| Order | Family | Species | Occurrence | FishBase name | Name in Country |
|---|---|---|---|---|---|
| Characiformes | Anostomidae | Abramites hypselonotus | native | Marbled headstander | Jikii |
| Characiformes | Acestrorhynchidae | Acestrorhynchus lacustris | native | dientudo | |
| Characiformes | Acestrorhynchidae | Acestrorhynchus pantaneiro | native | dientudo | |
| Pleuronectiformes | Achiridae | Achirus lineatus | native | Lined sole | |
| Characiformes | Characidae | Acrobrycon ipanquianus | native | Mojarra | |
| Siluriformes | Auchenipteridae | Ageneiosus inermis | native | Manduba | |
| Siluriformes | Auchenipteridae | Ageneiosus marmoratus | native | Bottlenose catfish | |
| Siluriformes | Auchenipteridae | Ageneiosus militaris | native | ||
| Siluriformes | Auchenipteridae | Ageneiosus ucayalensis | native | ||
| Siluriformes | Aspredinidae | Amaralia oviraptor | native | ||
| Siluriformes | Doradidae | Anadoras insculptus | native | armado | |
| Siluriformes | Doradidae | Anadoras weddellii | native | Armado | |
| Siluriformes | Loricariidae | Ancistrus cirrhosus | native | Jumbie teta | cascudo |
| Siluriformes | Loricariidae | Ancistrus hoplogenys | native | vieja | |
| Siluriformes | Loricariidae | Ancistrus piriformis | native | ||
| Siluriformes | Loricariidae | Ancistrus taunayi | native | ||
| Characiformes | Characidae | Andromakhe latens | native | ||
| Characiformes | Characidae | Andromakhe paris | endemic | Mojarra | |
| Characiformes | Characidae | Andromakhe saguazu | endemic | ||
| Characiformes | Characidae | Andromakhe stenohalina | native | ||
| Characiformes | Characidae | Andromakhe tupi | endemic | ||
| Characiformes | Parodontidae | Apareiodon affinis | native | Darter characine | Canivete |
| Characiformes | Parodontidae | Apareiodon piracicabae | native | ||
| Characiformes | Characidae | Aphyocharax alburnus | native | Goldencrown tetra | Mojarrita |
| Characiformes | Characidae | Aphyocharax anisitsi | native | Bloodfin tetra | Mojarrita |
| Characiformes | Characidae | Aphyocharax dentatus | native | Mojarrita | |
| Characiformes | Characidae | Aphyocharax nattereri | native | ||
| Characiformes | Characidae | Aphyocharax rathbuni | native | Redflank bloodfin | |
| Cichliformes | Cichlidae | Apistogramma borellii | native | Umbrella cichlid | |
| Cichliformes | Cichlidae | Apistogramma commbrae | native | Corumba cichlid | |
| Cichliformes | Cichlidae | Apistogramma pleurotaenia | native | ||
| Cichliformes | Cichlidae | Apistogramma trifasciata | native | ||
| Galaxiiformes | Galaxiidae | Aplochiton taeniatus | native | peladilla | |
| Galaxiiformes | Galaxiidae | Aplochiton zebra | native | peladilla | |
| Gymnotiformes | Apteronotidae | Apteronotus albifrons | native | Black ghost | cheroga |
| Gymnotiformes | Apteronotidae | Apteronotus brasiliensis | native | boca rachada | |
| Gymnotiformes | Apteronotidae | Apteronotus ellisi | endemic | ||
| Cichliformes | Cichlidae | Astronotus crassipinnis | native | ||
| Cichliformes | Cichlidae | Astronotus ocellatus | native | Oscar | acará |
| Characiformes | Characidae | Astyanax abramis | native | Acará-pixuma | |
| Characiformes | Characidae | Astyanax aramburui | native | ||
| Characiformes | Characidae | Astyanax asuncionensis | native | ||
| Characiformes | Characidae | Astyanax bimaculatus | native | Twospot astyanax | Canivete |
| Characiformes | Characidae | Astyanax cordovae | native | Mojarra | |
| Characiformes | Characidae | Astyanax jacuhiensis | native | ||
| Characiformes | Characidae | Astyanax lineatus | native | Lambari | |
| Characiformes | Characidae | Astyanax orbignyanus | native | ||
| Characiformes | Characidae | Astyanax paranahybae | native | Mojarra | |
| Characiformes | Characidae | Astyanax scabripinnis | native | Mojarra | |
| Siluriformes | Auchenipteridae | Auchenipterus nigripinnis | native | bagre | |
| Siluriformes | Auchenipteridae | Auchenipterus nuchalis | native | ||
| Siluriformes | Auchenipteridae | Auchenipterus osteomystax | native | Hocicón | |
| Cichliformes | Cichlidae | Australoheros angiru | native | ||
| Cichliformes | Cichlidae | Australoheros facetus | native | Chameleon cichlid | Peine |
| Cichliformes | Cichlidae | Australoheros forquilha | native | ||
| Cichliformes | Cichlidae | Australoheros kaaygua | native | ||
| Cichliformes | Cichlidae | Australoheros scitulus | native | ||
| Cichliformes | Cichlidae | Australoheros tembe | endemic | chanchita | |
| Cichliformes | Cichlidae | Australoheros ykeregua | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias alexandri | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias bellottii | native | Argentine pearlfish | Pavito |
| Cyprinodontiformes | Rivulidae | Austrolebias elongatus | endemic | ||
| Cyprinodontiformes | Rivulidae | Austrolebias guarani | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias monstrosus | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias nigripinnis | native | Blackfin pearlfish | |
| Cyprinodontiformes | Rivulidae | Austrolebias nonoiuliensis | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias robustus | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias toba | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias vandenbergorum | native | ||
| Cyprinodontiformes | Rivulidae | Austrolebias wichi | native | ||
