Chihuahuan Freshwater

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One of the pools in the Cuatrocienigas wetlands, at the heart of the Chihuahua Desert, Mexico.
© WWF-Canon / Edward PARKER

About the Area

The Chihuahan desert is one of the most biologically rich and diverse ecoregions in the world. The freshwater biota of the ecoregion is considered some of the most unique in the world because of its complexity and high level of endemism.

The Chihuahuan freshwater habitats support a diverse subtropical desert basin fauna with a high degree of local endemism. The river basins of this xeric ecoregion are remarkably different from one another, each containing unique species that have evolved overtime following a series of tectonic events and resulting geographic isolation.
Size:
898,000 sq. km (350,000 sq. miles)

Habitat type:

Xeric Basins

Geographic Location:
North America: southeast Arizona across New Mexico and west Texas and southward deep into Mexico

Conservation Status:
Critical/Endangered

Local Species

Within Cuatro Ciénegas, an interior basin containing hundreds of spring-fed pools in a desert environment, about half of the 20 species of fish, and 23 of the 34 species of freshwater mollusks are endemic. Some of these fish and mollusk species are restricted to individual pools of only a few square meters in size. Others have not changed appreciably from ancestral forms and are important relict species.

Species here include the aquatic box turtle (Terrapene coahuila), the endemic black softshell turtle (Trionyx ater), pond slider (Pseudemys scripta), plain-bellied water snake (Nerodia erythrogaster), and Cuatro Ciénegas cichlid (Cichlasoma minckleyi).

Three endangered endemic fishes are Cuatro Ciénegas shiner (Notropis xanthicara), Cuatro Ciénegas darter (Xiphophorus gordoni), and Sardinilla (Lucania interioris). Other endemic fishes are Cuatro Ciénegas gambusia (Gambusia longispinis), Robust gambusia (G. marshi), Yellowfin gambusia (G. alvarezi), Conchos pupfish (Cyprinodon eximius), Comanche springs pupfish (C. elegans), Bighead pupfish (C. pachycephalus), Devil's River minnow (Dionda diaboli), and Roundnose minnow (D. episcopa).

Tiny fish called Pecos gambusia give birth to live offspring rather than laying eggs. They also feed on mosquito larvae, helping to keep the mosquito population in check.

Among the endemic invertebrates, which are found predominantly in spring-fed habitats, are a number of aquatic snails and amphipods such as the Pecos assiminea (Assiminea sp.), Phantom Spring cochliopa (Cochliopa texana), Phantom Lake tryonia (Tryonia cheatumi), Phantom Spring amphipod (Gammarus hyalelloides), San Solomon amphipod (G. sp.), and Noel's amphipod (G. desperatus).

Featured species

Devil's River minnow (Dionda diaboli)

The Devils River minnow is a small fish, with adults reaching sizes of approximately 2 inches in length. The fish has a wedge-shaped caudal (near the tail) spot and pronounced lateral stripe extending through the eye to the snout. Double dash markings extend along the lateral line. The species has a narrow head and a body with prominent dark markings.

The minnow is found in channels of fast-flowing, spring-fed waters over gravel substrates the fish most often occurs where spring flow enters a stream, rather than in the spring outflow itself. Little information is available on life history characteristics, feeding patterns, or reproductive behaviors of this species. However, based on their long coiled intestinal tract, species of the genus Dionda are considered to feed primarily on algae.

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Threats

Water withdrawals as a result of population growth and agricultural activities, leads to the loss of critical habitat in this water-poor environment. Overgrazing, introduced species (e.g., cichlid Hemichromis guttatus and the crayfish Procambarus clarkii), potential large-scale tourism, mining, and pollution also threaten many freshwater communities.

Coordinated efforts of public and private organizations in both Mexico and the United States is leading to a broader understanding of the Chihuahuan Desert and the threats to its ecosystems. With this understanding will come a greater appreciation of the desert and new ways of addressing human needs while maintaining the biodiversity characteristic of the Chihuahuan Desert.

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WWF’s work

WWF, in Mexico and the US, is working with Mexican and American government agencies, landowners and local NGOs on a four-year project in the bi-national Rio Grande basin, which includes a large portion of the Chihuahuan Desert Ecoregion.

In particular, the project is: helping to implement water policy reforms that allocate water for ecological uses; demonstrating better water management practices through integrated watershed management pilot projects; and involving key stakeholders in the implementation of water policy reforms and restoration strategies that benefit the basin.

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