By Peter Petersen

Rio Olimar Grande

Region:  Treinta y Tres

In Laguna de Arnaud next to Rio Olimar Grande I caught this beauty of a Thick-lipped Eartheater Cichlid (Gymnogeophagus labiatus)

Laguna de Arnaud

The Long-lipped Whiptail Catfish (Loricariichthys anus) thrives in these water. The bottom here was a combination of sand and mud.

The Long-lipped Whiptail Catfish (Loricariichthys anus) seems very sensitive. The blood clots in the body and fins appeared shortly after the fish was taken out of water. After a short photo session the fish was quickly released.

A close-up ventral view of the Long-lipped Whiptail Catfish (Loricariichthys anus).

The water in Laguna de Arnaud is stagnant.

The Long-finned Cory's (Corydoras longipinnis) also called CW003 seem to live solitary lives. I rarely caught them together. The dorsal spine are longer in males. This is a typical male.

The Long-finned Cory's (Corydoras longipinnis) also called CW003 can vary in color and pattern. In most regions of Uruguay they have a yellow to orange belly as well as ventral and pelvic fins (with brown markings like above). 

The Santa Cruz Whiptail Catfish (Rineloricaria strigilata) is also native to Uruguay. Here is a lateral view of a specimen caught here in Laguna de Arnaud.

A dorsal view of the head of the Santa Cruz Whiptail Catfish (Rineloricaria strigilata).

The mouth of the same specimen of Santa Cruz Whiptail Catfish (Rineloricaria strigilata). This species seems to feed mainly on detritus and worms.

The Amazon freshwater crab (Dilocarcinus pagei) is also native to Uruguay. This species is widespread in South America.

The male Amazon freshwater crab (Dilocarcinus pagei) has a very large claw. I have only seen this species submerged. They do not seem to walk out of the water like related species.

Carapace view of the Amazon freshwater crab (Dilocarcinus pagei). Notice the spines.

The Smooth-cheek eartheater (Gymnogeophagus gymnogenys) is also present in this lagune and the main river. This is a mature male.

A young Smooth-cheek eartheater (Gymnogeophagus gymnogenys) from the lagune.

Rio Yi

Region: Durazno

In the Rio Yi we found many interesting species.

This river holds a special population of Gymnogeophagus meridionalis which have a very high dorsal fin. I only found this variation in Rio Yi.

The river bottom was muddy with sand, rocks and gravel.

In the river bottom  we found the invasive Golden Clam (Corbicula fluminea). This species normally belong in South East Asia.

But we also found another mollusc. This is the native Channeled Apple Snail (Pomacea canaliculata).

The Channeled Apple Snail (Pomacea canaliculata) lay eggs in clusters above water. The eggs are red or pink and are usually attached to plants.

Pimelodella australis seem to feed mainly on shrimps and fish fry.

The fish are collected quickly and put in buckets where they are sorted out. Most will go back to the river shortly after capture.

An adult female Jaguar livebearer (Jenynsia onca). This specimen is 6.5 cm TL.

The Blacklipped Pike Cichlid (Crenicichla celidochilus) is also found here. This species seems to feed on tetra's, livebearing fish, shrimps and insects.

This is a male Blacklipped Pike Cichlid (Crenicichla celidochilus). This specimen is 14.5 cm TL. Largest specimen we caught were 27.8 cm TL.

This is a female Blacklipped Pike Cichlid (Crenicichla celidochilus). This specimen is 12.5 cm TL.

On the edge of my photo-tank a Uruguay Stridulating Slantface Grasshopper (Orphulella punctata) decided to pay a visit.

Next to the road we found another interesting pike cichlid

We also found the Southern Dwarf Pike Cichlid (Crenicichla minuano) here. The largest specimen I caught was 13 cm. TL. This species seems to feed mainly on shrimps and insects. 

In this part of Rio Yi I caught a catfish species that I did not expect to find in here.

This is the face of the Southern Orange Spotted Pleco (Hemiancistrus meizospilos). This species seems to feed mainly on detritus, diatoms and unidentified worms.

