Cyprinodon bifasciatus
Twoline pupfish / cachorrito de Cuatro Ciénegas


En español




35-50 mm SL as adults, rarely >60 mm

Conservation Status

The Cuatro Ciénegas pupfish was considered to be of Special Concern by the American Fisheries Society in 1989, and listed as Threatened in 1994 by the Mexican Government.


Restricted to constant-temperature, thermal springs and their outflows of the western half of the Cuatro Ciénegas basin, Coahuila, México.


Locally common to abundant.

Habitat & Ecology

Cuatro Ciénegas pupfish occupy thermal springs and their immediate outflows, extending to deep, slow-moving parts of associated rivers and marshlands in summer but either migrating to warmer water or otherwise disappearing in winter. Males and females segregate when breeding, the former along shallow margins and the latter feeding almost continuously in aggregations near bottom offshore, sometimes at > 7.0 m deep. Young are generally distributed over soft bottoms at all depths, but most commonly in < 1.0 m of water. Foods consist primarily of detritus-rich, semi-flocculent substrate, but algae and small aquatic invertebrates also are eaten. They are strongly diurnal, resting on or within soft sediments at night


Males form breeding leks along habitat margins, usually in < 15 cm of water over soft bottoms. They are unusually aggressive, even for a pupfish, having been observed defending territories against predators including largemouth bass (Micropterus salmoides). Females remain offshore and feed, then individually move into the lek. Breeding is accomplished by a female moving to the bottom where clasped by the male, during which contact eggs are fertilized and deposited on or within the sediment (sometimes on vegetation or debris). In marshes, leks may be formed over beds of aquatic plants or algae. Eggs develop within substrate or on other surfaces in a few days. Young feed throughout the habitat, but tend to remain in shallower, marginal areas. Sexual maturity is reached in a few weeks. Highly colored males and small juveniles are present throughout the year in springs, but are evident (and only occur) in downflow habitats from March or April through October.


Some springs have been canalized resulting in reduced water levels and in some instances total desiccation. Reduced flow during prolonged drought of the past few years have resulted in losses in habitat, not only directly but also indirectly due to changes in thermal and headspring/downflow habitat relations. Cuatro Ciénegas and Coahuilan pupfishes (Cyprinodon atrorus), the latter living in variable, downflow habitats, may hybridize extensively. Reduced spring discharges result in diminution of marshes, bringing the preferred and required habitats of these two species into greater proximity and increasing potentials for introgressive hybridization. Extraction of groundwater exacerbates these conditions. As with other Cuatro Ciénegas fishes, introduced crayfish, molluscs, and perhaps fishes (none yet confirmed as naturalized) may be expected to result in ecosystem-level changes that influence the species in the future.

Conservation Actions

A substantial proportion of the Cuatro Ciénegas basin, including many springs, outflow channels, and other habitats occupied by this pupfish, were set aside in 1994 as a biological preserve. Specific conservation actions are, however, yet to be proposed or implemented.

Conservation Recommendations

Devise and implement conservation actions preventing further loss and change of habitat and prohibit introductions of non-indigenous organisms.

Important References


W. L. Minckley, Department of Zoology, Arizona State University, Tempe, Arizona 85287-1501

Link to Phil Pister's Environmental Biology of Fishes Cyprinodon paper

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