| Order | Family | Species | Occurrence | FishBase name | Name in Country |
|---|---|---|---|---|---|
| Characiformes | Anostomidae | Abramites hypselonotus | native | Marbled headstander | Jikii |
| Perciformes/Serranoidei | Anthiadidae | Acanthistius brasilianus | native | Argentine seabass | Mero |
| Perciformes/Serranoidei | Anthiadidae | Acanthistius patachonicus | native | Mero | |
| Tetraodontiformes | Ostraciidae | Acanthostracion quadricornis | native | Scrawled cowfish | |
| Characiformes | Acestrorhynchidae | Acestrorhynchus lacustris | native | dientudo | |
| Characiformes | Acestrorhynchidae | Acestrorhynchus pantaneiro | native | dientudo | |
| Pleuronectiformes | Achiropsettidae | Achiropsetta tricholepis | native | Prickly flounder | Lenguado |
| 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 | ||
| Perciformes/Cottoidei | Agonidae | Agonopsis asperoculis | native | ||
| Perciformes/Cottoidei | Agonidae | Agonopsis chiloensis | native | Snailfish | Aayakich |
| Lampriformes | Regalecidae | Agrostichthys parkeri | native | Streamer fish | |
| Aulopiformes | Notosudidae | Ahliesaurus berryi | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Aiakas kreffti | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Aiakas zinorum | native | ||
| Aulopiformes | Alepisauridae | Alepisaurus brevirostris | native | Short snouted lancetfish | |
| Alepocephaliformes | Alepocephalidae | Alepocephalus productus | native | Smalleye smooth-head | |
| Zeiformes | Oreosomatidae | Allocyttus verrucosus | native | Warty dory | |
| Scombriformes | Scombridae | Allothunnus fallai | native | Slender tuna | |
| Lamniformes | Alopiidae | Alopias vulpinus | native | Thresher | |
| Tetraodontiformes | Monacanthidae | Aluterus monoceros | native | Unicorn leatherjacket filefish | |
| Siluriformes | Aspredinidae | Amaralia oviraptor | native | ||
| Rajiformes | Rajidae | Amblyraja doellojuradoi | native | Southern thorny skate | |
| Rajiformes | Rajidae | Amblyraja frerichsi | native | Thickbody skate | |
| Rajiformes | Rajidae | Amblyraja georgiana | native | Antarctic starry skate | |
| Siluriformes | Doradidae | Anadoras insculptus | native | armado | |
| Siluriformes | Doradidae | Anadoras weddellii | native | Armado | |
| Syngnathiformes | Syngnathidae | Anarchopterus tectus | native | Insular pipefish | |
| Clupeiformes | Engraulidae | Anchoa hepsetus | native | Broad-striped anchovy | |
| Clupeiformes | Engraulidae | Anchoa marinii | native | Marini's anchovy | |
| Clupeiformes | Engraulidae | Anchoa tricolor | native | Piquitinga anchovy | |
| 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 | ||
| Trachichthyiformes | Anoplogastridae | Anoplogaster cornuta | native | Common fangtooth | |
| Acanthuriformes | Antigoniidae | Antigonia capros | native | Deepbody boarfish | |
| Gadiformes | Moridae | Antimora rostrata | native | Blue antimora | |
| Characiformes | Parodontidae | Apareiodon affinis | native | Darter characine | Canivete |
| Characiformes | Parodontidae | Apareiodon piracicabae | native | ||
| Scombriformes | Trichiuridae | Aphanopus mikhailini | native | Mikhailin's scabbardfish | |
| 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 | ||
| Aulopiformes | Paralepididae | Arctozenus risso | native | Spotted barracudina | |
| Perciformes/Zoarcoidei | Zoarcidae | Argentinolycus elongatus | native | ||
| Stomiiformes | Sternoptychidae | Argyropelecus aculeatus | native | Lovely hatchetfish | |
| Stomiiformes | Sternoptychidae | Argyropelecus gigas | native | Hatchetfish | |
| Stomiiformes | Sternoptychidae | Argyropelecus hemigymnus | native | Half-naked hatchetfish | |
| Stomiiformes | Stomiidae | Aristostomias polydactylus | native | ||
| Tetraodontiformes | Tetraodontidae | Arothron firmamentum | native | Starry toado | |
| Cichliformes | Cichlidae | Astronotus crassipinnis | native | ||
| Cichliformes | Cichlidae | Astronotus ocellatus | native | Oscar | acará |
| Perciformes/Uranoscopoidei | Uranoscopidae | Astroscopus sexspinosus | native | Brazilian stargazer | Cura |
| 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 | |
| Rajiformes | Arhynchobatidae | Atlantoraja castelnaui | native | Spotback skate | |
| Rajiformes | Arhynchobatidae | Atlantoraja cyclophora | native | Eyespot skate | |
| Rajiformes | Arhynchobatidae | Atlantoraja platana | native | La Plata skate | |
| Siluriformes | Auchenipteridae | Auchenipterus nigripinnis | native | bagre | |
| Siluriformes | Auchenipteridae | Auchenipterus nuchalis | native | ||
| Siluriformes | Auchenipteridae | Auchenipterus osteomystax | native | Hocicón | |
| Trachichthyiformes | Trachichthyidae | Aulotrachichthys atlanticus | native | Brazilian luminous roughy | |
| 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 | ||
| Perciformes/Zoarcoidei | Zoarcidae | Austrolycus depressiceps | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Austrolycus laticinctus | native | ||
| Scombriformes | Scombridae | Auxis rochei | native | Bullet tuna | |
| Scombriformes | Scombridae | Auxis thazard | native | Frigate tuna | |
| Siluriformes | Bagridae | Bagrus tucumanus | native | ||
| Tetraodontiformes | Balistidae | Balistes capriscus | native | Grey triggerfish | |
| Atheriniformes | Atherinopsidae | Basilichthys microlepidotus | native | ||
| Anguilliformes | Congridae | Bassanago albescens | native | Hairy conger | Congrio |
| Stomiiformes | Stomiidae | Bathophilus ater | native | Winged dragonfish | |
| Stomiiformes | Stomiidae | Bathophilus nigerrimus | native | Scaleless dragonfish | |
| Argentiniformes | Bathylagidae | Bathylagus antarcticus | native | Antarctic deepsea smelt | |
| Rajiformes | Arhynchobatidae | Bathyraja albomaculata | native | White-dotted skate | Raya de lunares |
| Rajiformes | Arhynchobatidae | Bathyraja brachyurops | native | Broadnose skate | Raya de los canales |
| Rajiformes | Arhynchobatidae | Bathyraja cousseauae | native | Joined-fins skate | Raya Aletas Juntas |
| Rajiformes | Arhynchobatidae | Bathyraja griseocauda | native | Graytail skate | |
| Rajiformes | Arhynchobatidae | Bathyraja macloviana | native | Patagonian skate | |
| Rajiformes | Arhynchobatidae | Bathyraja magellanica | native | Magellan skate | |
| Rajiformes | Arhynchobatidae | Bathyraja meridionalis | native | Dark-belly skate | |
| Rajiformes | Arhynchobatidae | Bathyraja multispinis | native | Multispine skate | |
| Rajiformes | Arhynchobatidae | Bathyraja papilionifera | native | ||
| Rajiformes | Arhynchobatidae | Bathyraja scaphiops | native | Cuphead skate | |
| Rajiformes | Arhynchobatidae | Bathyraja schroederi | native | Whitemouth skate | |
| Myliobatiformes | Dasyatidae | Bathytoshia centroura | native | Roughtail stingray | |
