Boundaries

This ecoregion includes the drainage basin of the Rio Paraíba do Sul and its tributaries. It is limited to the west by the Serra da Mantiqueira, the divide between the Paraíba do Sul basin and the São Francisco and Upper Paraná basins.

Topography

The Paraíba do Sul drains the Taubaté-Resende rift of the Serra do Mar (Great Escarpment) and Serra da Mantiqueira system, which forms one of the oldest drainage divides of the Brazilian Plateau (Martin et al. 1996; Modenesi-Gauttieri 2000; Dillenburg & Hesp 2009). The Paraíba basin is characterized by high relief with steep crystalline escarpments and alkaline massifs that rise 2600 m asl.

Freshwater habitats

The Rio Paraíba do Sul starts at the confluence of the rios Paraitinga and Paraibuna and flows 1120 km northwest to the Atlantic Ocean. Its left and right bank tributaries drain from the Serra da Mantiqueira and Serra do Mar, respectively. The Paraíba’s discharge is 874 m³/s and sediment load is 10.9 x 10⁶ t/yr (Dillenburg & Hesp 2009). Its upper middle section and coastal portion are navigable, but these are limited by rapids and waterfalls around São Fidélis. Historically, during high water the Paraíba do Sul flowed over into Lagoa Feia, a large complex of lakes south of the river’s mouth.

Terrestrial habitats

Several terrestrial ecoregions span the Paraíba do Sul basin, including Bahia interior forests in the Paraibuna, Pomba, and Muriae basins; Alto Paraná Atlantic forests bordering much of the main stem; and Serra do Mar coastal forests along the southern edge. Bahia interior forests comprise predominantly seasonal semi-deciduous forests. Alto Paraná Atlantic forests are also semi-deciduous forests that form a transition between the Serra do Mar coastal forests and cerrado further inland. The Serra do Mar coastal forests cover a strip of Atlantic moist forests along the Serra do Mar range. Pockets of restinga forests line the coast on nutrient-poor sandy soils (WWF 2001).

Description of endemic fishes

Despite the lower species richness, endemism is relatively high in the Paraíba do Sul, which has approximately 40% endemism at the species level. Seventy-eight percent of the trichomycterids are endemic, all within the genus Trichomycterus. There is also one endemic genus, Oligobrycon. This is represented by O. microstomus and is the only endemic characid in the ecoregion.

Other noteworthy fishes

Trichomycterus caipora is a newly described species from Lagoa Feia and Rio Macabu.

Justification for delineation

The Paraíba do Sul ecoregion falls within Southeastern Brazil’s coastal rivers ichthyographic province as outlined by Ringuelet (1975).

Level of taxonomic exploration

Good