| Siluriformes | Bagridae | Bagrus tucumanus | native | ||
| Atheriniformes | Atherinopsidae | Basilichthys microlepidotus | native | ||
| Siluriformes | Pimelodidae | Bergiaria platana | endemic | ||
| Siluriformes | Pimelodidae | Bergiaria westermanni | native | bagre | |
| Gymnotiformes | Hypopomidae | Brachyhypopomus brevirostris | native | Bluntnose knifefish | |
| Clupeiformes | Alosidae | Brevoortia aurea | native | Brazilian menhaden | Lacha |
| Clupeiformes | Alosidae | Brevoortia pectinata | native | Argentine menhaden | Lacha |
| Siluriformes | Loricariidae | Brochiloricaria chauliodon | native | ||
| Characiformes | Bryconidae | Brycon orbignyanus | native | Pirá-pitá | |
| Characiformes | Characidae | Bryconamericus agna | endemic | ||
| Characiformes | Characidae | Bryconamericus eigenmanni | native | ||
| Characiformes | Characidae | Bryconamericus exodon | native | Mojarra | |
| Characiformes | Characidae | Bryconamericus iheringii | native | Lambari | |
| Characiformes | Characidae | Bryconamericus ikaa | endemic | ||
| Characiformes | Characidae | Bryconamericus indefessus | native | ||
| Characiformes | Characidae | Bryconamericus mennii | endemic | ||
| Characiformes | Characidae | Bryconamericus poi | endemic | ||
| Characiformes | Characidae | Bryconamericus pyahu | endemic | ||
| Characiformes | Characidae | Bryconamericus rubropictus | native | ||
| Characiformes | Characidae | Bryconamericus stramineus | native | Lambari | |
| Characiformes | Characidae | Bryconamericus sylvicola | endemic | ||
| Characiformes | Characidae | Bryconamericus thomasi | native | ||
| Characiformes | Characidae | Bryconamericus uporas | native | ||
| Characiformes | Characidae | Bryconamericus ytu | endemic | ||
| Cichliformes | Cichlidae | Bujurquina vittata | native | Banded acara | acará |
| Siluriformes | Aspredinidae | Bunocephalus doriae | native | guitarrita | |
| Siluriformes | Callichthyidae | Callichthys callichthys | native | Cascarudo | amarillito |
| Siluriformes | Trichomycteridae | Cambeva ytororo | native | ||
| Cypriniformes | Cyprinidae | Carassius auratus | introduced | Goldfish | Pez chino |
| Pleuronectiformes | Achiridae | Catathyridium jenynsii | native | lenguado | |
| Pleuronectiformes | Achiridae | Catathyridium lorentzii | native | Lenguado | |
| Siluriformes | Cetopsidae | Cetopsis gobioides | native | bagre | |
| Siluriformes | Cetopsidae | Cetopsis starnesi | native | ||
| Cichliformes | Cichlidae | Chaetobranchopsis australis | native | ||
| Characiformes | Crenuchidae | Characidium borellii | native | ||
| Characiformes | Crenuchidae | Characidium occidentale | native | Mojarrita | |
| Characiformes | Crenuchidae | Characidium pterostictum | native | ||
| Characiformes | Crenuchidae | Characidium rachovii | native | Mojarrita | |
| Characiformes | Crenuchidae | Characidium tenue | native | Tritolo | |
| Characiformes | Characidae | Charax leticiae | native | Dentudo | |
| Characiformes | Characidae | Charax stenopterus | native | Dentudo transparente | |
| Characiformes | Characidae | Cheirodon ibicuhiensis | native | Mojarrita | |
| Characiformes | Characidae | Cheirodon interruptus | native | Uruguay tetra | Mojarrita |
| Cichliformes | Cichlidae | Cichlasoma dimerus | native | ||
| Siluriformes | Clariidae | Clarias gariepinus | introduced | North African catfish | |
| Characiformes | Triportheidae | Clupeacharax anchoveoides | native | ||
| Cyprinodontiformes | Poeciliidae | Cnesterodon decemmaculatus | native | Ten spotted live-bearer | madrecita |
| Cyprinodontiformes | Poeciliidae | Cnesterodon pirai | native | Almeida toothcarp | |
| Cyprinodontiformes | Poeciliidae | Cnesterodon raddai | native | Resistencia toothcarp | |
| Salmoniformes | Salmonidae | Coregonus clupeaformis | introduced | Lake whitefish | |
| Siluriformes | Callichthyidae | Corydoras aeneus | native | Bronze corydoras | pirá-itá |
| Siluriformes | Callichthyidae | Corydoras aurofrenatus | native | Goldhead cory | |
| Siluriformes | Callichthyidae | Corydoras carlae | native | Carla's cory | pirá-itá |
| Siluriformes | Callichthyidae | Corydoras ehrhardti | native | Olive cory | |
| Siluriformes | Callichthyidae | Corydoras ellisae | native | Two point cory | pirá-itá |
| Siluriformes | Callichthyidae | Corydoras gladysae | native | Gladys' cory | |
| Siluriformes | Callichthyidae | Corydoras hastatus | native | Dwarf corydoras | amarillito |
| Siluriformes | Callichthyidae | Corydoras longipinnis | native | Long-finned cory | |
| Siluriformes | Callichthyidae | Corydoras micracanthus | native | Andes cory | tachuela |
| Siluriformes | Callichthyidae | Corydoras microcephalus | native | Peppered Argentina cory | |
| Siluriformes | Callichthyidae | Corydoras paleatus | native | Peppered corydoras | amarillito |
| Siluriformes | Callichthyidae | Corydoras petracinii | native | Petracini's cory | |
| Siluriformes | Callichthyidae | Corydoras polystictus | native | Fine spotted cory | |
| Siluriformes | Callichthyidae | Corydoras undulatus | native | ||
| Characiformes | Characidae | Creagrutus beni | native | Goldstripe characin | |
| Cichliformes | Cichlidae | Crenicichla celidochilus | native | Blacklipped pike cichlid | |
| Cichliformes | Cichlidae | Crenicichla gaucho | native | ||
| Cichliformes | Cichlidae | Crenicichla hadrostigma | native | ||