| Scombriformes | Trichiuridae | Benthodesmus elongatus | native | Elongate frostfish | |
| Siluriformes | Pimelodidae | Bergiaria platana | endemic | ||
| Siluriformes | Pimelodidae | Bergiaria westermanni | native | bagre | |
| Beryciformes | Berycidae | Beryx decadactylus | native | Alfonsino | |
| Myctophiformes | Myctophidae | Bolinichthys indicus | native | Lanternfish | |
| Myctophiformes | Myctophidae | Bolinichthys photothorax | native | Spurcheek lanternfish | |
| Myctophiformes | Myctophidae | Bolinichthys supralateralis | native | Stubby lanternfish | |
| Eupercaria/misc | Haemulidae | Boridia grossidens | native | Borriqueta porgy | |
| Perciformes/Notothenioidei | Bovichtidae | Bovichtus argentinus | native | ||
| Gymnotiformes | Hypopomidae | Brachyhypopomus brevirostris | native | Bluntnose knifefish | |
| Scombriformes | Bramidae | Brama brama | native | Atlantic pomfret | |
| 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 |
| Blenniiformes | Labrisomidae | Calliclinus geniguttatus | native | ||
| Chimaeriformes | Callorhinchidae | Callorhinchus callorynchus | native | Plownose chimaera | Músico |
| Siluriformes | Trichomycteridae | Cambeva ytororo | native | ||
| Tetraodontiformes | Balistidae | Canthidermis maculata | native | Rough triggerfish | |
| Carangiformes | Carangidae | Caranx crysos | native | Blue runner | |
| Cypriniformes | Cyprinidae | Carassius auratus | introduced | Goldfish | Pez chino |
| Carcharhiniformes | Carcharhinidae | Carcharhinus brachyurus | native | Copper shark | |
| Carcharhiniformes | Carcharhinidae | Carcharhinus brevipinna | native | Spinner shark | |
| Carcharhiniformes | Carcharhinidae | Carcharhinus leucas | native | Bull shark | |
| Carcharhiniformes | Carcharhinidae | Carcharhinus longimanus | native | Oceanic whitetip shark | |
| Carcharhiniformes | Carcharhinidae | Carcharhinus plumbeus | native | Sandbar shark | |
| Carcharhiniformes | Carcharhinidae | Carcharhinus signatus | native | Night shark | |
| Lamniformes | Carchariidae | Carcharias taurus | native | Sand tiger shark | |
| Lamniformes | Lamnidae | Carcharodon carcharias | native | Great white shark | |
| Perciformes/Cottoidei | Liparidae | Careproctus acaecus | native | Appendageless snailfish | |
| Perciformes/Cottoidei | Liparidae | Careproctus aculeolatus | native | Small-spine snailfish | |
| Perciformes/Cottoidei | Liparidae | Careproctus cactiformis | native | ||
| Perciformes/Cottoidei | Liparidae | Careproctus macranchus | native | ||
| Perciformes/Cottoidei | Liparidae | Careproctus pallidus | native | ||
| Scombriformes | Caristiidae | Caristius fasciatus | native | Greenland manefish | |
| Scombriformes | Caristiidae | Caristius meridionalis | native | ||
| Ophidiiformes | Bythitidae | Cataetyx messieri | native | ||
| Pleuronectiformes | Achiridae | Catathyridium garmani | native | Lenguado | |
| Pleuronectiformes | Achiridae | Catathyridium jenynsii | native | lenguado | |
| Pleuronectiformes | Achiridae | Catathyridium lorentzii | native | Lenguado | |
| Siluriformes | Ariidae | Cathorops puncticulatus | native | ||
| Syngnathiformes | Centriscidae | Centriscops humerosus | native | Banded yellowfish | |
| Myctophiformes | Myctophidae | Centrobranchus nigroocellatus | native | Roundnose lanternfish | |
| Scombriformes | Centrolophidae | Centrolophus niger | native | Rudderfish | |
| Squaliformes | Etmopteridae | Centroscyllium fabricii | native | Black dogfish | |
| Squaliformes | Etmopteridae | Centroscyllium granulatum | native | Granular dogfish | |
| Myctophiformes | Myctophidae | Ceratoscopelus warmingii | native | Warming's lantern fish | |
| Siluriformes | Cetopsidae | Cetopsis gobioides | native | bagre | |
| Siluriformes | Cetopsidae | Cetopsis starnesi | native | ||
| Lamniformes | Cetorhinidae | Cetorhinus maximus | native | Basking shark | |
| Cichliformes | Cichlidae | Chaetobranchopsis australis | native | ||
| Perciformes/Notothenioidei | Channichthyidae | Champsocephalus esox | native | Pike icefish | Tsataki |
| 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 | |
| Stomiiformes | Stomiidae | Chauliodus minimus | native | ||
| Characiformes | Characidae | Cheirodon ibicuhiensis | native | Mojarrita | |
| Characiformes | Characidae | Cheirodon interruptus | native | Uruguay tetra | Mojarrita |
| Scombriformes | Chiasmodontidae | Chiasmodon niger | native | Black swallower | |
| Tetraodontiformes | Diodontidae | Chilomycterus spinosus | native | ||
| Carangiformes | Carangidae | Chloroscombrus chrysurus | native | Atlantic bumper | |
| 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 | |
| Gadiformes | Macrouridae | Coelorinchus aconcagua | native | Aconcagua grenadier | |
| Gadiformes | Macrouridae | Coelorinchus fasciatus | native | Banded whiptail | Granadero |
| Gadiformes | Macrouridae | Coelorinchus kaiyomaru | native | Campbell whiptail | |
| Gadiformes | Macrouridae | Coelorinchus marinii | native | Marini's grenadier | |
| Anguilliformes | Congridae | Conger orbignianus | native | Argentine conger | Congrio |
| Perciformes/Scorpaenoidei | Congiopodidae | Congiopodus peruvianus | native | Horsefish | Pez chancho |
| Eupercaria/misc | Haemulidae | Conodon nobilis | native | Barred grunt | |
| Eupercaria/misc | Priacanthidae | Cookeolus japonicus | native | Longfinned bullseye | |
| Salmoniformes | Salmonidae | Coregonus clupeaformis | introduced | Lake whitefish | |
| Eupercaria/misc | Labridae | Coris julis | native | Mediterranean rainbow wrasse | |
| 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 | ||
| Gadiformes | Macrouridae | Coryphaenoides filicauda | native | Grenadier | |
| Gadiformes | Macrouridae | Coryphaenoides subserrulatus | native | Longrayed whiptail | |
| Perciformes/Notothenioidei | Bovichtidae | Cottoperca gobio | native | Channel bull blenny | Yakouroum |
| Perciformes/Notothenioidei | Bovichtidae | Cottoperca trigloides | native | ||
| Perciformes/Cottoidei | Psychrolutidae | Cottunculus granulosus | native | Fathead | |
| 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 | ||
| Perciformes/Zoarcoidei | Zoarcidae | Crossostomus chilensis | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Crossostomus fasciatus | native | ||
| Characiformes | Characidae | Ctenobrycon alleni | native | ||
| Characiformes | Characidae | Ctenobrycon multiradiatus | native | ||
| Cypriniformes | Xenocyprididae | Ctenopharyngodon idella | introduced | Grass carp | Sogyo |
| Scombriformes | Nomeidae | Cubiceps caeruleus | native | Blue fathead | |
| Characiformes | Curimatidae | Curimatella dorsalis | native | Blanquillo | |
| Characiformes | Characidae | Cynopotamus argenteus | native | Dientudo jorobado | |
| Characiformes | Characidae | Cynopotamus kincaidi | native | Dentudo | |
