Elassomatidae
Gulf Coast pygmy sunfish
Elassoma gilberti
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.
Gulf Coast pygmy sunfish
Percidae
Gulf darter
Etheostoma swaini
Poeciliidae
Gulf Gambusia
Gambusia vittata
Atherinopsidae
Gulf silverside
Atherinella alvarezi
Auchenipteridae
Gulper Catfish
Asterophysus batrachus
Percidae
Gumbo darter
Etheostoma thompsoni
Cyprinidae
Gunther's baril
Opsarius radiolatus
Astroblepidae
Gunther's climbing catfish
Astroblepus guentheri
Percidae
Gurley Darter
Etheostoma gurleyense
Cichlidae
Guyana Flag Cichlid
Mesonauta guyanae
Sciaenidae
Guyanan croaker
Pachypops fourcroi
Salmonidae
Gwyniad
Coregonus pennantii
Nothobranchiidae
Gérys killi
Scriptaphyosemion geryi
Cyprinidae
Hadhramaut himri
Carasobarbus exulatus
Cyprinidae
Hainan Horse-Mouth
Opsariichthys hainanensis
Gobionidae
Hainanese Barbel Steed
Hemibarbus medius
Cyprinidae
Hairy puffer
Pao baileyi
Mastacembelidae
Half-banded Spiny Eel
Macrognathus circumcinctus
Acestrorhamphidae
Half-striped penguin tetra
Thayeria ifati
Cichlidae
Half-striped Pike Cichlid
Crenicichla semifasciata
Cobitidae
halfbanded loach
Pangio semicincta
Cichlidae
Halfbanded pike cichlid
Crenicichla geayi
Lebiasinidae
Halfbanded pyrrhulina
Pyrrhulina laeta
Lebiasinidae
Halfbanded Pyrrhulina
Pyrrhulina semifasciata
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.