Upper Paraná Rivers & Streams

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Iguaçu National Park, Paraná, Brazil.
© WWF-Canon / Michel GUNTHER

About the Area

The Paraná River is formed by the junction of the Grande and Paranaíba rivers in south-central Brazil, and flows into the Rio de la Plata in Argentina. It is the 10th longest river in the world at 4,695km. The Upper Paraná River includes approximately the first 3rd of the Paraná River Basin, and lies completely within Brazilian territory, except for a stretch within the Itaipu Reservoir. The upper Paraná River and its tributaries are distinguished both by their spectacular waterfalls, and the exceptional levels of freshwater biodiversity.

The Upper Paraná River Basin covers an area of 891,000km2. The climate in the Upper Paraná region is tropical/sub-tropical, with an annual average temperature of 15oC and more than 150cm precipitation per year.

The Upper Paraná Basin supports over 300 species of fish, with a high degree of local endemism in individual tributaries that is likely the result of isolation by waterfalls.

The Rio Iguazu, which is isolated from the Paraná River by the Iguazu falls, supports 65 species of fish, of which about 50 species are endemic. There is also high richness of other aquatic organisms, both vertebrates and invertebrates.

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Size:
900,000 sq. km ( 350,000 sq. miles)

Habitat type:
Large River Headwaters

Geographic Location:
Central and South-Central South America: Argentina, Brazil, and Paraguay

Conservation Status:
Critical/Endangered

Local Species
Among the migratory species present are a number of characiformes, including Prochilodus lineatus and Salminus maxillosus that migrate hundreds of kilometres upstream during springtime floods to spawn. One of the few anadromous species in this ecoregion is Atlantic sabretooth anchovy (Lycengraulis grossidens), which ascends the Paraguay River from the Atlantic and has been reported in the southernmost end of the upper Paraná River.

The only species of lungfish found in the Neotropics - Lepidosiren paradoxa, inhabits these waters. Two well-known piranha species, Serrasalmus spilopleura and S. marginatus, occur here as well.

The lagoons of Upper Paraná floodplain are the environments richest in diversity of phytoplankton, periphyton, rotifers, aquatic macrophytes, benthos and fishes; the greatest abundance of phytoplankton, zooplankton, aquatic macrophytes and fish is also observed here.

Featured species

Atlantic sabretooth anchovy (Lycengraulis grossidens)

The Atlantic sabretooth anchovy measures up to 23.5cm. It has a silver stripe up to twice the eye diameter at widest, which disappears in fishes over 10cm. In colour it is greyish blue dorsally with yellowish fins and translucent membranes and a blackish caudal margin.

Atlantic sabretooth anchovy cccurs in brackish estuaries and adjacent marine areas but also reaches freshwater. It forms moderate schools. As an anadromous species, it migrates from estuaries or the sea, but possibly the limnichthys of Lake Maracaibo and the amazonensis represent purely freshwater forms. In freshwater, it feeds principally on small fishes, prawns and copepods; also insect larvae. At sea, it feeds on fishes and various crustaceans.

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Threats
Impoundments, water diversions, waterways, and agriculture are among the biggest threats in this ecoregion. The Itaipu hydroelectric dam, with a massive generating capacity of over 12,000 megawatt, was built in 1979 on the Iguazu River. Its construction flooded approximately 100,000 hectares of land, and destroyed important aquatic habitats, including Guaíra Falls.

A number of additional dams and waterways are planned within the ecoregion that have the potential to effectively block fish migrations. Burning of land for soybean plantations, desertification of the land, agricultural pesticides, and untreated domestic sewage have affected the quality of water as well.
/ ©: WWF-Canon / Michel GUNTHER
Flooded Atlantic Rainforest for electric power, Itaipu, Paraná, Brazil.
© WWF-Canon / Michel GUNTHER
WWF’s work
WWF’s Upper Parana Atlantic Forest project aims to protect the forests surrounding the Parana River, with a focus on conservation of key species, in particular the jaguar. As a top predator, protection of this species acts as a conservation proxy for protecting other animals and plants that depend on the same habitat.

The project also seeks to implement a vision for biodiversity, a ‘green corridor’ law, and forest landscape restoration activities.

WWF’s Global Freshwater Programme aims to ensure healthy environmental processes in the world's richest river basins and ecoregions, including those threatened by unsustainable infrastructure such as dams, water diversions and waterways.

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Photos and graphics © WWF or used with permission. Text available under a Creative Commons licence.