| Eupercaria/misc | Sciaenidae | Cynoscion acoupa | native | Acoupa weakfish | |
| Eupercaria/misc | Sciaenidae | Cynoscion guatucupa | native | Stripped weakfish | |
| Eupercaria/misc | Sciaenidae | Cynoscion jamaicensis | native | Jamaica weakfish | |
| Eupercaria/misc | Sciaenidae | Cynoscion striatus | native | Striped weakfish | Pescadilla |
| 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 |
| Dactylopteriformes | Dactylopteridae | Dactylopterus volitans | native | Flying gurnard | |
| Perciformes/Zoarcoidei | Zoarcidae | Dadyanos insignis | native | ||
| Myliobatiformes | Dasyatidae | Dasyatis hypostigma | native | ||
| Myctophiformes | Myctophidae | Dasyscopelus obtusirostris | native | Bluntsnout lanternfish | |
| Carangiformes | Carangidae | Decapterus tabl | native | Roughear scad | |
| Characiformes | Characidae | Deuterodon luetkenii | native | ||
| Myctophiformes | Myctophidae | Diaphus bertelseni | native | Bertelsen's lanternfish | |
| Myctophiformes | Myctophidae | Diaphus dumerilii | native | Dumeril's lanternfish | |
| Myctophiformes | Myctophidae | Diaphus hudsoni | native | Hudson's lanternfish | |
| Myctophiformes | Myctophidae | Diaphus metopoclampus | native | Spothead lantern fish | |
| Myctophiformes | Myctophidae | Diaphus mollis | native | Soft lanternfish | |
| Myctophiformes | Myctophidae | Diaphus perspicillatus | native | Transparent lantern fish | |
| Myctophiformes | Myctophidae | Diaphus subtilis | 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 | ||
| Anguilliformes | Synaphobranchidae | Diastobranchus capensis | native | Basketwork eel | |
| Myctophiformes | Myctophidae | Diogenichthys atlanticus | native | Longfin lanternfish | |
| Perciformes/Serranoidei | Serranidae | Diplectrum radiale | native | Pond perch | Aguavina |
| Eupercaria/misc | Sparidae | Diplodus argenteus | native | South American silver porgy | |
| Rajiformes | Rajidae | Dipturus argentinensis | native | Argentine skate | Raya hocicuda de cola larga |
| Rajiformes | Rajidae | Dipturus flavirostris | native | ||
| Rajiformes | Rajidae | Dipturus trachyderma | native | Ray | |
| Torpediniformes | Narcinidae | Discopyge castelloi | native | Castello's apron numbfish | |
| Torpediniformes | Narcinidae | Discopyge tschudii | native | Apron ray | Raya eléctrica |
| Perciformes/Notothenioidei | Nototheniidae | Dissostichus eleginoides | native | Patagonian toothfish | Merluza negra |
| Perciformes/Serranoidei | Serranidae | Dules auriga | native | Cochero | Pez cochero |
| Carangiformes | Echeneidae | Echeneis naucrates | native | Live sharksucker | |
| Echinorhiniformes | Echinorhinidae | Echinorhinus brucus | native | Bramble shark | |
| Ophidiiformes | Carapidae | Echiodon cryomargarites | native | Messmate | |
| Stomiiformes | Stomiidae | Echiostoma barbatum | native | Threadfin dragonfish | |
| Gymnotiformes | Sternopygidae | Eigenmannia trilineata | native | ||
| Gymnotiformes | Sternopygidae | Eigenmannia virescens | native | Glass knifefish | banderita |
| Myctophiformes | Myctophidae | Electrona carlsbergi | native | Electron subantarctic | |
| Myctophiformes | Myctophidae | Electrona subaspera | native | Rough lanternfish | |
| Perciformes/Notothenioidei | Eleginopidae | Eleginops maclovinus | native | Patagonian blennie | Róbalo |
| Clupeiformes | Engraulidae | Engraulis anchoita | native | Argentine anchovy | Anchoíta |
| Characiformes | Triportheidae | Engraulisoma taeniatum | native | ||
| Siluriformes | Loricariidae | Epactionotus yasi | endemic | ||
| Siluriformes | Auchenipteridae | Epapterus dispilurus | native | ||
| Acropomatiformes | Epigonidae | Epigonus robustus | native | Robust cardinalfish | |
| Perciformes/Serranoidei | Epinephelidae | Epinephelus marginatus | native | Dusky grouper | |
| Squaliformes | Etmopteridae | Etmopterus bigelowi | native | Blurred smooth lantern shark | |
| Squaliformes | Etmopteridae | Etmopterus gracilispinis | native | Broadbanded lanternshark | |
| Squaliformes | Etmopteridae | Etmopterus granulosus | native | Southern lanternshark | |
| Squaliformes | Etmopteridae | Etmopterus pusillus | native | Smooth lanternshark | |
| Pleuronectiformes | Cyclopsettidae | Etropus longimanus | native | ||
| Eupercaria/misc | Gerreidae | Eucinostomus gula | native | Jenny mojarra | |
| Squaliformes | Dalatiidae | Euprotomicroides zantedeschia | native | Taillight shark | |
| Stomiiformes | Stomiidae | Eustomias enbarbatus | native | Barbate dragonfish | |
| Scombriformes | Scombridae | Euthynnus alletteratus | native | Little tunny | |
| Aulopiformes | Evermannellidae | Evermannella balbo | native | Balbo sabretooth | |
| Siluriformes | Loricariidae | Farlowella amazonum | native | ||
| Siluriformes | Loricariidae | Farlowella hahni | native | vieja | |
| Syngnathiformes | Fistulariidae | Fistularia petimba | native | Red cornetfish | |
| Stomiiformes | Stomiidae | Flagellostomias boureei | native | Longbarb dragonfish | |
| Galaxiiformes | Galaxiidae | Galaxias maculatus | native | Inanga | puye |
| Galaxiiformes | Galaxiidae | Galaxias platei | native | puye | |
| Carcharhiniformes | Galeocerdonidae | Galeocerdo cuvier | native | Tiger shark | |
| Characiformes | Characidae | Galeocharax humeralis | native | Dientudo | |
| Characiformes | Characidae | Galeocharax knerii | native | Dientudo | |
| Carcharhiniformes | Triakidae | Galeorhinus galeus | native | Tope shark | Tiburón vitaminico |
| Cyprinodontiformes | Poeciliidae | Gambusia affinis | introduced | Mosquitofish | orillero |
| Scombriformes | Scombridae | Gasterochisma melampus | native | Butterfly kingfish | |
| Siluriformes | Ariidae | Genidens barbus | native | White sea catfish | Bagre |
| Siluriformes | Ariidae | Genidens genidens | native | Guri sea catfish | |
| Siluriformes | Ariidae | Genidens machadoi | native | ||
| Siluriformes | Ariidae | Genidens planifrons | native | ||
| Ophidiiformes | Ophidiidae | Genypterus blacodes | native | Pink cusk-eel | Abadejo |
| Ophidiiformes | Ophidiidae | Genypterus brasiliensis | 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 | |
| Gobiesociformes | Gobiesocidae | Gobiesox marmoratus | native | Peje-sapo veteado | |
| Gobiiformes | Gobiidae | Gobiosoma hemigymnum | native | Half naked goby | |
| Gadiformes | Moridae | Guttigadus kongi | native | Austral cod | |
| 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 | ||
| Myctophiformes | Myctophidae | Gymnoscopelus bolini | native | Grand lanternfish | |
| Myctophiformes | Myctophidae | Gymnoscopelus nicholsi | native | Nichol's lanternfish | |
| Myctophiformes | Myctophidae | Gymnoscopelus piabilis | native | Southern blacktip lanternfish | |
| Anguilliformes | Muraenidae | Gymnothorax conspersus | native | Saddled moray | |