The largest specimen of the Southern Orange Spotted Pleco (Hemiancistrus meizospilos) we caught were 15,5 cm TL. The specimens in the photo above is 11 cm TL.

The size and the amount of the spots on the body/plates and fins is distinct for the Southern Orange Spotted Pleco (Hemiancistrus meizospilos).

Close up the Southern Orange Spotted Pleco (Hemiancistrus meizospilos) is even more beautiful. The spots on the lower part of the body is more light, almost yellow/creme in all of the specimens we caught. 

In the shallow water we found more pike cichlids.

The Eyestripe Pike Cichlid (Crenicichla scottii) is widespread in Uruguay.


The Two Spotted Pike Cichlids (Crenicichla lepidota) is also native to Uruguay.

We noticed some eartheating cichlids feeding in the shallow water.

It turned out to be the San Borja Eartheater (Gymnogeophagus tiraparae). The largest specimen we caught were 11 cm TL.

The San Borja Eartheater (Gymnogeophagus tiraparae) seem to feed mainly on small unidentified worms.

We only caught the San Borja Eartheater (Gymnogeophagus tiraparae) in Rio Yi.

A muddy area of the Rio Yi.

The Elongated Eartheater (Gymnogeophagus mekinos) is also present in this blackwater river.

Rio Santa Lucia Chico

Region: Florida


In the department of Florida I found this small river with Elongated Eartheater (Gymnogeophagus mekinos) also refered to as "Paso Pache". This is an adult male.

The habitat of these amazing cichlids. This is part of the Rio Santa Lucia Chico.

Most of the biotope looked like this. But I found a few aquatic plants here as well. Egeria densa, Hottonia species and Ludwigia helminthorrhiza.

The coloration of Elongated Eartheater (Gymnogeophagus mekinos) are remarkable. The blue spots on the gill cover seems to vary from specimen to specimen.

This crustacean is Aegla sp. “Santa Lucia Chico” (Dorsal view)

Aegla sp. “Santa Lucia Chico” (Lateral view).

In the same habitat I found: Characidium rachovii, Rineloricaria sp. ”Santa Lucia Chico”, Jenynsia lineata, Cnesterodon decemaculatus, Astyanax sp., Rainbow Eartheater (Gymnogeophagus terrapurpura), Rineloricaria sp. “Santa Lucia”, Crenicichla scottii, Pomacea canaliculata, Corbidula fluminea, Australoheros scitulus “Santa Lucia” and Heptapterus mustelinus.

A large female arachnid. The Uruguayan Tarantula (Grammostola quirogai) is probably the largest spider in the country. Even though the species is a little venomous, it is a calm species and you should not fear it. 

Arroyo Sarandi

Region: Canelones

This is Arroyo Sarandi.

The Parrot Feather Watermilfoil (Myriophyllum aquaticum) is a common aquatic plant here.

A juvenile Rainbow Eartheater (Gymnogeophagus terrapurpura).

An adult male Rainbow Eartheater (Gymnogeophagus terrapurpura).

The Southern Bacopa (Bacopa australis) grows up through the water surface. The water depth in the photo above is around 60 cm. Below these plants is an excellent fish biotope.

An adult male Eyestripe Pike Cichlid (Crenicichla scottii). This specimen is around 20 cm TL.

I observed the Eyestripe Pike Cichlid (Crenicichla scottii) feeding on Corydoras, Characins and shrimps.

In the shallow water some catfish were feeding between the rocks.

Unlike what I expected I only found Peppered cory's (Corydoras paleatus) swimming alone or a few together.

The Brazilian waterweed (Egeria densa) is native in Uruguay.

The largest specimens of the Peppered cory (Corydoras paleatus) I caught, were between 5-6 cm TL.

The Giant Swordplant (Echinodorus grandiflorus) above water.

