Poeciliidae
Barred Swordtail
Xiphophorus multilineatus
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.
Barred Swordtail
Poeciliidae
Barred topminnow
Quintana atrizona
Callichthyidae
barredtail corydoras
Corydoras cochui
Rivulidae
Barredtail pearlfish
Notholebias minimus
Percidae
Barrens darter
Etheostoma forbesi
Fundulidae
Barrens topminnow
Fundulus julisia
Poeciliidae
Barrigudinho
Fluviphylax palikur
Cichlidae
Barton's cichlid
Herichthys bartoni
Centrarchidae
Bartram’s Bass
Micropterus pucpuggy
Pangasiidae
basa fish
Pangasius bocourti
Loricariidae
Basilisk Pleco
Hypostomus basilisko
Cichlidae
Basket Hap
Mylochromis lateristriga
Cyprinidae
Bata
Labeo bata
Melanotaeniidae
Batanta Blue Rainbowfish
Melanotaenia synergos
Melanotaeniidae
Batanta rainbowfish
Melanotaenia batanta
Nothobranchiidae
Bates' killi
Aphyosemion batesii
Nemacheilidae
Batman loach
Paraschistura chrysicristinae
Cobitidae
Battalgil spined loach
Cobitis battalgilae
Bagridae
Bayad
Bagrus bajad
Percidae
Bayou darter
Etheostoma rubrum
Fundulidae
Bayou topminnow
Fundulus nottii
Percidae
Beaded darter
Etheostoma clinton
Cyprinidae
Beaked dace
Leuciscus burdigalensis
Cottidae
Bear Lake sculpin
Cottus extensus
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.