| Gymnotiformes | Gymnotidae | Gymnotus carapo | native | Banded knifefish | |
| Gymnotiformes | Gymnotidae | Gymnotus cuia | native | ||
| Gymnotiformes | Gymnotidae | Gymnotus inaequilabiatus | native | ||
| Myliobatiformes | Gymnuridae | Gymnura altavela | native | Spiny butterfly ray | |
| Gadiformes | Moridae | Halargyreus johnsonii | native | Slender codling | |
| Clupeiformes | Dorosomatidae | Harengula jaguana | native | Scaled herring | |
| Perciformes/Notothenioidei | Harpagiferidae | Harpagifer bispinis | native | Magellan plunderfish | |
| Siluriformes | Trichomycteridae | Hatcheria macraei | native | ||
| Blenniiformes | Tripterygiidae | Helcogrammoides cunninghami | native | Cunningham's triplefin | |
| Perciformes/Scorpaenoidei | Sebastidae | Helicolenus lahillei | native | Rubio | |
| Perciformes/Scorpaenoidei | Sebastidae | Helicolenus lengerichi | native | ||
| Siluriformes | Loricariidae | Hemiancistrus fuliginosus | native | ||
| Carangiformes | Carangidae | Hemicaranx amblyrhynchus | native | Bluntnose jack | |
| 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 | ||
| Hexanchiformes | Hexanchidae | Heptranchias perlo | native | Sharpnose sevengill shark | |
| Characiformes | Characidae | Heterocheirodon yatai | native | Mojarrita | |
| Eupercaria/misc | Priacanthidae | Heteropriacanthus cruentatus | native | Glasseye | |
| Hexanchiformes | Hexanchidae | Hexanchus griseus | native | Bluntnose sixgill shark | |
| Lophiiformes | Himantolophidae | Himantolophus appelii | native | Prickly footballfish | |
| Syngnathiformes | Syngnathidae | Hippocampus patagonicus | native | Patagonian seahorse | |
| 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 | |
| Anguilliformes | Nettastomatidae | Hoplunnis tenuis | native | Spotted pike-conger | |
| Gadiformes | Macrouridae | Hymenocephalus billsam | native | ||
| Myliobatiformes | Dasyatidae | Hypanus say | native | Bluntnose stingray | |
| Scombriformes | Centrolophidae | Hyperoglyphe antarctica | native | Bluenose warehou | |
| 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 | ||
| Blenniiformes | Blenniidae | Hypleurochilus fissicornis | 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 | ||
| Beloniformes | Hemiramphidae | Hyporhamphus unifasciatus | native | Common halfbeak | |
| 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 | |
| Scombriformes | Centrolophidae | Icichthys australis | native | Southern driftfish | |
| Stomiiformes | Stomiidae | Idiacanthus atlanticus | native | Black dragonfish | |
| Stomiiformes | Stomiidae | Idiacanthus fasciola | native | Ribbon sawtail fish | |
| Siluriformes | Pimelodidae | Iheringichthys labrosus | native | bagre trompudo | |
| Perciformes/Zoarcoidei | Zoarcidae | Iluocoetes fimbriatus | native | Barbada | |
| Siluriformes | Heptapteridae | Imparfinis hollandi | native | bagre anguila | |
| Siluriformes | Heptapteridae | Imparfinis mishky | native | ||
| Carangiformes | Istiophoridae | Istiophorus albicans | native | Atlantic sailfish | |
| Lamniformes | Lamnidae | Isurus oxyrinchus | native | Shortfin mako | |
| 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 | |
| Carangiformes | Istiophoridae | Kajikia albida | native | Atlantic white marlin | |
| Scombriformes | Scombridae | Katsuwonus pelamis | native | Skipjack tuna | |
| Centrarchiformes | Kyphosidae | Kyphosus incisor | native | Yellow sea chub | |
| Cichliformes | Cichlidae | Laetacara dorsigera | native | Redbreast acara | |
| Tetraodontiformes | Tetraodontidae | Lagocephalus laevigatus | native | Smooth puffer | |
| Lamniformes | Lamnidae | Lamna nasus | native | Porbeagle | |
| Myctophiformes | Myctophidae | Lampadena luminosa | native | Luminous lanternfish | |
| Myctophiformes | Myctophidae | Lampadena notialis | native | Notal lanternfish | |
| Myctophiformes | Myctophidae | Lampanyctus ater | native | Dusky lanternfish | |
| Myctophiformes | Myctophidae | Lampanyctus australis | native | Southern lanternfish | |
| Myctophiformes | Myctophidae | Lampanyctus pusillus | native | Pygmy lanternfish | |
| Myctophiformes | Myctophidae | Lampichthys procerus | native | Blackhead lanternfish | |
| Lampriformes | Lampridae | Lampris guttatus | native | Opah | |
| Lampriformes | Lampridae | Lampris immaculatus | native | Southern opah | |
| Gadiformes | Moridae | Lepidion ensiferus | native | Patagonian codling | |
| Myctophiformes | Myctophidae | Lepidophanes guentheri | native | Günther’s lanternfish | |
| 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 |
| Syngnathiformes | Syngnathidae | Leptonotus blainvilleanus | native | Deep-bodied pipefish | |
| Stomiiformes | Stomiidae | Leptostomias gladiator | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Letholycus magellanicus | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Letholycus microphthalmus | native | ||
| Myctophiformes | Myctophidae | Lobianchia dofleini | native | Dofleini's lantern fish | |
| Myctophiformes | Myctophidae | Lobianchia gemellarii | native | Cocco's lantern fish | |
| Acanthuriformes | Lobotidae | Lobotes surinamensis | native | Tripletail | |
| Lophiiformes | Lophiidae | Lophius gastrophysus | native | Blackfin goosefish | |
| Eupercaria/misc | Latilidae | Lopholatilus villarii | native | Tile fish | |
| 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 |
| Aulopiformes | Notosudidae | Luciosudis normani | native | Paperbones | |
| Perciformes/Zoarcoidei | Zoarcidae | Lycenchelys bachmanni | native | ||
| Clupeiformes | Engraulidae | Lycengraulis grossidens | native | Atlantic sabretooth anchovy | Anchoa |
| Perciformes/Zoarcoidei | Zoarcidae | Lycodapus australis | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Lycodonus malvinensis | native | ||
| Eupercaria/misc | Sciaenidae | Macrodon ancylodon | native | King weakfish | |
| Eupercaria/misc | Sciaenidae | Macrodon atricauda | native | Southern King Weakfish | |
| Aulopiformes | Lestidiidae | Macroparalepis affinis | native | ||
| Aulopiformes | Lestidiidae | Macroparalepis macrogeneion | native | Longfin barracudina | |
| Characiformes | Characidae | Macropsobrycon uruguayanae | native | Mojarrita | |
| Syngnathiformes | Centriscidae | Macroramphosus scolopax | native | Longspine snipefish | |
| Gadiformes | Macrouridae | Macrourus carinatus | native | Ridge scaled rattail | |
| Gadiformes | Macrouridae | Macrourus holotrachys | native | Bigeye grenadier | Granadero grande |
| Gadiformes | Macrouridae | Macrourus whitsoni | native | Whitson's grenadier | |
| Gadiformes | Macruronidae | Macruronus magellanicus | native | Patagonian grenadier | Argentino |
| Aulopiformes | Paralepididae | Magnisudis prionosa | native | Southern barracudina | |
