Home>>All Animals>>Fish>>Freshwater fish

Freshwater fish

Freshwater fish refers to fish that can live in waters with a salinity of less than 0.05%, or fish that must spend their entire lives in freshwater. There are nearly 3,000 species of fish in my country, of which more than 1,000 are freshwater fish. The more common freshwater fish species include Cypriniformes, Siluriformes, Characidae, Syngnathidae, Amphioxus, etc. Since freshwater environments are smaller in area than oceans but more diverse (rivers, lakes, wetlands, streams, mountain streams, groundwater systems, etc.), freshwater fish present rich morphological and biological diversity under the influence of geographical isolation, climate and hydrological conditions. The following will help your website users understand the evolutionary context and diverse distribution of freshwater fish, and also show their important position in ecology and human society.

I. Introduction to Freshwater Fishes

1. Definition and Key Characteristics

  • Habitat: Freshwater fishes primarily live in low-salinity waters (usually under 0.5‰), including rivers, lakes, swamps, streams, and other inland waters. Some species may frequent estuaries or slightly brackish water.

  • Osmoregulation: To prevent excessive water intake and electrolyte loss, freshwater fishes excrete large amounts of diluted urine and actively retain salts through their kidneys and gills.

  • Diversity: Despite covering a relatively small portion of Earth’s surface, freshwater ecosystems host a remarkable variety of fish species—often due to geographical barriers (waterfalls, river systems) and past climatic/tectonic events. Large lakes in Africa, the Amazon Basin, and Southeast Asian river networks are famous for their high fish diversity and endemism.

2. Major Groups

  • Cartilaginous Fishes (Class Chondrichthyes): Rare in fresh water; only a few examples (such as certain sawfishes or bull sharks) can enter or remain in freshwater habitats.

  • Bony Fishes (Class Osteichthyes): Specifically, the Actinopterygii (ray-finned fishes) dominate most freshwater environments (e.g., Cypriniformes, Siluriformes, Perciformes, Salmoniformes, Osteoglossiformes, etc.).

3. Ecological Value and Human Use

  • Aquatic Ecosystem Balance: Freshwater fishes occupy vital trophic roles, from benthic scavengers to top predators, contributing to nutrient cycling and ecosystem stability.

  • Fisheries and Aquaculture: Freshwater aquaculture (e.g., carp, tilapia, catfish) provides protein and economic benefits worldwide, while wild-capture fisheries also sustain local communities.

  • Ornamental and Cultural Significance: Ornamental fish trade (e.g., koi, goldfish, tropical aquarium species) and recreational fishing (angling) are culturally and economically important in many regions.

II. History and Evolution of Freshwater Fishes

  1. Origins and Early Evolution

  • The earliest jawed vertebrates date back to the Devonian period (around 400 million years ago). Even in these ancient times, freshwater habitats supported primitive fishes.

  • Over subsequent eras (Carboniferous, Permian, Mesozoic), bony fishes (including lungfish, lobe-finned fishes, and later the widespread ray-finned fishes) underwent significant diversification and adaptation to inland waters.

  1. Repeated Geographic Isolation and Adaptive Radiation

  • Continental drift, glaciations, and river system shifts led to the isolation of fish populations, encouraging independent evolutionary paths and high endemism.

  • Examples include African lungfish, South American electric eels, and Southeast Asian fighting fishes (Betta spp.), each illustrating unique adaptations to freshwater environments.

  1. Modern Freshwater Biodiversity

  • Today, freshwater fishes exceed 10,000 known species (about 40–45% of all fish species), yet inhabit less than 1% of Earth’s surface water.

  • Human activities (e.g., dam building, water diversion, pollution, introduction of alien species) now strongly influence many freshwater fish communities, prompting the need for conservation measures.

III. Major Orders and Families of Freshwater Fishes

Below is a classification focusing on bony fishes (Actinopterygii), which comprise the majority of freshwater species. Also included are rare instances of cartilaginous fishes that enter or live in fresh water.

A. Cartilaginous Fishes in Fresh Water (Rare Cases)

OrderFamilyRepresentative GenusExample SpeciesDistribution & Notes
Pristiformes (Sawfishes)Pristidae (Sawfishes)PristisSmalltooth Sawfish (Pristis pectinata), etc.Mostly coastal or estuarine; some individuals migrate into rivers. Overfished, now rare.
Carcharhiniformes (Ground Sharks)Carcharhinidae (Requiem Sharks)Carcharhinus leucas (Bull Shark)Bull Shark (Carcharhinus leucas)Can travel far upriver (e.g., Zambezi), exhibits high tolerance for low salinity waters.

B. Ray-Finned Fishes (Actinopterygii)

1. Order Cypriniformes (Carps, Minnows, Loaches)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
Cyprinidae (Carps & Minnows)Cyprinus (Carp), Carassius (Crucian Carp), Hypophthalmichthys (Silver/Bighead Carp), Ctenopharyngodon (Grass Carp)Common Carp (Cyprinus carpio), Goldfish (Carassius auratus), Silver Carp (Hypophthalmichthys molitrix), Grass Carp (Ctenopharyngodon idella)One of the world’s largest freshwater fish families, with major economic and ornamental importance (e.g., koi, goldfish).
(Loach families such as Nemacheilidae, etc.)Triplophysa (Stone Loach, e.g., high-altitude loaches)Tibetan Stone Loach (Triplophysa gigantea), etc.Often inhabiting upland or plateau streams; many species adapted to cold, fast-flowing waters.

