Railroad Valley Springfish

Crenichthys nevadae

Description

The robust-bodied Railroad Valley springfish, Crenichthys nevadae, is about 3 in (7 cm) long. It has a large, heavy head that is flattened above the eye; both the dorsal and anal fins are located far back, almost to the tail. Its color is greenish above and silvery beneath. Like other members of the order Cyprinodontiformes, the Railroad Valley springfish lacks spines in the fins; unlike other members of the order, its color is much less mottled and the lateral blotches are much bolder.

Behavior

Springfish live out their short lives within a narrowly defined, geographic area, feeding on insects and plant matter. From March through May, it is primarily herbivorous, then switches to a carnivorous diet of primarily ostracods. Breeding occurs year-round but ovary production documented from Big Warm Spring was greatest during the summer, declined in spring and fall, and was poorly developed in winter. When water temperatures were especially high, no larval fish were produced in any season. Reproduction seems to be severely restricted in water temperatures above 95°F (35°C). The ratio of males to females is even in the spring but the number of females almost doubles in the summer and fall.

Habitat

The Railroad Valley springfish is found in warm spring pools, outflow streams, and adjacent marshes. Outflows tend to be shallow and less than 3 ft (1 m) wide except for Big Warm Spring, which is several yards wide. The substrate of the head pools is typically sand, gravel or pebble with some decaying organic matter. Portions of some outflows contain dense mats of a nitrogen-fixing blue-green algae. Dense vegetation lines the pools and out-flows; salt grass is common in marshy areas. The springs and outflows at Lockes Ranch contain duck-weed and pondweed. Water temperatures in the headsprings range from 64-100°F (18.3-38.3°C). The critical maximum temperature of the Railroad Valley springfish has been recorded at 100°F (38.2°C).

Distribution

The Railroad Valley springfish is native to four thermal springs—Big, North, Hay Corral, and Reynolds—near Locke's Ranch and two thermal springs on the Duckwater Shoshone Indian Reservation—Big Warm and Little Warm. Additionally, the species has been introduced into Chimney Springs, about 6 mi (10 km) south of Locke's Ranch. This is a seepage area which forms small thermal ponds at Sodaville in Mineral County, Nevada. The springfish has also been introduced into springs at the source of Hot Creek, 40 mi (64 km) west of Locke's Ranch. The Big Warm Springs population no longer occurs in the headspring pool or in much of the outflow where it was once observed.

Threats

All of the springs inhabited by the Railroad Valley springfish have been physically altered, primarily to serve as watering holes for grazing livestock, and the species has declined in numbers as a result. Spring pools have been diked, waters diverted, and outflows channeled, reducing the amount of suitable habitat. Vegetation around some of the springs (particularly, North Spring) have also been trampled by the cattle. Habitats are further threatened by groundwater pumping, which causes a decrease in spring discharges. In 1981, the introduced springfish population at Chimney Springs was lost after spring discharge ceased altogether. Springfish were reintroduced into Chimney Springs when flows resumed. Several other springs in the region have also failed.

Non-native fishes, which have been introduced into the limited habitat, also threaten this spring-fish. Guppies have become established in Big Warm Spring and have nearly eliminated springfish from the main pool. Development of one outflow channel of Big Warm Spring as a fish farm resulted in escape of catfish into the spring system.

Conservation and Recovery

Critical Habitat has been designated for the springfish in Nye County to include six springs and associated streams and marshes within the historic range of the springfish. The designated area does not include habitat in the outflow creek of Big Warm Spring. Unauthorized introduced populations near Sodaville, in Chimney Springs, and Hot Creek are not included in the designation.

Conservation measures should include federal management of habitat at Locke's Ranch and the Duckwater Indian Reservation to control agricultural wastes that might affect groundwater quality and cattle grazing that degrades the habitat; modify the operation of the commercial catfish facility at Big Warm Springs to prohibit the escape of cat-fish into spring outflows; protection of the aquifer feeding the springs; and establishing new populations within the historical range of the species.

Federal listing of the Railroad Valley springfish has had some impact on the leasing of Bureau of Land Management lands for livestock grazing and mineral exploration.

Contact

U.S. Fish and Wildlife Service
Division of Endangered Species
911 N.E. 11th Ave.
Portland, Oregon 97232-4181
http://pacific.fws.gov/

References

Deacon, J. E., C. Hubbs, and B. J. Zahuranec. 1964."Some Effects of Introduced Fishes on the Native Fish Fauna of Southern Nevada." Southwestern Naturalist 12:31-44.

Deacon, J. E., and J. E. Williams. 1982. "Summer Food Habits of Fishes from Two Springs in East-Central Nevada." Southwestern Naturalist 27(4): 437-445.

Deacon, J. E., and J. E. Williams. 1984. "Annotated List of the Fishes of Nevada." Proceedings of the Biological Society of Washington 97(1):103-118.

Hubbs, C., and J. E. Deacon. 1964. "Additional Introduction of Tropical Fishes into Southern Nevada." Southwestern Naturalist 9:249-251.

U.S. Fish and Wildlife Service. 1986. "Determination of Threatened Status and Designation of Critical Habitat for the Railroad Valley Springfish." Federal Register 51: 10857-10865.

Williams, C. D. 1986. "Life History of the Railroad Valley Springfish, Crenichthys nevadae Hubbs, of East-Central Nevada." M.S. Thesis, California State University, Sacramento. 124 pp.