| Carangiformes | Istiophoridae | Makaira nigricans | native | Blue marlin | |
| Gadiformes | Macrouridae | Malacocephalus occidentalis | native | Western softhead grenadier | |
| Pleuronectiformes | Achiropsettidae | Mancopsetta maculata | native | Antarctic armless flounder | |
| Characiformes | Characidae | Markiana nigripinnis | native | Ipau | |
| Stomiiformes | Sternoptychidae | Maurolicus muelleri | native | Silvery lightfish | Yoalaakaci |
| Stomiiformes | Sternoptychidae | Maurolicus stehmanni | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Maynea puncta | native | ||
| 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 | |
| Lophiiformes | Melanocetidae | Melanocetus johnsonii | native | Humpback anglerfish | |
| Gadiformes | Melanonidae | Melanonus gracilis | native | Pelagic cod | |
| Cyprinodontiformes | Rivulidae | Melanorivulus punctatus | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Melanostigma gelatinosum | native | Limp eelpout | |
| Stomiiformes | Stomiidae | Melanostomias bartonbeani | native | Scaleless black dragonfish | |
| Eupercaria/misc | Sciaenidae | Menticirrhus americanus | native | Southern kingcroaker | |
| Gadiformes | Merlucciidae | Merluccius australis | native | Southern hake | Merluzón |
| Gadiformes | Merlucciidae | Merluccius hubbsi | native | Argentine hake | Merluza común |
| Gadiformes | Merlucciidae | Merluccius patagonicus | native | Patagonian hake | |
| Gadiformes | Merlucciidae | Merluccius tasmanicus | native | ||
| Myctophiformes | Myctophidae | Metelectrona ventralis | native | Flaccid lanternfish | |
| Characiformes | Serrasalmidae | Metynnis maculatus | native | Spotted metynnis | |
| Characiformes | Serrasalmidae | Metynnis mola | native | pacú | |
| Siluriformes | Pseudopimelodidae | Microglanis nigrolineatus | native | ||
| Siluriformes | Pseudopimelodidae | Microglanis parahybae | native | ||
| Syngnathiformes | Syngnathidae | Micrognathus crinitus | native | Banded pipefish | |
| Gadiformes | Gadidae | Micromesistius australis | native | Southern blue whiting | Polaca |
| Eupercaria/misc | Sciaenidae | Micropogonias furnieri | native | Whitemouth croaker | Corvina |
| Eupercaria/misc | Sciaenidae | Micropogonias undulatus | native | Atlantic croaker | |
| Centrarchiformes | Centrarchidae | Micropterus salmoides | introduced | Largemouth black bass | |
| Alepocephaliformes | Alepocephalidae | Mirognathus normani | native | Norman's smooth-head | |
| Myliobatiformes | Mobulidae | Mobula hypostoma | native | Lesser devil ray | |
| Characiformes | Characidae | Moenkhausia dichroura | native | Bandtail tetra | Mojarra |
| Characiformes | Characidae | Moenkhausia intermedia | native | Mojarra | |
| Characiformes | Characidae | Moenkhausia sanctaefilomenae | native | Redeye tetra | Mojarra |
| Tetraodontiformes | Molidae | Mola mola | native | Ocean sunfish | |
| Tetraodontiformes | Monacanthidae | Monacanthus ciliatus | native | Fringed filefish | |
| Ophidiiformes | Ophidiidae | Monomitopus americanus | native | ||
| Eupercaria/misc | Moronidae | Morone saxatilis | introduced | Striped bass | |
| Mugiliformes | Mugilidae | Mugil curema | native | White mullet | |
| Mugiliformes | Mugilidae | Mugil liza | native | Lebranche mullet | lisa |
| Mulliformes | Mullidae | Mullus argentinae | native | Argentine goatfish | Barbillo |
| Gadiformes | Muraenolepididae | Muraenolepis orangiensis | native | Patagonian moray cod | Yakouchlif |
| Carcharhiniformes | Triakidae | Mustelus canis | native | Dusky smooth-hound | |
| Carcharhiniformes | Triakidae | Mustelus fasciatus | native | Striped smooth-hound | |
| Carcharhiniformes | Triakidae | Mustelus schmitti | native | Narrownose smooth-hound | |
| Myctophiformes | Myctophidae | Myctophum affine | native | Metallic lantern fish | |
| Myliobatiformes | Myliobatidae | Myliobatis freminvillei | native | Bullnose eagle ray | |
| Myliobatiformes | Myliobatidae | Myliobatis goodei | native | Southern eagle ray | |
| Myliobatiformes | Myliobatidae | Myliobatis ridens | native | Shortnose eagle ray | Chucho ñato |
| Characiformes | Serrasalmidae | Myloplus tiete | native | pacucita | |
| Characiformes | Serrasalmidae | Mylossoma duriventre | native | brillantina | |
| Myxiniformes | Myxinidae | Myxine affinis | native | Patagonian hagfish | |
| Myxiniformes | Myxinidae | Myxine australis | native | ||
| Myxiniformes | Myxinidae | Myxine debueni | native | ||
| Myxiniformes | Myxinidae | Myxine fernholmi | native | ||
| Argentiniformes | Microstomatidae | Nansenia antarctica | native | ||
| Torpediniformes | Narcinidae | Narcine brasiliensis | native | Brazilian electric ray | |
| Carangiformes | Carangidae | Naucrates ductor | native | Pilotfish | |
| Centrarchiformes | Latridae | Nemadactylus bergi | native | Castaneta | Besugo blanco |
| Centrarchiformes | Latridae | Nemadactylus macropterus | native | Tarakihi | |
| Myxiniformes | Myxinidae | Nemamyxine kreffti | native | ||
| Anguilliformes | Nemichthyidae | Nemichthys curvirostris | native | Pale threadtail snipe eel | |
| Pleuronectiformes | Achiropsettidae | Neoachiropsetta milfordi | native | Finless flounder | |
| Zeiformes | Oreosomatidae | Neocyttus rhomboidalis | native | Spiky oreo | |
| Cyprinodontiformes | Rivulidae | Neofundulus ornatipinnis | native | ||
| Stomiiformes | Stomiidae | Neonesthes capensis | native | Cape snaggletooth | |
| Notacanthiformes | Notacanthidae | Notacanthus chemnitzii | native | Snubnosed spiny eel | |
| Atheriniformes | Notocheiridae | Notocheirus hubbsi | native | ||
| Aulopiformes | Paralepididae | Notolepis annulata | native | Ringed barracudina | |
| Myctophiformes | Myctophidae | Notolychnus valdiviae | native | Topside lampfish | |
| Perciformes/Zoarcoidei | Zoarcidae | Notolycodes schmidti | native | ||
| Myxiniformes | Myxinidae | Notomyxine tridentiger | native | ||
| Gadiformes | Moridae | Notophycis marginata | native | Dwarf codling | Brótola |
| Syngnathiformes | Centriscidae | Notopogon fernandezianus | native | Orange bellowfish | Pez trompeta |
| Hexanchiformes | Hexanchidae | Notorynchus cepedianus | native | Broadnose sevengill shark | |
| Myctophiformes | Myctophidae | Notoscopelus caudispinosus | native | Lobisomem | |
| Myctophiformes | Myctophidae | Notoscopelus resplendens | native | Patchwork lampfish | |
| 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 nigricans | native | ||
| 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 | |
| Perciformes/Zoarcoidei | Zoarcidae | Oidiphorus brevis | native | ||
| Carangiformes | Carangidae | Oligoplites saliens | native | Castin leatherjacket | |
| Carangiformes | Carangidae | Oligoplites saurus | native | Leatherjacket | |
| 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 |