2. Order Siluriformes (Catfishes)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
Siluridae (Sheatfishes)Silurus (Sheatfish)Amur Catfish (Silurus asotus), Wels Catfish, etc.Common in Eurasian fresh waters, often large-bodied, demersal predators/scavengers.
Clariidae (Airbreathing Catfishes)Clarias (Walking Catfish)African Sharptooth Catfish (Clarias gariepinus), etc.Native to Africa/Asia; possess accessory breathing organs, surviving in low-oxygen conditions.
Ictaluridae (North American Catfishes)IctalurusChannel Catfish (Ictalurus punctatus), etc.Important for aquaculture and recreational fishing in North America.
Callichthyidae (Armored Catfishes)Corydoras (Cory Catfish)Corydoras species (popular in aquariums)South American ornamental fish, equipped with bony plates; popular in hobby aquariums.

3. Traditional Order Perciformes (now extensively revised)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
Percidae (Perches)Perca (Perch), Sander (Pike-perch), etc.European Perch (Perca fluviatilis), Walleye (Sander vitreus), etc.Found in cool/temperate Northern Hemisphere waters; prized food and sport fish.
Cichlidae (Cichlids)Oreochromis (Tilapias), Cichla (Peacock Bass), Hemichromis, etc.Nile Tilapia (Oreochromis niloticus), Peacock Bass (Cichla ocellaris), etc.Highly adaptive in Africa and South/Central America; some species (e.g., tilapia) are significant in aquaculture or invasive.
Anabantidae/Osphronemidae (Labyrinth Fishes)Betta (Fighting Fish), Trichopodus (Gouramis), etc.Siamese Fighting Fish (Betta splendens), Three-spot Gourami (Trichopodus trichopterus)Possess auxiliary breathing organ (labyrinth), can survive in oxygen-poor waters; many are ornamental fish.

4. Order Salmoniformes (Salmon, Trout, etc.)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
SalmonidaeOncorhynchus, Salmo, HuchoChinook Salmon (Oncorhynchus tshawytscha), Atlantic Salmon (Salmo salar), Taimen (Hucho hucho), etc.Many are diadromous (breeding in fresh water but maturing in the sea); some remain fully freshwater. High commercial and recreational value.

5. Order Osteoglossiformes (Bonytongues)

FamilyRepresentative GenusExample SpeciesDistribution & Notes
Osteoglossidae (Bonytongues)Scleropages (Asian Arowana), Osteoglossum (Arowana)Silver Arowana (Osteoglossum bicirrhosum), Asian Arowana (Scleropages formosus)Found in South America and Southeast Asia; large ornamental fish prized for coloration and cultural value.

(Additional examples include characins, loaches, knifefishes, etc., found in global fresh waters.)

IV. Conclusion

  1. Multiple Evolutionary Lineages and Broad Diversity

    • Freshwater fishes do not descend from a single clade; they include a few cartilaginous species that tolerate fresh water and a vast array of bony fish orders. Geographical isolation and varied inland water systems have driven high speciation rates and local endemism.

  2. Ecological Functions and Economic Value

    • Freshwater fishes are key components of inland aquatic ecosystems (e.g., controlling algae, recycling nutrients, preying on insects).

    • They also support major industries: aquaculture, wild-capture fisheries, ornamental fish trade, sport fishing, and cultural traditions (e.g., koi, fighting fish).

  3. Conservation and Future Challenges

    • Habitat degradation, pollution, overfishing, and invasive species threaten many freshwater fish populations.

    • Protected river basins, habitat restoration, and breeding-and-release programs for endangered species are crucial for preserving freshwater biodiversity.

Through the above introduction and classification, you can have a more systematic understanding of the distribution and evolution of freshwater fish in modern animal systems, and appreciate their important significance in ecosystems and human society. If you need to further understand specific families, genera or species (such as morphological characteristics, distribution range, conservation status), it is recommended to refer to professional ichthyology books, regional freshwater fish atlases and the latest academic research literature. I hope this "Freshwater Fish Classification Encyclopedia" can meet your needs.

Marine fishs Freshwater fish Cypriniformes Siluriformes
Carassius auratus

Carassius auratus

Carassius auratus,Goldfish,Carassius auratus cantonensis Tchang,Xitou, crucian carp, crucian carp seeds, river crucian carp, moon crucian carp, ancient name crucian carp, crucian carp, cold crucian ca

Freshwater fish LC

Features：Body is oval, flattened laterally

Crucian carp is one of the typical bottom fishes with strong adaptability. It can survive in water with a pH value of 4 or pH value of 9, and can even live in spring water, sewage and industrial wastewater containing minerals. In addition, it can withstand severe cold (such as -10℃ to -15℃), and h...

