Mormyridae
Inga mormyrid
Mormyrus iriodes
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.
Inga mormyrid
Cichlidae
Inka dwarf cichlid
Apistogramma baenschi
Amphiliidae
Inkomati mountain catfish
Amphilius engelbrechti
Cyprinidae
Inle Carp
Cyprinus intha
Mastacembelidae
Inle Spiny Eel
Macrognathus caudiocellatus
Rivulidae
Inoã Killifish
Nematolebias papilliferus
Percidae
Iowa darter
Etheostoma exile
Prochilodontidae
Ipanema Prochilod
Prochilodus vimboides
Callichthyidae
Ipojuca catfish
Aspidoras depinnai
Cichlidae
Iporanga Cichlid
Geophagus iporangensis
Doradidae
Iquitos thorny catfish
Hemidoras morrisi
Sisoridae
Iran cat
Glyptothorax kurdistanicus
Cyprinidae
Iran cave barb
Garra typhlops
Gobiidae
Iranian Goby
Ponticola iranicus
Melanotaeniidae
Irian Jaya rainbowfish
Melanotaenia irianjaya
Ambassidae
Iridescent glassy perchlet
Parambassis apogonoides
Salmonidae
Irish pollan
Coregonus pollan
Cyprinidae
Ironcolor Shiner
Notropis chalybaeus
Eleotridae
Island Gudgeon
Allomogurnda insularis
Cyprinodontidae
Ispi pupfish
Orestias ispi
Cyprinidae
Issyk-Kul dace
Leuciscus bergi
Poeciliidae
Isthmian priapella
Priapella intermedia
Rivulidae
Isthmian rivulus
Cynodonichthys isthmensis
Potamotrygonidae
Itaituba Ray
Potamotrygon albimaculata
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.