Potamotrygonidae
Emperor Ray
Potamotrygon boesemani
FISH SPECIES
Freshwater Fish
Freshwater fish spend all or part of their lives in rivers, lakes, streams and wetlands. The label describes an environment, not one branch of the fish family tree, so freshwater species include many unrelated shapes and lineages.
FISH ATLAS / FIELD GUIDEFreshwater FishIN THIS CHAPTER01 / Characteristics02 / Lifestyle03 / Species04 / Field notes
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01 / NATURAL HISTORY
Characteristics
Freshwater habitats contain far less salt than seawater and can change quickly with seasons, floods and drought. Fish living there use many different strategies, from streamlined bodies for current to barbels that help find food near the bottom.
- 01River fish
- 02Lake fish
- 03Stream fish
02 / LIFESTYLE
Lifestyle
Life in freshwater follows the movement of water and food. Some fish hold position in a current and intercept drifting prey; others search plants or sediment for a meal. Changes in flow and water level can open feeding grounds or trigger movements toward spawning areas. These behaviors reflect how fish balance hydrodynamic energy expenditure against food intake.
OBSERVATION INDEX
- Holding position in a current
- Feeding among plants or sediment
- Movement with changing water levels
03 / SPECIES
Representative species
Discover representative species illustrating the ecological diversity, morphologies and adaptations of this group.
Emperor Ray
Acestrorhamphidae
Emperor tetra
Nematobrycon palmeri
Eleotridae
Empire gudgeon
Hypseleotris compressa
Cichlidae
Empress Dwarf Cichlid
Apistogramma hippolytae
Poeciliidae
Endlers guppy
Poecilia wingei
Clariidae
Engelsen's Catfish
Clarias engelseni
Ellopostomatidae
Enigmatic loach
Ellopostoma mystax
Gobiidae
Ephesus goby
Knipowitschia ephesi
Cyprinidae
Epiros minnow
Pelasgus thesproticus
Cyprinidae
Epiros riffle dace
Telestes pleurobipunctatus
Petromyzontidae
Epirus brook lamprey
Caspiomyzon graecus
Acestrorhamphidae
Equatorial Astyanax
Astyanax integer
Cyprinidae
Ereğli minnow
Garra kemali
Nothobranchiidae
Escherich's killi
Aphyosemion escherichi
Nothobranchiidae
Escherich's killi
Aphyosemion striatum
Nothobranchiidae
Escherich's killifish
Aphyosemion etsamense
Astroblepidae
Esmeralda's climbing catfish
Astroblepus cyclopus
Percidae
Etheostoma (Catonotus) nebra
Etheostoma nebra
Nemacheilidae
Ethiopian Loach
Afronemacheilus abyssinicus
Percidae
Etowah Bridled Darter
Percina freemanorum
Percidae
Etowah darter
Etheostoma etowahae
Salmonidae
Euphrates trout
Salmo euphrataeus
Siluridae
Eurasian catfish
Silurus biwaensis
Cyprinidae
European chub
Squalius cii
04 / FIELD NOTES
A closer look
What makes a fish freshwater?
It is recorded from inland waters with low salinity for all or part of its life cycle.
Are all freshwater fish closely related?
No. Freshwater is a habitat category that includes many separate evolutionary groups.
Can freshwater fish survive in seawater?
Most cannot; without physiological adaptations to excrete excess salt, their cells rapidly lose water through osmosis and dehydrate in hypertonic seawater.