| Cichliformes | Cichlidae | Crenicichla hu | native | ||
| Cichliformes | Cichlidae | Crenicichla iguassuensis | native | ||
| Cichliformes | Cichlidae | Crenicichla jupiaensis | native | ||
| Cichliformes | Cichlidae | Crenicichla lacustris | native | boca amarga | |
| Cichliformes | Cichlidae | Crenicichla lepidota | native | Pike cichlid | boca amarga |
| Cichliformes | Cichlidae | Crenicichla mandelburgeri | native | ||
| Cichliformes | Cichlidae | Crenicichla minuano | native | ||
| Cichliformes | Cichlidae | Crenicichla missioneira | native | ||
| Cichliformes | Cichlidae | Crenicichla niederleinii | native | juanita | |
| Cichliformes | Cichlidae | Crenicichla scottii | native | ||
| Cichliformes | Cichlidae | Crenicichla semifasciata | native | ||
| Cichliformes | Cichlidae | Crenicichla taikyra | native | ||
| Cichliformes | Cichlidae | Crenicichla tapii | native | ||
| Cichliformes | Cichlidae | Crenicichla tendybaguassu | native | ||
| Cichliformes | Cichlidae | Crenicichla tesay | native | ||
| Cichliformes | Cichlidae | Crenicichla tuca | native | ||
| Cichliformes | Cichlidae | Crenicichla vittata | native | boca amarga | |
| Cichliformes | Cichlidae | Crenicichla yaha | native | ||
| Cichliformes | Cichlidae | Crenicichla ypo | native | ||
| Characiformes | Characidae | Ctenobrycon alleni | native | ||
| Characiformes | Characidae | Ctenobrycon multiradiatus | native | ||
| Cypriniformes | Xenocyprididae | Ctenopharyngodon idella | introduced | Grass carp | Sogyo |
| Characiformes | Curimatidae | Curimatella dorsalis | native | Blanquillo | |
| Characiformes | Characidae | Cynopotamus argenteus | native | Dientudo jorobado | |
| Characiformes | Characidae | Cynopotamus kincaidi | native | Dentudo | |
| Characiformes | Curimatidae | Cyphocharax platanus | native | Curimbatasinho | |
| Characiformes | Curimatidae | Cyphocharax saladensis | native | Rosy curimata | Sabalito |
| Characiformes | Curimatidae | Cyphocharax spilotus | native | Sabalito | |
| Characiformes | Curimatidae | Cyphocharax voga | native | Curimbatasinho | |
| Cypriniformes | Cyprinidae | Cyprinus carpio | introduced | Common carp | Carpa |
| Characiformes | Characidae | Deuterodon luetkenii | native | ||
| Characiformes | Characidae | Diapoma alburnum | native | ||
| Characiformes | Characidae | Diapoma guarani | native | Mojarra | |
| Characiformes | Characidae | Diapoma lepiclastum | native | ||
| Characiformes | Characidae | Diapoma nandi | native | ||
| Characiformes | Characidae | Diapoma obi | native | ||
| Characiformes | Characidae | Diapoma pyrrhopteryx | native | ||
| Characiformes | Characidae | Diapoma terofali | native | ||
| Characiformes | Characidae | Diapoma uruguayense | native | ||
| Gymnotiformes | Sternopygidae | Eigenmannia trilineata | native | ||
| Gymnotiformes | Sternopygidae | Eigenmannia virescens | native | Glass knifefish | banderita |
| Characiformes | Triportheidae | Engraulisoma taeniatum | native | ||
| Siluriformes | Loricariidae | Epactionotus yasi | endemic | ||
| Siluriformes | Auchenipteridae | Epapterus dispilurus | native | ||
| Siluriformes | Loricariidae | Farlowella amazonum | native | ||
| Siluriformes | Loricariidae | Farlowella hahni | native | vieja | |
| Galaxiiformes | Galaxiidae | Galaxias maculatus | native | Inanga | puye |
| Galaxiiformes | Galaxiidae | Galaxias platei | native | puye | |
| Characiformes | Characidae | Galeocharax humeralis | native | Dientudo | |
| Characiformes | Characidae | Galeocharax knerii | native | Dientudo | |
| Cyprinodontiformes | Poeciliidae | Gambusia affinis | introduced | Mosquitofish | orillero |
| Siluriformes | Ariidae | Genidens barbus | native | White sea catfish | Bagre |
| Siluriformes | Ariidae | Genidens genidens | native | Guri sea catfish | |
| Siluriformes | Ariidae | Genidens planifrons | native | ||
| Petromyzontiformes | Geotriidae | Geotria australis | native | Pouched lamprey | |
| Petromyzontiformes | Geotriidae | Geotria macrostoma | native | Lamprea de bolsa | |
| Siluriformes | Auchenipteridae | Glanidium albescens | native | ||
| Siluriformes | Auchenipteridae | Glanidium ribeiroi | native | bagre | |
| Characiformes | Characidae | Gymnocharacinus bergii | endemic | Naked characin | Mojarra bronceada |
| Characiformes | Characidae | Gymnocorymbus ternetzi | native | Black tetra | Monjita |
| Cichliformes | Cichlidae | Gymnogeophagus australis | native | Uruguayan eartheater | acará |
| Cichliformes | Cichlidae | Gymnogeophagus balzanii | native | Argentine humphead | |
| Cichliformes | Cichlidae | Gymnogeophagus che | endemic | ||
| Cichliformes | Cichlidae | Gymnogeophagus jaryi | native | ||
| Cichliformes | Cichlidae | Gymnogeophagus meridionalis | native | ||
| Cichliformes | Cichlidae | Gymnogeophagus taroba | endemic | ||
| Gymnotiformes | Gymnotidae | Gymnotus carapo | native | Banded knifefish | |
| Gymnotiformes | Gymnotidae | Gymnotus cuia | native | ||
| Gymnotiformes | Gymnotidae | Gymnotus inaequilabiatus | native | ||
| Siluriformes | Trichomycteridae | Hatcheria macraei | native | ||
| Siluriformes | Loricariidae | Hemiancistrus fuliginosus | native | ||
| Characiformes | Characidae | Hemigrammus mahnerti | native | ||
| Characiformes | Characidae | Hemigrammus matei | native | ||
| Characiformes | Characidae | Hemigrammus ulreyi | native | ||