| Pleuronectiformes | Oncopteridae | Oncopterus darwinii | native | Remo flounder | Lenguado |
| Salmoniformes | Salmonidae | Oncorhynchus kisutch | introduced | Coho salmon | |
| Salmoniformes | Salmonidae | Oncorhynchus mykiss | introduced | Rainbow trout | trucha arco iris |
| Salmoniformes | Salmonidae | Oncorhynchus tshawytscha | introduced | Chinook salmon | |
| Lophiiformes | Oneirodidae | Oneirodes notius | native | ||
| Eupercaria/misc | Sciaenidae | Ophioscion adustus | native | Croaker | Burriqueta |
| Clupeiformes | Dorosomatidae | Opisthonema oglinum | native | Atlantic thread herring | |
| 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 |
| Eupercaria/misc | Sparidae | Pagrus pagrus | native | Red porgy | Besugo |
| Cyprinodontiformes | Rivulidae | Papiliolebias bitteri | native | ||
| Cyprinodontiformes | Rivulidae | Papiliolebias hatinne | native | ||
| Blenniiformes | Blenniidae | Parablennius pilicornis | native | Ringneck blenny | |
| Scombriformes | Gempylidae | Paradiplospinus antarcticus | native | Antarctic escolar | |
| Pleuronectiformes | Paralichthyidae | Paralichthys isosceles | native | Lenguado | |
| Pleuronectiformes | Paralichthyidae | Paralichthys orbignyanus | native | ||
| Pleuronectiformes | Paralichthyidae | Paralichthys patagonicus | native | Patagonian flounder | |
| Perciformes/Cottoidei | Liparidae | Paraliparis aspersus | native | ||
| Perciformes/Cottoidei | Liparidae | Paraliparis hubbsi | native | ||
| Eupercaria/misc | Sciaenidae | Paralonchurus brasiliensis | native | Banded croaker | |
| Siluriformes | Loricariidae | Paraloricaria agastor | native | ||
| Siluriformes | Loricariidae | Paraloricaria commersonoides | native | Vieja | |
| Siluriformes | Loricariidae | Paraloricaria vetula | native | Vieja | |
| Perciformes/Notothenioidei | Nototheniidae | Paranotothenia magellanica | native | Magellanic rockcod | |
| 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 | ||
| Carangiformes | Carangidae | Parona signata | native | Parona leatherjacket | Palometa |
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen brevicauda | native | Patagonian rockcod | |
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen cornucola | native | ||
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen elegans | native | ||
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen guntheri | native | Yellowfin notothen | |
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen jordani | native | ||
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen ramsayi | native | Longtail southern cod | |
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen sima | native | ||
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen tessellata | native | Black southern cod | |
| Perciformes/Notothenioidei | Nototheniidae | Patagonotothen wiltoni | native | ||
| Clupeiformes | Pristigasteridae | Pellona flavipinnis | native | Yellowfin river pellona | Lacha |
| Acropomatiformes | Pentacerotidae | Pentaceros richardsoni | native | Pelagic armourhead | |
| Scombriformes | Stromateidae | Peprilus crenulatus | native | ||
| Scombriformes | Stromateidae | Peprilus paru | native | American harvestfish | |
| Scombriformes | Stromateidae | Peprilus xanthurus | native | ||
| 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 |
| Perciformes/Percophoidei | Percophidae | Percophis brasiliensis | native | Brazilian flathead | Congrio real |
| 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 | ||
| Stomiiformes | Stomiidae | Photonectes braueri | native | Brauer's dragonfish | |
| Stomiiformes | Stomiidae | Photonectes mirabilis | native | Blueband dragonfish | |
| Perciformes/Zoarcoidei | Zoarcidae | Phucocoetes latitans | native | ||
| Characiformes | Iguanodectidae | Piabucus melanostoma | native | ||
| Characiformes | Serrasalmidae | Piaractus mesopotamicus | native | Pacu | baya |
| Perciformes/Zoarcoidei | Zoarcidae | Piedrabuenia ringueleti | native | ||
| 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 | ||
| Perciformes/Uranoscopoidei | Pinguipedidae | Pinguipes brasilianus | native | Brazilian sandperch | Turco |
| 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 |
| Perciformes/Zoarcoidei | Zoarcidae | Plesienchelys stehmanni | native | ||
| Eupercaria/misc | Sciaenidae | Pogonias cromis | native | Black drum | |
| Perciformes/Zoarcoidei | Zoarcidae | Pogonolycus elegans | native | ||
| Perciformes/Zoarcoidei | Zoarcidae | Pogonolycus marinae | native | ||
| Carangaria/misc | Polynemidae | Polydactylus oligodon | native | Littlescale threadfin | |
| Carangaria/misc | Polynemidae | Polydactylus virginicus | native | Barbu | |
| Acropomatiformes | Polyprionidae | Polyprion americanus | native | Wreckfish | Mero |
| Scombriformes | Pomatomidae | Pomatomus saltatrix | native | Bluefish | Anchoa |
| Characiformes | Characidae | Poptella paraguayensis | native | Mojarra | |
| Batrachoidiformes | Batrachoididae | Porichthys porosissimus | native | Bagre | |
| Beryciformes | Melamphaidae | Poromitra atlantica | native | ||
| 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 | ||
| Perciformes/Cottoidei | Liparidae | Praematoliparis anarthractae | native | ||
| Eupercaria/misc | Priacanthidae | Priacanthus arenatus | native | Atlantic bigeye | |
| Carcharhiniformes | Carcharhinidae | Prionace glauca | native | Blue shark | |
| Characiformes | Characidae | Prionobrama paraguayensis | native | ||
| Perciformes/Scorpaenoidei | Triglidae | Prionotus nudigula | native | Red searobin | |
| Perciformes/Scorpaenoidei | Triglidae | Prionotus punctatus | native | Bluewing searobin | Testolín de aleta azul |
| Rhinopristiformes | Pristidae | Pristis pectinata | native | Smalltooth sawfish | |
| Characiformes | Prochilodontidae | Prochilodus lineatus | native | Streaked prochilod | Carimbatá |
| Characiformes | Prochilodontidae | Prochilodus nigricans | native | Black prochilodus | |
| Myctophiformes | Myctophidae | Protomyctophum choriodon | native | Gaptooth lanternfish | |
| Myctophiformes | Myctophidae | Protomyctophum parallelum | native | Parallel lanternfish | |
| Myctophiformes | Myctophidae | Protomyctophum tenisoni | native | Tenison’s lanternfish | |
| 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 | ||
| Rajiformes | Arhynchobatidae | Psammobatis bergi | native | Blotched sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis extenta | native | Zipper sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis lentiginosa | native | Freckled sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis normani | native | Shortfin sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis parvacauda | native | Smalltail sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis rudis | native | Smallthorn sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis rutrum | native | Spade sand skate | |
