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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
Triphophysa minuta

Triphophysa minuta

Triphophysa minuta

Features:The individual is very small

Triphophysa minuta (Li, 1966) is a small fish of the genus Triphophysa of the family Cobitidae. It lives in a vast area of Xinjiang.Listed in the second level of the "List of National Key Protected Wildlife in China".Protect wild animals and stop eating game.Maintaining ecological balance...

T.xiangxiensis

T.xiangxiensis

T.xiangxiensis, formerly known as Xiangxi blind loach

Features:The pectoral fin grows faster than the body length and can reach the caudal fin

Xiangxi blind loach (T.xiangxiensis) is a fish of the genus T.xiangxiensis of the family Cobitidae. It is a cold-water cave fish that is only distributed in the Yuanjiang River system in Xiangxi, Hunan Province. It is a species endemic to my country.In 1984, the blind fish was discovered in an under...

Triplophysa siluroides

Triplophysa siluroides

Triplophysa siluroides,Catfish, catfish, slab head

Features:The head is large, flat, triangular in dorsal view, with a large, inferior, arc-shaped mouth.

Triplophysa siluroides, scientific name: Triplophysa siluroides (Herzenstein, 1888), is a fish of the genus Triplophysa in the family Cobitidae, and is the largest species in the family Cobitidae.The plateau loach often likes to lurk in the river sections with deep and turbulent gravel bottoms such...

Oreonectes anophthalmusZheng

Oreonectes anophthalmusZheng

Oreonectes anophthalmusZheng

Features:Fish for research purposes, no fishery value

The eyeless loach is named Oreonectes anophthalmusZheng in Latin. The eyeless loach found in Wuming is one of the earliest blind fish species found in my country. It is the second eyeless and pigmentless loach reported in the world. The number is extremely small. The eyeless loach has a very high st...

Leptobotia elongata

Leptobotia elongata

Leptobotia elongata,Flower fish, spotted loach, flower loach, red sand loach, fire army, flower loach

Features:A ferocious bottom-dwelling carnivorous fish, one of the largest loaches in the world

Leptobotia elongata (scientific name: Leptobotia elongata) is a fish of the genus Leptobotia in the family Cobitidae of the order Cypriniformes. It is a giant among loaches and one of the largest loaches in the world.The long thin loach is a warm-water bottom fish that likes to live in the middle an...

Leptobotia  flavolineata

Leptobotia flavolineata

Leptobotia flavolineata,Cow's tail, blind man

Features:There are more than 10 wide yellow-brown horizontal stripes on the sides of the body

The yellow-lined loach (scientific name: Leptobotia flavolineata) is a species of the genus Leptobotia, family Cypriniformes, class Actinopterygii, and is endemic to China.The yellow-lined loach looks very similar to the garfish, but the larger ones are much larger than the garfish. People in...

Leptobotia rubrilabris

Leptobotia rubrilabris

Leptobotia rubrilabris ,Red needle, red lipped loach

Features:Named after the reddish fish mouth

Red-lipped loach, Leptobotia rubrilabris (Dabry de Thiersant, 1872), belongs to the Cypriniformes, Cobitidae, and the genus Leptobotia. It is a fish endemic to the upper reaches of the Yangtze River.The red-lipped loach is larger, second only to the long loach. It has edible value. The population is...

Hypophthalmichthys harmandi

Hypophthalmichthys harmandi

Hypophthalmichthys harmandi,Silver carp, silver carp

Features:It has excellent economic traits such as high fat content, fast growth, large fatness and large trunk.

Hypophthalmichthys harmandi Sauvage, 1884 is a species of the genus Hypophthalmichthys in the family Cyprinidae and is a freshwater economic fish native to Hainan Island, Guangdong.Silver carp is a freshwater economic fish in Hainan Island, Guangdong Province. It mostly lives in open waters with slo...

Procypris mera

Procypris mera

Procypris mera ,Black carp, black carp, black crucian carp, black hook, black carp

Features:The body is laterally flattened and grows in a diamond shape, with a high back bulge, a small head and a long snout.

The Latin name of the black carp is Procypris mera (S. Y. Lin, 1933), and its foreign name is Chinese ink carp. It is a common and high-quality edible fish in Guangxi.Wuyuan carp is a fish in the middle and lower layers of rivers. It mostly lives in water bodies with rocky bottoms deep in the water,...

Procypris rabaudi

Procypris rabaudi

Procypris rabaudi,Rock carp,Water carp, black carp, rock carp, black carp

Features:It has the advantages of small body cavity, tender meat and delicious taste, and is a high-quality economic fish loved by people.

The Latin name of rock carp is Procypris rabaudi, and its foreign name is Rock carp. It is a high-quality economic fish.The rock carp is a wide-temperature fish, and its survival water temperature is 1.5℃-37℃, the living temperature range is 2~ 36℃, and the most suitable feeding temperature is 1...

Mesocyprinus fuxianensis

Mesocyprinus fuxianensis

Mesocyprinus fuxianensis

Features:The body is fusiform, with a groove on the crown of the pharyngeal teeth

Fuxian carp (scientific name: Mesocyprinus fuxianensis), a fish of the class of bony fishes of the phylum Chordata.Fuxian carp is concentrated in the middle and lower layers of the shallow waters along the coast, and a few individuals are also found in the middle and lower layers of the wading area,...