| Characiformes | Hemiodontidae | Hemiodus orthonops | native | Sardina de rio | |
| Siluriformes | Pimelodidae | Hemisorubim platyrhynchos | native | Porthole shovelnose catfish | gerupoca |
| Siluriformes | Heptapteridae | Heptapterus mandimbusu | native | ||
| Siluriformes | Heptapteridae | Heptapterus mbya | native | ||
| Siluriformes | Heptapteridae | Heptapterus mustelinus | native | Bagre | |
| Siluriformes | Heptapteridae | Heptapterus qenqo | native | ||
| Characiformes | Characidae | Heterocheirodon yatai | native | Mojarrita | |
| Siluriformes | Loricariidae | Hisonotus aky | endemic | ||
| Siluriformes | Loricariidae | Hisonotus charrua | native | ||
| Siluriformes | Loricariidae | Hisonotus hungy | native | ||
| Siluriformes | Loricariidae | Hisonotus maculipinnis | native | ||
| Siluriformes | Loricariidae | Hisonotus paulinus | native | ||
| Siluriformes | Trichomycteridae | Homodiaetus anisitsi | native | ||
| Characiformes | Erythrinidae | Hoplerythrinus unitaeniatus | native | Aimara | jejú |
| Characiformes | Erythrinidae | Hoplias australis | native | ||
| Characiformes | Erythrinidae | Hoplias malabaricus | native | Trahira | Taraira |
| Characiformes | Erythrinidae | Hoplias mbigua | endemic | ||
| Siluriformes | Callichthyidae | Hoplosternum littorale | native | Atipa | |
| Characiformes | Characidae | Hyphessobrycon auca | native | ||
| Characiformes | Characidae | Hyphessobrycon bifasciatus | native | Yellow tetra | |
| Characiformes | Characidae | Hyphessobrycon elachys | native | Mojarra | |
| Characiformes | Characidae | Hyphessobrycon eques | native | Jewel tetra | |
| Characiformes | Characidae | Hyphessobrycon igneus | native | ||
| Characiformes | Characidae | Hyphessobrycon isiri | native | ||
| Characiformes | Characidae | Hyphessobrycon meridionalis | native | ||
| Characiformes | Characidae | Hyphessobrycon nicolasi | native | ||
| Characiformes | Characidae | Hyphessobrycon reticulatus | native | ||
| Characiformes | Characidae | Hyphessobrycon togoi | native | ||
| Characiformes | Characidae | Hyphessobrycon wajat | native | ||
| Cypriniformes | Xenocyprididae | Hypophthalmichthys molitrix | introduced | Silver carp | Carpa plateada |
| Siluriformes | Pimelodidae | Hypophthalmus edentatus | native | Highwaterman catfish | bagre rosado |
| Siluriformes | Pimelodidae | Hypophthalmus oremaculatus | native | bagre rosado | |
| Gymnotiformes | Hypopomidae | Hypopomus artedi | native | morenita | |
| Siluriformes | Loricariidae | Hypoptopoma inexspectatum | native | ||
| Siluriformes | Loricariidae | Hypostomus alatus | native | acarí | |
| Siluriformes | Loricariidae | Hypostomus albopunctatus | native | cascudo | |
| Siluriformes | Loricariidae | Hypostomus arecuta | native | ||
| Siluriformes | Loricariidae | Hypostomus auroguttatus | native | ||
| Siluriformes | Loricariidae | Hypostomus borellii | native | vieja | |
| Siluriformes | Loricariidae | Hypostomus boulengeri | native | ||
| Siluriformes | Loricariidae | Hypostomus cochliodon | native | cascudo | |
| Siluriformes | Loricariidae | Hypostomus commersoni | native | Vieja negra | |
| Siluriformes | Loricariidae | Hypostomus cordovae | endemic | ||
| Siluriformes | Loricariidae | Hypostomus derbyi | native | Vieja de agua | |
| Siluriformes | Loricariidae | Hypostomus itacua | native | ||
| Siluriformes | Loricariidae | Hypostomus laplatae | native | vieja | |
| Siluriformes | Loricariidae | Hypostomus luteomaculatus | native | Vieja de agua | |
| Siluriformes | Loricariidae | Hypostomus microstomus | native | Vieja de agua | |
| Siluriformes | Loricariidae | Hypostomus myersi | native | Vieja de agua | |
| Siluriformes | Loricariidae | Hypostomus paranensis | native | Vieja de agua | |
| Siluriformes | Loricariidae | Hypostomus paulinus | native | cascudo | |
| Siluriformes | Loricariidae | Hypostomus piratatu | native | ||
| Siluriformes | Loricariidae | Hypostomus regani | native | cascudo | |
| Siluriformes | Loricariidae | Hypostomus roseopunctatus | native | ||
| Siluriformes | Loricariidae | Hypostomus spiniger | native | ||
| Siluriformes | Loricariidae | Hypostomus ternetzi | native | ||
| Siluriformes | Loricariidae | Hypostomus uruguayensis | native | vieja | |
| Siluriformes | Loricariidae | Hypostomus variostictus | native | cascudo | |
| Siluriformes | Pimelodidae | Iheringichthys labrosus | native | bagre trompudo | |
| Siluriformes | Heptapteridae | Imparfinis hollandi | native | bagre anguila | |
| Siluriformes | Heptapteridae | Imparfinis mishky | native | ||
| Siluriformes | Trichomycteridae | Ituglanis eichorniarum | native | ||
| Siluriformes | Loricariidae | Ixinandria steinbachi | native | Vieja | |
| Cyprinodontiformes | Anablepidae | Jenynsia alternimaculata | native | Lipeo livebearer | |
| Cyprinodontiformes | Anablepidae | Jenynsia lineata | native | Onesided livebearer | madrecita |
| Cyprinodontiformes | Anablepidae | Jenynsia luxata | native | Tajamar livebearer | |
| Cyprinodontiformes | Anablepidae | Jenynsia maculata | native | Spotted Salta livebearer | |
| Cyprinodontiformes | Anablepidae | Jenynsia obscura | native | Córdoba livebearer | orillero |
| Cyprinodontiformes | Anablepidae | Jenynsia sulfurica | native | ||
| Cyprinodontiformes | Anablepidae | Jenynsia tucumana | native | Tucumán livebearer | |
