Cyprinidae
Oily bitterling
Tanakia limbata
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.
Oily bitterling
Cyprinidae
Oily Gudgeon
Sarcocheilichthys biwaensis
Percidae
Okaloosa darter
Etheostoma okaloosae
Mormyridae
Okavango Churchill
Petrocephalus okavangensis
Alestidae
Okavango robber
Rhabdalestes maunensis
Mochokidae
Okavango suckermouth
Chiloglanis fasciatus
Cichlidae
Okavango tilapia
Tilapia ruweti
Elassomatidae
Okefenokee pygmy sunfish
Elassoma okefenokee
Salmonidae
Okumus trout
Salmo okumusi
Callichthyidae
Olga cory
Corydoras simulatus
Callichthyidae
Olive cory
Corydoras ehrhardti
Cyprinidae
Olive danio
Danio dangila
Percidae
Olive darter
Percina squamata
Goodeidae
Olive Skiffia
Skiffia lermae
Cyprinidae
Olivegreen ufipa barb
Enteromius olivaceus
Heptapteridae
Olmec Blind Catfish
Rhamdia macuspanensis
Poeciliidae
Olmec Priapella
Priapella olmecae
Poeciliidae
Olomina toothcarp
Brachyrhaphis olomina
Esocidae
Olympic mudminnow
Novumbra hubbsi
Salmonidae
omul
Coregonus migratorius
Cyprinidae
Onaç spring minnow
Pseudophoxinus ninae
Poeciliidae
One spot toothcarp
Phalloceros uai
Rivulidae
One-spine Pearlfish
Austrolebias univentripinnis
Lebiasinidae
Oneline pencilfish
Nannostomus unifasciatus
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.