Galaxiidae
Obscure Galaxias
Galaxias oliros
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.
Obscure Galaxias
Potamotrygonidae
ocellate river stingray
Potamotrygon motoro
Gobiidae
Ocellated Cling Goby
Sicyopterus ocellaris
Cyprinodontidae
Ocellated Killifish
Floridichthys polyommus
Anabantidae
Ocellated labyrinth fish
Ctenopoma muriei
Channidae
Ocellated snakehead
Channa pleurophthalma
Mastacembelidae
Ocellated spiny eel
Mastacembelus vanderwaali
Cyprinidae
Ocmulgee shiner
Cyprinella callisema
Stevardiidae
Odd Astyanax
Bryconamericus uporas
Serrasalmidae
Odysse's Piranha
Serrasalmus odyssei
Gobiidae
Ogasawara Freshwater Goby
Rhinogobius ogasawaraensis
Melanotaeniidae
Ogilby's rainbowfish
Melanotaenia ogilbyi
Mormyridae
Ogun mormyrid
Marcusenius brucii
Petromyzontidae
Ohio lamprey
Ichthyomyzon bdellium
Salmonidae
Ohrid belvica
Salmo ohridanus
Gobionidae
Ohrid gudgeon
Gobio ohridanus
Cyprinidae
Ohrid minnow
Pelasgus minutus
Cobitidae
Ohrid Spined Loach
Cobitis ohridana
Cyprinidae
Ohrid spirlin
Alburnoides ohridanus
Nemacheilidae
Ohrid Stone Loach
Barbatula sturanyi
Salmonidae
Ohrid trout
Salmo letnica
Cyprinidae
Oil Fish
Linichthys laticeps
Cyprinidae
Oil Fish
Pseudocrossocheilus liuchengensis
Cyprinidae
Oily bitterling
Acheilognathus coreanus
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.