The Pecos pupfish (''Cyprinodon pecosensis'') is a species of

pupfish Pupfish are a group of small killifish belonging to ten genera of the family Cyprinodontidae of ray-finned fish. Pupfish are especially noted for being found in extreme and isolated situations. They are primarily found in North America, South Am ...

in the family Cyprinodontidae. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the

Pecos River The Pecos River ( es, Río Pecos) originates in north-central New Mexico and flows into Texas, emptying into the Rio Grande. Its headwaters are on the eastern slope of the Sangre de Cristo mountain range in Mora County north of Pecos, New Mexico ...

watershed in eastern

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

and western

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

in the United States.

Distribution and Habitat

Despite once existing throughout the Pecos River, ''C. pecosensis'' populations have become increasingly isolated due to significant portions of their native habitat being removed. Following the introduction of ''

Cyprinodon variegatus The sheepshead minnow or sheepshead pupfish (''Cyprinodon variegatus'') is a species of ray-finned fish in the family Cyprinodontidae, the pupfishes. It is found in salt marsh and estuary environments and is native to the eastern coasts of North ...

'' (sheepshead minnow), pure Pecos pupfish populations have been further isolated and largely exist in scattered sinkholes, man-made impoundments, and marshes. Its natural habitat includes springs, sinkholes, and pools of streams.

Introduction of ''Cyprinodon variegatus''

'' is thought to have been introduced during the early 1980s, presumably via bait-bucket dumping. Shortly after the introduction of ''C. variegatus'', ''C. variegatus'' X ''C. pecosensis'' hybrids quickly became widespread, occupying an estimated 50% of the native Pecos pupfish range by 1985. The widespread success of hybrids, and quick range expansion throughout native Pecos pupfish waters, has been hypothesized to be the result of selection mechanisms for hybrids during a period when the native ''C. pecosensis'' population had experienced a reduction. Additionally, hybrid populations have been reported to have increased growth-rates and vigor (

Heterosis Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions of ...

), resulting in Pecos pupfish females to actively choose to mate with hybrids over pure male Pecos pupfish. Given this, conservation efforts have been difficult and efforts are being made to prevent ''C. variegatus'' from entering into isolated ''C. pecosensis'' populations.

References

Cyprinodon Endemic fauna of the United States Fish of the Western United States Freshwater fish of the United States Endemic fauna of Texas Natural history of New Mexico Pecos River Taxa named by Anthony A. Echelle Taxa named by Alice Fitch Echelle Fish described in 1978 Taxonomy articles created by Polbot {{Cyprinodontiformes-stub