Ctenopharyngodon

Ctenopharyngodon

Ctenopharyngodon,Grass carp, grass carp, oily grass carp, grass carp, white grass carp, grass carp, grass carp, thick fish, sea grass carp, mixed fish, black herring, etc.

Freshwater fish LC

Features：The body length is 3 to 4 times the body height, the body is brown and the abdomen is grayish white.

It is named because it eats grass (Li Shizhen of Ming Dynasty). In Erya, it is also called carp, which is the same as 鰀 (Guangyun); it is also called 鯶. Guo Pu of Jin Dynasty noted that "today's 鯶 is similar to trout but larger". Li Shizhen said that "its nature is relaxed, so...

Cyprinus acutidorsalis

Cyprinus acutidorsalis

Cyprinus acutidorsalis,Sea carp, sea crucian carp, triangular carp

Freshwater fish LC

Features：The body is extremely tall, with a significant bulge on the back, and then slopes down sharply. The head is short. port.

Sharp-finned carp is a unique species of carp that lives in the brackish and freshwater waters of a few estuaries in the South my country Sea for a long time. It has a mixed diet. Under natural conditions, it mainly feeds on aquatic invertebrate benthic organisms (such as gastropods, carps and polyc...

Cyprinus carpio

Cyprinus carpio

Cyprinus carpio,Common carp, carp, hairy fish, red fish, carp

Freshwater fish LC

Features：The body is spindle-shaped, with medium-sized round scales.

The scales have the character "十" in Wenli, hence the name carp (Li Shizhen's "Compendium of Materia Medica"). Also known as red carp, xuanju, huangji, and huangzhui; today it is commonly known as carpguaizi. Chixian Gong (Tang Dynasty Law. See "Kangxi Dictionary")...

Flower head dragon eye

Flower head dragon eye

Red and White Dragon-eye with Tiger-head

Freshwater fish LC

Features：

The Flowery Dragon Eye is famous for its beautiful red and white markings. As one of the ornamental fish, it is deeply loved by players for its beautiful appearance. Although the tumor on the top is not thick, if the color is red, white, or red and white, it will be more popular and its value will d...

Acipenser sinensis

Acipenser sinensis

Sturgeon, sturgeon, yellow sturgeon, tuna, sturgeon shark, king tuna

Freshwater fish LC

Features：One of the oldest vertebrates

The Chinese sturgeon is the largest and longest-lived freshwater fish. (After the extinction of the Chinese sturgeon)The Chinese sturgeon is the oldest vertebrate on Earth and a descendant of the ancient stickleback, the common ancestor of fish, with a history of 140 million years. It lived in the s...

Psephurus gladius

Psephurus gladius

Chinese swordfish, sword-nosed white sturgeon, elephant fish, elephant nose fish, swordfish, sturgeon, anglerfish, tuna, Yangtze white sturgeon

Freshwater fish LC

Features：The king of Chinese freshwater fish (extinct)

The white sturgeon is one of the largest freshwater fish, named for its lighter color. It is also known as the harp fish, the swordfish, and the ancient name tuna. Like the Chinese sturgeon, it has existed for 150 million years and is one of the very few ancient fish that survived from the Cretaceou...

Acipenser dabryanus

Acipenser dabryanus

Sand Lazi, small Lazi, sturgeon, sturgeon, Yangtze sturgeon

Freshwater fish LC

Features：One of the three species of sturgeons in China's Yangtze River (extinct in the wild)

Acipenser dabryanus is a type of sturgeon. It is one of the precious large fish species unique to my country, and its external morphology is similar to that of the Chinese sturgeon. It is one of the three types of sturgeons living in the Yangtze River (Acipenser dabryanus, Chinese sturgeon, and Chin...

Arapaima gigas

Arapaima gigas

Arapaima, walrus fish, elephant fish, frigate dragon, giant dragon

Freshwater fish LC

Features：One of the largest freshwater fish in the world.

There is a kind of big fish in South America that is not afraid of piranhas. Not only that, they eat piranhas. This big fish that can easily prey on piranhas is the Arapaima, also known as the walrus fish.Arapaima is a remnant of ancient freshwater fish, which is estimated to have appeared 100 milli...

Atractosteus spatula

Atractosteus spatula

Alligator gar, ghost rocket, lucky crocodile, giant gar, malleus gar, crocodile rocket

Freshwater fish LC

Features：It is a prehistoric fish that has lived on Earth for more than 100 million years.

The alligator gar is named for its short snout like an alligator and two rows of dagger-like teeth. It is the largest of the seven existing species of North American gar. It is a prehistoric fish that has lived on Earth for more than 100 million years. Fossils date back to the Upper Cretaceous. In a...

Heteroconger hassi

Heteroconger hassi

Garden Eel,Heteroconger eel

Freshwater fish LC

Features：Extremely timid, might even be frightened to death.

Heteroconger eels live in groups of hundreds (sometimes thousands) of individuals. The largest males usually live in the center of the group, positioning themselves in the best spots to build a home and get food. When they are not hiding, these fish sway like leaves of seaweed, hence the name "...

Email: jsset#163.com (change # to @) Please indicate your purpose of visit!
Guangdong ICP No. 2022053326 XML| map| Chinese