In this specific little pool I caught these; From the top: Uruguay Pike Characin (Oligosarcus jenynsii), Eyestripe Pike Cichlid (Crenicichla scottii), Wedge-spot tetra (Bryconamericus iheringii), Clear-finned Dragonfin tetra (Pseudocorynopoma stanleyi)

Aguas Blancas

Region: Lavalleja

In this clear water stream we found many Uruguay Sword Plants (Echinodorus uruguayensis).

On the leaves of these aquatic plants we caught the Uruguay Dwarf Pleco (Hisonotus charrua). This is an adult.

A clear view of the Uruguay Sword Plant (Echinodorus uruguayensis) in the shallow water. 

Amoungst the roots of the aquatic plants we found South American Bumblebee Catfish possibly: Microglanis carlae, Microglanis cottoides or Microglanis malanarbai.

Between the rocks in the fast flowing waters we found two interesting species of loricarids.

The Uruguay Bristlenose (Ancistrus taunayi) in Aguas Blancas has a reddish coloration. This is a young specimen of around 7 cm TL. 

Young male Uruguay Bristlenose (Ancistrus taunayi) around 6 cm TL.

A young female Uruguay Bristlenose (Ancistrus taunayi) around 6.5 cm TL.

This is a juvenile La Plata Pleco (Hypostomus laplatae) from Aguas Blancas. I caught many of these. They seem to be a common species in that river. This specimen is around 3 cm TL.

As the La Plata Pleco (Hypostomus laplatae) grows up the red stripes in the fins disappear and the spots appear. The specimen on the right is around 19 cm TL. 

Most La Plata Pleco (Hypostomus laplatae) we found were very red when around 5-7 cm. This specimen is 6.8 cm TL.

A dorsal view of the same specimen of La Plata Pleco (Hypostomus laplatae)

In this forest of Uruguay Sword Plant (Echinodorus uruguayensis) we found many interesting species

This is the face of the Elongated Eartheater (Gymnogeophagus mekinos)

This specimen of Elongated Eartheater (Gymnogeophagus mekinos) is an adult male and measured 16 cm TL.

This bottom was full of whiptail catfish

Whiptail catfish (Rineloricaria sp.)

Whiptail catfish (Rineloricaria sp.)

Whiptail catfish (Rineloricaria sp.)

Arroyo de Las Pavas

Region: Trienta y Tres

This biotope is very diverse. The bottom consists of rocks and mud in this particular spot.

The Spotted Pike Cichlid (Crenicichla punctata) in the natural habitat. In the background you can faintly see a Thick-lipped Eartheater Cichlid (Gymnogeophagus labiatus).

This stream is very narrow and shallow in some parts.


A pair of Australoheros sp. aff. facetus. Female above and male below. The population in the stream are especially beautiful.

A common bird here is the Rufous-collared Sparrow (Zonotrichia capensis). Like many other sparrows, this species thrive near human settlements.

The Giant Swordplant (Echinodorus grandiflorus), Southern Bacopa (Bacopa australis), Floating Ludwigia (Ludwigia helminthorrhiza) are all present here.

Between the rocks we found the Uruguay Bristlenose (Ancistrus taunayi). The population is this stream has green spots.

The Uruguay Bristlenose (Ancistrus taunayi) seem grow up to around 15 cm TL.

The green coloration is most clear in water. This specimen of the Uruguay Bristlenose (Ancistrus taunayi) is around 12 cm TL

The Uruguay Bristlenose (Ancistrus taunayi) is widespread in the country.

The Southern Lapwing (Vanellus chilensis) is also native to Uruguay. It is a common species here.

The plant Tillandsia aeranthos belong to the Bromeliad family (Bromeliaceae). many species in this family are epiphytes.

In this biotope I noticed several species of characins swimming fast by. One of which are a very common aquarium fish.

The Buenos Aires tetra (Psalidodon anisitsi). This species was formerly known as Hyphessobrycon anisitsi and Hemigrammus anisitsi.

Above water the Buenos Aires tetra (Psalidodon anisitsi) looks a little different. This is the same 7 cm TL specimen.

