Amazon Fish: The Extraordinary Ichthyofauna of Mamirauá Reserve
- 3 days ago
- 5 min read
Mamirauá Reserve is home to 541 fish species within one of the largest flooded forests in the world. Discover the ichthyofauna and the várzea ecosystem that makes it possible.
Mamirauá Sustainable Development Reserve, located in the heart of the state of Amazonas between the Solimões and Japurá rivers, is the largest protected várzea area in the world, covering more than 1.1 million hectares. It is precisely this condition, a forest that exists between water and land, flooding and drying in recurring cycles, that explains one of the most remarkable facts about Amazonian biodiversity: the reserve is home to 541 fish species across 45 families and 15 orders, representing approximately 20% of all valid fish species currently known across the entire Amazon Basin
This number represents an 86% increase compared to the reserve’s first species inventory published in the 1990s and is the result of decades of field expeditions and taxonomic work carried out primarily by the Mamirauá Institute for Sustainable Development, in partnership with the National Institute of Amazonian Research (INPA) and PUC-RS.
It is in this setting that Uakari Lodge is located, a floating lodge situated within the Mamirauá Reserve. Designed to adapt to the water cycle and operated in partnership with local communities and the Mamirauá Institute, the lodge serves as a starting point for discovering the flooded forest and closely observing the dynamics that support one of the greatest diversities of fish in the Amazon.
How the várzea sustains such fish diversity
The explanation for this richness does not lie in a single factor, but in the structure of the environment itself. The Amazonian várzea is a floodplain ecosystem sustained by white-water rivers such as the Solimões, whose sediment load gives unusual fertility to both water and soil.
In Mamirauá, the annual flood cycle raises river levels between 7 and 15 meters for approximately six months, completely transforming the landscape: what was forest becomes flooded woodland, what was lake becomes channel, and what was dry ground becomes riverbed.
This constant disturbance regime directly affects the composition of aquatic fauna. High levels of environmental variation across floodplain lakes limit the ability of any single species to dominate these environments completely, favoring the coexistence of extremely high diversity. No species can monopolize resources for long enough. The result is a mosaic of ecological niches occupied by hundreds of species that, in other environments, would compete much more exclusively.
The Most Representative Orders
Among the 541 species recorded in the reserve, the richest orders are Siluriformes, which include catfish and armored catfish, with 209 species, and Characiformes, which include piranhas, tambaqui, matrinxã and curimatã, with 185 species. In third place are Gymnotiformes, the electric fishes, with 78 species.
This distribution reflects a typical pattern of Neotropical fish communities, but in Mamirauá it occurs on a scale that few protected environments can sustain.
Featured Species
Pirarucu (Arapaima gigas)
The pirarucu is the largest scaled freshwater fish in the world and one of the Amazon’s most iconic species. It can reach three meters in length and weigh up to 200 kilograms.
It has two respiratory systems, one branchial and one aerial, which means it must surface periodically to breathe. This characteristic, which makes counting easier for community fishery managers, is also central to the participatory management model developed by the Mamirauá Institute since 1999.
Since then, natural stocks of the species in managed areas of the reserve have increased by approximately 620%, and more than 1,165 fishers have participated in the program. It is considered one of the most thoroughly documented cases of fish stock recovery through community management in the world.
Tambaqui (Colossoma macropomum)
The tambaqui is the largest scaled fish in the Amazon Basin after the pirarucu and one of the most economically important species for riverside communities in the region.
Frugivorous and omnivorous, it uses the flood season to enter the flooded forest and feed on fruits and seeds that fall into the water, playing an important role in seed dispersal.
Its meat is highly valued in regional cuisine, which is why freshly prepared tambaqui frequently appears on the menu at Uakari Lodge.
Piranha (Serrasalmus e Pygocentrus spp.)
Piranhas belong to the order Characiformes and are among the best-known fish in the Amazon, although their reputation greatly exaggerates their aggressiveness.
In Mamirauá Reserve, they play an important ecological role as predators and scavengers, helping maintain the balance of other fish populations. Traditional piranha fishing is one of the activities offered at Uakari Lodge, always conducted safely by local guides and with respect for the environment.
Arowana (Osteoglossum bicirrhosum)
Arowanas belong to the family Osteoglossidae, a group of fish considered evolutionarily ancient and known for their bony tongues, which gave the family its name.
They are carnivorous and remarkable jumpers, capable of capturing insects, small birds and even bats in midair. During the breeding season, the offspring remain protected inside the male’s mouth for several weeks. The species occurs throughout the Amazon and Tocantins-Araguaia basins and is commonly found in the lakes and channels of the reserve.
Discus Fish (Symphysodon aequifasciatus)
The discus fish is one of the most admired ornamental fish in the world, and western Amazonia is its natural habitat.
Its diet includes crustaceans, insects, small fish, leaves and fruit. It prefers lakes, lagoons and calm, shallow stretches of river, conditions that the floodplain of Mamirauá provides in abundance, especially during the transition periods between high and low water.
Peacock Bass (Cichla spp.)
Peacock bass is one of the main predators in Amazonian floodplain lakes and a species of great importance for recreational fishing.
It belongs to the family Cichlidae and is adapted to calm, slightly turbid waters such as the interior lakes of the reserve.
Its presence in Mamirauá’s ecosystems is considered an indicator of aquatic ecosystem health, since it is sensitive to changes in water quality.
New Species Still Await Description
Beyond the 541 species already recorded, surveys conducted in the reserve have resulted in the description of 28 new species to science, with 110 type series deposited in scientific collections.
And there is still territory left to explore: the more isolated areas in the northwestern portion of the reserve remain poorly sampled, and future surveys are expected to reveal previously undocumented records and, potentially, species that have yet to be formally described.
In 2014, researchers from the Mamirauá Institute discovered two fish species never before documented in Brazil, Pyrrhulina zigzag and Apistogrammoides pucallpaensis, at the boundary between Mamirauá and the Auati-Paraná Extractive Reserve, a reminder that biodiversity in this region still holds surprises.
Experiencing the Fish of Mamirauá at Uakari Lodge
At Uakari Lodge, the connection with local ichthyofauna happens in tangible ways: through canoe excursions across flooded forests and channels, where it is possible to observe arowanas leaping near the banks and schools of piranhas moving through the water; through traditional fishing experiences guided by local riverside experts; through conversations with researchers from the Mamirauá Institute, who work just a few kilometers from the lodge; and through the menu, where pirarucu and tambaqui are prepared using techniques developed by local communities.
The richness of Mamirauá’s fish is not an isolated phenomenon, but the direct result of decades of environmental protection, community-based management and continuous scientific research. It is also what gives meaning to the experience of being there, floating above one of the most biodiverse aquatic ecosystems on the planet.
Come discover Mamirauá Reserve and Uakari Lodge. Follow Uakari on Instagram and stay up to date with the latest news. Ready to experience it? Make your reservation.
