Salmonidae
Marbled trout
Salmo marmoratus
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.
Marbled trout
Loricariidae
Marbled Whiptail Catfish
Loricaria luciae
Loricariidae
Marcapata Bristlenose Catfish
Ancistrus marcapatae
Trichomycteridae
Margay pencil catfish
Trichomycterus maracaya
Ictaluridae
Margined madtom
Noturus insignis
Cottidae
Margined sculpin
Cottus marginatus
Cyprinidae
Marico barb
Enteromius motebensis
Atherinidae
Marjorie's hardyhead
Craterocephalus marjoriae
Gobionidae
Markakul Gudgeon
Gobio acutipinnatus
Cichlidae
Marlier's Julie
Julidochromis marlieri
Cyprinidae
Marmara barbel
Barbus oligolepis
Adrianichthyidae
Marmorated medaka
Oryzias marmoratus
Cichlidae
Maroni eartheater
Geophagus harreri
Acestrorhamphidae
Maroni Jupiaba
Jupiaba maroniensis
Potamotrygonidae
Marques' Freshwater Stingray
Potamotrygon marquesi
Crenuchidae
Marsh's Darter
Characidium marshi
Cyprinidae
Martenstyn's barb
Systomus martenstyni
Percichthyidae
Mary River cod
Maccullochella mariensis
Cichlidae
Mary's cichlid
Bujurquina mariae
Percidae
Maryland darter
Etheostoma sellare
Cichlidae
Masamiche
Cribroheros rostratus
Cyprinidae
Mascara Barb
Dawkinsia assimilis
Catostomidae
Mascota Jumprock
Moxostoma mascotae
Callichthyidae
Masked corydoras
Corydoras metae
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.