In the pools between the rocks I noticed some cichlids.

Thick-lipped Eartheater Cichlids (Gymnogeophagus labiatus) in their habitat. A dominant male in front, a recessive male in the middle and a female in the background.

In the photo tank the colors of the Thick-lipped Eartheater Cichlid (Gymnogeophagus labiatus) are easier to see. But I also noticed that many of the cichlids here were carrying Mycobacterium.

This Southern Long-nosed Armadillo (Dasypus hybridus) was very curious and came quite close. 

Uruguay have many species of amphibians due to the wetlands and seasonal swifts. During spring you can find many tadpoles. At this stage it's called a froglet. This is the Montevideo Tree Frog (Boana pulchella).

We also found the Lesser Swimming Frog (Pseudis minuta) in this stream. In this country many species develop in the same season because of the extreme temperature change from winter to summer. Which can range from -5 to 43 degrees C.

The coloration of the Lesser Swimming Frog (Pseudis minuta) froglets can vary a little. This is a different specimen.

This froglet belong to the species Uruguay Harlequin Frog (Lysapsus limellum).

From the car I could watch a dark morph of the Southern White-tailed Hawk (Geranoaetus albicaudatus albicaudatus) a large bird of prey native to Uruguay and in the wing mirror a beautiful sunset.


The sunset turned out like this

Sierra de Rios

Region: Cerro Largo

The stream was almost dried out which made is easy for us to see the fish despite the many aquatic plants.

This adult male of the Clear-finned Dragonfin tetra (Pseudocorynopoma stanleyi) was 7.5 cm TL and caught in the open water while it was feeding on mosquitos on the water surface.

The Great Pampa-Finch (Embernagra platensis) is a native bird of Uruguay. The seem to be most common in the northern part of the country. 

From above the surface I noticed schoals of characins and some earth-eating cichlids feeding in the bottom.

These fish species turned out to be:  Wedge-spot tetra (Bryconamericus iheringii), Crimson-skinned Southern Cichlid (Australoheros sp. Red Ceibal) and Smooth-cheek eartheater (Gymnogeophagus gymnogenys).

In this habitat we found some very rare cichlids.

The White Southern Cichlid (Australoheros sp. White ceibal). Male on the right and female on the left.

We found only a few of the White Southern Cichlid (Australoheros sp. White ceibal) the first time we visited this biotope. Next time we were a bit more thorough and found 15 specimen. They were all released after a short photo session.

A curious Great Kiskadee (Pitangus sulphuratus) landed on the wired fence and observed me closely.

The White Southern Cichlid (Australoheros sp. White ceibal) seem to feed mainly on detritus and Parrot Feather Watermilfoil (Myriophyllum aquaticum).

Here the White Southern Cichlid (Australoheros sp. White ceibal) is compared to the sympatric Crimson-skinned Southern Cichlid (Australoheros sp. Red Ceibal) a common species in the region.

A predator in these waters are the Patagonian Racer (Pseudablabes patagoniensis). We observed this snake feed on fish. It was the only aquatic reptile we caught at this location (Sierra de Rios).

Another predator is this Cocoi Heron (Ardea cocoi). This bird species seem to feed mainly on fish and amphibians.

The Greater Rhea (Rhea americana) is the largest bird of South America. It can weigh up to 27 kilos. Sadly this bird is listed as Near Threatened due to habitat loss and hunting.

The Red-legged Seriema (Cariama cristata) is a predator bird which seem to feed mainly on insects, lizards, amphibians, small mammals and even snakes. 

The roads in Uruguay are pretty good and the road toll system works very well. This makes it easy go get around this beautiful  and interesting country.

Arroyo Ceibalito

Region: Cerro Largo

This small stream holds some very interesting species.

This Southern Toothless characins (Steindachnerina biornata) is around 11 cm TL.

The population of Southern Toothless characins (Steindachnerina biornata), Most were around the same size. We did not see juveniles.

