Osphronemidae
Apollo Betta
Betta apollon
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.
Apollo Betta
Cyprinidae
Apollo sharkminnow
Luciosoma setigerum
Cichlidae
Apoparuana Cichlid
Bujurquina apoparuana
Percidae
Appalachia darter
Percina gymnocephala
Sternopygidae
Apure Knifefish
Rhabdolichops caviceps
Astroblepidae
Apurimac climbing catfish
Astroblepus sabalo
Esocidae
Aquitanian pike
Esox aquitanicus
Cyprinidae
Arabian Bream
Acanthobrama hadiyahensis
Cyprinidae
Arabian himri
Carasobarbus apoensis
Cobitidae
Arachthos spined loach
Cobitis arachthosensis
Cyprinidae
Arade chub
Squalius aradensis
Poeciliidae
Araguaia toothcarp
Phalloceros leticiae
Cyprinidae
Aranayaka danio
Devario memorialis
Arapaimidae
Arapaima
Arapaima gigas
Nemacheilidae
Aras loach
Oxynoemacheilus araxensis
Salmonidae
Arctic grayling
Thymallus arcticus
Rivulidae
Arenal rivulus
Cynodonichthys fuscolineatus
Melanotaeniidae
Arfak rainbowfish
Melanotaenia arfakensis
Rivulidae
Argentine pearlfish
Austrolebias bellottii
Erythrinidae
Argentine Wolf Fish
Hoplias argentinensis
Cottidae
Arges sculpin
Cottus transsilvaniae
Cobitidae
Ariake Stripe Spined Loach
Cobitis kaibarai
Cichlidae
Aristochromis deep
Otopharynx lithobates
Percidae
Arkansas darter
Etheostoma cragini
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.