| Rajiformes | Arhynchobatidae | Psammobatis scobina | native | Raspthorn sand skate | |
| Characiformes | Curimatidae | Psectrogaster curviventris | native | Blanquillo | |
| Characiformes | Characidae | Psellogrammus kennedyi | native | Mojarrita | |
| Characiformes | Anostomidae | Pseudanos trimaculatus | native | Threespot headstander | |
| Rhinopristiformes | Rhinobatidae | Pseudobatos horkelii | native | Brazilian guitarfish | |
| Rhinopristiformes | Rhinobatidae | Pseudobatos percellens | native | Chola guitarfish | |
| Siluriformes | Aspredinidae | Pseudobunocephalus iheringii | native | guitarrita | |
| Siluriformes | Aspredinidae | Pseudobunocephalus rugosus | native | guitarrita | |
| Characiformes | Characidae | Pseudocorynopoma doriae | native | Dragonfin tetra | Mojarra de velo |
| Zeiformes | Oreosomatidae | Pseudocyttus maculatus | native | Smooth oreo dory | |
| Siluriformes | Loricariidae | Pseudohemiodon devincenzii | native | ||
| Siluriformes | Loricariidae | Pseudohemiodon laticeps | native | Vieja | |
| Siluriformes | Loricariidae | Pseudohemiodon platycephalus | native | ||
| Perciformes/Uranoscopoidei | Pinguipedidae | Pseudopercis numida | native | Namorado sandperch | |
| Perciformes/Uranoscopoidei | Pinguipedidae | Pseudopercis semifasciata | native | Argentinian sandperch | Chanchito |
| 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 | ||
| Perciformes/Cottoidei | Psychrolutidae | Psychrolutes marmoratus | 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 | |
| Carangiformes | Rachycentridae | Rachycentron canadum | native | Cobia | |
| Clupeiformes | Clupeidae | Ramnogaster arcuata | native | Jenyns's sprat | Sardina |
| Clupeiformes | Clupeidae | Ramnogaster melanostoma | native | Uruguay river sprat | Mandufia |
| Ophidiiformes | Ophidiidae | Raneya brasiliensis | native | Banded cusk eel | |
| Lampriformes | Regalecidae | Regalecus glesne | native | King of herrings | |
| Carangiformes | Echeneidae | Remora remora | native | Shark sucker | |
| 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 |
| Orectolobiformes | Rhincodontidae | Rhincodon typus | native | Whale shark | |
| Siluriformes | Loricariidae | Rhinelepis aspera | native | acarí | |
| Siluriformes | Loricariidae | Rhinelepis strigosa | native | Vieja | |
| Siluriformes | Doradidae | Rhinodoras dorbignyi | native | Marieta | |
| Myliobatiformes | Rhinopteridae | Rhinoptera bonasus | native | Cownose ray | |
| Blenniiformes | Clinidae | Ribeiroclinus eigenmanni | native | ||
| 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 | |
| Rajiformes | Arhynchobatidae | Rioraja agassizii | native | Rio skate | |
| Characiformes | Characidae | Roeboides descalvadensis | native | Parana scale-eating characin | Dientudo |
| Characiformes | Characidae | Roeboides microlepis | native | Dentudo | |
| Characiformes | Characidae | Roeboides prognathus | native | Dientudo | |
| Beryciformes | Rondeletiidae | Rondeletia loricata | native | Redmouth whalefish | |
| Acropomatiformes | Epigonidae | Rosenblattia robusta | native | Stout cardinalfish | |
| Scombriformes | Gempylidae | Ruvettus pretiosus | native | Oilfish | |
| Gadiformes | Moridae | Salilota australis | native | Tadpole codling | Bacalao austral |
| 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 |
| Scombriformes | Scombridae | Sarda sarda | native | Atlantic bonito | Bonito |
| Clupeiformes | Dorosomatidae | Sardinella aurita | native | Round sardinella | |
| Aulopiformes | Synodontidae | Saurida brasiliensis | native | Brazilian lizardfish | |
| Eupercaria/misc | Scaridae | Scarus guacamaia | native | Rainbow parrotfish | |
| Scombriformes | Centrolophidae | Schedophilus griseolineatus | native | ||
| 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 | ||
| Carcharhiniformes | Atelomycteridae | Schroederichthys bivius | native | Narrowmouthed catshark | |
| Siluriformes | Trichomycteridae | Scleronema milonga | native | ||
| Scombriformes | Scombridae | Scomber colias | native | Atlantic chub mackerel | |
| Scombriformes | Scombridae | Scomber japonicus | native | Chub mackerel | Magrú |
| Beloniformes | Scomberesocidae | Scomberesox saurus | native | Atlantic saury | |
| Beloniformes | Scomberesocidae | Scomberesox scombroides | native | King gar | Aguja |
| Aulopiformes | Scopelarchidae | Scopelarchoides kreffti | native | Twin-striped pearleye | |
| Myctophiformes | Myctophidae | Scopelopsis multipunctatus | native | Multispotted lanternfish | |
| Aulopiformes | Notosudidae | Scopelosaurus hamiltoni | native | Smallscale waryfish | |
| Aulopiformes | Notosudidae | Scopelosaurus lepidus | native | Blackfin waryfish | |
| Carcharhiniformes | Scyliorhinidae | Scyliorhinus boa | native | Boa catshark | |
| Carcharhiniformes | Scyliorhinidae | Scyliorhinus haeckelii | native | Freckled catshark | |
| Perciformes/Scorpaenoidei | Sebastidae | Sebastes oculatus | native | Patagonian redfish | Cabarilla |
| Carangiformes | Carangidae | Selar crumenophthalmus | native | Bigeye scad | |
| Carangiformes | Carangidae | Selene setapinnis | native | Atlantic moonfish | |
| Carangiformes | Carangidae | Selene vomer | native | Lookdown | |
| Carangiformes | Carangidae | Seriola lalandi | native | Yellowtail amberjack | |
| Carangiformes | Carangidae | Seriola rivoliana | native | Longfin yellowtail | |
| Scombriformes | Centrolophidae | Seriolella caerulea | native | White warehou | Cojinova |
| Scombriformes | Centrolophidae | Seriolella porosa | native | Choicy ruff | Savorín |
| Scombriformes | Centrolophidae | Seriolella punctata | native | Silver warehou | |
| 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 | ||
| Beryciformes | Melamphaidae | Sio nordenskjoldii | native | Nordenskjold's bigscale | |
| Squaliformes | Somniosidae | Somniosus antarcticus | native | Southern sleeper shark | |
| Siluriformes | Pimelodidae | Sorubim lima | native | Duckbill catfish | bico de pato |
| Siluriformes | Loricariidae | Spatuloricaria evansii | native | vieja | |
| Tetraodontiformes | Tetraodontidae | Sphoeroides pachygaster | native | Blunthead puffer | |
| Carangaria/misc | Sphyraenidae | Sphyraena guachancho | native | Guachanche barracuda | |
| Carcharhiniformes | Sphyrnidae | Sphyrna lewini | native | Scalloped hammerhead | |
| Carcharhiniformes | Sphyrnidae | Sphyrna tiburo | native | Bonnethead | |
| Carcharhiniformes | Sphyrnidae | Sphyrna tudes | native | Smalleye hammerhead | |
| Carcharhiniformes | Sphyrnidae | Sphyrna zygaena | native | Smooth hammerhead | |
| Clupeiformes | Clupeidae | Sprattus fuegensis | native | Falkland sprat | Sardina |
