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Exploring freshwater fish habitats in the rainforest of Peru

Exploring freshwater fish habitats in Peru

Exploring freshwater fish habitats in the rainforest of Peru
Rhett A. Butler,
November 27, 2005

Many popular tropical freshwater aquarium fish originate in the world’s tropical rainforests. The Amazon Basin is a particularly rich source of fish — 5000 species are estimated to be swimming in its many streams, rivers, and lakes.

This fall the editor of, a leading environmental science and tropical freshwater fish information site, traveled to the Peruvian Amazon and examined habitats for freshwater fish. As a result of this effort, two new “biotope” descriptions have been posted on the site. The descriptions include underwater photographs for those interested in replicating the natural conditions of these habitats.

What is a biotope aquarium?

A biotope aquarium is an aquarium that is modeled after a natural habitat. The fish, plants, water chemistry, light conditions, and tank furnishings are similar to those that can be found in a specific natural setting. Biotope aquariums are generally popular among “purist” fish enthusiasts interested in the ecology of the fish they keep.

The biotopes

Aerial photo of oxbow lakes and a river in the Peruvian Amazon.’s new biotope descriptions are based on habitats in the southeastern part of Peru, arguably the most biodiverse place on the planet.

Amazon oxbow lake biotope

Virtually all lakes in this part of the Amazon are oxbow lakes. An oxbow lake is a crescent-shaped lake formed when a river changes course. In lowland Amazonia where soft alluvial soils dominate, meandering rivers gradually shift due to erosion and sediment deposition. Oxbow lakes typically form when loops in the river become so extreme that the main channel erodes a new straighter route, leaving the river bend apart from the river. As time passes, the oxbow lake becomes increasingly distant from the main channel. Water conditions change as the water stagnates.

Oxbow lakes are an important source of aquarium fish throughout the Amazon. Some of the best known tropical freshwater fish — including discus, hatchetfish, and tetras — are found in such lakes.

The new biotope profile looks specifically at two oxbow lakes found along the Madre de Dios and Tambopata rivers in the Madre de Dios river system upstream of Puerto Maldonado.

Amazon oxbow lake biotope profile

Amazon stream biotope

Underwater photo of Bladderwort, an aquatic plant, in the oxbow lake.

Small rainforest streams are common in this part of Peru. They generally arise from springs and range in width from a few inches to 10-14 feet and have a length that rarely exceed 3 miles (5 km). Because these streams usually run under the protective cover of the forest canopy they are generally cooler than rivers and oxbow lakes.

The new biotope profile examines a rainforest stream flowing into the Madre de Dios River. Present in the stream were cichlids, tetras and Corydoras catfish.

Amazon stream biotope profile

A broader look at aquarium fisheries in southeastern Peru

The rio Madre de Dios probably has more than 600 species, many of which have yet to be described, according to work by Michael Goulding, an expert in Amazonian fish, and other researchers in their book Amazon Headwaters – Rivers, Wildlife, and Conservation in Southeastern Peru. Despite this diversity, the ornamental fish industry — worth nearly $1 billion in wholesale value worldwide — only arrived in the region in 2002. Already the market looks promising with the region’s moderate high water season being seen as a distinct advantage over to other parts of the Amazon where aquarium trade fisheries shut down for months during the rainy season. Further, the high number of endemic species make the rio Madre de Dios system attractive for the commercial aquarium fish trade.

Executed properly, the aquarium fisheries trade offers opportunities for conservation and development. Project Amazonas and Project Piaba, in Iquitos, Peru and Brazil, respectively, have worked with local fisherman to encourage the sustainable harvest of aquarium fish while promoting environmental education in local communities and ecotourism.

Freshwater habitats globally threatened

Industrial gold mining operation that has turned the Rio Huaypetue into a large pit of mud, sand, and chemicals. Runnoff from the mine flows down a much-diminished version of the Rio Huaypetue and eventually into the Amazon River.

Focusing on the native environments of tropical freshwater fish species is increasingly important today given onslaught of threats — from deforestation, waterway modification and dam construction, the introduction exotic species, pollution, climate change and over-exploitation — facing these ecosystem. For now, southeastern Peru has escaped most of these risks to its freshwater biota. Overfishing of migratory fish species well downstream may have had a limited impact on local fisheries, while pollution and increaded sediment loads has affected rivers downstream from a small number of industrial gold mines. Still, the next time you pick out a colorful tropical fish from your local pet store, take a minute to remember that, at one time, it probably originated in some distant rainforest that may well be under threat today.

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