Cyprinodon atrorus
Bandfin pupfish / cachorrito del Bolsón


En español




25-30 mm SL as adults, rarely >40 mm

Conservation Status

Listed as Threatened by the Mexican Government in 1994.


Restricted to saline lakes and pools, marshes and non-thermal springs and their outflows throughout much of the Cuatro Ciénegas basin, Coahuila, México.


Common to remarkably abundant in restricted, local areas.

Habitat & Ecology

Coahuilan pupfish occupy habitats varying from hypersaline (to >95 gm/l, and higher), seasonally hot, shallow and otherwise severe lakes and pools through marshlands to quiet, non-thermal springheads. Little daily or seasonal movements occur at water temperatures of < 15°C, when different sexes and sizes of fish intermingle in loose aggregations. At temperatures < 10°C most individuals are dormant, on or within the substrate or within clumps of algae or other vegetation. Maximum temperature known to be tolerated in nature is 47.2°C; no living fish were present at 48°C. Feeding, breeding and other activities are most pronounced between 25 and 45°C when males form territories. Males and females remain strongly segregated except at times of actual breeding. They rarely live in water >25 cm, despite presence of far deeper places at some locales (e.g., springheads), and are characteristically in water < 5.0 cm deep. They associate with soft, flocculent, algae-rich bottoms, from which they feed on detritus, algae and small invertebrates.


Male Coahuilan pupfish tend to set up territories in exceedingly shallow water, usually < 5.0 cm, and may be solitary or in small, loosely aggregated leks. Territory size, levels of defensive posturing and activity and even spawning display vary with habitat, being far less developed in areas of dense vegetation or other high heterogeneity. A female enters a territory quickly to be confronted by the male, dips to the bottom with the male, spawns, hesitates, then moves to spawn again or rapidly away. Eggs hatch in a few days and young feed throughout the habitat, and with impunity within territories . Growth is rapid, to sexual maturity in a few weeks at summer temperatures.


Reduced volumes of flow during drought result in vast losses of shallow, marginal Coahuilan pupfish habitats. Some springs have further been canalized resulting in reduced water levels and in some instances desiccation, both of springheads and downflow marshes. In both cases, these pupfish are forced into channels (or canals) and thus into contact with Cuatro Ciénegas pupfish (Cyprinodon bifasciatus), the latter living almost exclusively in stable, thermal springs, moving downstream in summer in natural outflows and canals. Coahuilan and Cuatro Ciénegas pupfishes hybridize extensively under such conditions. Reduced spring discharge also results in diminution of marshes, bringing the preferred and required habitats of the two species into greater proximity and increasing the probabilities for introgression. Extraction of groundwater within and adjacent to springs exacerbates these conditions. As with other Cuatro Ciénegas fishes, non-indigenous crayfish, molluscs, and perhaps fishes (none yet confirmed as naturalized) may be anticipated to result in ecosystem-level changes that will influence the species in the future.

Conservation Actions

A substantial proportion of the Cuatro Ciénegas basin, including many springs their outflow channels, and other habitats inhabited 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. Especially needed are provisions to maintain lateral and downflow marshes, which are quickly and permanently drained by canalization of springheads

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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