| Cichliformes | Cichlidae | Laetacara dorsigera | native | Redbreast acara | |
| Ceratodontiformes | Lepidosirenidae | Lepidosiren paradoxa | native | South American lungfish | Lepidosirena |
| Characiformes | Anostomidae | Leporellus pictus | native | Boga | |
| Characiformes | Anostomidae | Leporinus acutidens | native | Araçau | |
| Characiformes | Anostomidae | Leporinus friderici | native | Threespot leporinus | |
| Characiformes | Anostomidae | Leporinus lacustris | native | ||
| Characiformes | Anostomidae | Leporinus octofasciatus | native | Araçau pinima | |
| Characiformes | Anostomidae | Leporinus platycephalus | native | ||
| Characiformes | Anostomidae | Leporinus striatus | native | Boga estriada | |
| Siluriformes | Callichthyidae | Lepthoplosternum pectorale | native | Chaco catfish | cascarudo |
| Siluriformes | Loricariidae | Loricaria apeltogaster | native | ||
| Siluriformes | Loricariidae | Loricaria holmbergi | native | ||
| Siluriformes | Loricariidae | Loricaria luciae | native | ||
| Siluriformes | Loricariidae | Loricaria simillima | native | ||
| Siluriformes | Loricariidae | Loricaria tucumanensis | native | guitaarra | |
| Siluriformes | Loricariidae | Loricariichthys anus | native | ||
| Siluriformes | Loricariidae | Loricariichthys edentatus | native | ||
| Siluriformes | Loricariidae | Loricariichthys labialis | native | Maimingué | |
| Siluriformes | Loricariidae | Loricariichthys melanocheilus | native | ||
| Siluriformes | Loricariidae | Loricariichthys platymetopon | native | ||
| Siluriformes | Loricariidae | Loricariichthys rostratus | native | ||
| Siluriformes | Pimelodidae | Luciopimelodus pati | native | Pati | morre-morre |
| Clupeiformes | Engraulidae | Lycengraulis grossidens | native | Atlantic sabretooth anchovy | Anchoa |
| Characiformes | Characidae | Macropsobrycon uruguayanae | native | Mojarrita | |
| Characiformes | Characidae | Markiana nigripinnis | native | Ipau | |
| Siluriformes | Loricariidae | Megalancistrus parananus | native | cascudo | |
| Siluriformes | Callichthyidae | Megalechis thoracata | native | ||
| Characiformes | Anostomidae | Megaleporinus elongatus | native | Boga | |
| Characiformes | Anostomidae | Megaleporinus macrocephalus | native | ||
| Characiformes | Anostomidae | Megaleporinus obtusidens | native | Boga | |
| Siluriformes | Pimelodidae | Megalonema argentinum | endemic | patí de aletas negras | |
| Siluriformes | Pimelodidae | Megalonema platanum | native | bagre blanco | |
| Cyprinodontiformes | Rivulidae | Melanorivulus punctatus | native | ||
| Characiformes | Serrasalmidae | Metynnis maculatus | native | Spotted metynnis | |
| Characiformes | Serrasalmidae | Metynnis mola | native | pacú | |
| Siluriformes | Pseudopimelodidae | Microglanis nigrolineatus | native | ||
| Siluriformes | Pseudopimelodidae | Microglanis parahybae | native | ||
| Centrarchiformes | Centrarchidae | Micropterus salmoides | introduced | Largemouth black bass | |
| Characiformes | Characidae | Moenkhausia dichroura | native | Bandtail tetra | Mojarra |
| Characiformes | Characidae | Moenkhausia intermedia | native | Mojarra | |
| Characiformes | Characidae | Moenkhausia sanctaefilomenae | native | Redeye tetra | Mojarra |
| Eupercaria/misc | Moronidae | Morone saxatilis | introduced | Striped bass | |
| Mugiliformes | Mugilidae | Mugil liza | native | Lebranche mullet | lisa |
| Characiformes | Serrasalmidae | Myloplus tiete | native | pacucita | |
| Characiformes | Serrasalmidae | Mylossoma duriventre | native | brillantina | |
| Cyprinodontiformes | Rivulidae | Neofundulus ornatipinnis | native | ||
| Atheriniformes | Atherinopsidae | Odontesthes argentinensis | native | Baboso | |
| Atheriniformes | Atherinopsidae | Odontesthes bonariensis | native | Argentinian silverside | Pejerrey |
| Atheriniformes | Atherinopsidae | Odontesthes hatcheri | native | pejerrey | |
| Atheriniformes | Atherinopsidae | Odontesthes humensis | native | ||
| Atheriniformes | Atherinopsidae | Odontesthes incisa | native | Cornalito | |
| Atheriniformes | Atherinopsidae | Odontesthes orientalis | native | ||
| Atheriniformes | Atherinopsidae | Odontesthes perugiae | native | juncalero | |
| Atheriniformes | Atherinopsidae | Odontesthes platensis | native | ||
| Atheriniformes | Atherinopsidae | Odontesthes smitti | native | ||
| Characiformes | Characidae | Odontostilbe microcephala | native | mojarra | |
| Characiformes | Characidae | Odontostilbe paraguayensis | native | ||
| Characiformes | Characidae | Odontostilbe pequira | native | mojarra | |
| Characiformes | Characidae | Oligosarcus amome | native | ||
| Characiformes | Characidae | Oligosarcus bolivianus | native | Dientudo | |
| Characiformes | Characidae | Oligosarcus brevioris | native | dientudo | |
| Characiformes | Characidae | Oligosarcus hepsetus | native | ||
| Characiformes | Characidae | Oligosarcus itau | native | ||
| Characiformes | Characidae | Oligosarcus jenynsii | native | dentudo | |
| Characiformes | Characidae | Oligosarcus longirostris | native | dientudo | |
| Characiformes | Characidae | Oligosarcus menezesi | endemic | ||
| Characiformes | Characidae | Oligosarcus oligolepis | native | blanquillo | |
| Characiformes | Characidae | Oligosarcus paranensis | native | dientudo | |
| Siluriformes | Diplomystidae | Olivaichthys cuyanus | native | bagre aterciopelado | |