 These Southern Bacopa (Bacopa australis) might not seem like a real fish habitat, but these shallow waters actually contain many interesting species of fish.

Feeling a bit nostalgic after finding a species named in honour of an old zoologist and naturalist from my homeland. The Danish Christian Frederik Lütken. This is Lütken's Tetra (Deuterodon luetkenii) originally described as Tetragonopterus luetkenii and recently known as Hyphessobrycon luetkenii.  

A female Dusky millions fish (Phalloceros caudimaculatus) with Black spot disease (Diplopstomiasis).


The bottom was a combination of mud, sand and gravel. The plant here is the Two-leaf Water Fern (Regnellidium diphyllum), a common species in Uruguay.

Perfect conditions for the Cadéa Whiptail Catfish (Rineloricaria cadeae)

Cadéa Whiptail Catfish (Rineloricaria cadeae) pair. Male on the right and female on the left.

I noticed that males of the Cadéa Whiptail Catfish (Rineloricaria cadeae) have extended anal and pelvic fins. 

The mouth of the Cadéa Whiptail Catfish (Rineloricaria cadeae)

Like many other whiptails the Cadéa Whiptail Catfish (Rineloricaria cadeae) have "brushes" of odontodes on both sides of the head.

We caught many interesting species here. Even an undescribed cichlid.

A male Crimson-skinned Southern Cichlid (Australoheros sp.)

A female Crimson-skinned Southern Cichlid (Australoheros sp.)

The Parrot Feather Watermilfoil (Myriophyllum aquaticum) is native to Uruguay. In many countries around the world this species is considered a pest as an invasive plant. But here in its natural range is has an important task. This plant absorbs nutrients and maintains the good water quality in the rivers.

A young Buenos Aires tetra (Psalidodon anisitsi). This fish is 2.8 cm TL.

This specimen belong to the family of freshwater crustaceans called Aeglidae. These are native to South America. This is Uruguay Squat Crab (Aegla uruguayana).

The abdomen is partly tucked under the thorax of these crabs. The carapace length of the largest species may reach around 6 cm. This is the Uruguay Squat Crab (Aegla uruguayana).

These Uruguay Squat Crab (Aegla uruguayana) seem to feed mainly on detritus and carrion.

Arroyo Convento

Region: Cerro Largo

This almost dried out stream near the city of Melo contained many interesting species.


A fully grown Flower Tetra (Hyphessobrycon igneus). This specimen is 6 cm TL. 

The Flower Tetra (Hyphessobrycon igneus) is metallic green on the sides of the body. This is very clear when you hold them above water.  

The shallow water made it possible for us to see many of the species here even before we entered this slow moving stream.

Between the plants we found Long-finned Cory's (Corydoras longipinnis) also called CW003.

Over the sandy bottom we could see several cichlid species passing by.

The Smooth-cheek eartheater (Gymnogeophagus gymnogenys) was one of them. The specimens we caught here had many blue scales compared to other locations.

We also found the Stripefin eartheater (Gymnogeophagus rhabdotus) at this location.

Rio Yaguarón

Region: Cerro Largo

This river is the border between Brazil and Uruguay.

We found the Spotted Pike Cichlid (Crenicichla punctata) to be abundant in this river.

A close up of the head of the Spotted Pike Cichlid (Crenicichla punctata).

Around this small island we noticed characins feeding on the terristrial leaves of the aquatic plant known as Pearl Weed (Micranthemum tweediei). Another plants found here is the Longstem Sword Plant (Echinodorus longiscapus)

The tetra turned out to be the Oval-spot Characin (Astyanax abramis).

An adult Oval-spot Characin (Astyanax abramis). This specimen is 7.5 cm TL.

Pearl Weed (Micranthemum tweediei) is very common in this region.

In the very shallow water next to the mudbank or actually under the mud I caught many Jaguar Mud-catfish (Scleronema minutum)

The Jaguar Mud-catfish (Scleronema minutum) seem to be very common here. They seem to grow to about 5 cm TL.

