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Ecoregion Description

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Species Richness

# of Endemic Species


209: Chagres

Major Habitat Type:

tropical and subtropical coastal rivers


Scott Smith, Michele Thieme




This ecoregion lies along the Caribbean coast of Panama, and extends from the eastern boundary of the Río Calovebora in the west to the eastern boundary of the Río Acla in the east. 

Drainages flowing into:

Caribbean Sea

Main rivers or other water bodies:

The major rivers in this ecoregion are the Río Chagres, Río Indio, and Río Cocle del Norte. Lakes Gatún and Alhajuela are man-made lakes in the Chagres basin that form part of the Panama Canal. The Canal bisects this ecoregion beginning at Colón in the north and ending at Panama City in the south. All of the water required for the operation of the canal is derived from the Chagres basin.


The interior boundary of the ecoregion runs along the end of the Cordillera Central, the Cordillera de San Blas, and part of the Serranía del Darién. Elevations range from over 1300 m above sea level (asl) in the Cordillera Central to only about 150 m asl in the east. The coastal plain is short throughout the Chagres ecoregion, but particularly short in the east where the mountains nearly meet the sea.


Panama’s climate is tropical, with monthly mean temperatures above 18 oC. The dry season occurs between mid-December and April and the wet season occurs between May and November (World Wildlife Fund  2001). The average annual precipitation is 2800 mm.

Freshwater habitats:

Historically, the Chagres ecoregion was characterized by short and steep coastal rivers and longer coastal rivers with extensive floodplains and lagoons. Today, there are few inland aquatic habitats in Panama. The most extensive of these are around the artificial reservoirs of Lake Gatún and Lake Alajuela (Angehr 2005). The small lakes and swamps around these two large lakes produce large amounts of methane from decaying aquatic vegetation (Condit et al. 2001).

Rainfall influences stream flow in the ecoregion, with the driest months occurring from January through March (Angermeier & Schlosser 1989). The headwaters of the Río Chagres – Frijolito, Frijoles, and Quebrada Juan Grande – are small forest streams that typically have continuous flow, but can rapidly become hypoxic when stagnant in backwaters, flood channels, and pools of temporary tributaries. A less common phenomenon occurs during the late dry season when the main channels become stagnant, trapping fish in larger hypoxic pools (Kramer, unpubl. obs.; Kramer 1983).

Terrestrial Habitats:

Lowland moist forests (including Isthmian Atlantic moist forests and Chocó-Darién moist forests) historically covered most of the ecoregion (World Wildlife Fund 2001). Today, forests near the Atlantic coast have almost no deciduous trees (Condit et al. 2000). Talamancan montane forests are still found at higher elevations, and the remote forests east of Lake Alajuela are largely undisturbed, with extensive areas of near pristine old-growth trees.

Fish Fauna:

Chagres is one of the most speciose ecoregions in lower Mesoamerica with over 50 species of primary and secondary freshwater fishes (Smith and Bermingham 2005). Moreover, the community composition of the Chagres ecoregion is very different from that found in the northern ecoregions of lower Mesoamerica. The freshwater fish fauna is much more similar to the faunas found in northwestern Colombia; the species richness of Characidae and Loricariidae in northwestern Colombia far surpasses the species richness of other freshwater fish families (Smith and Bermingham 2005). A similar pattern is found in the Chagres ecoregion, where 37% of the freshwater fishes are characids and 11% are loricariids. In contrast, the secondary freshwater fish families Cichlidae and Poeciliidae, which dominate the freshwater fish communities of the northern ecoregions in lower Mesoamerica, each make-up only 9% of the total species richness of the Chagres ecoregion.

Description of endemic fishes:

There is one strictly endemic species that inhabits this ecoregion: the characiid Roeboides carti. Some near-endemics include the characids Brycon chagrensis, Odontostilbe mitoptera, and Guatemalan headstander (Roeboides guatemalensis); and the aplocheilid, Rivulus montium (Smith and Bermingham 2005).

Other noteworthy aquatic biotic elements:

Lake Gatún is the most extensive freshwater ecosystem in Panama. Many waterbird species breed around the lake, which is also used by migrant species (Angehr 2005). Introduced species, however, have had an impact on populations of birds such as kingfishers, herons, terns, snail kites, and limpkins (Zaret & Paine 1973). The Panama Canal watershed overlaps three areas of bird endemism. These are primarily found at higher elevations, including the watershed’s periphery (Condit et al. 2001).

More than four amphibian Red List species are found in this ecoregion in the following genera: Atelopus, Hylomantis, Hyloscirtus and Craugastor (GAA 2006). Amphibian diversity peaks in Soberanía National Park, where there is a mix of arid and humid tropical amphibian assemblages from the Central American lowlands. This pattern is also reflected in birds and the diverse mixture of forests in the park (Condit et al. 2001).

Justification for delineation:

Fish provinces from Bussing (1976) were revised and subdivided on the basis of application of a similarity index to sub-basin fish presence/absence data.

Level of taxonomic exploration:

The level of taxonomic exploration in the Chagres ecoregion is particularly good in the Río Chagres basin, as well as in the Río Cocle del Norte , Río Miguel de la Borda, and the Río Indio. Many of the small drainage basins found in Kuna Yala have also been well explored.


Bussing, W. A. (1976)"Geographic distribution of the San Juan ichthyofauna of Central America with remarks on its origin and ecology" In Thorson, T.B. (Ed.). Investigations of Nicaraguan lakes. (pp. 157-175) Lincoln, Nebraska: University of Nebraska.

Smith, S. A.,Bermingham, E. (2005). "The biogeography of lower Mesoamerican freshwater fishes" Journal of Biogeography 32(10) 1835-1854.

World Wildlife, Fund (2001). "Terrestrial Ecoregions of the World" 2005 (2005;

The Nature Conservancy World Wildlife Fund
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