Poeciliidae
Gila topminnow
Poeciliopsis occidentalis
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.
Gila topminnow
Salmonidae
Gila trout
Oncorhynchus gilae
Terapontidae
Gilbert's grunter
Pingalla gilberti
Pimelodidae
Gilded catfish
Zungaro zungaro
Poeciliidae
Gill's molly
Poecilia gillii
Salmonidae
Gillaroo
Salmo stomachicus
Cyprinidae
Gillbar barb
Enteromius kessleri
Protopteridae
Gilled African Lungfish
Protopterus amphibius
Percidae
Gilt darter
Percina evides
Claroteidae
Giraffe catfish
Auchenoglanis occidentalis
Osphronemidae
Gladiator Betta
Betta gladiator
Cyprinidae
Glass barb
Oxygaster anomalura
Characidae
Glass bloodfin tetra
Prionobrama filigera
Pseudomugilidae
Glass blue-eye
Kiunga ballochi
Siluridae
Glass catfish
Kryptopterus bicirrhis
Siluridae
Glass catfish
Kryptopterus vitreolus
Characidae
Glass Fish
Leptagoniates steindachneri
Cyprinidae
Glass fish
Parachela oxygastroides
Ambassidae
Glass fish
Parambassis siamensis
Characidae
Glass Headstander
Charax apurensis
Characidae
Glass headstander
Charax gibbosus
Characidae
Glass Headstander
Charax notulatus
Characidae
Glass headstander
Charax stenopterus
Characidae
Glass headstander
Roeboides ilseae
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.