Sometimes I spotted the eyes of Jaguar Mud-catfish (Scleronema minutum) near the surface of the mud or sand.

On this rocky shelf we caught several Whiptail Catfish.

The Elongated Whiptail Catfish (Rineloricaria longicauda) seem to prefer flowing water. We always found them in medium to fast current.

We found the Elongated Whiptail Catfish (Rineloricaria longicauda) mostly in sandy or mud bottoms but also in rocky shelfs.

The Elongated Whiptail Catfish (Rineloricaria longicauda) seems to feed mainly on detritus.

We found the Elongated Whiptail Catfish (Rineloricaria longicauda) to be common in this riversystem.


On many of the rocks in this river we found river weeds (Podostemaceae). This species is most likely Podostemum rutifolium as Podostemum comatum have flowers occuring on distinct short stems and we did not see this. Member of this genus are clonal and spread by prostrate (green) roots that attach tightly to rocks. 

We also found the Southern Driftwood Catfish (Trachelyopterus lucenai) in this border-river. This species seems to feed mainly on shrimps, insects, juvenile loricariid catfish and characins. Largest specimen we found were 18 cm. TL.

During dry season you can walk across the Rio Yaguarón in many places.

Mouth of the Long-lipped Whiptail Catfish (Loricariichthys anus). We observed this species feeding on worms, insect larvae and small crustaceans.

Face of the Long-lipped Whiptail Catfish (Loricariichthys anus)

This specimen of the Long-lipped Whiptail Catfish (Loricariichthys anus) is 33 cm TL.

Head of the Long-lipped Whiptail Catfish (Loricariichthys anus) seen from above.

A lateral view of the Long-lipped Whiptail Catfish (Loricariichthys anus)

Dorsal view of the Long-lipped Whiptail Catfish (Loricariichthys anus)

Habitat of the Long-lipped Whiptail Catfish (Loricariichthys anus)

In this river we found specimens of Thick-lipped Eartheater Cichlid (Gymnogeophagus labiatus) with Hypertrophied lips

Same specimen of Thick-lipped Eartheater Cichlid (Gymnogeophagus labiatus) above water.

This young Commersons Pleco (Hypostomus commersoni) is 10.5 cm TL. This species seems to feed on diatoms, detritus and plant matter.

This is a mature Commersons Pleco (Hypostomus commersoni). This specimen was 44 cm TL.

The full image of my first Commersons Pleco (Hypostomus commersoni). This photo is from my first trip to Uruguay back in 2009.

A young 7 cm TL female Smooth-cheek Eartheater (Gymnogeophagus gymnogenys)

A young 8.5 cm TL male Smooth-cheek Eartheater (Gymnogeophagus gymnogenys)

A pair of Two Spotted Pike Cichlids (Crenicichla lepidota) Male above and female below.

The bottom in this river varies a lot.

We found two species of freshwater clam in this river. An invasive species: Corbicula fluminea and a native species: Diplodon piceus.

In the shade we founds large shoals og crustaceans.

The freshwater prawn (Pseudopalaemon bouvieri) is abundant here. 

This small swampy area in this field has been connected to the main river during rainy season. I were looking for killifish but I only found crustaceans.

I found many Southern Crayfish (Parastacus pilimanus) here. They were feeding on the grass.

Cañada del Vigia

Region: Cerro Largo

The stream varies from muddy pools with still water like this.

To fast flowing shallow waters with rocky and sandy bottom like in this photo above.

In the fast flow between the rocks we found the Southern Blackspotted Pleco (Hemiancistrus punctulatus). The largest specimens we found were around 15 cm TL.

The mouth of the Southern Blackspotted Pleco (Hemiancistrus punctulatus). This species seem to feed mainly on diatoms and detritus.

This young specimen of Southern Blackspotted Pleco (Hemiancistrus punctulatus) is 4.5 cm TL.

The Southern Blackspotted Pleco (Hemiancistrus punctulatus) here have a greenish coloration when you see them underwater.

In the very shallow water I noticed characins resting on the bottom.