Cyprinus micristius

Cyprinus micristius

Cyprinus micristius,Caihu, Ma fish, Mabian fish, medium carp

Features:The body is similar to that of a carp, with flat sides, a slightly raised back, and a round and straight belly.

Small carp (scientific name: Cyprinus (Mesocyprinus) micristius) is a species endemic to my country, belonging to the subgenus Cyprinus of the genus Cyprinus, subgenus Cyprinus of the genus Cyprinus, subfamily Cyprinidae of the family Cyprinidae.The small carp has a mixed diet, mainly animal bait, m...

Cyprinus pellegrini

Cyprinus pellegrini

Cyprinus pellegrini,Bighead fish, Luyu, Jiangchuan bighead fish, Bell's carp

Features:The body is similar to that of a carp, with a large and wide head that is longer than the body height.

The Latin name of big-headed carp is Cyprinus pellegrini, which belongs to the Cyprinidae family and the Cyprinidae genus.China's rivers and streams have historically been rich in "big-headed carp", but there is no definite research material on when it originated. However, according to...

Oxygymnocypris stewartii

Oxygymnocypris stewartii

Oxygymnocypris stewartii,Naked carp

Features:The body is slender, slightly laterally flattened, the head is long and conical, and the snout is long and pointed.

The Latin name of sharp naked carp is Oxygymnocypris stewartii. It is a fish of the genus Oxygymnocypris in the family Cyprinidae. The origin of this species is in the Nianchu River.Due to the high altitude and low annual average water temperature, a special ecological environment has been formed. T...

Diptychus maculatus Steindachner

Diptychus maculatus Steindachner

Diptychus maculatus Steindachner,Cucumber fish, stick fish

Features:A special type of schizothorax fish that has a fresh cucumber flavor when cooked

Diptychus maculatus Steindachner is a small cold-water fish.Diptychus maculatus Steindachner is a small cold-water fish.Diptychus maculatus Steindachner generally lives in the main and tributary water environment. It likes to live in rivers with water temperatures below 20℃. Feeds on benthic organi...

Gymnodiptychus pachycheilus

Gymnodiptychus pachycheilus

Gymnodiptychus pachycheilus,Heavy lip flower fish, hemp fish, stone flower fish

Features:Sports long, tail handle is fine round, head cone -shaped, kiss protruding, lower mouth, horseshoe -shaped, jaw without sharp keratin edges, well -developed lips, thick and fleshy

Thick lip naked lip fish scientific name Gymnodiptychus Pachycheilus, belongs to carp, carp, cracked belly fish subcare, naked heavy lip fish.The thick lip naked lip fish inhabits the Kuogu River of the highland of the river, such as Qinghai, Gansu, Sichuan, and the upper reaches of the Yellow River...

Aspiorhynchuslaticeps

Aspiorhynchuslaticeps

Aspiorhynchuslaticeps,Big-Head Schizothoracin,Xinjiang big head fish, big head fish, tiger fish

Features:It is one of the most protected species, and the treatment is comparable to the giant panda on land

Flat kiss fish Latin scientific name ASPIORHYNCHUSLATICEPS, foreign name Big-Head Schizothoracin, is a species that gradually settled in the northwest with the rise of the Qinghai-Tibet Plateau. In the water body with high water temperature or slow flow of lakes. Most of the habitats are wide in the...

Schizothorax taliensis

Schizothorax taliensis

Schizothorax taliensis,Dali bow fish, bow fish, rod fish

Features:Has an important position in the fishery and tourism industry

Dali Latin name Schizothorax Taliensis is a carp family and cracked fish.Dali cracking fish is different from other cracking fish. It is a type of life that is suitable for living in a quiet water environment. It is usually an upper and middle -level in the water area in the lake. I like to consume...

Schizothorax(Racoma)biddulphi

Schizothorax(Racoma)biddulphi

Schizothorax(Racoma)biddulphi,Tarim schizothoracin,Pointed mouth fish

Features:Xinjiang is unique to fish, eggs are poisonous

Tarima Latin Name SchizoThorax (Racoma) Biddulphi (Günther, 1876), two method Tarim Schizothoracin, is the main economic fish unique to the Tarim water system.> The cracked fish in the tower is a cold water -based fish, living in rivers flowing water and lake environment. The meat is delicious a...

schizothoraxwaltoniregan,

schizothoraxwaltoniregan,

schizothoraxwaltoniregan,Pointed mouth

Features:It is one of the main economic fish in Tibet.

SchizothoraxWaltoniregan belongs to the cracks and belly fishya, which is only distributed in the middle and upper reaches of the Yarlung Tibetan River in my country. It is a unique species in my country.> In the past, it was considered that the plateau fish had spawned once a year, but the uncle...

Schizothorax davidi

Schizothorax davidi

Schizothorax davidi,Racoma davidi,Heavy -duty fine -scale fish, elegant fish, heavy mouth, heavy lip and fine -scale fish, fine turtles

Features:It is known for its "Ya'an casserole fish head" with the Qikou 以 与 与

Schizothorax (Racoma) Davidi (Sauvage, 1880) is a fish that belongs to the genus of carp.The weight of the lobed belly is fat, rich in fat. Growing faster and larger individuals, generally can grow to 1-3 kg, and the largest individual can reach 10 kg. Rich output, the yield in the production area i...