| Squaliformes | Dalatiidae | Squaliolus laticaudus | native | Spined pygmy shark | |
| Squaliformes | Squalidae | Squalus acanthias | native | Picked dogfish | |
| Squaliformes | Squalidae | Squalus blainville | native | Longnose spurdog | |
| Squaliformes | Squalidae | Squalus cubensis | native | Cuban dogfish | |
| Squaliformes | Squalidae | Squalus lobularis | native | Atlantic lobefin dogfish | |
| Squaliformes | Squalidae | Squalus mitsukurii | native | Shortspine spurdog | |
| Squatiniformes | Squatinidae | Squatina argentina | native | Argentine angelshark | |
| Squatiniformes | Squatinidae | Squatina guggenheim | native | Angular angel shark | |
| Squatiniformes | Squatinidae | Squatina occulta | native | Hidden angel shark | |
| Siluriformes | Pimelodidae | Steindachneridion scriptum | native | bagre | |
| Characiformes | Curimatidae | Steindachnerina biornata | native | ||
| Characiformes | Curimatidae | Steindachnerina brevipinna | native | Blanquillo | |
| Characiformes | Curimatidae | Steindachnerina conspersa | native | ||
| Tetraodontiformes | Monacanthidae | Stephanolepis hispida | native | Planehead filefish | |
| Stomiiformes | Sternoptychidae | Sternoptyx diaphana | native | Diaphanous hatchet fish | |
| Gymnotiformes | Sternopygidae | Sternopygus macrurus | native | Longtail knifefish | cuchilla |
| Stomiiformes | Stomiidae | Stomias affinis | native | Günther's boafish | |
| Stomiiformes | Stomiidae | Stomias boa | native | Boa dragonfish | |
| Stomiiformes | Stomiidae | Stomias gracilis | native | ||
| Stomiiformes | Stomiidae | Stomias longibarbatus | native | Longbarb scaly dragonfish | |
| Scombriformes | Stromateidae | Stromateus brasiliensis | native | Southwest Atlantic butterfish | Pampanito |
| Siluriformes | Loricariidae | Sturisoma barbatum | native | vieja | |
| Siluriformes | Loricariidae | Sturisoma robustum | native | ||
| Myctophiformes | Myctophidae | Symbolophorus barnardi | native | Barnards lanternfishes | |
| Myctophiformes | Myctophidae | Symbolophorus boops | native | Bogue lanternfish | |
| Pleuronectiformes | Cynoglossidae | Symphurus jenynsi | native | Jenyn's tonguefish | sol |
| Pleuronectiformes | Cynoglossidae | Symphurus tessellatus | native | ||
| Pleuronectiformes | Cynoglossidae | Symphurus trewavasae | native | Trewavas' tonguefish | |
| Rajiformes | Arhynchobatidae | Sympterygia acuta | native | Bignose fanskate | |
| Rajiformes | Arhynchobatidae | Sympterygia bonapartii | native | Smallnose fanskate | |
| Synbranchiformes | Synbranchidae | Synbranchus marmoratus | native | Marbled swamp eel | anguila |
| Syngnathiformes | Syngnathidae | Syngnathus acus | native | Greater pipefish | |
| Syngnathiformes | Syngnathidae | Syngnathus folletti | native | ||
| Syngnathiformes | Syngnathidae | Syngnathus pelagicus | native | Sargassum pipefish | |
| Myctophiformes | Myctophidae | Taaningichthys bathyphilus | native | Deepwater lanternfish | |
| Characiformes | Characidae | Tetragonopterus argenteus | native | Chanquete | |
| Characiformes | Characidae | Tetragonopterus signatus | native | ||
| Torpediniformes | Torpedinidae | Tetronarce puelcha | native | Argentine torpedo | |
| Batrachoidiformes | Batrachoididae | Thalassophryne montevidensis | native | ||
| Characiformes | Gasteropelecidae | Thoracocharax stellatus | native | Spotfin hatchetfish | Chirola |
| Scombriformes | Scombridae | Thunnus alalunga | native | Albacore | Albacora |
| Scombriformes | Scombridae | Thunnus albacares | native | Yellowfin tuna | Aleta amarilla |
| Scombriformes | Scombridae | Thunnus maccoyii | native | Southern bluefin tuna | |
| Scombriformes | Scombridae | Thunnus obesus | native | Bigeye tuna | Ojos grandes |
| Scombriformes | Scombridae | Thunnus thynnus | native | Atlantic bluefin tuna | Atún aleta azul |
| Scombriformes | Gempylidae | Thyrsites atun | native | Snoek | Pez sierra |
| Scombriformes | Gempylidae | Thyrsitops lepidopoides | native | White snake mackerel | Caballa blanca |
| Pleuronectiformes | Paralichthyidae | Thysanopsetta naresi | native | Lenguado | |
| Siluriformes | Auchenipteridae | Trachelyopterus albicrux | native | bagre cruz blanca | |
| Siluriformes | Auchenipteridae | Trachelyopterus ceratophysus | native | ||
| Siluriformes | Auchenipteridae | Trachelyopterus galeatus | native | ||
| Siluriformes | Auchenipteridae | Trachelyopterus teaguei | native | bagre | |
| Carangiformes | Carangidae | Trachinotus carolinus | native | Florida pompano | Pampano |
| Carangiformes | Carangidae | Trachinotus goodei | native | Great pompano | |
| Carangiformes | Carangidae | Trachinotus marginatus | native | Plata pompano | |
| Lampriformes | Trachipteridae | Trachipterus jacksonensis | native | Blackflash ribbonfish | |
| Carangiformes | Carangidae | Trachurus lathami | native | Rough scad | Surel |
| Carangiformes | Carangidae | Trachurus murphyi | native | Chilean jack mackerel | |
| Siluriformes | Doradidae | Trachydoras paraguayensis | native | Armado | |
| Batrachoidiformes | Batrachoididae | Triathalassothia argentina | native | ||
| Scombriformes | Trichiuridae | Trichiurus lepturus | native | Largehead hairtail | Sabre |
| 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 | ||
| Stomiiformes | Stomiidae | Trigonolampa miriceps | native | Threelight dragonfish | |
| Characiformes | Triportheidae | Triportheus angulatus | native | Sapo | |
| Characiformes | Triportheidae | Triportheus nematurus | native | ||
| Characiformes | Triportheidae | Triportheus paranensis | native | Tetra | Dientudo |
| Eupercaria/misc | Sciaenidae | Umbrina canosai | native | Argentine croaker | Pargo blanco |
| Gadiformes | Phycidae | Urophycis brasiliensis | native | Brazilian codling | Brótola |
| Gadiformes | Phycidae | Urophycis cirrata | native | Gulf hake | Brótola |
| Gadiformes | Phycidae | Urophycis mystacea | native | ||
| Perciformes/Cottoidei | Liparidae | Volodichthys herwigi | native | ||
| Perciformes/Cottoidei | Liparidae | Volodichthys smirnovi | native | ||
| Stomiiformes | Phosichthyidae | Woodsia meyerwaardeni | native | Austral lightfish | |
| Carangiformes | Xiphiidae | Xiphias gladius | native | Swordfish | Pez espada |
| Siluriformes | Aspredinidae | Xyliphius barbatus | native | guitarrita | |
| Pleuronectiformes | Paralichthyidae | Xystreurys rasilis | native | Lenguado | |
| Rhinopristiformes | Trygonorrhinidae | Zapteryx brevirostris | native | Lesser guitarfish | |
| Rajiformes | Rajidae | Zearaja brevicaudata | native | Short tail Yellownose skate | |
| Zeiformes | Zeidae | Zenopsis conchifer | native | Silvery John dory | San Pedro |
| Siluriformes | Pimelodidae | Zungaro jahu | native | Manguruyu | |
| Siluriformes | Pimelodidae | Zungaro zungaro | native | Gilded catfish | apretador |