In most regions of Uruguay we found the Yellow-finned Darter (Characidium pterostictum). This species seems to grow to around 7 cm TL.

The vertical stripes of the Yellow-finned Darter (Characidium pterostictum) can show up and disappear instantly. The two photos above are same specimen.

We found a specimen of William’s South-American Side-necked Turtle (Phrynops williamsi) in this stream as well. The species is regarded as Vulnerable (VU) by the IUCN.

William’s South-American Side-necked Turtle (Phrynops williamsi) head seen from below.

William’s South-American Side-necked Turtle (Phrynops williamsi) has a very distinct color pattern.

We observed this specimen of William’s South-American Side-necked Turtle (Phrynops williamsi) feeding on aquatic plants and fish. This omnivorous species is native to Brazil, Argentina and Uruguay.

I noticed a predator hiding under the river bank feeding on characins passing by. This predator is called Tararira by the indigenous people.

This turned out to be the main predator here; the Southern Trahira (Hoplias australis). This species feed on most fish species including spiny catfishes.

I also caught this Trahira (Hoplias sp.) But I am not sure which species it is. It could be same species with a different color pattern. The Wolf Fish are known to do color change quite rapidly.

Here we also found another canine-named animal. The family of Wolf Spiders are called Lycosidae. I have not been able to identify this species so far.

The Uruguay Bristlenose (Ancistrus taunayi) is widespread in this country. The color pattern varies from region to region. Most common is the green type like this one.

The Uruguay Bristlenose (Ancistrus taunayi) can also be red, orange and yellow but the other physical characters are roughly the same. Most specimens had this light blue belly.

Lateral view of the Uruguay Bristlenose (Ancistrus taunayi).

Sunset over Cerro Largo. 

Arroyo Sauce de Solis

Region: Canelones

Sometimes looking at google maps satelite view results in the discovery of new spots of amazing habitats. This place was far in on a farmers land and we had to ask permission to enter his property. Luckily the native people of Uruguay are usually very helpful and friendly.

The Uruguay Pike Characin (Oligosarcus jenynsii) is a widespread species. We found this predator in most regions of the country.

The Uruguay Pike Characin (Oligosarcus jenynsii) has razor sharp teeth and seem to feed mainly on other characins, live bearers and shrimps.

Notice the very large eyes of the Uruguay Pike Characin (Oligosarcus jenynsii). As most other predators they face forward. This fish hunts very much by eye sight.

The population of Chameleon cichlid (Australoheros facetus) in these waters have a much more pointy head/mouth. I noticed that the bottom of this stream consisted only of larger rocks. So they might have evolved a more pointy head in order to feed between these rocks.

Under the rocks in the shallow fast flowing parts of this stream we found a special Bristlenose pleco.  

The population of Uruguay Bristlenose (Ancistrus taunayi) in this stream has yellow spots and slightly orange fins. I only found this coloration in fish from this stream.

In this photo alone you can see Southern Bacopa (Bacopa australis), Floating Ludwigia (Ludwigia helminthorrhiza), Parrot Feather Watermilfoil (Myriophyllum aquaticum), Sand Spikerush (Eleocharis montevidensis) and Brazilian Pennywort (Hydrocotyle leucocephala)

Between the aquatic plants we found Rainbow Eartheater's (Gymnogeophagus terrapurpura). This species is an omnivore, feeding on zooplankton, macroinvertebrates, and periphyton. 

Rio Negro

Region: Tacuarembó 


Small stream running into Rio Negro from Tacuarembó.

The Jacuhy Pleco (Hypostomus aspilogaster) is also native to Uruguay and are present in these waters. This species seems to feed mainly on algae, plant matter and detritus. This is a young specimen around 13 cm TL.

In this brown habitat we found a true jewel of Uruguay. A Characin I had never heard about, before visiting this amazing country.

The Red-eyed Uruguay Tetra (Ectrepopterus uruguayensis) has a beautiful rainbow coloration when it's in breeding condition

Here we also found the Blackscaled Cichlid (Cichlasoma dimerus). This adult male is around 10 cm TL.

