Leon Springs Pupfish

views updated

Leon Springs Pupfish

Cyprinodon bovinus

ListedAugust 15, 1980
FamilyCyprinodontidae (Killifish)
DescriptionSmall, robust, dusky gray to iridescent blue fish.
HabitatShallow, open streams.
FoodInvertebrates, detritus, diatoms, and vascular plants.
ReproductionSpawning may occur twice a day during summer and less actively as water temperature cools.
ThreatsOil pollution, groundwater pumping, hybridization.


Leon Springs pupfish, Cyprinodon bovinus, is a small, robust-bodied fish, about 1.5 in (4 cm) long at maturity. Its color varies from dusky gray to iri-descent blue. It has a wider head and body than other Cyprinodon species and is further distinguished in the following characteristics. C. variegatus, the sheepshead minnow, has pronounced vertical bars on its sides and trunk which are absent inC. bovinus ; C. elegans (the Commanche Springs pup-fish [see separate entry]) has a speckled color pattern uniques among Cyprinodon ; C. pecosensis (the Pecos pupfish) does not have the fully scaled abdomen and the bright yellow pigment on the dorsal and caudal fins in breeding males that occur inC. bovinus.


Pupfish do much of their feeding from the muddy bottom. Their diet consists of tiny invertebrates, detritus, diatoms, and vascular plants, especially algae.

Although breeding occurs throughout the year, spawning is most active during the summer. When water temperature is warm enough, spawning may occur twice a day. The male pupfish dig pits in the feeding areas and aggressively defend the territory from other males. They guard small spawning areas in shallow water, where the females deposit eggs. Development of the eggs is dependent upon water temperature; hatching occurs in two to three weeks, or longer. Newly hatched fry move near the creek edge or into the outskirts of a marsh margin.

C. bovinus mates readily with other Cyprinodon species, and hybridization has severely reduced the number of pure individuals. There is some evidence that female C. bovinus prefer males of other Cyprinodon species.


The Leon Springs pupfish inhabits quiet shallow saline springs, pools, and outflow streams. The pup-fish has an extended breeding season, wide salinty and temperature tolerances, and broad food habits, and appears to thrive in a simple community with few competing species. Where there is high salinity, few trees grow along the banks but filamentous algae is abundant during parts of the year. Substrates are primarily hard clay or soft mud, which is washed away during heavy rains. During extended cold periods the pupfish may either migrate upstream to thermal spring seeps or bury into the warmer mud substrate.


This pupfish was discovered in 1851 at Leon Springs, 8 mi (13 km) west of Fort Stockton in southwestern Texas. Sometime before 1938, the pupfish disappeared from the spring and was thought to be extinct. In 1958, Leon Springs dried up because of excessive groundwater pumping. In 1965 the species was rediscovered at Diamond Y Spring in Pecos County, 9 mi (14.5 km) north of Fort Stockton.

The Leon Springs pupfish probably survives only in Diamond Y Spring and Leon Creek, its outflow stream. Recently, this small population has been stable with summer densities reaching three or more fish per square meter.


Much of the original habitat of this pupfish was destroyed by diversion of water for irrigation and excessive groundwater pumping. In recent years, the Diamond Y Spring has experienced diminishing flow and will probably dry up if pumping continues at the present rate. In addition, the springs area is in the midst of an active oil and gas field. A refinery is located upstream from the main spring head for the pupfish's habitat. The oil companies have acted to minimize leakage into Diamond Y Spring and Leon Creek, but past oil spills have caused considerable fish mortality, and the potential for further accidents still exists. In 1974 the common sheepshead minnow was released into Leon Creek. Interbreeding between it and the Leon Springs pupfish resulted in extensive hybridization, threatening the genetic purity of the species. The pupfish competes for territorial sites with the plains killifish and with all other fish in the spring flows for food. Because most Cyprinodon species historically occurred in isolation from other members of its genus, they have not adapted well to the presence of other fish. The Pecos pupfish, C. pecosensis, is a particular threat because its salinity tolerance is similar to C. bovinus.

Conservation and Recovery

Springs and seeps feeding the pupfish's habitat have some salinity that makes the water less suitable for human needs and these springs have not gone dry as have other springs tapped for irrigation purposes. The survival of the species depends upon the continued water depth of these springs. These springs also provide a safe haven against competitive fish species unless non-native fish are introduced by humans.

A carefully supervised fish poisoning program and intensive selective seining efforts successfully removed all sheepshead minnows and hybrids by August 1978. Although the present Leon Springs pupfish population seems to be genetically pure, the habitat remains accessible and still vulnerable to the release of harmful exotic fishes.

The entire known range of this species from the head of Diamond Y Spring downstream to above the State Highway 18 crossing has been designated as Critical Habitat. In cooperation with the Soil Conservation Service, the Trans-Pecos Soil and Water Conservation District constructed a protective dike around one of the springs to ensure that an oil spill would not reach the habitat.

The Recovery Plan calls for a number of proactive conservation measures. They include: 1) continued cooperation with private landowners, the Texas Parks and Wildlife Service, and oil and gas companies drilling in the habitat areas in order to protect the springs and the aquifer from contaminants or from reduction in water levels; 2) construction of dikes to prevent groundwater flow into the springs; 3) with signs around the habitat, warn visitors of the extreme danger of introducing exotic fish; 4) establish emergency actions in case of spring failure; 5) maintain the captive population at Dexter National Fish Hatchery and conduct research as to the C. bovinus 's reproductive requirements, disease and parasites, and the effect of changes in stream flow. Wild populations should be studied for the effects of competition and predation by other fish, survivorship, and the effect of the physical characteristics of the habitat on the species.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P. O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915


Echelle, A. A., and C. Hubbs. 1978. "Haven for Endangered Pupfish." Texas Parks and Wildlife Magazine 36: 9-12.

Kennedy, S. E. 1978. "Life History of the Leon Springs Pupfish, Cyprinodon bovinus." Copeia 1977: 93-103.

U. S. Fish and Wildlife Service. 1985. "Leon Springs Pupfish Recovery Plan." U. S. Fish and Wildlife Service, Albuquerque.