Twoline pupfish / cachorrito de Cuatro Ciénegas
CYPRINODONTIDAE - pupfishes
35-50 mm SL as adults, rarely >60 mm
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.
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.
- Arnold, E. T. 1972. Behavioral ecology of two pupfishes (Cyprinodontidae, genus Cyprinodon) from northern México. Ph.D. Dissertation. Arizona State University, Tempe.
- ______. 1983. Pupfishes (genus Cyprinodon) of Cuatro Ciénegas: Hybridization in an intermediate habitat. Proceedings of the Desert Fishes Council. 5(1972): 114 (abstract only).
- Miller, R. R. 1968. Two new species of the genus Cyprinodon from the Cuatro Ciénegas basin, Coahuila, México. Occasional Papers of the University of Michigan, Museum of Zoology. 659: 1-15.
- ______. 1978. Composition and derivation of the native fish fauna of the Chihuahuan Desert region. Pp. 365-382, in R. H. Wauer & D. Riskind (eds.). Transactions of the Symposium of the Biological Resources of the Chihuahuan Desert Region, United States and México. US National Parks Service Transactions and Proceedings Series. 3(1977). US Government Printing Office, Washington, DC.
- ______. 1981. Coevolution of deserts and pupfishes (genus Cyprinodon) in the American Southwest. Pp. 39-94, in R. J. Naiman & D. J. Soltz (eds.). Fishes in North American Deserts. J. Wiley & Sons, NY.
- Minckley, W. L. 1969. Environments of the Bolsón of Cuatro Ciénegas, Coahuila, México, with special reference to the aquatic biota. Texas Western Press, University of Texas El Paso Science Series. 2: 1-65.
- ______. 1978. Endemic fishes of the Cuatro Ciénegas basin, Coahuila, México. Pp. 383-404, in R. H. Wauer & D. Riskind (eds.). Transactions of the Symposium of the Biological Resources of the Chihuahuan Desert Region, United States and México. US National Parks Service Transactions and Proceedings Series. 3(1977). US Government Printing Office, Washington, DC.
- ______. 1992. Three decades near Cuatro Ciénegas, México: Photographic documentation and a plea for area conservation. Pp. 81-110, in M. R. Sommerfeld & D. M. Kubly (eds.). Limnology and Aquatic Biology of the Southwest, Proceedings of a Special Symposium to Honor Professor Gerald Ainsworth Cole. 34th Annual Meeting of the Arizona-Nevada Academy of Science, Tempe, AZ, 21 April 1990. Journal of the Arizona-Nevada Academy of Science. 26(2).
- ______. 1994. A bibliography for natural history of the Cuatro Ciénegas basin and environs, Coahuila, México. Proceedings of the Desert Fishes Council. 25(1993): 47-64.
- Secretaria de Desarrollo Social. 1994. Decrito por elque se declara como Area Natural Protegida, con el carácter de Area de Protección de flora y fauna, la región conocida como "Cuatrociénegas", con una superficie de 84,347-47-00 Has. ubicada en el Municipio de Cuatrociénegas, Estado de Coahuila. Diario Oficial De La Federación, México, CDXCIV. 5-11.
- Secretaria de Desarrollo Social. 1994. Norma Oficial Mexicana NOM-059-ECOL-1994, que determina las especies y subspecies de flora y fauna silvestres y acuáticas en peligro de extinción, amenazadas, raras y sujetas a protección especial, y que establece especificaciones para su protección. Diario Oficial De La Federación, México, CDLXXVIII. 2-60.
- Williams, J. E., Bowman, D. B., Brooks, J. E., Echelle, A. A., Edwards, R. J., Hendrickson, D. A. & Landye J. J. 1989. Fishes of North American endangered, threatened, or of special concern: 1989. Fisheries. (Bethesda, MD) 14(6): 12-20.
W. L. Minckley, Department of Zoology, Arizona State University, Tempe, Arizona 85287-1501