The Salado River freshwater ecoregion, FEOW ecoregion 137, is a northeastern Mexican freshwater ecoregion centered on the Río Salado system. It drains parts of Coahuila, Nuevo León, and Tamaulipas before it connects to the Río Bravo/Rio Grande system. This ecoregion should not be confused with the Llanos El Salado closed-basin ecoregion of the Mexican Plateau. The Salado River ecoregion is part of the broader Río Bravo region, but FEOW treats it as a distinct unit because of its characteristic fish fauna and drainage history.

The ecoregion’s habitats include desert-margin streams, intermittent tributaries, spring-fed reaches, pools, riffles, lowland channels, reservoirs, irrigation canals, drainage ditches, mineral-rich waters, and modified river sections. Flow is strongly influenced by aridity, seasonal rainfall, groundwater, springs, reservoirs, irrigation, salinity, and drought. Permanent aquatic habitats may depend on springs, reservoirs, or perennial river sections, making these refuges especially important for native fishes.

The fish fauna is a mixture of northeastern Mexican, Río Bravo, desert-margin, spring-associated, and groundwater-associated elements. Important groups include cyprinids, catostomids, ictalurids, cyprinodontids, poeciliids, darters, centrarchids in some contexts, cave or groundwater fishes, and cichlids. FEOW identifies Notropis saladonis, the Salado shiner, as the only strict endemic of the ecoregion. Other characteristic near-endemic or regional fishes include Dionda diaboli, Dionda melanops, Cyprinella rutila, Etheostoma segrex, and Prietella phreatophila.

Cyprinids are among the defining fishes of the region. Notropis saladonis, Dionda diaboli, Dionda melanops, and Cyprinella rutila represent the flowing-water, spring-run, and desert-stream component of the fauna. These fishes depend on perennial flow, suitable substrates, and acceptable water quality. Darters and subterranean fishes add further conservation value. Etheostoma segrex is associated with the Salado de Nadadores, while Prietella phreatophila represents the groundwater or cave-fish component of the ecoregion.

Poeciliids and cyprinodontids are also important in springs, vegetated margins, slow channels, and variable lowland waters. Species of Gambusia, Cyprinodon, and related genera occur in the broader northeastern Mexican and Río Bravo context, especially in spring-fed or warm shallow habitats. These small fishes may be locally abundant and ecologically important, but their status should be assessed carefully by locality, as neighboring closed basins, spring systems, and Río Bravo tributaries may contain different assemblages.

Cichlids are native to the Salado River ecoregion, but the native cichlid fauna is limited. The principal native species is Herichthys cyanoguttatus, the Río Grande cichlid or Texas cichlid. This species is native to northeastern Mexico and southern Texas in the Río Bravo / Rio Grande region. It should be distinguished from Herichthys minckleyi, which is endemic to Cuatro Ciénegas, and from Pánuco-associated Herichthys species such as Herichthys labridens and Herichthys bartoni.

Taxonomic and locality caution are important. The Salado River ecoregion is close to several other biologically important northeastern Mexican ecoregions, including Cuatro Ciénegas, Lower Grande - Bravo, San Juan River, and Mayrán - Viesca. Records from the Río Salado, Salado de Nadadores, Río San Juan, Cuatro Ciénegas, Río Bravo tributaries, Ocampo, or Pánuco-related waters should not be merged without locality evidence. Drainage assignment is essential for accurate FFM records.

Introduced fishes should be treated separately from the native fauna. Tilapiines such as Oreochromis niloticus, Oreochromis aureus, Oreochromis mossambicus, and related aquaculture forms may occur in reservoirs, ponds, canals, irrigation systems, or modified waters, but they are not part of the native Salado River fish fauna. Other introduced fishes may include stocked sport fishes, carps, aquarium releases, or aquaculture escapees. These species can affect native fishes through predation, competition, habitat alteration, disease, and changes in the food web.

Conservation priorities include protecting springs, groundwater systems, perennial stream reaches, subterranean waters, riparian vegetation, and water quality. Major threats include groundwater extraction, spring-flow reduction, river regulation, reservoir construction, irrigation withdrawals, salinization, pollution, sewage discharge, agricultural runoff, mining impacts, livestock pressure, channel modification, invasive fishes, and climate-driven drought. For FFM, the Salado River should be treated as a northeastern Mexican Río Bravo-associated ecoregion, important for endemic and near-endemic cyprinids, darters, subterranean fishes, spring-associated species, and the native Río Grande cichlid Herichthys cyanoguttatus.

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.