ABSTRACT

Threatened fishes of the world: Cyprinodon (Cyprinodontidae).

Edwin P. Pister Desert Fishes Council, P.O. Box 337, Bishop, California 93515, U.S.A.

Common names

The pupfishes as a group are often mistakenly referred to as the "desert pupfish." Actually, there exists only one true "desert pupfish," Cyprinodon macularius macularius.

Conservation status

Williams et al. (1989) list from the American Southwest l6 pupfishes: 7 species, and 9 subspecies of 3 additional species. Because most of them exist in desert habitats, they are often incorrectly lumped together as "desert pupfish." All of the above, in addition to 16 species (6 undescribed) from Mexico, are considered to be endangered, threatened, or of special concern. Only 2 North American members of the pupfish genus Cyprinodon are currently not in jeopardy.

Identification

Pupfish are small and aggressive, exhibiting distinct sexual dimorphism. They are deep bodied with terminal mouths. In the Death Valley hydrographic area of eastern California and western Nevada, adults range in total length from the Devils Hole pupfish (C. diabolis) at 19 mm. to the Owens pupfish (C. radiosus) at 50 mm. The deeper bodied males of many pupfish species become brilliantly colored during breeding season, when most are highly territorial.

Distribution

Most North American pupfishes are found scattered throughout the American Southwest and northern Mexico.

Abundance

Seasonal abundance varies by habitat. The Owens pupfish may reach summertime population sizes of several thousand although restricted to only a few permanent habitats. Populations decrease in wintertime. Devils Hole pupfish populations range annually from about 200 to 700.

Habitat and ecology

In the Death Valley area, pupfishes evolved following pluvial periods which accompanied the Pleistocene Epoch when huge lakes and watercourses were gradually reduced to desert springs and small streams. Their isolation created an evolutionary circumstance not unlike the Galapagos Islands which so strongly influenced the thinking of Charles Darwin concerning the origin of species. Pupfish may occupy spring pools, marshes, and running water. They feed primarily on substrate, taking mouthfuls of material, chewing it, then expelling the remainder through the mouth or gill covers. Pupfish also feed on aquatic insects, crustaceans, snails, and eggs. They are ecological generalists and tolerate a broad range of environmental variables. Pupfish are among the most heat-tolerant of all fishes and can withstand wide ranges in temperature. Owens pupfish thrive in shallow, warm water that hot summer days bring to desert marshes. This same habitat may be covered with an inch or two of ice during wintertime when air temperatures drop well below 0°C. Conversely, Devils Hole pupfish live in the upper reaches of a cavern so vast that its depth has never been determined, and in water at a constant 33°C. Some live in water that exceeds 38°C and tolerate up to 45°C for short periods. Daily fluctuations may be as much as 15-20°C. Others live in pools several times the salinity of sea water.

Reproduction

Pupfish are egg layers, spawning over an extended period of 7 or 8 months. Normally it takes only 2-4 months to reach maturity after hatching. Once a pupfish reaches a strong swimming stage it may live for 6-9 months. In marshes, pupfish spawned in autumn do not mature until the following spring (about 6 months), whereas those spawned in March or April will mature by early summer. In constant- temperature warm springs, pupfish mature in 2-4 months year around. In marshes and ponds, where fishes are dormant over winter, some may live for 2-3 years (Soltz and Naiman 1978).

Threats

"If a North American desert fish species is not currently listed as endangered, it will not be long before it reaches that point" (Pister 1990, p. 186.). This sobering prediction is based upon rapid human population growth in a very arid portion of North America. For instance, the rapidly growing city of Las Vegas, Nevada, is located near key pupfish habitats lying within Ash Meadows National Wildlife Refuge. Each time a new home connects to a domestic water supply, it directly or indirectly extracts water from an aquatic habitat. The same situation is occurring throughout the southwestern U.S. and northern Mexico, many parts of which receive annual precipitation of less than 100 mm. Both surface and groundwater resources are rapidly being depleted. Adding to the overall problem is physical destruction of aquatic habitats by farming operations and urban development.

Conservation action

The Desert Fishes Council, a group of some 300 university research scientists and government biologists and resource managers, was formed in 1970 "dedicated to the conservation of North America's arid land ecosystems." Membership is worldwide, with a strong representation of Mexican scientists. Council members work as, and with, government agency biologists in implementing species recovery efforts (in the U.S.) under the Endangered Species Act of 1973, a law currently under strong political attack. Enormous talent exists within the Council, summarized in a recent book (Minckley and Deacon 1991).

Conservation recommendations

Our only realistic hope of preserving this marvelous biological resource lies in educating the public and gaining their support. Changing people's values constitutes a major challenge and task. Problems to be surmounted therefore lie more in the realm of philosophy than in science. Science has clearly defined the problems of species preservation, but only by moving biodiversity issues higher on public priority lists do we hold any hope of saving this resource for the benefit and enjoyment of future generations.

References

Minckley, W.L., and J.E. Deacon (eds.). 1991. Battle Against Extinction: Native Fish Management in the American West. University of Arizona Press, Tucson.

Pister, E.P. 1990. Desert fishes: an interdisciplinary approach to endangered species conservation in North America. Journal of Fish Biology (1990)37(Supplement A), 183-187.

Soltz, D.L., and R.J. Naiman. 1978. The Natural History of Native Fishes in the Death Valley System. Natural History Museum of Los Angeles County, California. Science Series 30, 1-76.

Williams, J.E., J.E. Johnson, D.A. Hendrickson, S. Contreras-Balderas, J.D. Williams, M. Navarro-Mendoza, D-.E. McAllister, and J.E. Deacon. 1989. Fishes of North America endangered, threatened, or of special concern. Fisheries 14(6), 2-20.

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Last modified: 06 June 2004

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