Gymnarchidae
Aba
Gymnarchus niloticus
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.
Aba
Loricariidae
Acary avion
Acanthicus adonis
Siluridae
Acheloos catfish
Silurus aristotelis
Cyprinidae
Acheloos roach
Leucos panosi
Gobiidae
Acheron spring goby
Knipowitschia milleri
Cyprinidae
Adana bleak
Alburnus adanensis
Callichthyidae
Adolfo's catfish
Corydoras adolfoi
Lepidarchidae
Adonis tetra
Lepidarchus adonis
Cyprinidae
Adour minnow
Phoxinus bigerri
Cyprinidae
Adriatic roach
Leucos aula
Salmonidae
Adriatic trout
Salmo obtusirostris
Cyprinidae
Aegean chub
Squalius fellowesii
Gobionidae
Aegean gudgeon
Gobio bulgaricus
Cyprinidae
Aegean minnow
Phoxinus strymonicus
Cyprinidae
Aeroplane Fish
Raiamas nigeriensis
Siluridae
Afghanistan silurus
Pterocryptis gangelica
Arapaimidae
African arowana
Heterotis niloticus
Cyprinidae
African banded barb
Enteromius fasciolatus
Bagridae
African bullhead
Lophiobagrus cyclurus
Schilbeidae
African Butter Catfish
Schilbe mystus
Cichlidae
African butterfly cichlid
Anomalochromis thomasi
Cyprinidae
African carp
Labeo coubie
Cyprinidae
African carp
Labeo parvus
Cyprinidae
African carp
Labeo senegalensis
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.