Close up the Blackscaled Cichlid (Cichlasoma dimerus) is pure artwork. Nature is by far the best artist!

The Spotted Pimelodus (Pimelodus maculatus) is a common predator in this river. They seem to prey on characins, livebearing fish, cichlids, shrimps and insects here

North West Uruguay 

Region: Artigas

In this cloudy habitat in Rio Uruguay we found a large species of eartheater cichlid.

We only found the Argentine humphead (Gymnogeophagus balzanii) in this drainage. This species seems to feed mainly on detritus, worms and small crustaceans.

Otocinclus flexilis seem to be a solitary fish and they seem to grow a bit larger than others in the genus. This specimen is around 7 cm TL.

This specimen of the Slender Banjo Catfish (Pseudobunocephalus iheringii) is around 6.5 cm TL. This species is found on muddy, sandy and rocky river bottoms.

On the leaves in this forest of Uruguay Sword Plants (Echinodorus uruguayensis) we found an interesting species of loricarid.

The Green Uruguay Dwarf Pleco (Hisonotus ringueleti) seem to feed mainly on diatoms.

We only found the Green Uruguay Dwarf Pleco (Hisonotus ringueleti) in the region of Artigas. This species seem to grow to around 6 cm TL.

The Green Uruguay Dwarf Pleco (Hisonotus ringueleti) seem very depended on Sword Plants (Echinodorus). We only found them on species belonging to this genus of plants.

Even though this next species seems most common in the large rivers, you can also be lucky to find them in the small streams like this.

The Rose-spotted Pleco (Hypostomus roseopunctatus) seems most active at night. This specimen is around 25 cm TL.

In my opinion one of the most impressive and beautiful of North West Uruguay. This is the Parrot leporinus (Leporinus amae).


The red scales of the Parrot leporinus (Leporinus amae) change color from different angles. Notice the red scales above the lateral line in these photos above.

They seem to feed mainly on Parrot Feather Watermilfoil (Myriophyllum aquaticum) and green algae belonging to Chlorophyta often in these shallow waters.

The largest specimens of the Parrot leporinus (Leporinus amae) we found were around 15 cm TL.

 Another headstanders in these waters is the Striped Leporinus (Leporinus striatus). The largest specimens we found were around 15 cm TL. The specimen above a male and around 12 cm TL.

This Striped Leporinus (Loeprinus striatus) is a female and just around 10 cm TL from same location.


A special thanks to:


 Wilson Sebastián Serra Alanis (Cichlidae, Characidae, Loricariidae, Siluriformes)

Roberto Esser dos Reis (Rineloricaria)

Marcelo Loureiro Barrella (Loricariidae)

Sven Kullander (Cichlidae)

C. Thomas Philbrick (Podostemaceae)

Steven Grant (Heptapteridae, Callichthyidae

Luiz Tencatt (Callichthyidae)

Julian Dignall "Jools" (Siluriformes) PlanetCatfish  

Felipe Alonso (Cichlidae)

Flávio Lima (Characidae)

Dan Olsen (web support) 

Sandro Santos (Aeglidae

Franco Teixeira de Mello (Networking; Aeglidae)  


Best Regards 

Peter Petersen


In memory of a dear friend who showed me around Uruguay for the first time back in 2009

Felipe "Pipo" Cantera 1961-2017



Rio Xingú

Wildlife in and around the river system

images/banners/image_hover/IMGP0460%20400x400.jpg#joomlaImage://local-images/banners/image_hover/IMGP0460 400x400.jpg?width=400&height=400

Costa Rica

Birds, lizards, frogs, freshwater fish, rainforest and dry forest



Ladybird spider (Photo article coming soon)



Amager Fælled a nature hot spot in Copenhagen, Denmark

Sorry, this website uses features that your browser doesn’t support. Upgrade to a newer version of Firefox, Chrome, Safari, or Edge and you’ll be all set.