwelling invertebrates and fish | Usually hides on the riverbed and prefers sandy or muddy bottoms. |
6. Paddlefish
Paddlefish are named after their long, paddle-shaped snouts. They are found in freshwater rivers of the USA and China, where they filter-feed on plankton and efficiently use the habitat.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Freshwater rivers in the U.S. and China | Up to 30 years | Up to 2 meters | 20-50 kg | Mainly plankton | Feeds by filtering food from the water, usually found in wide rivers. |
7. Giant Barb
The Giant Barb is a vibrant fish found in the rivers of Southeast Asia. This species has an oversized body, intricate patterns, and striking colour which makes it vital for the freshness of biodiversity in the region.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Rivers in Southeast Asia | Up to 30 years | Up to 1.5 meters | 50-100 kg | Plants and small invertebrates | Usually found in groups and prefers clear waters. |
8. White Sturgeon
The White Sturgeon is a beautiful fish residing off the Pacific coast. The distinct bony scutes and the size of this fish have fascinated many fish enthusiasts and even conservationists.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Pacific coast of North America | Up to 100 years | Up to 6 meters | 200-600 kg | Bottom-dwelling organisms and fish | One of the largest freshwater fish, usually found in rivers and lakes. |
9. Nile Perch
Nile perch are enormous fish that are carnivorous and live in the Nile River. Their size makes them appealing to sport fishing, but their strength makes them the apex predator within the ecosystem.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Nile River in Africa | Up to 20 years | Up to 2 meters | 100-200 kg | Mainly other fish | A carnivorous fish that lives in lakes and rivers. |
10. Siberian Taimen
Fishermen enjoy catching Siberian Taimen due to their bold nature and large physique. This species of freshwater fish is found in the frosty rivers of Siberia and is a prime example of how nature adapts to harsh conditions.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Rivers in Siberia | Up to 50 years | Up to 2 meters | 50-90 kg | Fish and small mammals | A large predatory fish usually found in clear, cold waters |
11. Bull Sharks
Unlike most sharks, Bull sharks can live in freshwater and saltwater. Rivers and estuaries are where they are regularly located. Their range of adaptation makes them efficient predators in these regions.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Warm ocean waters, occasionally in freshwater | Up to 16 years | Up to 3.5 meters | 90-230 kg | Fish and marine mammals | Can adapt to freshwater environments, often found in estuaries and rivers. |
12. Freshwater Sawfish
These ancient fish are found in rivers in Southeast Asia and Australia. The Freshwater sawfish have an interesting morphology with long snouts and saw-like teeth. They hunt their prey using their unique snouts.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Rivers in Southeast Asia and Australia | Up to 30 years | Up to 7 meters | 200-300 kg | Mainly fish and bottom-dwelling organisms | Uses its saw-like snout to catch prey, usually found in estuaries and freshwater areas. |
13. Salween Rita Catfish
Salween Rita Catfish is another catfish which is unique as it is known to fewer people. It is a very important fish as its characteristics make it highly therapeutic and along with its adaptability makes it an essential contributor to the nutrient-rich freshwater systems.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Salween River basin | Up to 15 years | Up to 1 meter | 10-20 kg | Small fish and invertebrates | Lives in clear rivers and is typically a bottom-dwelling fish. |
14. Irrawaddy Mystus
The Irrawaddy Mystus is a rare catfish that lives in the Irrawaddy River basin. It is an important fish for local fishermen along the river due to its unique patterns along the body. This fish helps with the biological equilibrium of its ecosystem.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Irrawaddy River basin | Up to 20 years | Up to 1 meter | 5-10 kg | Small fish and invertebrates | Lives in both freshwater and brackish environments, prefers calm waters. |
15. Jau
These species of big catfish known as the Jau are commonly found in the Amazon River. They deftly navigate through its waters and because of their size, power and beauty, they are an essential part of the ecosystem as well as the locals’ fishing.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Amazon River basin | Up to 20 years | Up to 1.5 meters | 50-100 kg | Fish and aquatic animals | A carnivorous fish usually found in deep waters. |
16. Discus Ray
The appealing species of the Discus Ray attracts the most attention in the Amazon River due to its vibrant coloration, unique shape, and as a popular addition in the fish aquarium hobbyist community. This contributes greatly to the biodiversity of that river.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Amazon River basin | Up to 15 years | Up to 1 meter | 30-50 kg | Mainly bottom-dwelling invertebrates | Usually found on the riverbed and prefers warm waters. |
17. Giant Siamese Carp
For many, the Giant Siamese Carp is a well-known cultural symbol, native to the Mekong River. It is regarded as a unique fish due to its large size and gregarious nature.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Mekong River basin | Up to 50 years | Up to 3 meters | 200-300 kg | Aquatic plants and algae | Usually found in groups and prefers clear waters. |
18. Common Carp
Common carp is one of the many species of fish that are originally from Asia, and is known as the one that is most widely distributed around the world. They have become a part of local culture due to their adaptability in numerous environments.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Found worldwide (originally from Asia) | Up to 20 years | Up to 1 meter | 5-30 kg | Plants and bottom-dwelling organisms | Highly adaptable, can survive in a variety of environments. |
19. Humpback Mahseer
The Humpback Mahseer fish is one of the most spectacular fishes found in South Asian rivers. They are an essential part of their habitats, and due to their unique body shape and powerful swimming skills, they are also sought after by anglers.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Rivers in South Asia | Up to 10 years | Up to 1 meter | 10-20 kg | Small fish and invertebrates | Active in fast-flowing waters and prefers clear environments. |
20. Murray Cod
Murray Cod are popular fishing targets because of their weight and bulk, which make them known as the pride of Australia. Aside from being a source of food, these fish play an important role in the ecology of the Murray River.
| Habitat | Lifespan | Growth Size | Adult Weight Range | Diet | Living Characteristics |
| Murray River in Australia | Up to 50 years | Up to 1.8 meters | 20-100 kg | Fish and invertebrates | A carnivorous fish usually found in rivers and lakes. |
Final Thoughts
These oversized freshwater fish, also magnificent in their form, are crucial to the health and balance of the ecosystems. Every single species possesses a distinctive tale of its own which makes the study of these astonishing fishes an enthralling journey into the realm of freshwater biodiversity.