| Siluriformes | Diplomystidae | Olivaichthys mesembrinus | native | ||
| Siluriformes | Diplomystidae | Olivaichthys viedmensis | native | Otuno | Bagre aterciopelado |
| Salmoniformes | Salmonidae | Oncorhynchus kisutch | introduced | Coho salmon | |
| Salmoniformes | Salmonidae | Oncorhynchus mykiss | introduced | Rainbow trout | trucha arco iris |
| Salmoniformes | Salmonidae | Oncorhynchus tshawytscha | introduced | Chinook salmon | |
| Siluriformes | Doradidae | Ossancora eigenmanni | native | Armado | |
| Siluriformes | Loricariidae | Otocinclus affinis | native | Golden otocinclus | |
| Siluriformes | Loricariidae | Otocinclus arnoldi | native | ||
| Siluriformes | Loricariidae | Otocinclus vittatus | native | ||
| Siluriformes | Doradidae | Oxydoras kneri | native | Armao | |
| Eupercaria/misc | Sciaenidae | Pachypops fourcroi | native | Guyanan croaker | |
| Eupercaria/misc | Sciaenidae | Pachyurus bonariensis | native | La Plata croaker | Corvina del rio |
| Cyprinodontiformes | Rivulidae | Papiliolebias bitteri | native | ||
| Cyprinodontiformes | Rivulidae | Papiliolebias hatinne | native | ||
| Siluriformes | Loricariidae | Paraloricaria agastor | native | ||
| Siluriformes | Loricariidae | Paraloricaria commersonoides | native | Vieja | |
| Siluriformes | Loricariidae | Paraloricaria vetula | native | Vieja | |
| Siluriformes | Pimelodidae | Parapimelodus valenciennis | native | bagarito | |
| Siluriformes | Trichomycteridae | Parastegophilus maculatus | native | camarón | |
| Siluriformes | Trichomycteridae | Paravandellia oxyptera | native | Pantanal parasitic catfish | chupa sangre |
| Characiformes | Parodontidae | Parodon carrikeri | native | ||
| Characiformes | Parodontidae | Parodon nasus | native | Boguita | |
| Characiformes | Parodontidae | Parodon suborbitalis | native | ||
| Clupeiformes | Pristigasteridae | Pellona flavipinnis | native | Yellowfin river pellona | Lacha |
| Centrarchiformes | Percichthyidae | Percichthys colhuapiensis | endemic | Largemouth perch | Percas boconas |
| Centrarchiformes | Percichthyidae | Percichthys laevis | native | ||
| Centrarchiformes | Percichthyidae | Percichthys trucha | endemic | Creole perch | Percas de boca chica |
| Cyprinodontiformes | Poeciliidae | Phalloceros caudimaculatus | native | Dusky millions fish | barrigudinho |
| Cyprinodontiformes | Poeciliidae | Phalloptychus januarius | native | January toothcarp | |
| Cyprinodontiformes | Poeciliidae | Phallotorynus victoriae | native | Argentinian toothcarp | Madrecita |
| Characiformes | Characidae | Phenacogaster tegatus | native | ||
| Characiformes | Iguanodectidae | Piabucus melanostoma | native | ||
| Characiformes | Serrasalmidae | Piaractus mesopotamicus | native | Pacu | baya |
| Siluriformes | Heptapteridae | Pimelodella cristata | native | ||
| Siluriformes | Heptapteridae | Pimelodella gracilis | native | Graceful pimelodella | bagre |
| Siluriformes | Heptapteridae | Pimelodella griffini | native | ||
| Siluriformes | Heptapteridae | Pimelodella laticeps | native | bagre cantor | |
| Siluriformes | Heptapteridae | Pimelodella mucosa | native | ||
| Siluriformes | Heptapteridae | Pimelodella taeniophora | native | ||
| Siluriformes | Pimelodidae | Pimelodus absconditus | native | bagre | |
| Siluriformes | Pimelodidae | Pimelodus albicans | native | bagre | |
| Siluriformes | Pimelodidae | Pimelodus argenteus | native | bagre | |
| Siluriformes | Pimelodidae | Pimelodus blochii | native | Bloch's catfish | |
| Siluriformes | Pimelodidae | Pimelodus brevis | native | bagre | |
| Siluriformes | Pimelodidae | Pimelodus maculatus | native | amarillo | |
| Siluriformes | Pimelodidae | Pimelodus mysteriosus | native | ||
| Siluriformes | Pimelodidae | Pimelodus ornatus | native | bagre | |
| Siluriformes | Pimelodidae | Pimelodus ortmanni | native | ||
| Eupercaria/misc | Sciaenidae | Plagioscion squamosissimus | native | South American silver croaker | Corvina |
| Eupercaria/misc | Sciaenidae | Plagioscion ternetzi | native | Freshwater croaker | Corvina |
| Clupeiformes | Dorosomatidae | Platanichthys platana | native | River Plate sprat | Mandufia |
| Siluriformes | Doradidae | Platydoras armatulus | native | Southern striped raphael | Armado |
| Siluriformes | Doradidae | Platydoras costatus | native | Raphael catfish | armado |
| Characiformes | Characidae | Poptella paraguayensis | native | Mojarra | |
| Siluriformes | Trichomycteridae | Potamoglanis johnsoni | native | ||
| Characiformes | Curimatidae | Potamorhina squamoralevis | native | Blanquillo | |
| Beloniformes | Belonidae | Potamorrhaphis eigenmanni | native | pez aguja | |
| Myliobatiformes | Potamotrygonidae | Potamotrygon amandae | native | ||
| Myliobatiformes | Potamotrygonidae | Potamotrygon falkneri | native | Largespot river stingray | Raya |
| Myliobatiformes | Potamotrygonidae | Potamotrygon histrix | native | Porcupine river stingray | Raya |
| Myliobatiformes | Potamotrygonidae | Potamotrygon motoro | native | South American freshwater stingray | Arraia |
| Myliobatiformes | Potamotrygonidae | Potamotrygon schuhmacheri | native | ||
| Characiformes | Characidae | Prionobrama paraguayensis | native | ||
| Characiformes | Prochilodontidae | Prochilodus lineatus | native | Streaked prochilod | Carimbatá |
