Cichlidae
Arroyo cichlid
Theraps irregularis
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.
Arroyo cichlid
Galaxiidae
Arthurs paragalaxias
Paragalaxias mesotes
Eleotridae
Aru gudgeon
Oxyeleotris aruensis
Cichlidae
Arua Apisto
Apistogramma arua
Cyprinidae
Arulius barb
Dawkinsia arulius
Percidae
Ashy darter
Etheostoma cinereum
Osteoglossidae
Asian arowana
Scleropages formosus
Akysidae
Asian Banjo Catfish
Acrochordonichthys rugosus
Bagridae
Asian bumblebee catfish
Pseudomystus siamensis
Bagridae
Asian cory
Chandramara chandramara
Bagridae
Asian Golden Tiger Catfish
Hemibagrus variegatus
Siluridae
Asian Leaf Catfish
Silurichthys indragiriensis
Bagridae
Asian redtail catfish
Hemibagrus wyckioides
Adrianichthyidae
Asinua ricefish
Oryzias asinua
Cyprinidae
Asir garra
Garra buettikeri
Cyprinidae
Asoka barb
Systomus asoka
Percidae
Asprete
Romanichthys valsanicola
Badidae
Assam Badis
Badis assamensis
Bagridae
Assamese batasio
Batasio tengana
Channidae
Assamese snakehead
Channa stewartii
Cyprinidae
Assuan labeo
Labeo horie
Mormyridae
Athi elephant-snout fish
Mormyrus tenuirostris
Cyprinidae
Athi sardine
Neobola fluviatilis
Callichthyidae
Atipa
Hoplosternum littorale
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.