Gobionidae
Nichols' Gudgeon
Gnathopogon nicholsi
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.
Nichols' Gudgeon
Cyprinidae
Nicolaus's spirlin
Alburnoides nicolausi
Cyprinidae
Niger barb
Labeobarbus bynni
Lepidarchidae
Niger tetra
Arnoldichthys spilopterus
Cichlidae
Night Aulonocara
Aulonocara hueseri
Percichthyidae
Nightfish
Bostockia porosa
Cobitidae
Nikolsky's weatherfish
Misgurnus nikolskyi
Distichodontidae
Nile distichodus
Distichodus nefasch
Poeciliidae
Nile killifish
Micropanchax loati
Cyprinidae
Nile labeo
Labeo niloticus
Cyprinidae
Nile minnow
Leptocypris niloticus
Latidae
Nile perch
Lates niloticus
Cichlidae
Nile tilapia
Oreochromis niloticus
Bagridae
Nilgiri mystus
Hemibagrus punctatus
Cyprinidae
Nilgiri osteobrama
Osteobrama neilli
Cyprinidae
Nilgiris Barb
Hypselobarbus dubius
Cyprinidae
Nilgiris garra
Garra stenorhynchus
Poeciliidae
Nine ray toothcarp
Phalloceros enneaktinos
Cyprinidae
ningu
Labeo victorianus
Gobiidae
ninja goby
Schismatogobius saurii
Cyprinidae
Nippon Baratanago
Rhodeus smithii
Cichlidae
Nkhomo-benga Peacock
Aulonocara baenschi
Distichodontidae
Nkupe
Distichodus mossambicus
Mordaciidae
Non-parasitic lamprey
Mordacia praecox
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.