| Characiformes | Prochilodontidae | Prochilodus nigricans | native | Black prochilodus | |
| Characiformes | Characidae | Psalidodon anisitsi | native | Buenos Aires tetra | Mojarra |
| Characiformes | Characidae | Psalidodon chico | native | ||
| Characiformes | Characidae | Psalidodon correntinus | native | Mojarra | |
| Characiformes | Characidae | Psalidodon eigenmanniorum | native | Chato | |
| Characiformes | Characidae | Psalidodon endy | native | ||
| Characiformes | Characidae | Psalidodon erythropterus | native | Mojarra | |
| Characiformes | Characidae | Psalidodon fasciatus | native | Banded astyanax | Lambari |
| Characiformes | Characidae | Psalidodon gymnogenys | native | Mojarra | |
| Characiformes | Characidae | Psalidodon hermosus | native | ||
| Characiformes | Characidae | Psalidodon ita | endemic | Mojarra | |
| Characiformes | Characidae | Psalidodon leonidas | endemic | Mojarra | |
| Characiformes | Characidae | Psalidodon ojiara | endemic | ||
| Characiformes | Characidae | Psalidodon pampa | native | ||
| Characiformes | Characidae | Psalidodon pellegrini | native | Mojarra | |
| Characiformes | Characidae | Psalidodon powelli | native | ||
| Characiformes | Characidae | Psalidodon puka | native | ||
| Characiformes | Characidae | Psalidodon pynandi | native | ||
| Characiformes | Characidae | Psalidodon rutilus | native | ||
| Characiformes | Characidae | Psalidodon troya | endemic | Mojarra | |
| Characiformes | Characidae | Psalidodon tumbayaensis | native | ||
| Characiformes | Curimatidae | Psectrogaster curviventris | native | Blanquillo | |
| Characiformes | Characidae | Psellogrammus kennedyi | native | Mojarrita | |
| Characiformes | Anostomidae | Pseudanos trimaculatus | native | Threespot headstander | |
| Siluriformes | Aspredinidae | Pseudobunocephalus iheringii | native | guitarrita | |
| Siluriformes | Aspredinidae | Pseudobunocephalus rugosus | native | guitarrita | |
| Characiformes | Characidae | Pseudocorynopoma doriae | native | Dragonfin tetra | Mojarra de velo |
| Siluriformes | Loricariidae | Pseudohemiodon devincenzii | native | ||
| Siluriformes | Loricariidae | Pseudohemiodon laticeps | native | Vieja | |
| Siluriformes | Loricariidae | Pseudohemiodon platycephalus | native | ||
| Siluriformes | Pseudopimelodidae | Pseudopimelodus mangurus | native | Manguruyú amarillo | |
| Siluriformes | Pimelodidae | Pseudoplatystoma corruscans | native | Spotted sorubim | cachorro (juvenil) |
| Siluriformes | Pimelodidae | Pseudoplatystoma fasciatum | native | Barred sorubim | cachorro (juvenil) |
| Siluriformes | Pimelodidae | Pseudoplatystoma reticulatum | native | ||
| Beloniformes | Belonidae | Pseudotylosurus angusticeps | native | aguja de rio | |
| Beloniformes | Belonidae | Pseudotylosurus microps | native | ||
| Siluriformes | Aspredinidae | Pterobunocephalus depressus | native | ||
| Siluriformes | Doradidae | Pterodoras granulosus | native | Granulated catfish | Armado común |
| Cyprinodontiformes | Rivulidae | Pterolebias longipinnis | native | Longfin killie | |
| Siluriformes | Loricariidae | Pterygoplichthys ambrosettii | native | Vieja de agua | |
| Characiformes | Serrasalmidae | Pygocentrus nattereri | native | Red piranha | coicoa |
| Characiformes | Lebiasinidae | Pyrrhulina australis | native | pirrulina | |
| Characiformes | Lebiasinidae | Pyrrhulina melanostomus | native | Blackmouth pyrrhulina | |
| Characiformes | Lebiasinidae | Pyrrhulina rachoviana | native | Fanning pyrrhulina | |
| Clupeiformes | Clupeidae | Ramnogaster arcuata | native | Jenyns's sprat | Sardina |
| Clupeiformes | Clupeidae | Ramnogaster melanostoma | native | Uruguay river sprat | Mandufia |
| Siluriformes | Heptapteridae | Rhamdella aymarae | endemic | ||
| Siluriformes | Heptapteridae | Rhamdella cainguae | native | ||
| Siluriformes | Heptapteridae | Rhamdella jenynsii | native | ||
| Siluriformes | Heptapteridae | Rhamdia quelen | native | South American catfish | bagre |
| Gymnotiformes | Rhamphichthyidae | Rhamphichthys hahni | endemic | Roundnose knifefish | |
| Gymnotiformes | Rhamphichthyidae | Rhamphichthys rostratus | native | Trompet knifefish | anguila picuda |
| Characiformes | Cynodontidae | Rhaphiodon vulpinus | native | Biara | Machete |
| Siluriformes | Loricariidae | Rhinelepis aspera | native | acarí | |
| Siluriformes | Loricariidae | Rhinelepis strigosa | native | Vieja | |
| Siluriformes | Doradidae | Rhinodoras dorbignyi | native | Marieta | |
| Siluriformes | Loricariidae | Ricola macrops | native | Vieja de cola | |
| Siluriformes | Loricariidae | Rineloricaria catamarcensis | native | Vieja | |
| Siluriformes | Loricariidae | Rineloricaria felipponei | native | vieja | |
| Siluriformes | Loricariidae | Rineloricaria isaaci | native | ||
| Siluriformes | Loricariidae | Rineloricaria lima | native | vieja de aqua | |
| Siluriformes | Loricariidae | Rineloricaria microlepidogaster | native | vieja | |
| Siluriformes | Loricariidae | Rineloricaria misionera | native | ||
| Siluriformes | Loricariidae | Rineloricaria parva | native | Vieja de agua | |
| Characiformes | Characidae | Roeboides descalvadensis | native | Parana scale-eating characin | Dientudo |
| Characiformes | Characidae | Roeboides microlepis | native | Dentudo | |
| Characiformes | Characidae | Roeboides prognathus | native | Dientudo | |
