The Quintana Roo - Motagua freshwater ecoregion, FEOW ecoregion 202, is a tropical and subtropical coastal-river ecoregion on the Caribbean slope of southeastern Mexico and northern Central America. The Mexican portion includes southern and eastern Quintana Roo, especially systems associated with the Río Hondo, Laguna de Bacalar, coastal lagoons, cenotes, springs, wetlands, mangroves, and brackish coastal channels. The full FEOW ecoregion extends southward through Belize, eastern Guatemala, and the western edge of Honduras to the Motagua River and the Gulf of Honduras.

The northern part of the ecoregion is strongly influenced by limestone karst. Surface rivers may be limited or discontinuous, while groundwater, cenotes, springs, coastal lagoons, mangroves, marshes, and brackish wetlands are especially important. Farther south, in Belize, Guatemala, and Honduras, rivers are more developed at the surface and include forest streams, lowland channels, floodplain lagoons, swamps, estuaries, and larger river systems such as the Motagua. The Mexican sector should therefore be treated mainly as a Caribbean lowland, karst, lagoon, cenote, and wetland system rather than as a classic mountain-river basin.

The fish fauna includes cichlids, poeciliids, characids, catfishes, atherinopsids, gobies, sleepers, mullets, eels, gars, snooks, and other peripheral or estuarine-associated fishes. Lower coastal and lagoonal habitats are especially important because many species tolerate or regularly use both fresh and brackish waters. In Quintana Roo, freshwater fauna is closely associated with coastal lagoons, mangroves, groundwater-fed systems, and estuarine transitions, making the boundary between freshwater and brackish habitats ecologically important.

Poeciliids are important throughout the ecoregion. Species of Gambusia, Heterandria, Poecilia, Priapella, Xiphophorus, and related genera may occur in different drainage contexts, especially in springs, streams, vegetated margins, ditches, lagoons, and lowland waters. In the Mexican sector, livebearers are especially important in the warm lowland, spring, lagoon, and disturbed-water fauna, where they often coexist with cichlids and other peripheral fishes.

Peripheral and estuarine-associated fishes are also central to the ecoregion. Gobies, sleepers, mullets, eels, snooks, and other coastal fishes use river mouths, lagoons, mangroves, brackish channels, and sometimes inland freshwaters. These species are particularly important in Quintana Roo, where coastal wetlands, mangroves, and lagoon systems form a major part of the freshwater-to-marine gradient. For FFM, these habitats should be treated as integral parts of the ecoregion rather than as marginal coastal additions.

Cichlids are native and very important to the Quintana Roo-Motagua ecoregion. They do not form a lake-type species flock, but they represent a rich Middle American Caribbean-slope assemblage associated with rivers, karstic waters, lagoons, swamps, lowland channels, estuarine margins, and larger river systems farther south. Important genera in the wider ecoregion include Amatitlania, Archocentrus, Astatheros, Chuco, Cribroheros, Cryptoheros, Mayaheros, Oscura, Parachromis, Paraneetroplus, Petenia, Rocio, Theraps, Thorichthys, Trichromis, and Vieja, depending on locality and taxonomy.

In the Mexican portion, two of the most important native cichlids are Mayaheros urophthalmus and Petenia splendida. Mayaheros urophthalmus, the Mayan cichlid, is native to the Atlantic slope of Mexico and northern Central America, including the Yucatán Peninsula, and is especially associated with lowland rivers, marshes, mangrove swamps, coastal lagoons, and brackish-tolerant habitats. Petenia splendida, the bay snook, is another important native cichlid of lowland rivers, lagoons, wetlands, and structurally complex waters.

Other cichlids in the broader ecoregion include species associated with Belize, Guatemala, Lago Izabal, Río Dulce, Polochic, Sarstún, and the Motagua drainage. These include taxa such as Amphilophus margaritifer, Archocentrus spinosissimus, Vieja godmanni, and Vieja microphthalma, among others. These records are important for the FEOW ecoregion as a whole, but they should not be applied automatically to Quintana Roo without evidence of locality.

Introduced fishes should be treated separately from the native fauna. Tilapiines such as Oreochromis niloticus, Oreochromis mossambicus, and related aquaculture forms may occur in reservoirs, ponds, canals, lagoons, and modified waters, but they are not part of the native fauna. Other non-native fishes may arrive through aquaculture, stocking, aquarium releases, or accidental movement between basins, especially in modified habitats and lagoon systems.

Conservation priorities include protecting groundwater, cenotes, springs, Río Hondo habitats, Laguna de Bacalar and related lagoon systems, mangroves, wetlands, estuaries, riparian vegetation, and water quality. Major threats include deforestation, coastal development, mangrove loss, groundwater pollution, sewage, agricultural runoff, wetland drainage, invasive fishes, salinization, lagoon degradation, and climate-driven changes in rainfall, drought, storms, and sea level. For FFM, Quintana Roo - Motagua should be treated as Mexico’s Caribbean freshwater-brackish ecoregion, important for karst waters, coastal lagoons, livebearers, euryhaline cichlids, peripheral fishes, and the ecological connections among groundwater, wetlands, mangroves, and the Caribbean coast.

This account is based in part on information from Freshwater Ecoregions of the World (FEOW), © WWF/TNC, used as a reference for educational and scientific purposes. See: http://www.feow.org.