| Characiformes | Bryconidae | Salminus brasiliensis | native | Dorado | Dorado |
| Characiformes | Bryconidae | Salminus hilarii | native | Dorado plateado | |
| Salmoniformes | Salmonidae | Salmo salar | introduced | Atlantic salmon | Landloked salmon |
| Salmoniformes | Salmonidae | Salmo trutta | introduced | Sea trout | trucha europea |
| Salmoniformes | Salmonidae | Salvelinus fontinalis | introduced | Brook trout | trucha de arroyo |
| Salmoniformes | Salmonidae | Salvelinus namaycush | introduced | Lake trout | trucha de lago |
| Characiformes | Anostomidae | Schizodon borellii | native | Aracú pintado | |
| Characiformes | Anostomidae | Schizodon isognathus | native | ||
| Characiformes | Anostomidae | Schizodon nasutus | native | Boga | |
| Characiformes | Anostomidae | Schizodon platae | endemic | ||
| Characiformes | Anostomidae | Schizodon succinctus | native | ||
| Siluriformes | Trichomycteridae | Scleronema milonga | native | ||
| Characiformes | Characidae | Serrapinnus calliurus | native | mojarra curvada | |
| Characiformes | Characidae | Serrapinnus notomelas | native | ||
| Characiformes | Serrasalmidae | Serrasalmus auriventris | native | ||
| Characiformes | Serrasalmidae | Serrasalmus maculatus | native | ||
| Characiformes | Serrasalmidae | Serrasalmus marginatus | native | catirina | |
| Characiformes | Serrasalmidae | Serrasalmus nigricauda | native | ||
| Characiformes | Serrasalmidae | Serrasalmus spilopleura | native | Speckled piranha | catirina |
| Siluriformes | Trichomycteridae | Silvinichthys bortayro | native | ||
| Siluriformes | Trichomycteridae | Silvinichthys gualcamayo | native | ||
| Siluriformes | Trichomycteridae | Silvinichthys huachi | native | ||
| Siluriformes | Trichomycteridae | Silvinichthys leoncitensis | native | ||
| Siluriformes | Trichomycteridae | Silvinichthys mendozensis | native | ||
| Siluriformes | Trichomycteridae | Silvinichthys pachonensis | native | ||
| Siluriformes | Trichomycteridae | Silvinichthys pedernalensis | native | ||
| Siluriformes | Pimelodidae | Sorubim lima | native | Duckbill catfish | bico de pato |
| Siluriformes | Loricariidae | Spatuloricaria evansii | native | vieja | |
| Siluriformes | Pimelodidae | Steindachneridion scriptum | native | bagre | |
| Characiformes | Curimatidae | Steindachnerina biornata | native | ||
| Characiformes | Curimatidae | Steindachnerina brevipinna | native | Blanquillo | |
| Characiformes | Curimatidae | Steindachnerina conspersa | native | ||
| Gymnotiformes | Sternopygidae | Sternopygus macrurus | native | Longtail knifefish | cuchilla |
| Siluriformes | Loricariidae | Sturisoma barbatum | native | vieja | |
| Siluriformes | Loricariidae | Sturisoma robustum | native | ||
| Synbranchiformes | Synbranchidae | Synbranchus marmoratus | native | Marbled swamp eel | anguila |
| Characiformes | Characidae | Tetragonopterus argenteus | native | Chanquete | |
| Characiformes | Characidae | Tetragonopterus signatus | native | ||
| Characiformes | Gasteropelecidae | Thoracocharax stellatus | native | Spotfin hatchetfish | Chirola |
| Siluriformes | Auchenipteridae | Trachelyopterus albicrux | native | bagre cruz blanca | |
| Siluriformes | Auchenipteridae | Trachelyopterus ceratophysus | native | ||
| Siluriformes | Auchenipteridae | Trachelyopterus galeatus | native | ||
| Siluriformes | Auchenipteridae | Trachelyopterus teaguei | native | bagre | |
| Siluriformes | Doradidae | Trachydoras paraguayensis | native | Armado | |
| Siluriformes | Trichomycteridae | Trichomycterus alterus | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus belensis | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus borellii | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus boylei | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus catamarcensis | endemic | ||
| Siluriformes | Trichomycteridae | Trichomycterus corduvensis | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus heterodontus | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus hualco | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus minus | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus pseudosilvinichthys | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus ramosus | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus riojanus | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus roigi | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus spegazzinii | native | yuska | |
| Siluriformes | Trichomycteridae | Trichomycterus tenuis | native | bagre serrano | |
| Siluriformes | Trichomycteridae | Trichomycterus varii | native | ||
| Siluriformes | Trichomycteridae | Trichomycterus yuska | endemic | ||
| Siluriformes | Trichomycteridae | Tridentopsis cahuali | native | ||
| Cyprinodontiformes | Rivulidae | Trigonectes aplocheiloides | native | ||
| Cyprinodontiformes | Rivulidae | Trigonectes balzanii | native | ||
| Characiformes | Triportheidae | Triportheus angulatus | native | Sapo | |
| Characiformes | Triportheidae | Triportheus nematurus | native | ||
| Characiformes | Triportheidae | Triportheus paranensis | native | Tetra | Dientudo |
| Siluriformes | Aspredinidae | Xyliphius barbatus | native | guitarrita | |
| Siluriformes | Pimelodidae | Zungaro jahu | native | Manguruyu | |
| Siluriformes | Pimelodidae | Zungaro zungaro | native | Gilded catfish | apretador |